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Terra Mission (EOS/AM-1)

Spacecraft     Launch    Mission Status     Sensor Complement    EOS    References

Terra (formerly known as EOS/AM-1) is a joint Earth observing mission within NASA's ESE (Earth Science Enterprise) program between the United States, Japan, and Canada. The US provided the spacecraft, the launch, and three instruments developed by NASA (CERES, MISR, MODIS). Japan provided ASTER and Canada MOPITT. The Terra spacecraft is considered the flagship of NASA's EOS (Earth Observing Satellite) program. In February 1999, the EOS/AM-1 satellite was renamed by NASA to “Terra”. 1) 2) 3) 4)

The objective of the mission is to obtain information about the physical and radiative properties of clouds (ASTER, CERES, MISR, MODIS); air-land and air-sea exchanges of energy, carbon, and water (ASTER, MISR, MODIS); measurements of trace gases (MOPITT); and volcanology (ASTER, MISR, MODIS). The science objectives are:

• To provide the first global and seasonal measurements of the Earth system, including such critical functions as biological productivity of the land and oceans, snow and ice, surface temperature, clouds, water vapor, and land cover;

• To improve the ability to detect human impacts on the Earth system and climate, identify the “fingerprint” of human activity on climate, and predict climate change by using the new global observations in climate models;

• To help develop technologies for disaster prediction, characterization, and risk reduction from wildfires, volcanoes, floods, and droughts

• To start long-term monitoring of global climate change and environmental change.

Complemented by aircraft and ground-based measurements, Terra data will enable scientists to distinguish between natural and human-induced changes.

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Figure 1: Illustration of the Terra spacecraft (image credit: NASA)

Spacecraft:

Terra consists of a spacecraft bus built by Lockheed Martin Missiles and Space (LMMS) in Valley Forge, PA. The spacecraft is constructed with a truss-like primary structure built of graphite-epoxy tubular members. This lightweight structure provides the strength and stiffness needed to support the spacecraft throughout its various mission phases. The zenith face of the spacecraft is populated with equipment modules (EMs) housing the various spacecraft bus components. The EMs are sized and partitioned to facilitate pre-launch integration and test of the spacecraft.

EPS (Electrical Power Subsystem): A large single-wing solar array (size of 9 m x 5 m = 45 m2), deployed on the sunlit side of the spacecraft, maximizes both its power generation capability and the cold-space FOV (Field of View) available to instrument and equipment module radiators. The average power of the satellite is 2.53 kW provided by a GaAs/Ge solar array (max of 7.5 kW @ 120 V at BOL). The solar array is based on on a prototype lightweight flexible blanket solar array technology developed by TRW (use of single-junction GaAs/Ge photovoltaics). A coilable mast is used for the deployment of the solar array. The Terra spacecraft represents the first orbiting application of a 120 VDC high voltage spacecraft electrical power system implemented by NASA. A PDU (Power Distribution Unit) has been designed to provide 120 DC (±4%) under any load conditions. This regulated voltage, in turn, is achieved via a sequential shunt unit (SSU) and the 2 BCDUs. A NiH2 (nickel hydrogen) battery is used (54 cells series connected) to provide power during eclipse phases of the orbit. 5) 6) 7)

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Figure 2: Coilable mast deployer for the Terra solar array (image credit: NASA)

GN&C (Guidance Navigation and Control) subsystem: Terra is a three-axis stabilized design with a single rotating solar array. The GN&C subsystem is made up of sensors, actuators, an ACE (Attitude Control Electronics) unit, and software. A three-channel IRU (Inertial Reference Unit) determines body rates in all control modes. Solid-state star trackers provide fine attitude updates, processed by a Kalman filter to maintain precise 3-axis inertial knowledge. A 3-axis magnetometer senses the Earth's geomagnetic field, primarily for magnetic unloading of reaction wheels, but also as a sensor to determine an attitude failure during a deep space calibration maneuver. 8)

The backup sensors include an ESA (Earth Sensor Assembly) for roll and pitch sensing, and coarse sun sensors for pitch and yaw sensing of the sun line relative to the solar array. A fine sun sensor is used in the event that one star tracker fails or during the backup stellar acquisition mode. In addition to these sensors, a gyro-compassing computation is performed for backup yaw attitude determination.

A reaction wheel assembly provides primary attitude control. During normal mode, a wheel speed controller is available to bias the wheel speeds at a range that avoids zero rpm crossings (stagnation point). Magnetic torquer rods regulate the wheel momentum to < 25% capacity in four-wheel mode and < 50% capacity in the three-wheel mode (backup mode). Thrusters are used for attitude control during all velocity change maneuvers and for backup attitude control and wheel momentum unloading.

GN&C is a fault-tolerant system that includes an FDIR (Fault Detection, Isolation and Recovery) capability unique to each of the different operational control modes. If an attitude fault is detected, FDIR transfers all control functions to the ACE unit configured to use all redundant hardware. Once in safe mode, FDIR is disabled.

Sensor component

Units

Manufacturer/model

Mission heritage

Solid State Star Tracker (SSST)

2

BATC / CT-601

MSX, XTE

Earth Sensor Assembly) (ESA)

2

Ithaco / conical scanning

UARS

Coarse Sun Sensor (CSS)

2

Adcole / 42060

UARS

Fine Sun Sensor (FSS)

1

Adcole / 42070

TOPEX

Three Axis Magnetometer (TAM)

2

NASA/GSFC

EUVE, UARS

Inertial Reference Unit (IRU)

2

Kearfott / SKIRU-DII

XTE

 

 

 

 

Actuator component

Units

Manufacturer/model

Heritage

Reaction Wheel Assembly (RWA)

4

Honeywell / EOS-AM

Similar to EUVE

Magnetic Torquer Rod (MTR)

3

Ithaco / TR500CFR

EUVE

Attitude Control Thruster

6 (x 2)

Olin Aerospace (Primex)

 

Delta-v thruster

2 (x 2)

Olin Aerospace (Primex)

 

Table 1: Overview of GN&C sensors and actuators

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Figure 3: Artist' view of the Terra spacecraft in orbit (image credit: NASA)

The design life of the Terra spacecraft is six years. The spacecraft bus is of size of 6.8 m (length) x 3.5 m (diameter) and has a total launch mass of 5,190 kg. The total payload mass is 1155 kg.

RF communications: The primary Terra telemetry data transmissions are via TDRS (Tracking & Data Relay Satellite) system. A steerable HGA (High Gain Antenna) and associated electronics are mounted on a deployed boom extending from the zenith side of the spacecraft. This location maximizes the amount of time available for TDRS communications via this antenna without obstruction by other pads of the spacecraft. Emergency communication is done via the nadir or zenith omni antenna. Command and engineering telemetry data are transmitted in S-band. The science data recorded onboard are transmitted via Ku-band at 150 Mbit/s. The nominal mode of operation is to acquire two 12 minute TDRSS contacts per orbit. During each TDRSS contact, both S-band and Ku-band transmission is being used.

The average data rate of the payload is 18.545 Mbit/s (109 Mbit/s peak); onboard recorders for data collection of one orbit. Mission operations are performed at GSFC. 9)

Broadcast of data: Besides Ku-band and S-band communication, Terra is also capable of downlinking science data via X-band. The X-band communication can be operated in three different modes, Direct Broadcast (DB), Direct Downlink (DDL) and Direct Playback (DP). DB and DDL is used to directly transmit real-time MODIS and ASTER science data respectively to users.

The DAS (Direct Access System) provides a backup option for direct transmission in X-band. DAS supports transmission of data to ground stations of qualified EOS users around the world. These users fall into three categories:

- EOS team participants and interdisciplinary scientists

- International meteorological and environmental agencies

- International partners who require data from their EOS instruments

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Figure 4: The Terra spacecraft in the cleanroom of LMMS at Valley Forge (image credit: LMMS)


Launch: The launch of the Terra spacecraft took place on Dec. 18, 1999 from VAFB, CA, on an Atlas-Centaur IIAS rocket.

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Figure 5: Photo of the Terra satellite launch on 18 Decmber 1999 (6:57 UTC) from VAFB, CA (image credit: NASA)

Orbit: Sun-synchronous circular orbit, altitude = 705 km, inclination = 98.5º, period = 99 minutes (16 orbits per day, 233 orbit repeat cycles). The descending nodal crossing is at 10:30 AM.

Orbit determination is performed by TONS (TDRS Onboard Navigation System) which estimates Terra's position and velocity, drag coefficient, and master oscillator frequency bias. TONS is updated by Doppler measurements at the spacecraft's receivers and provides the attitude control software with a desired pointing ephemeris. Ground-based orbital elements are uplinked daily for backup navigation.

As of March 1, 2001, the Landsat-7, EO-1, SAC-C and Terra satellites are flying the so-called “morning constellation” or “morning train” (a loose formation demonstration of a single virtual platform). There is 1 minute separation between Landsat-7 and EO-1, a 15 minute separation between EO-1 and SAC-C, and a 1 minute separation between SAC-C and Terra. The objective is to compare coincident observations (imagery) from various instruments (synergistic effects). 10)

Figure 6: NASA's Terra mission at 10 years on-orbit (video credit: NASA)


Note: As of March 2020, the previously single large Terra file has been split into two files, to make the file handling manageable for all parties concerned, in particular for the user community.

This article covers the Terra mission and its imagery in the period 2020, in addition to some of the mission milestones.

Terra status and imagery in the period 2018-1999




Mission status and imagery for the period 2020-2019

• June 3, 2020: A structure in the Nares Strait known as an “ice arch” was still intact in late May 2020 when the MODIS instrument on NASA’s Terra satellite acquired this natural-color image. But check it out while you still can. This natural gatekeeper—which prevents sea ice from exiting the Arctic Ocean and drifting southward into Baffin Bay—typically breaks up each year by June or July. 11)

- The Arctic Ocean is considered a semi-enclosed ocean, as it is surrounded almost entirely by land. The northern coastlines of these land masses—Eurasia, North America, Greenland—and some scattered islands keep most of the sea ice penned up, making it less mobile than sea ice that forms around Antarctica.

- There are a few passageways, however, that allow ice to escape in spring and summer. The main passage is through the Fram Strait between northeast Greenland and Svalbard. Another is through the Nares Strait between northwest Greenland and Ellesmere Island. Nares Strait is relatively narrow, but a southward flowing current ensures plenty of Arctic sea ice is lost there each year.

- How much ice is lost via the Nares Strait depends in part on how soon the ice arch breaks up each year. In 2019 the ice arch collapsed early, crumbling in mid-April and allowing ice to flow freely by May. Early breakups also occurred in 2017, 2010, and 2008. In 2007, the arch failed to form at all.

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Figure 7: The ice arch in 2020 has proved to be more stable. Satellite images show the arch intact on May 22 and it remained so as of the publishing of this story (image credit: NASA Earth Observatory, images by Lauren Dauphin and Joshua Stevens, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kathryn Hansen)

- According to Walt Meier, a sea ice researcher at the National Snow and Ice Data Center, the timing of the breakup depends on factors including ice thickness, air temperature, and wind direction. Thick ice is more stable and tends to break-up later than thin ice. In the strait, thick ice can build up during winters with cold air temperatures; it can also accumulate from thick, multi-year ice that drifts in from the north and gets “wedged” in the strait.

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Figure 8: By spring, warmer temperatures begin to melt the ice, causing it to thin and weaken. Temperatures in spring 2020 have been warmer than normal over the Nares Strait, although not as extreme as other parts of the Arctic including Siberia (image credit: NASA Earth Observatory)

- But you need more than thin ice and warm temperatures to destroy the ice arch. “Warmer temperatures in the spring don’t necessarily indicate an early break-up,” Meier said. “The ice needs to be weak enough to break up, but then the winds blowing in the right direction give it a ‘final kick’ for the arch to collapse.”

- The “right direction” refers to winds blowing parallel to the strait, forcing ice southward. Meier noted that over the past few months, a low-pressure circulation pattern in the central Arctic has resulted in winds blowing perpendicular to Nares Strait. “These are not winds that would tend to initiate the break-up,” he said.

- Meier speculated that this same wind pattern could be responsible for churning up the sea ice and causing tough conditions for the Polarstern—an icebreaker currently drifting in Arctic sea ice for the MOSAiC science expedition. “So, that large-scale circulation may have contributed to both ridging and thicker ice along Polarstern's route,” Meier said, “as well as winds that are favorable to preserving the arch.”

• May 20, 2020: The Gran Chaco is not the most well-known forest in South America. It is second in size and biodiversity to the neighboring Amazon rainforest. Unlike the moist Amazon, the Gran Chaco is located in a semi-arid climate; its vegetation is less colorful. But like the Amazon, the Gran Chaco has been facing rapid deforestation over recent years. 12)

- The Gran Chaco spans about 650,000 km2 (250,000 square miles) in Argentina, Paraguay, Bolivia, and Brazil—making it the largest dry forest in South America. It largely consists of shrubs and hardwood trees that provide habitat for thousands of plant species and hundreds of animal species. The native Wichí people have hunted and gathered on this land for decades.

- But observations by Landsat satellites indicate that roughly 20 percent—142,000 km2 (55,000 square miles)—of the forest was converted into farmland or grazing land from 1985-2013. From 2010 to 2018, more than 29,000 km2 (11,000 square miles) of the Gran Chaco was cleared for farms and ranches, according to the non-profit Guyra Paraguay. Much of the clearing took place in Argentina.

- The images of Figures 9 and 10, acquired with MODIS on NASA's Terra satellite, show the deforestation over a span of two decades around the Salta Province of northern Argentina. Much of the cleared land has been converted to farmland for growing soybeans and raising livestock. Argentina is the third-largest soybean producer in the world. Research shows that soybean production was a direct driver of deforestation in the forest in the 2000s. As soybean producers felt more pressure to keep up with global demand, they needed to find untapped land and began clearing forests and arid regions. Advances in technology made it easier to grow crops on these marginal lands, which were previously difficult to cultivate.

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Figure 9: The MODIS image of 18 December 2000 shows a mix of cleared land and greener areas (image credit: NASA Earth Observatory)

- Controlling deforestation in Gran Chaco has been challenging. In 2007, Argentina enacted a national “forest law” mandating that local governments regulate the expansion of large-scale farming and establish practices to protect native forests. However, research shows that local governments were unable to enforce the law in certain protected zones, some of which actually experienced an increase in deforestation after the law was passed.

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Figure 10: The MODIS image of 24 December 2019 shows much of the forest replaced by large fields (image credit: NASA Earth Observatory, images by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kasha Patel)

• April 21, 2020: On March 25, 2020, the Indian government placed its 1.3 billion citizens under a strict lockdown to reduce the spread of the COVID-19 coronavirus. The country-wide mandate decreased activity at factories and severely reduced car, bus, truck, and airplane traffic. After just a week of reduced human activities, NASA satellite sensors observed aerosol levels at a 20-year low for this time of year in northern India. 13)

- Every year, aerosols from anthropogenic (human-made) sources contribute to unhealthy levels of air pollution in many Indian cities. Aerosols are tiny solid and liquid particles suspended in the air that reduce visibility and can damage the human lungs and heart. Some aerosols have natural sources, such as dust storms, volcanic eruptions, and forest fires. Others come from human activities, such as the burning of fossil fuels and croplands. Human-made aerosols tend to contribute most of the smaller particles that have greater potential for damaging human health.

- “We knew we would see changes in atmospheric composition in many places during the lockdown,” said Pawan Gupta, a Universities Space Research Association (USRA) scientist at NASA’s Marshall Space Flight Center. “But I have never seen aerosol values so low in the Indo-Gangetic Plain at this time of year.”

- In a typical early spring in the Ganges Valley of northern India, human activities generate the majority of aerosols. Motor vehicles, coal-fired power plants, and other industrial sources around urban areas produce nitrates and sulfates; coal combustion also produces soot and other carbon-rich particles. Rural areas add smoke—rich in black carbon and organic carbon—from cooking and heating stoves and from prescribed burns on farms (though farming fires more often occur at other times of year). By all accounts, the 2020 lockdown reduced those human-made emission sources.

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Figure 11: The first five maps above show aerosol optical depth (AOD) measurements over India during the same March 31 to April 5 period for each year from 2016 through 2020. The sixth map (anomaly) shows how AOD in 2020 compared to the average for 2016-2019. Aerosol optical depth is a measure of how light is absorbed or reflected by airborne particles as it travels through the atmosphere. If aerosols are concentrated near the surface, an optical depth of 1 or above indicates very hazy conditions. An optical depth, or thickness, of less than 0.1 over the entire atmospheric vertical column is considered “clean.” The data were retrieved by the MODIS instrument on NASA’s Terra satellite (NASA Earth Observatory images by Joshua Stevens, using Terra MODIS analysis courtesy of Pawan Gupta/USRA/NASA. Story by Kasha Patel with image interpretation from Hiren Jethva, Rob Levy, and Ralph Kahn)

- Scientists expect aerosol levels to increase slightly in upcoming weeks in parts of India as seasonal dust storms begin. Dust concentrations are typically low in March and early April, before temperatures rise and strong westerly winds blow sand in from the Thar Desert and Arabian Peninsula. The question is whether overall AOD will remain below normal.

- “The hard part with understanding aerosols is that particles can move based on wind patterns and other meteorology,” said Robert Levy, program leader for NASA’s MODIS aerosol products. “You have to disentangle what is caused by the human fingerprint versus a meteorological factor.”

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Figure 12: The chart shows daily average aerosol optical depth measurements over northern India from January 1 to April 5, 2020, as compared to the 2016-2019 average. Note that the rise in AOD at the end of February coincided with fire activity in the Indian state of Punjab and in neighboring Pakistan(image credit: NASA Earth Observatory)

- In the first few days of the lockdown, it was difficult to observe a change in the pollution signature. “We saw an aerosol decrease in the first week of the shutdown, but that was due to a combination of rain and the lockdown,” said Gupta. Around March 27, heavy rain poured over vast areas of northern India and helped clear the air of aerosols. Aerosol concentrations usually increase again after such heavy precipitation.

- “After the rainfall, I was really impressed that aerosol levels didn’t go up and return to normal,” Gupta added. “We saw a gradual decrease, and things have been staying at the level we might expect without anthropogenic emissions.”

- According to Gupta, AOD levels in northern India at the beginning of April were significantly below the norm for this time of year and the lowest in 20 years of MODIS observations. Ground observation stations in India have also reported a decrease in particle pollution in the region. Anecdotally, people in the northern state of Punjab have reported seeing the Himalayas for the first time in decades.

- In southern India though, the story is a little hazier. Satellite data show aerosol levels have not yet decreased to the same extent; in fact, levels seem to be slightly higher than in the past four years. The reasons are unclear, but could be related to recent weather patterns, agricultural fires, winds, or other factors.

- This a model scientific experiment,” said Levy about the lockdown and its effects on pollution. “We have a unique opportunity to learn how the atmosphere reacts to sharp and sudden reductions in emissions from certain sectors. This can help us separate how natural and human sources of aerosols affect the atmosphere.”

• April 20, 2020: Some Antarctic icebergs can persist for many years. A newborn child could go off to school, learn to drive, and become an adult all within the span of time it takes some of the largest icebergs to break up and melt away. Iceberg A-68A—now just a few months shy of its third birthday—is a youngster compared to some. But the mammoth berg has already had an impressive journey. 14)

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Figure 13: The huge Antarctic iceberg has floated into warmer waters, but it is still mostly intact. On April 9, 2020, the MODIS instrument on NASA’s Terra satellite acquired this image of A-68A floating about 230 km west-southwest of the South Orkney Islands. The 95-mile-long iceberg appears to dwarf the 80-mile-long island chain (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kathryn Hansen)

- In this image, A-68A is about 500 miles from where it broke away from the Larsen C Ice Shelf in July 2017. The journey, however, was not exactly direct. In its first year, the iceberg moved just 45 km (28 miles) as tides shuffled the Delaware-sized block of ice back and forth, occasionally smashing it against a rocky outcrop on the Antarctic Peninsula. The region’s powerful currents eventually won, and the iceberg has since been winding its way north through the Southern Ocean.

- A-68A seems to have hit the brakes in recent weeks, rotating in place without moving far. NASA/UMBC glaciologist Christopher Shuman thinks the berg could be caught up in a circulating mass of water, or “gyre.” Christopher Readinger, a scientist at the U.S. National Ice Center (NIC), agrees that a gyre or smaller-scale eddy could explain the berg’s motion. “This is behavior we’ve seen many times before with other bergs downstream of the peninsula,” Readinger said. “They just start circling for no apparent reason.”

- Icebergs passing through this area eventually get kicked to the east when they encounter the powerful Antarctic Circumpolar Current, which funnels through the Drake Passage. From that point, the ice can whip north into the warmer waters of the South Atlantic—a region where icebergs melt, break down, and ultimately die. That has been the fate of many fragments of another iceberg, B-15. The Connecticut-sized berg was the largest ever measured by satellites, but 20 years after breaking from the Ross Ice Shelf, only one piece is still large enough to be tracked by the NIC.

- A-68A is not quite at that point. “I’m surprised at how well it’s sticking together,” Readinger said. “It’s been in warmer water for a few months now and it’s not exactly a very thick berg, so I expect it will break up sometime soon, but it’s showing no signs of that yet.”

• April 4, 2020: Russia’s Lake Beloye holds just over 6 km3 of fresh water; drops in a bucket compared to the 24,000 km3 in Lake Baikal, the world’s largest freshwater lake by volume. Yet Beloye still manages to make a stately appearance in satellite imagery.

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Figure 14: On March 17, 2020, the MODIS instrument on NASA's Terra satellite acquired this image of Lake Beloye in Russia’s Vologda region. It stands out in part because its water is shallowly spread across more than 1,000 km2 — larger than the average lake area in this part of northwest Russia (image credit: NASA Earth Observatory, image by Joshua Stevens, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kathryn Hansen)

- It also stands out because of the stark contrast of lake ice—some of it is likely snow-covered—with the surrounding landscape. The lake usually freezes over in early November and breaks up in late April. Thawing already appeared to be underway when this image was acquired, with thin gray ice along the southern coast near the historic town of Belozersk. If you click on this time series of raw images, small areas of open water were visible by March 30, before fresh snow appeared to cover the ice again on April 1.

- The shape of the lake is strikingly round. Many of the lakes in this region fill valleys and depressions left behind at the end of the last Ice Age when the enormous ice sheets retreated. That could be the case here or, as another source points out, the water could be filling a 100-million-year-old impact crater.

- While this image makes the lake appear isolated in the landscape, it’s actually connected to a series of rivers and canals that form the Volga-Baltic Waterway. In the area visible in this image, the waterway includes the Kovzha River, Lake Beloye, the Belozersky Canal (constructed along the lake’s southern side as a bypass), and the Sheksna River. This waterway, in turn, is connected to an even larger system of inland waterways known as the Unified Deep Water System of European Russia.

• March 30, 2020: Could Satellites Help Head Off a Locust Invasion? Researchers are using satellite data to understand where locusts may spread during the largest infestation in eastern Africa in decades.— A single desert locust (Schistocerca gregaria) can consume its body weight in vegetation in one day. That may not sound like much for one 2.5-gram locust, but when 40 million of them gather—considered a small swarm—they can devour as much food as 35,000 people. In one day, a small swarm can jeopardize a farmer’s livelihood. 15)

- Since December 2019, croplands in Kenya have been inundated by the voracious insects. By January 2020, at least 70,000 hectares (173,000 acres) of land were infested—Kenya’s worst locust event in 70 years. In February, the swarms spread to ten countries in eastern Africa, threatening food supplies for millions of people. Ethiopia and Somalia have seen their worst locust infestations in 25 years. The United Nations (UN) has warned that the upcoming rainy season may make things worse.

- NASA-funded scientists are partnering with the UN and relief organizations to better understand where locusts are likely to swarm. Using remote sensing observations of soil moisture and vegetation, researchers are tracking how environmental conditions influence locust life cycles and hoping to stop outbreaks before they spread.

- “The approach that helps prevent large-scale infestations is to catch the locusts very early in their life stages and get rid of their nesting grounds,” said Lee Ellenburg, the food security and agriculture lead for SERVIR at NASA’s Marshall Space Flight Center. The joint program between NASA and the U.S. Agency for International Development (USAID) uses satellite data to improve environmental decision-making in developing nations. The team also partnered with staff at the Desert Locust Information System of the UN Food and Agriculture Organization (FAO) to learn more about locust behavior.

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Figure 15: This image shows average soil moisture over eastern Africa for January 14-20, 2020, during the early stages of the locust invasion. The preliminary estimates—developed by scientists at UCAR (University Corporation for Atmospheric Research) and the University of Colorado—use NASA’s CYGNSS (Cyclone Global Navigation Satellite System) microsatellites and are integrated with NASA’s model-based Land Information System (image credit: NASA Earth Observatory, images by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview and soil moisture data from Cyclone Global Navigation Satellite System (CYGNSS) microsatellites integrated with NASA's model-based Land Information System. Story by Kasha Patel)

- The two maps (Figures 15 and 16) show two important environmental parameters for locust development: soil moisture and vegetation. Soil moisture is important because females almost always lay their eggs in wet, warm, sandy soil. In general, they do not lay their eggs unless the soil is moist down to 5-10 cm (2-4 inches) below the surface. After eggs hatch, the abundance of nearby vegetation becomes the important parameter because it provides sustenance for maturing locusts and guides migration patterns.

- Desert locusts have three main life stages: egg, hopper, and adult. Once they are mature adults, locusts are difficult to find on the ground and eradicate because they can fly 50 to 150 kilometers (30 to 90 miles) per day, especially if winds are strong. However, eggs and hoppers (when they’re still developing wings) have limited mobility and are easier to target.

- “The data we have so far show a strong correlation between the location of sandy, moist soils and locust activity,” said Ashutosh Limaye, NASA’s chief scientist for SERVIR. “Wherever there are moist, sandy locations, there are locusts banding or breeding.” Desert locusts rapidly reproduce, so SERVIR researchers are working with FAO to pinpoint potential breeding locations and suggest targeted areas for pesticide sprays.

- “Our goal is to learn from FAO how to find out where the breeding grounds are,” Ellenburg added. “If the prevailing conditions indicate that locusts will hatch and be taking off, the goal is to go early and destroy their nesting grounds.”

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Figure 16: This map depicts changes in green vegetation across eastern Africa between Dec 15, 2019, and March 15, 2020. Derived from data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, the Normalized Difference Vegetation Index (NDVI) is a measure of the health and greenness of vegetation based on how much red and near-infrared light it reflects. Healthy vegetation with lots of chlorophyll reflects more near-infrared light and less visible light (image credit: NASA Earth Observatory)

- “Once locusts lay the eggs and hatch, they start looking for vegetation to feed on,” said Catherine Nakalembe, a food security researcher with SERVIR and NASA Harvest. “They start migrating, looking for more to eat, and then keep multiplying.”

- Nakalembe says vegetation across the region is much greener than average years—in fact, the greenest vegetation observed by satellite since 2000 for the December to March time period. Between October and December 2019, the Horn of Africa received up to four times more rainfall than average, making it one of the wettest “short rain seasons” in four decades. The extra rain made for robust plant growth and bountiful conditions for locusts.

- With the upcoming “long rain season” (March through May) in east Africa, conditions could be ripe for more infestations, Nakalembe notes. The NASA team is refining several satellite datasets to assess the damage already caused and to create forecasts of where and how much longer locust outbreaks might occur.

- “We work in close coordination with national ministries through our regional partners, and we hope the outcomes from our ongoing work can ultimately support those who are in the front line of managing the current outbreak,” said Nakalembe.

- The NASA SERVIR and Harvest programs are working closely with Global and Regional FAO offices, USAID, World Food Program (WFP), the SERVIR Hub in East and Southern Africa at the Regional Center of Resources for Mapping Development (RCMRD) in Nairobi, Kenya, the SERVIR Hub in West Africa at the AGRHYMET based in Niamey, Niger, the Greater Horn of Africa IGAD Climate Prediction and Applications Center, NASA Short-term Prediction Research and Transition Center (SPoRT) NASA Earth Science Disasters Program, and several satellite missions to provide information and direction on where resources should be directed to mitigate locust outbreaks.

• March 24, 2020: Winter is loosening its grip on the Northern Hemisphere, and greens and browns are replacing white on the landscape. But the seasonal change in March 2020 in Northern Europe is less dramatic than most years. 16)

- While snow covered much of Norway and the northern parts of Sweden and Finland, the southern end of each country appeared snow-free—including the capital cities of Oslo, Stockholm, and Helsinki. (For a seasonal comparison, see this image from March 2018.) The cities were virtually snow-free for much of winter 2019-20. For example, Helsinki saw no new snowfall in January or February, according to news reports. Numerous ski resorts across Europe had to rely on imported and artificial snow.

- Warm winter temperatures were one reason for the sparse snowfall. According to NOAA, the December 2019 to February 2020 period was the warmest on record in Europe, and the January-February period was the warmest on record for the Northern Hemisphere. “The strong polar vortex has kept much of the frigid air in the Arctic, leaving the mid-latitudes warmer and generally less snowy than normal,” said Jennifer Francis, a scientist at Woods Hole Research Center.

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Figure 17: This natural-color satellite image shows snow cover in Scandinavia and the Baltic region in early spring 2020. It is a composite of two images acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite on March 20 and 21. The composite maximizes the cloud-free area visible from space (image credit: NASA Earth Observatory images by Joshua Stevens, using data from the Level 1 and Atmospheres Active Distribution System (LAADS) and Land Atmosphere Near real-time Capability for EOS (LANCE), and MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kathryn Hansen)

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Figure 18: This map shows land surface temperature anomalies for January to March 2020 in northern Europe. Orange and red colors indicate areas that were warmer than average for the same three-month period from 2003 to 2018. The map is based on MODIS data from NASA’s Aqua satellite. Note that the map depicts land surface temperatures (LSTs), not air temperatures. LSTs are a measure of how hot the surface would feel to the touch and can sometimes be significantly hotter or cooler than air temperatures (image credit: NASA Earth Observatory)

- As a consequence of a strong polar vortex, the polar jet stream—westerly winds in the lower atmosphere that help move weather systems around the planet—stayed farther north than normal this winter. As a result, Francis noted, Pacific storms hit places like Washington and British Columbia while depriving the Sierras of snowfall. Atlantic storms, meanwhile, pummeled the United Kingdom and northwest Europe, but avoided parts of Central and Northern Europe.

• March4, 2020: In August 2019, fires in the Amazon dominated the news, inspiring concern from presidents and prime ministers to pop stars to the Pope. As smoke darkened South American skies, people wondered: What caused the fires? Were they unusual? What did they mean for the rainforest? 17)

- Editor’s Note: This story is part of a series. Please read part 1, part 2, and part 3 for a more complete picture of Amazon deforestation.

- Scientists at NASA and other international agencies worked overtime to answer such questions, using the satellite and ground-based information available in real-time. But the reality of science, statistics, and satellite observations is that understanding the causes and effects of a fire season takes time. Six months later, some of the answers are coming into clearer focus.

- “There is no question the 2019 Amazon fires were unusual, but they were unusual in specific areas and ways,” said Douglas Morton, chief of the Biospheric Sciences Laboratory at NASA’s Goddard Space Flight Center. “Fortunately, we did not see forest fires burning uncontrolled through the rainforest like we have during past drought years. What we did see was a worrisome increase in deforestation fires in certain parts of Brazil.”

- Despite the nasty start to the 2019 fire season, year-end tallies of fire hot spot detections and burned area did not break all-time records. “The real nightmare scenario would have been deforestation fires at the level we had in 2019 during a drought year,” said Alberto Setzer, a senior scientist at Brazil’s National Institute for Space Research (INPE). “You would have seen fires spreading into the rainforest and burning unchecked for months.”

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Figure 19: The reality of science, statistics, and satellites is that a deep understanding of the causes, effects, and severity of a fire season takes time. - The first signs that 2019 could be an especially tumultuous fire season emerged in the northern Brazilian state of Roraima. Between January and April 2019, satellites detected record numbers of hot spots, especially in areas where reports of deforestation were common, explained Setzer. By August, skies were unusually smoky across several states, many state governments had declared emergencies, and controversies about deforestation data and environmental policy simmered in the media (image credit: NASA Earth Observatory, images by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview, Fire Information for Resource Management System (FIRMS) data from NASA EOSDIS, and Landsat data from the USGS. Burned area anomalies data are courtesy of Louis Giglio. Story by Adam Voiland)

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Figure 20: But it was not until the effects of the fires reached São Paulo, Brazil’s media and financial capital, that they became front page news. On August 19, 2019, accumulated smoke from fires in the Amazon and from particularly smoky fires in dry forests along the Bolivia-Paraguay border blew southeast, combined with unusually low clouds, and turned day into night in the city. People were baffled, and the eyes of the world turned to the fires in the rainforest. “There was an incredible hunger for information,” said Louis Giglio, a fire scientist at the University of Maryland and NASA Goddard (image credit: NASA Earth Observatory)

- When fire outbreaks occur, it can be hard to assess their extent or severity from the ground, but satellites can help. The Moderate Resolution Imaging Spectroradiometer (MODIS) and the Visible Infrared Imaging Radiometer Suite (VIIRS) instruments on NASA and NOAA satellites detect hot spots associated with fires on a daily basis.

- “These ‘active fire’ data are one of the first things people look at,” said Giglio. “But it can be difficult to interpret what all those red spots on a map mean in real time, especially if you’re not an expert in remote sensing. It can be tough even if you are an expert in remote sensing.”

- One of the key things to remember about active fire maps such as the one maintained by NASA’s Fire Information for Resource Management System (FIRMS) is how different the fires can be, cautioned Giglio. In tropical South America, red dots may represent small seasonal agricultural fires burning in pastures or between fields; the same dots can also represent big piles of dried wood being torched after rainforest clearcutting; some may represent a fast-spreading grass fire or brush fire in dried-out wetlands or shrubby savannas; and still others may be knee-high fires creeping through the understory of rainforests.

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Figure 21: MODIS fire detections in Brazil in the time frame 1 January 2003 to 31 December 2019 (image credit: NASA Earth Observatory)

- If you look at the total number of hotspots or square kilometers of burned area that satellites detected across South America, just in Brazil, or in certain Brazilian states in 2019, the raw numbers from FIRMS and INPE’s fire monitoring system do not stand out. The line chart above shows the total fire counts as observed in Brazil over nearly two decades of MODIS data.

- “If you are comparing fire detections or burned area from 2019 to the full MODIS record,” said Morton, “realize that you are comparing a year without extreme drought or uncontrolled forest fires to years such as 2005, 2007, and 2010 when there were.” Also, fire activity was extremely high in the early years (2001-2004) of MODIS observations because it was not until 2004 that Brazil enacted a series of environmental regulations that reduced fires and the rate of deforestation.

- During the past few years, there has been less emphasis on environmental enforcement and fire prevention, so deforestation has been increasing. “One of the ways some people have tried to game the system in recent years is by clearing land in a way that is difficult for satellites to detect—by clearing thin strips along the edge of the rainforest, for instance,” said Morton. “In 2019, deforestation fires started earlier in the dry season, and people burned large clearings. It was similar to fire activity in years with limited environmental enforcement and high deforestation, such as 2003-2004.”

- There is another reason the 2019 fire counts and burned area did not end up at the top of the long-term fire records. As public outrage peaked in August and September, the Brazilian government deployed tens of thousands of soldiers to the rainforest to fight fires. Then heavy rains dampened fire activity across much of Amazonia. By October, fire counts and burned area tallies had fallen to nearly record-low levels in many areas.

- “If the military hadn’t intervened and the rains hadn’t picked up, there is no doubt that the totals for the year would have been much higher,” said Setzer.

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Figure 22: MODIS fire detections in Amazonas (State in Brazil) in the time frame 1 January 2003 to 31 December 2019 (image credit: NASA Earth Observatory)

- “Tallying active fire detections for a given area is a reasonable first step if you’re trying to quickly assess or characterize a fire season or fire outbreak. But it’s only that — a first step,” explained Niels Andela, one of Morton’s colleagues at NASA. “By looking at other measures like the intensity, location, and duration of fires, it became clear that 2019 was a departure from the norm.”

- One important point to understand: not all of the red spots on fire activity maps in 2019 were deforestation fires in the rainforest. “A closer look at land cover maps and high-resolution satellite imagery shows that many of the fire detections in 2019 were located in shrublands, grasslands, and savannas that people wouldn’t recognize as rainforest,” explained Giglio. According to INPE data, 34 percent of the total fire hot spots detected in Brazil in 2019 were in Amazonia, the rainforest. In contrast, 50 percent were in the Cerrado, a savanna region with spotty tree cover, plenty of pastures and farms, and large numbers of fires every year. Five percent or less burned in the Brazilian Pantanal—a grassy wetland region in southwestern Brazil—or other biomes.

- But in certain areas, the story looks different. Fires were especially common along the Trans-Amazonian highway in Brazil’s far western state of Amazonas. According to Giglio, MODIS made 11,516 fire detections in Amazonas in August, the second most the sensor has ever observed for the state in that month. As shown by the burned area map at the top of the page, severe fires also occurred along key highways in Parã, Mato Grosso, and Rondônia where new deforestation of rainforest is common.

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Figure 23: MODIS fire observations on 28 October 2019 (image credit: NASA Earth Observatory)

- While fire activity declined sharply in September across the Brazilian rainforest, fire detections continued to rise in the Cerrado in September. And the Pantanal in Brazil received little relief from either the military or the weather. Intense fires—many of them uncontrolled pasture fires and some ignited by lightning—raced through dried grasslands there, as well as through nearby dry forests in Paraguay and Bolivia (most notably the Gran Chaco and Chiquitano forests) from August until November. The fires in this region jump out as an area of particularly anomalous burning in the burned area map at the top of the page. But if you look at the number of fire detections for Brazil, Paraguay, or Bolivia or for certain ecoregions, the numbers do not necessarily stand out because the fire detections get divided between three countries and multiple ecoregions.

- “One of the things I was reminded of during the 2019 Amazon fires—and after many big fire events around the world—is that you have to be really aware of how people are defining boundaries when you are interpreting statistics,” said Giglio. “If you aren’t careful, it is easy for important stories or anomalies to get lost or under- or over-represented.”

- For Setzer, 2019 was a potent reminder of the value of remote sensing. “In Brazil, we had people taking extreme views on both sides of this debate,” he said. “In August, we had people saying nothing of note was happening. You had others saying the entire rainforest had burned down. What actually happened was somewhere in the middle.”

- “We had a lot of scrutiny from politicians, from other scientists, from the media, even from common people who compared the satellite data on the Internet to what they were seeing on the ground. Virtually everybody came to the same conclusion: the satellite data was correct. And based on the satellite monitoring, control measures were taken,” said Setzer.

- For Morton and Andela, the 2019 fires underscored how much technology has improved and how much research is left to do. “There is a lot more we can glean from the data that satellites are already collecting—especially a measure of intensity called fire radiative power—and from nighttime observations of fires from VIIRS,” said Andela, who is currently working on a study about the 2019 fire season and a project with a NASA/USAID SERVIR Amazonia team to track understory fires with VIIRS. “Since VIIRS is extremely sensitive to fires and now there are two copies of VIIRS in orbit, our ability to detect and track small fires—even those burning underneath the canopy—has increased dramatically.”

- “But we also need new platforms for tracking fires because MODIS and VIIRS only take data during just a few short time windows each day,” said Morton, who is in the process of developing plans for a mission that would make measurements several times each day. “That leaves us guessing about what fires are doing the rest of the day.”

• February 28, 2020: The South Sandwich Islands are a string of small volcanic peaks in a remote part of the South Atlantic Ocean near Antarctica and South America. The three tallest islands—Saunders, Montagu, and Bristol—approach at least 1000 meters (3,300 feet) above sea level. 18)

- “Imagine being on a motor boat looking back at triangular, banded patterns forming behind you as wake waves ripple through the water,” said NASA research meteorologist Galina Wind. “This is the same effect, except the mountains are stationary and the surrounding air is rushing by at a good clip. The moving air hits the still mountain in the same way the prow of a moving boat hits still water.”

- As air funneled around the islands in February, its temperature and humidity was just right for the crests of the lee waves to rise and cool the air and form clouds. “At the wave crest, you get clouds. At the wave dip, no clouds,” said Wind. “Who knew mountains in the middle of the ocean and motor boats on a lake had so much in common?”

- Wave clouds would have formed on the leeward side all of the islands in the image, even though the patterns were not easily visible behind all of them. “For the three northern islands, the wakes are there, but there is another cloud layer on top, partially ruining the view,” said Wind. “Clouds have a habit of being multi-layered.”

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Figure 24: As shown by this natural-color satellite image, that was enough height to disrupt air masses flowing around the islands and to create an interlocking series of mountain-wave clouds. The image was acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite around 11 a.m. local time on February 5, 2020, as westerly winds blew over the islands (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Adam Voiland)

• February 25, 2020: In late February 2020, strong Saharan winds picked up dust from Africa and carried it over the Canary Islands, severely reducing visibility and disrupting travel by land and air. Some public officials described it as the worst sandstorm in decades. 19)

- Such dust events, known to islanders as “La Calima,” typically last several days. They are provoked by hot, dry southeasterly or easterly winds blowing out from Morocco and Western Sahara, and they are sometimes associated with the Saharan air layer. Calima storms turn the skies orange or red over the island chain.

- Due to strong winds—with gusts up to 120 kilometers (75 miles) per hour—and poor visibility, all airports across the Canary Islands were closed on February 22 and most stayed closed until February 24. Close to 800 flights were cancelled or re-routed. Some roads were also shut down due to limited visibility.

- Schools and universities were closed on February 24, and people were advised to keep their windows shut and to stay indoors due to poor air quality. Some Carnival events were postponed or curtailed due to the dusty conditions. Strong winds also whipped the flames from several wildfires on Tenerife and Gran Canaria, forcing the evacuation of 2,000 people.

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Figure 25: The MODIS instrument on NASA’s Terra and Aqua satellites acquired these natural-color images of the storm on February 22 and 23, 2020. Gran Canaria, Fuerteventura, and Lanzarote appeared to be hardest hit by the storm, which started abruptly on February 22 and continued as rain clouds started to roll in on the 24th. Visibility was reduced to tens of meters in some places (NASA Earth Observatory, images by Joshua Stevens, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Michael Carlowicz)

• February 5, 2020: Persistent heavy rains across the Mississippi River watershed swelled the river to its banks, occasionally causing water to spill onto floodplains in late January 2020. By early February, the river was near or above flood stage in parts of Arkansas, Tennessee, Mississippi, and Louisiana, though high water has already crested in most places. 20)

- As of February 4, the NOAA Advanced Hydrological Prediction Service reported 3 river gauges with moderate flooding, 12 with minor flooding, and 17 near flood stage along the Lower Mississippi. The river crested in Natchez, Mississippi, on January 30, and approached major flood stage near Baton Rouge, Louisiana, on February 1. On the morning of February 4, the National Weather Service (NWS) was still issuing flood warnings for the river near Baton Rouge, Donaldsonville, and Red River Landing.

- NWS scientists noted that soils were nearly saturated across large sections of the Upper Mississippi watershed, leaving little capacity to soak up new rainfall. Much of the rainfall this winter has ended up flowing down the river. The Lower Mississippi usually sees its highest waters in April.

- In 2019, the Mississippi River was at or above flood stage for most of January through early August. Much of the region is still trying to rebuild and repair infrastructure as the 2020 spring flood season looms.

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Figure 26: The MODIS instrument on NASA’s Terra satellite acquired this false-color image of the Mississippi Delta and the lower reaches of the river on 2 February 2020 (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Mike Carlowicz)

• December 18, 2019: Twenty years of Terra in our lives. Twenty years ago, many of us connected to the internet listening to the tones of the dial-up modem. We stressed about how Y2K was going to impact our increasingly computer-dependent lives on New Year’s Eve, 2000. - But we survived Y2K and now we scroll through the internet silently on our phones. 21)

Figure 27: Terra’s suite of instruments allows us to understand our world well beyond what we knew twenty years ago, when Terra launched. In those twenty years, new applications and contributions to science have been made possible (video credit: NASA)

- There is no question that technology has changed. But, at the same time that our lives on Earth were being shaped by our access to technology, 705 kilometers above us, a satellite was changing how we understood our planet. Designed and built in the 1980s and 90s, NASA and Lockheed Martin engineers set out to build a satellite that could take simultaneous measurements of Earth’s atmosphere, land, and water. Its mission – to understand how Earth is changing and to identify the consequences for life on Earth.

- For 20 years, Terra, the flagship Earth observing satellite, has chronicled those changes. Season after season, Terra data continues to help us understand how the evolving systems of our planet affect our lives – and how we can use that data to benefit society.

• The following images represent five different views from the Terra satellite instruments of the difficult fire season in Australia in southern hemisphere spring. 22)

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Figure 28: This image was acquired on 17 December 2019 with MODIS (Moderate Resolution Imaging Spectroradiometer) on Terra. The false-color image combines visible and infrared light (bands 7-2-1) to distinguish fire burn scars (orange to brown) from healthy vegetation (green) in New South Wales, Australia. Red pixels represent areas where Terra detected heat signatures indicative of active fire (image credit: NASA Earth Observatory, image by Joshua Stevens and Lauren Dauphin using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Michael Carlowicz)

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Figure 29: This image was acquired on 7 December 2919 by ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) on Terra. ASTER shows active fire fronts at night west of Newcastle, Australia. ASTER observes in 14 wavelengths and provides the highest-resolution imagery that Terra can collect. Scientists use ASTER data to create detailed maps of land surface temperature, emissivity, reflectance, and elevation (image credit: NASA Earth Observatory, image by Joshua Stevens and Lauren Dauphin, using data from the ASTER Science Team. Story by Michael Carlowicz)

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Figure 30: The MOPITT (Measurements of Pollution in the Troposphere) instrument measured the levels of carbon monoxide (CO) in the atmosphere (shown above) on December 8, 2019. Normal levels of CO are less than 2 on this scale. Released by the burning of plants and fossil fuels, carbon monoxide is an odorless gas that is dangerous to breathe; it also can lead to the formation of ground-level ozone. Higher in the atmosphere, CO is a signal of the amount of greenhouse gas being pumped into our ever-warming air (image credit: NASA Earth Observatory, image by Joshua Stevens and Lauren Dauphin, using MOPITT data courtesy of Helen Worden/National Center for Atmospheric Research. Story by Michael Carlowicz)

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Figure 31: Armed with nine cameras that look ahead and behind the orbit of the satellite, the Multi-angle Imaging SpectroRadiometer (MISR) is a key instrument for measuring aerosol concentrations and properties in the atmosphere. These data, collected on November 14, 2019, show plumes of aerosol-laden smoke rising from fires in New South Wales. The left image is natural-color, while the right image uses stereoscopic pattern matching to discern the height of clouds and of the smoke plumes in the atmosphere (image credit: NASA Earth Observatory, image by Joshua Stevens and Lauren Dauphin, using MISR data courtesy of David Diner/NASA/JPL/Caltech. Story by Michael Carlowicz.)

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Figure 32: Finally, the CERES (Clouds and the Earth’s Radiant Energy System) sensor observes solar radiation entering Earth’s atmosphere and being absorbed, emitted, and reflected by its surfaces. The map depicts CERES measurements of outgoing longwave radiation for the month of November 2019—a measure of the heat being emitted back into space. The arid lands of Australia normally emit a lot of heat. In this case, the data offer signs of the unusually hot and dry conditions on the continent that have helped fuel the dangerous fire season (image credit: NASA Earth Observatory, image by Joshua Stevens and Lauren Dauphin, using CERES data from NASA Earth Observations (NEO). Story by Michael Carlowicz)

- Two decades after its launch, Terra has flown a distance equal to a trip to the planet Neptune. Along the way, it has collected some of the longest data records of different characteristics of our planet. The satellite is healthy and should continue to serve as a key tool for NASA’s studies of Earth.

• December 10, 2019: Most of the Antarctic continent is buried under the planet’s largest single mass of ice. But there are a few landmarks that stand out from the endless white, including a volcano that continuously emits gases and occasionally erupts. Mount Erebus is Earth’s southernmost active volcano. 23)

- The area was just days away from constant 24-hour sunlight when this image was acquired. The Sun angle was still low enough that morning to illuminate the volcano’s eastern slopes, while the volcano cast a mighty shadow to the west. That’s not hard to do, given that the volcano stands 3,794 meters above sea level—the second-tallest of more than 100 known Antarctic volcanoes.

- Erebus is the dominant feature of Ross Island, which juts out of the Ross Sea and the Ross Ice Shelf. Nearby research facilities—including the U.S. McMurdo Station just 35 km away—means the volcano has been accessible to and well-studied by researchers.

- Although not visible in this image (Figure 33), gases regularly rise from the lava lake on the volcano’s summit. On occasion, a large bubble of gas, or “gas slug,” rises up from within the volcano and triggers a Strombolian eruption. This eruption type can eject masses of molten rock up to 250 meters from the lake.

- Beyond the volcano and its shadow, sunlight illuminates vivid blue patches amid the white. These areas are clear of surface snow, exposing glacial ice. Nearby areas that appear smooth are the snow- and ice-topped waters of McMurdo Sound. The flat expanse is disrupted by the Erebus Ice Tongue—fast-flowing glacial ice that cuts into the sound like a knife.

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Figure 33: Erebus is featured in this image acquired on October 19, 2019, by the ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) instrument on NASA’s Terra satellite. The image is false-color but looks natural, which is a result of visible and near-infrared wavelengths of light (ASTER bands 3, 2, 1). The low Sun angle illuminated the eastern slopes of the Antarctic volcano, casting a long shadow to the west (image credit: NASA Earth Observatory, image by Joshua Stevens, using data from NASA/METI/AIST/Japan Space Systems, and U.S./Japan ASTER Science Team. Story by Kathryn Hansen)

• December 5, 2019: Chances are good that you have heard of the jet stream, a river of fast-moving air in the upper levels of the atmosphere. World War II pilots were among the first to notice jet stream winds, which play a key role in steering air masses and storms around the globe.

- Jet streaks—pockets of extremely fast winds embedded within the jet stream—are mentioned less often. Yet they are important to the formation of winter storms because they are associated with rising air, which can trigger clouds and precipitation.

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Figure 34: Circulation around a jet streak—a fast-moving pocket of air within the jet stream—formed this distinctive arc of clouds. The presence of a jet streak is not often apparent in natural-color satellite imagery, but occasionally there are tell-tale signs. That was the case on November 28, 2019, when the MODIS instrument on NASA’s Terra satellite captured this image of a wide arc of clouds stretching across the northern United States. At the time, a powerful winter storm was building in the East (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Adam Voiland)

- “The arc is a cirrus cloud associated with the jet streak. There was just enough moisture and upward motion to create localized cirrus clouds on the poleward side of the jet stream,” explained Emily Berndt, a Short-term Prediction Research and Transition Center (SPoRT) scientist at NASA’s Marshall Space Flight Center.

- When the image was acquired, air was circulating around the entrance of the jet streak near Nebraska. As air enters a jet streak, it generally speeds up. In this case, warmer air was rising to the south of the cloud band, and cooler air was sinking north of it.

- Rising air tends to produce clouds: air cools as it rises, and cooler air can hold less moisture. This causes water vapor to condense into droplets or ice particles. “After the cirrus clouds formed, strong winds associated with the jet streak whisked them downstream, pulling them north and east,” noted SPoRT scientist Christopher Hain.

- The winter storm associated with this jet streak proved to be a significant one, blowing across the Midwest and New England and dropping more than 1 foot (0.3 meters) of snow in some areas.

• November 30, 2019: At first glance, the Daisenryo Kofun (alternately, the Daisen Kofun) looks like a forest on a hill. But underneath those trees lies a tomb so grand that it rivals the Taj Mahal and Egyptian pyramids. 24)

- Shaped like a keyhole, the burial site is surrounded by three moats and measures more than 300 meters (1,000 feet) wide and 450 meters (1,500 feet) long—twice as long as the base of the Great Pyramid. Supposedly built by about 2,000 men working daily for almost 16 years, the tomb is one of the largest in the world.

- The Daisenryo Kofun is one of about fifty burial sites still intact today in the city of Sakai, near Osaka, Japan. Each kofun (which means “ancient grave”) varies in size and takes different shapes—but most often keyholes, squares, or circles. Kofun were popular in Japan between the third and sixth century, which is referred to as the Kofun Period.

- The Daisenryo Kofun is the largest in Japan, but little is known about what lies inside. One glimpse came in 1872, when a severe storm damaged the site and revealed a treasure-trove of valuables from inside—helmets, glass bowls, and clay figures known as haniwa. Because kofun are considered sacred religious sites, further archaeological research was prohibited. Even today, no one is permitted to go beyond the bridge over the second moat.

- Kofun demonstrate a highly sophisticated funerary system, but also a represent the growth of social and economic hierarchies in a developing Japan. The flat, arable land needed to build a kofun was rare in mountainous Japan, and it was a commodity that only the extremely wealthy could afford. The Daisenryo Kofun is thought to hold Japanese Emperor Nintoku, but other kofun were built by non-royal, wealthy elites in Japan— a reflection of the country’s growing wealth in the era. Historians believe kofun are the first signs of a rigid social and economic structure emerging in Japan. Because of its historical significance, the Mozu-Furuichi Kofun Group is listed as a UNESCO World Heritage site.

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Figure 35: This image shows several kofun collectively known as the Mozu-Furuichi Kofun Group. The image of Sakai was acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite on October 11, 2017. This false-color scene includes green, red, and near-infrared light, a combination that helps differentiate components of the landscape. Water is black, vegetation is green, and urban areas are gray (image credit: NASA Earth Observatory, image by Joshua Stevens, using data from NASA/METI/AIST/Japan Space Systems, and U.S./Japan ASTER Science Team. Story by Kasha Patel)

• November 6, 2019: A new NASA study shows that over the last 20 years, the atmosphere above the Amazon rainforest has been drying out, increasing the demand for water and leaving ecosystems vulnerable to fires and drought. It also shows that this increase in dryness is primarily the result of human activities. 25)

- Scientists at NASA's Jet Propulsion Laboratory in Pasadena, California, analyzed decades of ground and satellite data over the Amazon rainforest to track both how much moisture was in the atmosphere and how much moisture was needed to maintain the rainforest system.

- "We observed that in the last two decades, there has been a significant increase in dryness in the atmosphere as well as in the atmospheric demand for water above the rainforest," said JPL's Armineh Barkhordarian, lead author of the study. "In comparing this trend to data from models that estimate climate variability over thousands of years, we determined that the change in atmospheric aridity is well beyond what would be expected from natural climate variability."

- So if it's not natural, what's causing it? Barkhordarian said that elevated greenhouse gas levels are responsible for approximately half of the increased aridity. The rest is the result of ongoing human activity, most significantly, the burning of forests to clear land for agriculture and grazing. The combination of these activities is causing the Amazon's climate to warm.

- When a forest burns, it releases particles called aerosols into the atmosphere — among them, black carbon, commonly referred to as soot. While bright-colored or translucent aerosols reflect radiation, darker aerosols absorb it. When the black carbon absorbs heat from the sun, it causes the atmosphere to warm; it can also interfere with cloud formation and, consequently, rainfall.

Why It Matters

- The Amazon is the largest rainforest on Earth. When healthy, it absorbs billions of tons of carbon dioxide (CO2) a year through photosynthesis — the process plants use to convert CO2, energy and water into food. By removing CO2 from the atmosphere, the Amazon helps to keep temperatures down and regulate climate.

- But it's a delicate system that's highly sensitive to drying and warming trends.

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Figure 36: The image shows the decline of moisture in the air over the Amazon rainforest, particularly across the south and southeastern Amazon, during the dry season months — August through October — from 1987 to 2016. The measurements are shown in millibars (image credit: NASA/JPL-Caltech, NASA Earth Observatory)

- Trees and plants need water for photosynthesis and to cool themselves down when they get too warm. They pull in water from the soil through their roots and release water vapor through pores on their leaves into the atmosphere, where it cools the air and eventually rises to form clouds. The clouds produce rain that replenishes the water in the soil, allowing the cycle to continue. Rainforests generate as much as 80% of their own rain, especially during the dry season.

- But when this cycle is disrupted by an increase in dry air, for instance, a new cycle is set into motion — one with significant implications, particularly in the southeastern Amazon, where trees can experience more than four to five months of dry season.

- "It's a matter of supply and demand. With the increase in temperature and drying of the air above the trees, the trees need to transpire to cool themselves and to add more water vapor into the atmosphere. But the soil doesn't have extra water for the trees to pull in," said JPL's Sassan Saatchi, co-author of the study. "Our study shows that the demand is increasing, the supply is decreasing and if this continues, the forest may no longer be able to sustain itself."

- Scientists observed that the most significant and systematic drying of the atmosphere is in the southeast region, where the bulk of deforestation and agricultural expansion is happening. But they also found episodic drying in the northwest Amazon, an area that typically has no dry season. Normally always wet, the northwest has suffered severe droughts over the past two decades, a further indication of the entire forest's vulnerability to increasing temperatures and dry air.

- If this trend continues over the long term and the rainforest reaches the point where it can no longer function properly, many of the trees and the species that live within the rainforest ecosystem may not be able to survive. As the trees die, particularly the larger and older ones, they release CO2 into the atmosphere; and the fewer trees there are, the less CO2 the Amazon region would be able to absorb — meaning we'd essentially lose an important element of climate regulation.

- The study, "A Recent Systematic Increase in Vapor Pressure Deficit Over Tropical South America," was published in October in Scientific Reports. The science team used data from NASA's Atmospheric Infrared Sounder (AIRS) instrument aboard the Terra satellite. 26)

• November 4, 2019: Thousands of acres damaged by the ongoing Kincade Fire in Northern California's Sonoma County are visible in this new image from the ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer ) instrument aboard NASA's Terra satellite. The image was taken at 11:01 a.m. PST (2:01 p.m. EST) on Nov. 3, 2019. The burned area appears dark gray in ASTER's visible channels. Hotspots, where the fire is still smoldering, appear as yellow dots in ASTER's heat-sensing, thermal infrared channels. 27)

- After starting on Oct. 23, forcing residents to evacuate, the fire had burned 77,758 acres (31,467 hectar) and destroyed 372 structures by 3 November, according to the California Department of Forestry and Fire Protection. It is now over 80% contained.

- The town of Healdsburg is in the center of the image, which covers an area of about 24 by 25 miles (39 by 40 kilometers).

- ASTER is one of five Earth-observing instruments launched in December 1999 on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region and its high spatial resolution of 15 to 90 meters, ASTER images Earth to map and monitor the planet's changing surface. Japan's Ministry of Economy, Trade and Industry built the instrument. NASA's Jet Propulsion Laboratory in Pasadena, California, is responsible for the American portion of the joint U.S.-Japan science team that validates and calibrates the instrument and the data products associated with it.

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Figure 37: A large burn scar can be seen from space where the Kincade Fire has burned through Sonoma County, California. The image was taken on 3 November 2019, by the ASTER instrument aboard NASA's Terra satellite (image credit: NASA/JPL-Caltech)

• October 17, 2019: In a future with higher temperatures and other climate changes, Alaska’s boreal forests could look significantly different than they do now. According to a new study that is part of NASA’s ABoVE (Arctic Boreal Vulnerability Experiment), the warmer, drier conditions of the future could lead to a net loss of plant life in some regions of Alaska, while also changing the ratio of species that grow in them. These vegetation changes caused by global climate change could, in turn, affect Arctic climate in complex ways. 28)

- Boreal forests of high northern latitudes contain conifers, such as the black and white spruce that dominate Alaskan forests, and deciduous trees, like aspen and birch. In a warmer future, the ratio of conifers to deciduous trees is likely to change, with aspen and birch trees increasing compared to black and white spruce.

- A research team led by Adrianna Foster of Northern Arizona University adapted and ran a computer model capable of making detailed simulations down to the level of individual trees. The scientists depicted the future landscape in a portion of eastern Alaska under two climate change scenarios: one in which greenhouse gas emissions are moderately reduced, and one in which they continue to increase at current rates.

- In both scenarios, the total biomass—the amount of plants and trees—decreased across the study area, though there were some different nuances by area. Cooler, wetter areas saw increases in biomass, as did areas at higher elevations. Areas that are already dry today saw biomass loss in the future, as trees competed for increasingly scarce moisture and nutrients. In some areas, more drought-tolerant species thrived up to a point, then died as soils became too dry.

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Figure 38: The map shows the projected gain or loss of biomass across a study area in central Alaska; it is based on the climate scenario where greenhouse gas emissions continue to increase at present rates. Across the center of the region, drier areas lose trees and plants, while cooler, wetter areas and higher elevations see gains (image credit: NASA Earth Observatory image by Joshua Stevens, using data courtesy of Foster, A. C., et al. (2019), and data from NASA/METI/AIST/Japan Space Systems, and U.S./Japan ASTER Science Team. Story by Jessica Merzdorf, NASA/GSFC)

- “Deciduous trees can tolerate drought a little better than spruce trees can. They also grow faster,” said Foster, the study’s lead author. “So with fires increasing and the climate getting drier, the landscape becomes better suited to the deciduous species that can move in and outcompete the spruce, which is slower-growing and stressed by drought.”

- Boreal forest fires are expected to become more frequent and severe in a warmer, drier climate, and these fires also will play an important role in the proportion of which tree species grow. “Deciduous species can more easily regenerate on exposed soil,” Foster explained. “So when we have these combinations of more drying, more severe fires, and more exposed soil, the deciduous species will be able to colonize very quickly. Under past conditions, they would then be replaced by conifers. But under climate change, the conifers may die off, leaving a deciduous forest.”

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Figure 39: In this plot, overall biomass decreases between 2000 and 2100 under the climate scenario with no greenhouse gas reduction, and the proportions of species also changes. The proportion of birches decreases steadily, while white spruce dominates the landscape until the end of the century (image credit: NASA Earth Observatory image by Joshua Stevens, using data courtesy of Foster, A. C., et al. (2019), and data from NASA/METI/AIST/Japan Space Systems, and U.S./Japan ASTER Science Team. Story by Jessica Merzdorf, NASA/GSFC)

- Changing the number of deciduous forests in Alaska’s boreal region could have complex effects on the climate. Deciduous trees lose their leaves for part of the year, allowing more sunlight to reflect off the land surface during colder, snowier periods. This can help lower air temperatures. Thawing permafrost and increased precipitation in some areas will release more water into the soil, allowing increased growth in some cooler areas, especially of black spruce.

- But that melting permafrost will also release carbon into the atmosphere, acting as a positive feedback that contributes to warming. The loss of trees to fire or stress will mean biomass is lost and more carbon is put back into or left in the atmosphere. “Most of the carbon that is locked up in the boreal zone is in the soils,” she said. “So when we have the shift from boggy, black spruce forest to drier, deciduous forest, we are releasing a lot of carbon into the atmosphere from the soils.”

- As the species and climate change, these processes could feed back into the climate in complex ways. “It’s not a linear relationship,” Foster noted. “We have all these interacting factors, and some are counteracting each other. It’s really an uncertain future.”

October 8, 2019: The team behind one of NASA’s most productive Earth-observing satellite missions and a leading scientist who has studied the impact of humans on global land cover changes have been honored with the 2019 William T. Pecora Award for achievement in Earth remote sensing. 29)

- The awards were presented 7 October at the 21st William T. Pecora Memorial Remote Sensing Symposium and the 38th International Symposium on Remote Sensing of Environment in Baltimore, Md.

- The annual award is sponsored by NASA and the Department of the Interior's U.S. Geological Survey (USGS). First presented in 1974, the Pecora Award recognizes outstanding contributions of individuals and groups toward the understanding of the Earth through remote sensing. The award honors the memory of William T. Pecora, former USGS Director and Interior Under-Secretary.

- NASA’s Terra team was recognized with the 2019 group award for significant contributions in all areas of Earth science, with scientific impacts and a legacy that make it one of the most successful missions in NASA’s long line of Earth Observing System satellites. The Terra satellite was launched in 1999 and continues to provide a wide range of global environmental observations.

- The team developed innovative techniques to characterize the environmental status and health of our planet. The Terra satellite and its products have appeared regularly in news coverage of tropical storms, natural disasters, snowstorms, and air quality reports.

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Figure 40: Attending the Oct. 7 awards ceremony were (left to right) Terra team members Michael Abrams, NASA Jet Propulsion Laboratory; James Drummond, Dalhousie University; Robert Wolfe, NASA Goddard Space Flight Center; (far right) Vince Salomonson, University of Utah (retired); and Marie-Josee Bourassa representing the Canadian Space Agency, one of NASA’s partners on the mission (image credit: NASA)

- Terra data have been used by multiple federal agencies for volcanic ash monitoring, weather forecasting, forest fire monitoring, carbon management, and global crop assessment. The Terra team has shown ingenuity and perseverance in developing new calibration methods to increase data quality, ultimately leading to a cohesive long-term record of many environmental quantities with unprecedented accuracy.

- Terra has provided a suite of observations that have greatly improved scientists’ understanding of the Earth-atmosphere system. The mission is arguably one of the most successful Earth-sensing satellites ever deployed. More than 19,000 publications using Terra data products have been produced, and the rate of publication has been increasing steadily over the years, demonstrating increased usage of Terra data products by the scientific community.

- The 2019 individual award was presented to Thomas R. Loveland for his outstanding contributions to the field of Earth science as a leading USGS scientist and chief scientist at the USGS Earth Resources Observation and Science Center. Loveland has devoted his career to understanding how the Earth’s surface is changing through mapping and monitoring land cover and land use, which has resulted in groundbreaking global land cover research.

- Loveland’s work has paid particular attention to the impact of human activities on land cover. He has been involved in capacity building nationally and internationally, for example, through the Famine Early Warning Systems Network in Africa, which saves human lives by directing response to areas impacted by famine and informing preparation for future famine.

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Figure 41: Thomas Loveland, senior scientist at the U.S. Geological Survey in Sioux Falls, South Dakota, received the 2019 individual Pecora Award for his contributions to the field of Earth science (image credit: U.S. Geological Survey)

- Loveland has led the development of innovative monitoring programs, produced exciting new land cover and land use change products. He has steered efforts to improve the Landsat satellite missions, ensuring that the data are freely available to the entire community. He led the IGBP (International Geosphere-Biosphere Program) global land cover effort, which brought to fruition the first truly global effort to map land cover with remote sensing.

- Loveland has been a leader in the development of multiple operational programs for land cover mapping and monitoring in the United States. From 2006 to 2016, he served as co-lead for the NASA/USGS Landsat Science Team, where his innovative and visionary ideas advanced land-imaging science and future Landsat mission planning.

- For six decades, NASA has used the vantage point of space to understand and explore our home planet, improve lives and safeguard our future. NASA’s observations of Earth’s complex natural environment are critical to understanding how our planet’s natural resources and climate are changing now and could change in the future.

• September 25, 2019: A few tropical cyclones spin into the northwestern reaches of the Arabian Sea each, and some bring damaging winds and rain into the Arabian Peninsula. That was the case on September 24, 2019, when Tropical Cyclone Hikaa made landfall over Oman. 30)

- After encountering the coast of Oman and the dry air over the peninsula, the storm continued moving westward and weakened. Forecasters predicted heavy rainfall in some coastal areas, and officials advised people to stay away from low-lying areas. They also warned that rough seas could be dangerous for fishing boats.

- Of all tropical cyclones that occur around the planet each year, only 7 percent are in the North Indian Ocean. They infrequently brush the Arabian Peninsula, and the region can go years without a storm. That said, 2018 brought more storms than usual, with three significant cyclones—Sagar, Mekunu, and Luban—bringing damaging wind and rain to Yemen and Oman. Cyclones tend to occur here in spring and autumn, so the final count for 2019 remains to be seen.

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Figure 42: MODIS on NASA’s Terra satellite acquired this image at 10:45 a.m. Gulf Standard Time (06:45 Universal Time) on 24 September 2019 as the storm’s outer bands moved over Oman. Later that day, the India Meteorological Department reported maximum winds between 120-130 km/hr. That’s the equivalent of a category 1 storm on the Saffir-Simpson wind scale (image credit: NASA Earth Observatory image by Joshua Stevens, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kathryn Hansen)

• September 18, 2019: The past few fire seasons in Indonesia have been pretty quiet, but a profusion of fire in Kalimantan, the Indonesian part of Borneo, and Sumatra in September 2019 has once again blanketed the region in a pall of thick, noxious smoke. Many schools have closed and several airports have canceled, diverted, or delayed flights in recent weeks as smoke lingered over the two islands, according to news reports. 31)

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Figure 43: MODIS on NASA's Terra satellite captured this image of Borneo on September 15, 2019. Smoke hovered over the islands and has triggered air quality alerts and health warnings in Indonesia and neighboring countries. Many of the fires were burning in Kalimantan, which is known for having extensive peat deposits, which are made up of a mixture of partly decayed plant materials formed in wetlands. Satellites have detected evidence of fires burning in this region throughout much of August, but the number and intensity of the fires increased in the first week of September (image credit: NASA Earth Observatory image by Joshua Stevens, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Adam Voiland)

- Fires are a common occurrence in Kalimantan in September and October because farmers burn off agricultural and logging debris to clear the way for crops and livestock. In Kalimantan, the intent is often to prepare the land for new plantings of oil palm and acacia pulp.

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Figure 44: The Operational Land Imager (OLI) on Landsat-8 acquired this image, which shows fires burning in several oil palm areas in southern Borneo. Shortwave-infrared observations have been overlain on a natural-color image to highlight the locations of active fires (image credit: NASA Earth Observatory, image by Joshua Stevens, using Landsat data from the U.S. Geological Survey. Story by Adam Voiland)

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Figure 45: The map shows organic carbon data from the GEOS forward processing (GEOS-FP) model, which assimilates information from satellite, aircraft, and ground-based observing systems. To simulate organic carbon, modelers make use of satellite observations of aerosols and fires. GEOS-FP also ingests meteorological data like air temperature, moisture, and winds to project the plume’s behavior. In this case, smoke has stayed relatively close to the source of the fires because winds have generally been gentle (image credit: NASA Earth Observatory, map by Joshua Stevens, using GEOS-5 data from the Global Modeling and Assimilation Office at NASA/GSFC. Story by Adam Voiland)

- GEOS FP, like other weather and climate models, uses mathematical equations that represent physical processes to calculate what is happening in the atmosphere. The model calculates the position and concentration of organic carbon plumes every five minutes. The model ingests new aerosol data at three hour intervals, new meteorological data at six hour intervals, and new fire data on a daily basis.

- Peat maps available through the Center for International Forestry Research’s Borneo Atlas indicate that many of the fires were burning in or near areas with underlain with peat—a mixture of partly decayed plant material formed in wetlands. Peat fires tend to be difficult to extinguish, often smoldering under the surface for months until wet season rains arrive.

- Peat fires release large amounts of gases and particles, including carbon dioxide, methane, and fine particulate matter (PM2.5). Carbon dioxide and methane are potent greenhouse gases that warm the climate. PM2.5 is a mix of fine particulates known for having negative health effects.

- PM2.5—including types of aerosols called organic carbon and black carbon—are thought to be especially harmful because the particles are small enough to enter the lungs and bloodstream. Health research links exposure to black carbon to respiratory diseases, heart problems, and premature deaths. Evidence increasingly points to the toxicity of organic aerosols as well, though the health effects are less studied than some other particle types.

- As he has done in past fire seasons, NASA Goddard Institute for Space Studies scientist Robert Field has been tracking the progression of the fire season in Indonesia. “They are really in the thick of another major event now. It is reminiscent of 2015, though buildup of smoke started a few weeks later this year because of rains in mid-August,” said Field, who is working on a project to better understand how various meteorological variables affect the likelihood that of vegetation burning. As part of that effort, he is also working on a NASA applied sciences project to integrate more satellite-based precipitation measurements into a fire danger monitoring system used by the Indonesian Meteorological, Climatological and Geophysical Agency.

- “The fire counts from MODIS and VIIRS satellites have not been quite as high as they were in 2015 because of the late start, but the day-to-day increases in activity are now comparable to 2015,” said Field. “However, it is worth keeping in mind that many of these fires are burning underground or in areas with such thick smoke that satellites can’t detect them.”

- During two past big fires years in Indonesia—1997 and 2015—El Nino conditions caused droughts that were major factors in exacerbating the fires. In 2019, El Nino conditions were neutral, but an oscillation of sea surface temperatures called the Indian Ocean Dipole appears to be responsible for the dry conditions this year, explained Field.

• September 9, 2019: The Serengeti is the site of the largest unaltered animal migration in the world. Around 1.5 million wildebeest—translating to “wild cattle” in Afrikaans—travel around the Serengeti plains for about seven months every year in search of pasture and water. The migration is considered one of the natural wonders of the world, attracting hundreds of thousands of tourists each year. 32)

- The journey of the wildebeest begins at the southern tip of the Serengeti plains in a region of Tanzania called Ndutu. The area is known for its short grass, which is rich in nutrients. From December to March, the majority of wildebeest congregate in Ndutu for food. Each February, wildebeest mothers give birth to thousands of calves here within a four- to six-week period—around 8,000 calves per day.

- Ndutu lies in the northern section of the Ngorongoro Conservation Area. The Ngorongoro landscape originated some 20 million years ago when the eastern side of Africa started to crack and rift. The rifting allowed for Earth's crust to thin and for molten materials to pile up and form volcanoes. Today, the Ngorongoro area includes a volcanic caldera. The ash left behind by the ancient volcanoes makes the soil here fertile for crops (outside of the conservation area) and for the savanna grasslands that feed so many animals.

- The Serengeti ecosystem—determined by the area covered by the migration—extends from the Maswa Game Reserve (Tanzania) to the south, to the Grumeti and Ikorongo Game Reserves (Tanzania) in the east, to Maasai Mara National Reserve in the north in Kenya, and to Loliondo Game Controlled Area (Tanzania) in the west. The Serengeti National Park is located in the center and covers around 15,000 km2 (5,800 square miles).

- When the drought arrives around April and May, the wildebeest leave Ndutu to begin a clockwise migration around the plains following the rains and the lush grasses they help sprout. The patterns have been repeating for at least a million years, according to the fossil record.

- Around May, the wildebeest first head for the long grass plains and woodland of the Serengeti’s western corridor, near Lake Victoria. By June or July, they arrive in the northern Serengeti plains, where they encounter arguably the hardest parts of their journey: the crocodile-infested Grumeti and Mara Rivers. The Grumeti lies adjacent to the Serengeti National Park, whereas the Mara is the only river that flows perennially through the park. The Mara River is also the major obstacle separating the wildebeest from the short, sweet grasses in Maasai Mara in Kenya. Many tourists visit from July to October for the chance to see thousands of wildebeest cross the river.

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Figure 46: This image shows a clear view of the Serengeti plains on February 4, 2018, as observed by the MODIS instrument on the NASA’s Terra satellite (image credit: NASA Earth Observatory image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview, story by Kasha Patel)

- By November of each year, the rainy season begins again in the southern Serengeti and the wildebeest return to Ndutu. In total, the wildebeest—along with hundreds of thousands of zebras, gazelles, and predators who join the journey—travel about 1,000 km.

- Since the migration is triggered by the dry season and rains, the exact timing and locations of the migration can vary from year to year. In 2019, the wildebeest were spotted crossing the Mara River earlier than usual as the dry season arrived early. Research suggests that variations in seasonal flooding and drought (due to climate change) may further alter when and where the wildebeest migrate.

• August 27, 2019: Every summer, vast expanses of the Canadian prairie in Saskatchewan, Alberta, and Manitoba turn a bright shade of yellow. The reason: canola fields reaching peak bloom. 33)

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Figure 47: The MODIS instrument on on NASA’s Terra satellite captured this image of yellow-tinged fields stretching across the three provinces on July 22, 2019 (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Adam Voiland)

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Figure 48: A day later, OLI (Operational Land Imager) on Landsat-8 acquired a more-detailed view of canola in bloom near Regina, Saskatchewan (image credit: NASA Earth Observatory, image by Lauren Dauphin, using Landsat data from the U.S. Geological Survey, Story by Adam Voiland)

- Canola, a cultivar of rapeseed, is a member of the Brassica family, which includes cabbages and mustards. After flowering, canola plants produce brown oil-rich seeds that are about the size of poppies. When ground up, these seeds yield an oil that is widely used for cooking and high-protein meal used in animal feed.

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Figure 49: OLI detail image of canola in bloom near Regina, Saskatchewan (image credit: NASA Earth Observatory, image by Lauren Dauphin, using Landsat data from the U.S. Geological Survey, Story by Adam Voiland)

- According to the Canada Canola Association, Canadian farmers began to grow rapeseed during World War II to produce an inedible oil that was used as a lubricant in steam engines. In the decades following the war, Canadian plant breeders developed new varieties of rapeseed that had much lower levels of glucosinolates and erucic acids—undesirable substances that made rapeseed products taste bad or were thought to cause health problems. In 1978, the Western Canadian Oilseed Crushers trademarked these “double low” rapeseeds as canola (shorthand for Canadian oil, low acid).

- In recent decades, canola has become a cash crop for Canada, with much of the harvest getting exported. Since the mid-1980s, the footprint has spread significantly, with the total canola-growing area increasing by more than threefold, with particularly fast growth in Saskatchewan. The biggest importer of canola oil and meal is the United States, accounting for about 52 percent of oil exports and 69 percent of meal exports in 2018, according to the Canadian Canola Association.

• July 10, 2019: Scientists using NASA satellite observations have discovered the largest bloom of macroalgae in the world. In a paper published on July 5, 2019, in Science, researchers described new observations of the “Great Atlantic Sargassum Belt.” 34) 35)

- Led by researchers from the University of South Florida (USF) College of Marine Science, the team confirmed that the belt of brown macroalgae called Sargassum can grow so large that it blankets the surface of the tropical Atlantic Ocean from the west coast of Africa to the Gulf of Mexico. This happened in 2018 when more than 20 million tons of Sargassum—heavier than 200 fully loaded aircraft carriers—floated in surface waters and wreaked havoc on shorelines in the tropical Atlantic, the Caribbean Sea, and the Gulf of Mexico.

- The scientists used environmental data and some direct ocean sampling to suggest that the belt forms seasonally in response to two key nutrient inputs. In the spring and summer, Amazon River discharge adds nutrients to the ocean, and those nutrients may have increased in recent years due to increased deforestation and fertilizer use. In the winter, upwelling off the West African coast delivers nutrients from deep waters to the ocean surface where the Sargassum grows. Based on numerical simulations, the scientists found that the bloom takes its shape in response to prevailing ocean currents.

- “The evidence for nutrient enrichment is preliminary and based on limited field data and other environmental data, and we need more research to confirm this hypothesis,” said USF scientist Chuanmin Hu, who led the study and has studied Sargassum using satellites since 2006. “On the other hand, based on the last 20 years of data, I can say that the belt is very likely to be a new normal.”

- Hu spearheaded the work with first author Mengqiu Wang, a postdoctoral scholar in his Optical Oceanography Lab at USF. The team included others from USF, Florida Atlantic University, and Georgia Institute of Technology. Key data for the study came from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA’s Terra and Aqua satellites.

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Figure 50: This map depicts the monthly mean density of Sargassum in the Atlantic Ocean in each July from 2011 to 2018 (image credit: NASA Earth Observatory images by Joshua Stevens, using MODIS data courtesy of Wang, M., et al. (2019). Story by Kristen Kusek, University of South Florida; edited by Michael Carlowicz. This research was funded by NASA’s Earth Science Division, the NOAA RESTORE Science Program, the JPSS/NOAA Cal/Val project, the National Science Foundation, and a William and Elsie Knight Endowed Fellowship)

- In patchy doses in the open ocean, Sargassum contributes to ocean health by providing habitat for turtles, crabs, fish, and birds and by producing oxygen via photosynthesis. But too much of this seaweed makes it hard for certain marine species to move and breathe, especially when the mats crowd the coast. When Sargassum dies and sinks to the ocean bottom in large quantities, it can smother corals and seagrasses. On the beach, rotten Sargassum releases hydrogen sulfide gas and smells like rotten eggs.

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Figure 51: This photo shows abundant Sargassum off of the Florida Keys in 2014 (image credit: NASA Earth Observatory)

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Figure 52: The photo shows Sargassum along a beach in Cancun, Mexico in 2015 (image credit: NASA Earth Observatory)

- Before 2011, most of the pelagic Sargassum in the ocean was primarily found floating in patches around the Gulf of Mexico and Sargasso Sea. The Sargasso Sea is located on the western edge of the central Atlantic Ocean and named after its popular algal resident. Christopher Columbus first reported Sargassum in the 15th century, and many boaters are familiar with this seaweed.

- In 2011, Sargassum populations started to explode in places they hadn’t been before, and it arrived in vast amounts that suffocated shorelines and introduced a nuisance for local environments and economies. Some countries, such as Barbados, declared a national emergency in 2018 because of the toll this once-healthy seaweed took on tourism.

- “The ocean’s chemistry must have changed in order for the blooms to get so out of hand,” Hu said. Sargassum reproduces vegetatively, and it probably has several initiation zones around the Atlantic Ocean. It grows faster when nutrient conditions are favorable and when its internal clock ticks in favor of reproduction.

- Wang, Hu, and colleagues analyzed fertilizer consumption patterns in Brazil, Amazon deforestation rates, Amazon River discharge, and nitrogen and phosphorus measurements taken from parts of the Atlantic Ocean, among other ocean properties. While the data are preliminary, the pattern seems clear: the explosion in Sargassum correlates to increases in deforestation and fertilizer use, both of which have increased since 2010.

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Figure 53: This plot shows the monthly mean area covered by the seaweed, as observed by MODIS from 2000 to 2018 (image credit: NASA Earth Observatory)

- The team identified key factors critical to bloom formation: a large seed population in the winter left over from a previous bloom; nutrient input from West Africa upwelling in winter; and nutrient input in the spring or summer from the Amazon River. In addition, Sargassum only grows well when salinity is normal and surface temperatures are normal or cooler. As noted in the images above, major blooms occurred in every year between 2011 and 2018 except 2013. No bloom occurred that year because the seed populations measured during winter of 2012 were unusually low, Wang said.

- “This is all ultimately related to climate change because it affects precipitation and ocean circulation and even human activities, but what we’ve shown is that these blooms do not occur because of increased water temperature,” Hu said. “They are probably here to stay.”

- “The scale of these blooms is truly enormous, making global satellite imagery a good tool for detecting and tracking their dynamics through time,” said Woody Turner, manager of NASA’s Ecological Forecasting Program.

• June 25, 2019: Unlike some of its perpetually active neighbors on the Kamchatka Peninsula, Raikoke Volcano on the Kuril Islands rarely erupts. The small, oval-shaped island most recently exploded in 1924 and in 1778. 36)

- The dormant period ended around 4:00 a.m. local time on June 22, 2019, when a vast plume of ash and volcanic gases shot up from its 700-meter-wide crater. Several satellites—as well as astronauts on the International Space Station—observed as a thick plume rose and then streamed east as it was pulled into the circulation of a storm in the North Pacific.

- On the morning of June 22, astronauts shot a photograph (Figure 54) of the volcanic plume rising in a narrow column and then spreading out in a part of the plume known as the umbrella region. That is the area where the density of the plume and the surrounding air equalize and the plume stops rising. The ring of clouds at the base of the column appears to be water vapor.

- “What a spectacular image. It reminds me of the classic Sarychev Peak astronaut photograph of an eruption in the Kuriles from about ten years ago,” said Simon Carn, a volcanologist at Michigan Tech. “The ring of white puffy clouds at the base of the column might be a sign of ambient air being drawn into the column and the condensation of water vapor. Or it could be a rising plume from interaction between magma and seawater because Raikoke is a small island and flows likely entered the water.”

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Figure 54: Astronaut photograph ISS059-E-119250 was acquired on June 22, 2019, with a Nikon D5 digital camera and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by a member of the Expedition 59 crew (image credit: NASA Earth Observatory, story by Adam Voiland)

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Figure 55: The MODIS instrument on NASA’s Terra satellite acquired this image on the morning of 22 June. At the time, the most concentrated ash was on the western edge of the plume, above Raikoke. By the next day, just a faint remnant of the ash remained visible to MODIS [image credit: NASA Earth Observatory, image by Joshua Stevens using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview, Story by Adam Voiland, with information from Erik Klemetti (Denison University), Simon Carn (Michigan Tech), and Andrew Prata (Barcelona Supercomputing Center)]

- The image of Figure 56 of VIIRS on Suomi NPP shows the plume a few hours later. After an initial surge of activity that included several distinct explosive pulses, activity subsided and strong winds spread the ash across the Pacific.

- Since ash contains sharp fragments of rock and volcanic glass, it poses a serious hazard to aircraft. The Tokyo and Anchorage Volcanic Ash Advisory Centers have been tracking the plume closely and have issued several notes to aviators indicating that ash had reached an altitude of 13 kilometers. Meanwhile, data from the CALIPSO satellite indicate that parts of the plume may have reached 17 kilometers.

- In addition to tracking ash, satellite sensors can also track the movements of volcanic gases. In this case, Raikoke produced a concentrated plume of sulfur dioxide (SO2) that separated from the ash and swirled throughout the North Pacific as the plume interacted with the storm.

- “Radiosonde data from the region indicate a tropopause altitude of about 11 km, so altitudes of 13 to 17 km suggest that the eruption cloud is mostly in the stratosphere,” said Carn. “The persistence of large SO2 amounts over the last two days also indicates stratospheric injection.”

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Figure 56: This image is an oblique composite view based on data from VIIRS (Visible Infrared Imaging Radiometer Suite) on Suomi NPP (image credit: NASA Earth Observatory, image by Joshua Stevens, using VIIRS data of the Suomi National Polar-orbiting Partnership)

• June 11, 2019: Los Glaciares National Park in Patagonia gets its name from the plentiful glaciers flowing from the flanks of the Andes Mountains. Where some of the park’s most notable glaciers end, a series of colorful glacial lakes begin. 37)

- Most of these glaciers end in water, where their fronts can lose ice by melting and through calving icebergs. Numerous studies have focused on the glaciers on the west side of the southern icefield that dispense ice and meltwater to the Pacific Ocean. But the icefield is losing plenty of ice on its eastern side too, through glaciers that end in freshwater lakes.

- Lago Argentino and Lago Viedma are the two main freshwater lakes connected to Los Glaciares National Park (Figure 57). These lakes, as well as nearby Lago San Martin, are filled with so much fine sediment from the glaciers—also known as glacial flour—that they appear milky turquoise when viewed from space.

- Notice that Lago Viedma is much grayer than Lago Argentino and Lago San Martin. That’s because Lago Viedma receives sediment-rich-water directly from Viedma glacier—the second-largest in Patagonia. The meltwater pouring out near Upsala glacier is equally gray, but the color changes as the water flows through the fjord. Most of the sediment particles settle to the bottom before reaching the main body of Lago Argentina, which appears bluer.

- In recent years, scientists have identified ways in which these freshwater-calving glaciers differ from those that end in seawater. Teasing out those differences is important for understanding the various mechanisms responsible for melting and calving.

- Shin Sugiyama, a researcher at Hokkaido University, showed that the high sediment concentration in the freshwater lakes can affect the water’s thermal structure near the ice front. The sediment causes cold, turbid meltwater from the bottom of a submerged glacier to stay at depth. In contrast, cold meltwater from the bottom of a glacier submerged in seawater tends to rise and be replaced with warm water. That means that melting at a glacier’s front in a freshwater lake is probably limited compared to that of its western, seawater-terminating counterpart—at least at depth.

- Sugiyama pointed out that even among the freshwater lakes there could be differences in the ice-water interaction. “As suggested by the water colors, conditions are very different at each lake,” Sugiyama said. “I am curious how those glaciers ending in different lakes behave differently in the future.”

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Figure 57: MODIS on NASA's Terra satellite acquired this natural-color image of the South Patagonian Icefield on February 4, 2019. Spanning about 13,000 km2 of Chile and Argentina, the icefield is the southern hemisphere’s largest expanse of ice outside of Antarctica. Together with the northern icefield, ice in this region is being lost at some of the highest rates on the planet. Much of the loss happens through more than 60 major outlet glaciers—channels of ice that descend from the icefield (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kathryn Hansen)

• June 6, 2019: As summer approaches and hours of sunlight increase in the northern hemisphere, the oceans come alive with blooms of phytoplankton. In early June 2019, a stunning bloom colored the waters off the coast of Norway. 38)

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Figure 58: Phytoplankton in the Norwegian Sea are visible in this image, acquired on June 5, 2019, with the MODIS instrument on NASA’s Terra satellite. The bloom, shown here off Nordland and Trøndelag counties, likely includes plenty of Emiliania huxleyi—a species of coccolithophore with white scale-like shells made of calcium carbonate. The mixture of calcium carbonate and ocean water appears milky blue-green. Some of the color may come from sediment or from other species of phytoplankton (image credit: NASA Earth Observatory image by Joshua Stevens, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview, Story by Kathryn Hansen)

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Figure 59: This image, photographed by Stig Bjarte Haugen of the Norwegian Institute of Marine Research, shows what E. huxleyi looks like though a microscope. (Note that the green hue was added for aesthetic reasons.) Each microalga is just a fraction of the diameter of a human hair. But when rapid cell division leads to an explosive bloom, you get a high enough concentration that they become visible from space (image credit: NASA Earth Observatory, photo by Stig Bjarte Haugen/Norwegian Institute of Marine Research)

- Previous natural-color satellite images show signs of the milky blue-green color in this area starting in mid-May. Follow the coastline south, and you can see more colorful phytoplankton visible between areas of cloud cover. Even the waters of some fjords, including Sognefjord (Norway’s largest and deepest)—are abloom with E. huxleyi.

- E. huxleyi is harmless to fish and people. The same is not true, however, for the species Chrysochromulina leadbeateri. Although not visible in this image, high concentrations of Chrysochromulina were responsible for suffocating millions of farmed salmon in northern Norway. According to news reports, this type of phytoplankton is commonly found in the waters around Norway, but warm weather contributed to their rapid spread in May.

• June 4, 2019: Situated along the Nile River, the modern city of Luxor stands as a relic of one of the most venerated metropolises of ancient Egypt. Then known as Thebes, the city was the capital of ancient Egypt at two separate times and home to prominent temples, chapels, and towers. Although those structures have weathered over the centuries, the ruins still make Luxor one of the world’s greatest open air museums. 39)

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Figure 60: This image of Luxor and its surroundings was acquired on 15 November 2018, by the ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) instrument on NASA’s Terra satellite. This false-color scene is shown in green, red, and near-infrared light, a combination that helps differentiate components of the landscape. Water is black, vegetation is red, and urban areas are brown to gray (image credit: NASA Earth Observatory, image by Lauren Dauphin, using data from NASA/METI/AIST/Japan Space Systems, and U.S./Japan ASTER Science Team. Story by Kasha Patel)

- The legendary temples of Luxor attract tourists from around the world. The Luxor Temple (now with a fast-food restaurant next door—not a relic of ancient Egypt) lies at the modern city’s center. The temple served as “the place of the First Occasion” where the god Amun-Ra (to whom the city of Thebes was dedicated) experienced rebirth during the pharaoh’s annual coronation ceremony. Over time, the sandstone temple has eroded from contact with salty groundwater, so it is currently undergoing treatment.

- Another notable landmark is the Karnak Temple Complex, a collection of temples that were developed over more than 1,000 years. At its peak, Karnak was one of the largest religious complexes in the world, covering 80 hectares (200 acres). It is home to one of the most significant and largest religious building ever built—the Temple of Amun-Ra, where the god was believed to have lived on Earth with his wife and son (who also have temples in the complex). A row of human-headed sphinxes—known as the Avenue of Sphinxes—once lined the three-kilometer path from Karnak to the Luxor Temple.

- The Egyptians also created massive underground mausoleums to bury and honor their pharaohs in the area. On the west bank of the Nile River, near the hills, Egyptians built an inconspicuous vault called the “Valley of Kings,” where more than 60 tombs have been found. One of the most famous housed the boy King Tutankhamun (commonly known as King Tut). That tomb was found almost entirely preserved—the most intact tomb ever found.

• May 22, 2019: When satellites observe large dust plumes over Japan, the dust typically comes from vast deserts in Central Asia and arrives on westerly winds. However, on May 20, 2019, the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite acquired an image of a different type of dust event—a plume streaming from farmland near Shira and Kiyosato in northern Hokkaido. 40)

- The seasonal rhythms of farming likely contributed as well. Landsat satellite imagery suggests that many fields in the area had little green vegetation or may have been tilled recently, both of which would make it easier for gusty winds to pick up dust.

- Scientists who routinely monitor global dust storm activity say it is unusual for Japan to produce such a large dust plume. Though on average there are 20 teragrams (20 x 1012 grams, or 20 million tons) of dust in the air at any one time, most of it comes from large deserts in North Africa, the Middle East, and Central Asia. Only about 5 percent of global emissions come from middle and high-latitude areas.

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Figure 61: Unusually dry weather in April and May 2019 likely dried out the land surface and made it easier for strong southerly winds to lift so much dust. In the nearby town of Betsukai, the Japan Meteorological Agency recorded wind gusts as fast as 60 km/hr on May 20, noted Teppei Yasunari, an atmospheric scientist with Hokkaido University’s Arctic Research Center. Dust storms typically can occur if winds exceed 40 km/hr (image credit: NASA Earth Observatory, image by Adam Voiland, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Caption by Adam Voiland)

• May 6, 2019: As soon as the snow melts in springtime, widespread fires typically emerge in far northeastern Russia. On 3 May 2019, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired this false-color image of a large burn scar along the Amur River in Russia’s Khabarovsk region. The image was composed using visible and infrared light (bands 7-2-1), which makes it easier to distinguish burned areas. 41)

- The Amur River Valley is a mosaic of farmland, forests, shrubs, and grasslands. It is known for being a productive agricultural region, and most of these fires were probably triggered by farmers burning off old plant debris to prepare their fields for a new crop. Some of the fires may have begun on farmland, but then escaped control and grew larger as they moved into nearby wildlands.

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Figure 62: The large burn scar near the center of the image emerged west of the town of Naykhin on April 28, 2019, and then spread rapidly north through swampy grasslands near Lake Bolon. Separate fires that burned within the past few weeks left the scars to the north, west, and south (image credit: NASA Earth Observatory image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview and using Landsat data from the U.S. Geological Survey. Story by Adam Voiland)

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Figure 63: The fire near Naykhin on 30 April 2019 caught the attention of atmospheric scientists for producing what was likely the first pyrocumulus of the year in the Northern Hemisphere. Pyrocumulus clouds—sometimes called “fire clouds”—are tall, cauliflower-shaped, and appear as opaque white patches bubbling up from darker smoke in satellite images. Fires that produce pyrocumulus clouds tend to spread smoke much higher and farther than those that do not (image credit: NASA Earth Observatory image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview and using Landsat data from the U.S. Geological Survey. Story by Adam Voiland)

- In order for scientists to classify a cloud as pyrocumulus, cloud top temperatures observed by satellites must be -40°C (-40°F) or cooler. According to University of Wisconsin meteorologist Scott Bachmeier, this cloud passed that threshold at 03:10 Universal Time, a few hours after the Operational Land Imager (OLI) on Landsat 8 acquired the natural-color shown image above. At that time, low-lying gray smoke streamed from an actively burning fire front as the beginning stages of the pyrocumulus cloud billowed up over the fire.

• May 02, 2019: With some areas that receive just a few millimeters of rain per year and some that see none at all, the Atacama Desert in northern Chile is one of the driest places in the world. When it does rain, the landscape can transform. 42)

- The desert extends along the western edge of the Andes Mountains, which produce an intense rain shadow effect. The desert also sits next to a cool ocean current that chills the air and limits how much moisture it can hold. And often a zone of persistent high pressure blocks storms from moving into the area.

- Still, water occasionally finds its way to the Atacama, as it did in January and February 2019. Storms, which are usually restricted to the highest parts of the Andes, dropped enough rain in the foothills to cause damaging floods in Arica, Tarapacá, and Antofagasta. The western slopes of the Andes were hit particularly hard, with several ground-based weather stations recording between 100 – 200 millimeters (4 – 8 inches) of rain. Between February 4 – 6, 2019, satellites measured more than 50 millimeters falling in wide bands near Calama and Camiña. According to news reports, several people died, hundreds of homes were destroyed, and thousands of people lost power due to the floods.

- However, the rush of water left its mark on this hyper-arid region in a positive way, too. By March 2019, land surfaces that are typically brown and barren were blanketed with wildflowers and other vegetation. While the wildflowers are not easily visible in natural-color imagery from satellites, several sensors make observations of infrared light that make the greenup more apparent.

- The map depicts the Normalized Difference Vegetation Index (NDVI), a measure of the health and greenness of vegetation based on how much red and near-infrared light it reflects. Healthy vegetation with lots of chlorophyll reflects more near-infrared light and less visible light.

- Wildflower blooms happen occasionally in the southern part of the Atacama Desert in winter. The last big event was in 2017. “This year is different and less studied because it is occurring in austral fall and farther north,” said René Garreaud, an Earth scientist at the Universidad de Chile. “It should be interesting to investigate the cause of last summer’s storms and see if the rain increases groundwater levels in the Pampa del Tamarugal.

- A recent analysis of satellite NDVI observations collected between 1981 and 2015 identified 13 Atacama greening events, with most beginning in the winter and remaining until the following summer.

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Figure 64: The NDVI anomaly map is based on data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite between April 14 – 28, 2019. The map contrasts vegetation health against the long-term average (2000 – 2012) for that period. Greens indicate vegetation that is more widespread or abundant than normal for the time of year. The most greening occurred at elevations between 2500 – 3000 meters in a band that extended for hundreds of kilometers [image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Adam Voiland, with information from René Garreaud (Universidad de Chile)]

• April 22, 2019: Once the second-largest saltwater lake in the Middle East, Lake Urmia attracted birds and bathers to bask in its turquoise waters in northwest Iran. Then beginning in the 1970s, nearly three decades of drought and high water demands on the lake shriveled the basin, shrinking it by 80 percent. 43)

- Recent torrential rains have replenished the water levels of this aquatic gem once known as “the turquoise solitaire of Azerbaijan.” At its greatest extent, Lake Urmia once covered a surface area of 5,000 km2 (2,000 square miles).

- The fresh pulse of water came from intense rains during the fall of 2018 and spring 2019. In late March and early April 2019, 26 of Iran’s 31 provinces were affected by deadly flooding from the rain and the seasonal melting of snow cover in the mountains.

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Figure 65: These images, acquired by Terra MODIS, show Lake Urmia (also Orumiyeh or Orumieh) on 5 February, 2019, and 12 April 12 2019, before and after the recent floods in the region. The rains were reported to be the heaviest Iran has seen in 50 years. After the spring rains, the depth of the lake increased by 62 cm (24 inches) compared to the spring of 2018 (image credit: NASA Earth Observatory, images by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kasha Patel)

• April 9, 2019: Most people will never see Pine Island Glacier in person. Located near the base of the Antarctic Peninsula—the “thumb” of the continent—the glacier lies more than 2,600 km (1,600 miles) from the tip of South America. That’s shorter than a cross-country flight from New York to Los Angeles, but there are no runways on the glacier and no infrastructure. Only a handful of scientists have ever set foot on its ice. 44)

- While this outlet glacier is just one of many around the perimeter of Antarctica, data collected from the ground, air, and space confirm that Pine Island is worth extra attention. It is, along with neighboring Thwaites Glacier, one of the main pathways for ice entering the Amundsen Sea from the West Antarctic Ice Sheet and one the fastest-retreating glaciers in Antarctica. Collectively, the region contains enough vulnerable ice to raise global sea level by 1.2 meters (4 feet).

Figure 66: The animation shows a wide view of Pine Island Glacier (PIG) and the long-term retreat of its ice front. Images were acquired by the MODIS instrument on NASA’s Terra satellite from 2000 to 2019. Notice that there are times when the front appears to stay in the same place or even advance, though the overall trend is toward retreat (image credit: NASA Earth Observatory animation by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview)

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Figure 67: NASA Earth Observatory map by Lauren Dauphin, using Reference Elevation Model of Antarctica (REMA) data from the Polar Geospatial Center at the University of Minnesota.

- “The process of how a large outlet glacier like Pine Island ‘shrinks’ has some interesting twists,” said Bob Bindschadler, an emeritus NASA glaciologist who landed on Pine Island Glacier’s ice shelf in 2008.

- Decades of investigations have given scientists a better idea of the quirks of PIG’s behavior. For example, data collected during science flights in 2009 led researchers to discover a deep-water channel (Figure 68) that could funnel warm water to the glacier’s underbelly and melt it from below.

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Figure 68: NASA Earth Observatory map by Jesse Allen, based on a model by Michael Studinger of NASA IceBridge and gravity data from Columbia University

- Bindschadler explained that a shrinking outlet glacier is usually doing three things: thinning (mostly at the seaward edge), retreating, and accelerating. The acceleration stretches the glacier, causing the thinning and likely making the ice more prone to crevassing (cracking) “upstream.”

- Fractures near the seaward edge cause the ice to calve off as icebergs, a normal part of life for glaciers that extend over water. If icebergs calve off at a rate that matches the glacier’s acceleration, the ice front stays in the same place.

- But over the long term at Pine Island, you can see that the ice front has retreated inland, which means the calving rate has increased more than the glacier has accelerated. “This underlies our concern that retreating outlet glaciers can ‘shrink’ rapidly,” Bindschadler said.

• March 22, 2019: On Dec. 18, 2018, a large "fireball" - the term used for exceptionally bright meteors that are visible over a wide area - exploded about 16 miles (26 km) above the Bering Sea. The explosion unleashed an estimated 173 kilotons of energy, or more than 10 times the energy of the atomic bomb blast over Hiroshima during World War II. 45)

- Two NASA instruments aboard the Terra satellite captured images of the remnants of the large meteor. The image sequence shows views from five of nine cameras on the Multi-angle Imaging SpectroRadiometer (MISR) instrument taken at 23:55 UTC (Coordinated Universal Time), a few minutes after the event. The shadow of the meteor's trail through Earth's atmosphere, cast on the cloud tops and elongated by the low sun angle, is to the northwest. The orange-tinted cloud that the fireball left behind by super-heating the air it passed through can be seen below and to the right the center of Figure 69.

Figure 69: This image sequence shows views from five of nine cameras on the MISR instrument, taken at 23:55 UTC (image credit: NASA/GSFC/LaRC/JPL-Caltech, MISR Team)

- The fireball observed on 18 December 2018 was the most powerful meteor to be observed since 2013; however, given its altitude and the remote area over which it occurred, the object posed no threat to anyone on the ground. Fireball events are actually fairly common and are recorded in the NASA Center for Near Earth Object Studies database.

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Figure 70: The MODIS instrument captured this true-color image showing the remnants of a meteor's passage, seen as a dark shadow cast on thick, white clouds on Dec. 18, 2018. MODIS captured the image at 23:50 UTC (image credit: NASA/GSFC)

• March 12, 2019: Tropical Cyclone Idai is poised to move inland over East African countries that were already soaked by flooding rain from the same storm system earlier this month. 46)

- The storm system first developed as a tropical disturbance on March 3 and grew by March 5 into a tropical depression with winds measuring 30 knots. In the process, it dropped heavy rain on Mozambique and Malawi and spawned deadly floods. By March 11, the storm had tracked eastward into the warm channel between the coast of Africa and Madagascar, where it strengthened into an intense tropical cyclone.

- Now on a southwestward track, forecasts call for Idai to reach Mozambique by March 14-15, bringing a second round of wind and heavy rain to the region.

- “Several cyclones in the past have started over Mozambique and then moved over water and intensified into more organized systems, although this type of situation is not common,” said Corene Matayas, a researcher at University of Florida who has studied cyclones in this area. It is relatively common, however, to see cyclone tracks in the Mozambique Channel that meander and loop, due to weak steering currents.

- Cyclones that form in the channel tend to be weaker than those that form over the Southwest Indian Ocean, north and east of Madagascar. But Matayas points out that regardless of where a cyclone forms, some have reached their highest intensity within a day before landfall. Tropical Cyclone Eline in February 2000, for example, passed over Madagascar and the Mozambique Channel, and then quickly intensified just before landfall in Mozambique.

- “Keys to intensification are warm ocean waters to sufficient depth, the absence of strong winds in the upper troposphere, and being contained inside of a moist air mass,” Matayas said. “These conditions are all present right now.”

- Most tropical cyclone activity in the Southwest Indian basin occurs between October and May, with activity peaking in mid-January and again in mid-February to early March. Idai is the seventh intense tropical cyclone of the basin’s 2018-2019 season.

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Figure 71: MODIS on on NASA’s Terra satellite acquired this image of the cyclone on March 12, 2019, as it spun across the Mozambique Channel. Around this time, the potent storm carried maximum sustained winds of about 90 knots (105 miles/165 kilometers per hour)—equivalent to a category 2 storm on the Saffir-Simpson wind scale (image credit: NASA Earth Observatory, image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Kathryn Hansen)

• March 4, 2019: Unseasonably warm temperatures swept across the United Kingdom and much of Europe in February 2019. The month started with snow and freezing temperatures in the United Kingdom, but provisional statistics from the UK Met Office indicate February 2019 was the second warmest February on record for the country. England, Scotland, and Wales all recorded their warmest meteorological winter days and hottest February days since record-keeping began in 1910. 47)

- Kew Gardens in London recorded 21.2° Celsius (70.1° Fahrenheit) on February 26, a new record for the warmest winter day in the United Kingdom. Scotland experienced its warmest winter day with 18.3°C (64.9°F) at Aboyne, Aberdeenshire, on February 21. Wales also broke its existing record, reaching 20.8°C (69.4°C) in Porthmadog, Gywnedd, on February 26.

- The high temperatures were the product of a large area of high pressure that stalled and trapped warm air over Europe. The clear, dry conditions allowed more sunshine to warm the ground. (February 2019 was the second sunniest on record for the United Kingdom as a whole.) The high-pressure system also drew in warm air from the North Atlantic near the Canary Islands.

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Figure 72: The maps of Figures 72 and 73 show land surface temperature anomalies for February 11-25, 2019. Reds and oranges depict areas that were hotter than average for the same two-week period from 2000-2012; blues were colder than average. White pixels were normal, and gray pixels did not have enough data, most likely due to excessive cloud cover. This temperature anomaly map is based on data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite (image credit: NASA Earth Observatory, image by Joshua Stevens, using data from the Level 1 and Atmospheres Active Distribution System (LAADS) and Land Atmosphere Near real-time Capability for EOS (LANCE), story by Kasha Patel)

Legend to Figure 72: The map depicts land surface temperatures (LSTs), not air temperatures. LSTs reflect how hot the surface of the Earth would feel to the touch and can sometimes be significantly hotter or cooler than air temperatures.

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Figure 73: While the UK was experiencing record-breaking warmth, increased temperatures spread across central and eastern Europe—so much that spring barley harvesting may start early. Forecasters say the weather over central Europe will be warmer and drier-than-normal through May (image credit: NASA Earth Observatory, image by Joshua Stevens, using data from the Level 1 and Atmospheres Active Distribution System (LAADS) and Land Atmosphere Near real-time Capability for EOS (LANCE), story by Kasha Patel)

• February 28, 2019: The 2015-2016 El Niño event brought weather conditions that triggered regional disease outbreaks throughout the world, according to a new NASA study that is the first to comprehensively assess the public health impacts of the major climate event on a global scale. 48)

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Figure 74: Increased sea surface temperatures in the equatorial Pacific Ocean characterizes an El Niño, which is followed by weather changes throughout the world (image credit: NASA Goddard’s Scientific Visualization Studio)

- El Niño is an irregularly recurring climate pattern characterized by warmer than usual ocean temperatures in the equatorial Pacific, which creates a ripple effect of anticipated weather changes in far-spread regions of Earth. During the 2015-2016 event, changes in precipitation, land surface temperatures and vegetation created and facilitated conditions for transmission of diseases, resulting in an uptick in reported cases for plague and hantavirus in Colorado and New Mexico, cholera in Tanzania, and dengue fever in Brazil and Southeast Asia, among others.

- “The strength of this El Niño was among the top three of the last 50 years, and so the impact on weather and therefore diseases in these regions was especially pronounced,” said lead author Assaf Anyamba, a research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “By analyzing satellite data and modeling to track those climate anomalies, along with public health records, we were able to quantify that relationship.”

- The study utilized a number of climate datasets, among them land surface temperature and vegetation data from the Moderate Resolution Imaging Spectroradiometer aboard NASA’s Terra satellite, and NASA and National Oceanic and Atmospheric Administration precipitation datasets. The study was published on 13 February 2019 in the journal Nature Scientific Reports. 49)

- Based on monthly outbreak data from 2002 to 2016 in Colorado and New Mexico, reported cases of plague were at their highest in 2015, while the number of hantavirus cases reached their peak in 2016. The cause of the uptick in both potentially fatal diseases was an El Niño-driven increase in rainfall and milder temperatures over the American Southwest, which spurred vegetative growth, providing more food for rodents that carry hantavirus. A resulting rodent population explosion put them in more frequent contact with humans, who contract the potentially fatal disease mostly through fecal or urine contamination. As their rodent hosts proliferated, so did plague-carrying fleas.

- A continent away, in East Africa’s Tanzania, the number of reported cases for cholera in 2015 and 2016 were the second and third highest, respectively, over an 18-year period from 2000 to 2017. Cholera is a potentially deadly bacterial infection of the small intestine that spreads through fecal contamination of food and water. Increased rainfall in East Africa during the El Niño allowed for sewage to contaminate local water sources, such as untreated drinking water. “Cholera doesn’t flush out of the system quickly,” Anyamba said, “so even though it was amplified in 2015-2016, it actually continued into 2017 and 2018. We’re talking about a long-tailed, lasting peak.”

- In Brazil and Southeast Asia, during the El Niño dengue fever proliferated. In Brazil the number of reported cases for the potentially deadly mosquito-borne disease in 2015 was the highest from 2000 to 2017. In Southeast Asia, namely Indonesia and Thailand, the number of reported cases, while relatively low for an El Niño year, was still higher than in neutral years. In both regions, the El Niño produced higher than normal land surface temperatures and therefore drier habitats, which drew mosquitoes into populated, urban areas containing the open water needed for laying eggs. As the air warmed, mosquitoes also grew hungrier and reached sexual maturity more quickly, resulting in an increase in mosquito bites.

Figure 75: How the 2015-2016 El Niño triggered outbreaks across the globe (video credit: NASA Goddard's Scientific Visualization Studio)

- The strong relationship between El Niño events and disease outbreaks underscores the importance of existing seasonal forecasts, said Anyamba, who has been involved with such work for the past 20 years through funding from the U.S. Department of Defense. Countries where these outbreaks occur, along with the United Nations’ World Health Organization and Food and Agriculture Organization, can utilize these early warning forecasts to take preventive measures to minimize the spread of disease. Based on the forecast, the U.S. Department of Defense does pre-deployment planning, and the U.S. Department of Agriculture (USDA) takes measures to ensure the safety of imported goods.

- “Knowledge of the linkages between El Niño events and these important human and animal diseases generated by this study is critical to disease control and prevention, which will also mitigate globalization,” said co-author Kenneth Linthicum, USDA center director at an entomology laboratory in Gainesville, Florida. He noted these data were used in 2016 to avert a Rift Valley fever outbreak in East Africa. “By vaccinating livestock, they likely prevented thousands of human cases and animal deaths.”

- “This is a remarkable tool to help people prepare for impending disease events and take steps to prevent them,” said co-author William Karesh, executive vice president for New York City-based public health and environmental nonprofit EcoHealth Alliance. “Vaccinations for humans and livestock, pest control programs, removing excess stagnant water — those are some actions that countries can take to minimize the impacts. But for many countries, in particular the agriculture sectors in Africa and Asia, these climate-weather forecasts are a new tool for them, so it may take time and dedicated resources for these kinds of practices to become more utilized.”

- According to Anyamba, the major benefit of these seasonal forecasts is time. “A lot of diseases, particularly mosquito-borne epidemics, have a lag time of two to three months following these weather changes,” he said. “So seasonal forecasting is actually very good, and the fact that they are updated every month means we can track conditions in different locations and prepare accordingly. It has the power to save lives.”

• February 18, 2019: In Spanish, Sierra Nevada means “snowy mountain range.” During the past few months, the range has certainly lived up to its name. After a dry spell in December, a succession of storms in January and February 2019 blanketed the range. 50)

- In many areas, snow reports have been coming in feet not inches. Back-to-back storms in February dropped eleven feet (3 meters) of snow on Mammoth Mountain—enough to make it the snowiest ski resort in the United States. More than 37 feet (11 meters) have fallen at the resort since the beginning of winter, and meteorologists are forecasting that yet another storm will bring snow this week.

- Statistics complied by the California Department of Water Resources indicate that the mountain range had a snow water equivalent that was 130 percent of normal as of February 11, 2019. It was just 44 percent of normal on Thanksgiving 2018. Last season, on February 15, 2018, snow cover was at a mere 21 percent of normal.

- Some of the snow has come courtesy of atmospheric rivers, a type of storm system known for transporting narrow, low-level plumes of moisture across long ocean distances and dumping tremendous amounts of precipitation on land.

- The condition of Sierra Nevada snowpack has consequences that go well beyond ski season. Spring and summer melt from the Sierra Nevada plays a crucial role in recharging California’s reservoirs. Though conditions could change, California drought watchers are cautiously optimistic that the boost to the snowpack will insulate the state from drought this summer.

- The reservoirs are already in pretty good shape. Cal Water data show that most of the reservoirs are already more than half-full, and several have water levels that are above the historical average for the middle of February.

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Figure 76: A succession of storms in January and February dumped huge amounts of snow on the Sierra Nevada. The MODIS instrument on NASA's Terra satellite acquired these natural-color images of the Sierra Nevada on February 11, 2019, and February 15, 2018. In addition to the much more extensive snow cover in 2019, notice the greener landscape on the western slopes of the range (image credit: NASA Earth Observatory, images by Joshua Stevens, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Adam Voiland)

• February 12, 2019: The world is literally a greener place than it was twenty years ago, and data from NASA satellites has revealed a counterintuitive source for much of this new foliage. A new study shows that China and India—the world’s most populous countries—are leading the increase in greening on land. The effect comes mostly from ambitious tree-planting programs in China and intensive agriculture in both countries. 51)

- Ranga Myneni of Boston University and colleagues first detected the greening phenomenon in satellite data from the mid-1990s, but they did not know whether human activity was a chief cause. They then set out to track the total amount of Earth’s land area covered by vegetation and how it changed over time.

- The research team found that global green leaf area has increased by 5 percent since the early 2000s, an area equivalent to all of the Amazon rainforests. At least 25 percent of that gain came in China. Overall, one-third of Earth’s vegetated lands are greening, while 5 percent are growing browner. The study was published on February 11, 2019, in the journal Nature Sustainability. 52)

- “China and India account for one-third of the greening, but contain only 9 percent of the planet’s land area covered in vegetation,” said lead author Chi Chen of Boston University. “That is a surprising finding, considering the general notion of land degradation in populous countries from overexploitation.”

- This study was made possible thanks to a two-decade-long data record from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA’s Terra and Aqua satellites. An advantage of MODIS is the intensive coverage they provide in space and time: the sensors have captured up to four shots of nearly every place on Earth, every day, for the past 20 years.

- “This long-term data lets us dig deeper,” said Rama Nemani, a research scientist at NASA’s Ames Research Center and a co-author of the study. “When the greening of the Earth was first observed, we thought it was due to a warmer, wetter climate and fertilization from the added carbon dioxide in the atmosphere. Now with the MODIS data, we see that humans are also contributing.”

- China’s outsized contribution to the global greening trend comes in large part from its programs to conserve and expand forests (about 42 percent of the greening contribution). These programs were developed in an effort to reduce the effects of soil erosion, air pollution, and climate change.

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Figure 77: Over the last two decades, the Earth has seen an increase in foliage around the planet, measured in average leaf area per year on plants and trees. Data from NASA satellites shows that China and India are leading the increase in greening on land. The effect stems mainly from ambitious tree planting programs in China and intensive agriculture in both countries (image credit: NASA Earth Observatory, image by Joshua Stevens, using data courtesy of Chen et al., (2019). Story by Abby Tabor, NASA Ames Research Center, with Mike Carlowicz, Earth Observatory)

- Another 32 percent of the greening change in China, and 82 percent in India, comes from intensive cultivation of food crops. The land area used to grow crops in China and India has not changed much since the early 2000s. Yet both countries have greatly increased both their annual total green leaf area and their food production in order to feed their large populations. The agricultural greening was achieved through multiple cropping practices, whereby a field is replanted to produce another harvest several times a year. Production of grains, vegetables, fruits and more have increased by 35 to 40 percent since 2000.

- How the greening trend may change in the future depends on numerous factors. For example, increased food production in India is facilitated by groundwater irrigation. If the groundwater is depleted, this trend may change. The researchers also pointed out that the gain in greenness around the world does not necessarily offset the loss of natural vegetation in tropical regions such as Brazil and Indonesia. There are consequences for sustainability and biodiversity in those ecosystems beyond the simple greenness of the landscape.

- Nemani sees a positive message in the new findings. “Once people realize there is a problem, they tend to fix it,” he said. “In the 1970s and 80s in India and China, the situation around vegetation loss was not good. In the 1990s, people realized it, and today things have improved. Humans are incredibly resilient. That’s what we see in the satellite data.”

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Figure 78: This map shows the increase or decrease in green vegetation—measured in average leaf area per year—in different regions of the world between 2000 and 2017. Note that the maps of Figures 77 and 78 are not measuring the overall greenness, which explains why the Amazon and eastern North America do not stand out, among other forested areas (image credit: NASA Earth Observatory, image by Joshua Stevens, using data courtesy of Chen et al., (2019). Story by Abby Tabor, NASA Ames Research Center, with Mike Carlowicz, Earth Observatory)

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Figure 79: Ambitious tree-planting programs and intensified agriculture have led to more land area covered in vegetation ((image credit: NASA Earth Observatory, image by Joshua Stevens, using data courtesy of Chen et al., (2019). Story by Abby Tabor, NASA Ames Research Center, with Mike Carlowicz, Earth Observatory)

• February 6, 2019: For the ranchers and soybean farmers of northwestern Argentina, January 2019 was a remarkably wet month. 53)

- After several weeks of storms that dropped about five times more rain than usual, floods have inundated millions of hectares of farmland, forced thousands of people to evacuate, and even turned some unsuspecting cattle into swimmers. Some areas received a year’s worth of rain in the first two weeks of January, according to the Buenos Aires Times.

- The flooding has caused more than $2 billion in agricultural damage, according to one estimate. That makes it Argentina’s second-most-expensive flood on record.

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Figure 80: This MODIS image shows the flooding along the Paraná River on 4 February 2019, composed in false color, using a combination of infrared and visible light (MODIS bands 7-2-1). Flood water appears black; vegetation is bright green (image credit: NASA Earth Observatory image by Lauren Dauphin, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Adam Voiland)

• February 1, 2019: While much of North America is enduring exceptionally cold winter temperatures, Australia is coping with all-time record summer heat. 54)

- An unusual, prolonged period of heatwaves has been sweeping over Australia for most of the summer, including the country's hottest December on record. The intense heat has caused numerous deaths, power outages, and severe fires. The heatwaves started in late November when Queensland saw record-breaking temperatures on the north tropical and central coasts.

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Figure 81: This map shows land surface temperature anomalies from January 14-28, 2019. Red colors depict areas that were hotter than average for the same two-week period from 2000-2012; blues were colder than average. White pixels were normal, and gray pixels did not have enough data, most likely due to excessive cloud cover. This temperature anomaly map is based on data from MODIS on NASA’s Terra satellite (image credit: NASA Earth Observatory, image by Lauren Dauphin, using data from the Level 1 and Atmospheres Active Distribution System (LAADS) and Land Atmosphere Near real-time Capability for EOS (LANCE). Story by Kasha Patel)

- Note that the map depicts LSTs (Land Surface Temperatures), not air temperatures. LSTs reflect how hot the surface of the Earth would feel to the touch and can sometimes be significantly hotter or cooler than air temperatures. (To learn more about land surface temperatures and air temperatures, read: Where is the Hottest Place on Earth?).

- The summer of 2018-19 has brought seven of the ten hottest days on record for Australia. The most potent heatwave so far occurred from January 11-18, when nationally averaged mean temperatures exceeded 40°C (104°F) for five days in a row. Nationally, January 15th ranked as the second-warmest day ever in Australia, falling 0.02°C short of the all-time record from January 2013. Adelaide recorded the hottest temperature for any Australian state capital in 80 years, reaching 46.4°C (116°F) on January 25.

- A few factors have contributed to the severe summer, starting with a dearth of strong weather fronts that would typically cool the country. In summer, sunlight heats the Australian landmass more quickly than the surrounding ocean. This difference in heating usually draws in moist air over northern Australia, which gradually brings about westerly winds that bring in cooler and rainy conditions with the monsoon.

- But this summer the rains didn't develop. Weather patterns in northern Australia were largely static, providing no significant weather systems to clear out the persistent hot air mass. The city of Darwin usually experiences the beginning of the monsoon in late December, but as of January 22, rainy patterns still had not set in. Western Australia also experienced sparse thunderstorms and no monsoonal activity in December. Northwesterly winds and various weather systems dragged hot air east and south across the Northern Territory, South Australia, western Queensland, New South Wales, and Victoria.

- The increased temperatures are a continuation of a longer warming trend for Australia. Twenty of the warmest years on record have occurred in the past 22 years; the last four have been the hottest on record. Throughout 2018, maximum temperatures for each month were above the country’s average.

• January 30, 2019: Desperately cold weather is now gripping the Midwest and Northern Plains of the United States, as well as interior Canada. The culprit is a familiar one: the polar vortex. 55)

- A large area of low pressure and extremely cold air usually swirls over the Arctic, with strong counter-clockwise winds that trap the cold around the Pole. But disturbances in the jet stream and the intrusion of warmer mid-latitude air masses can disturb this polar vortex and make it unstable, sending Arctic air south into middle latitudes.

- That has been the case in late January 2019. Forecasters are predicting that air temperatures in parts of the continental United States will drop to their lowest levels since at least 1994, with the potential to break all-time record lows for January 30 and 31. With clear skies, steady winds, and snow cover on the ground, at least 90 million Americans could experience temperatures at or below zero degrees Fahrenheit (-18° Celsius), according to the U.S. National Weather Service (NWS).

- Figure 82 is not a traditional forecast, but a reanalysis of model input fixed in time—a representation of atmospheric conditions near dawn on January 29, 2019. Measurements of temperature, moisture, wind speeds and directions, and other conditions are compiled from NASA satellites and other sources, and then added to the model to closely simulate observed reality. Note how some portions of the Arctic are close to the freezing point—significantly warmer than usual for the dark of mid-winter—while masses of cooler air plunge toward the interior of North America.

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Figure 82: This map shows air temperatures at 2 meters above ground at 09:00 Universal Time (4 a.m. Eastern Standard Time) on January 29, 2019, as represented by the Goddard Earth Observing System Model, Version 5. GEOS-5 is a global atmospheric model that uses mathematical equations run through a supercomputer to represent physical processes (image credit: NASA Earth Observatory, image by Joshua Stevens, using GEOS-5 data from the Global Modeling and Assimilation Office at NASA GSFC, Story by Michael Carlowicz)

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Figure 83: You can almost feel that cold in this natural-color image, acquired on January 27, 2019, by MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Terra satellite. Cloud streets and lake-effect snow stretch across the scene, as frigid Arctic winds blew over the Great Lakes (image credit: NASA Earth Observatory, image by Joshua Stevens, using MODIS data from NASA EOSDIS/LANCE and GIBS/Worldview. Story by Michael Carlowicz)

- NWS meteorologists predicted that steady northwest winds (10 to 20 miles per hour) were likely to add to the misery, causing dangerous wind chills below -40°F (-40°C) in portions of 12 states. A wind chill of -20°F can cause frostbite in as little as 30 minutes, according to the weather service.

- Meteorologists at The Washington Post pointed out that temperatures on 31 January 2019, in the Midwestern U.S. will be likely colder than those on the North Slope of Alaska.

Figure 84: Animated AIRS image of the polar vortex moving from Central Canada into the U.S. Midwest from January 20 through January 29. The illustration shows temperatures at an altitude of about 300-500 m above the ground. The lowest temperatures are shown in purple and blue and range from -40 degrees Fahrenheit (also -40 degrees Celsius) to -10ºF (-23ºC). As the data series progresses, you can see how the coldest purple areas of the air mass scoop down into the U.S. (image credit: NASA/JPL-Caltech AIRS Project) 56)


Minimize Terra continued


Sensor complement: (ASTER, CERES (2 units), MISR, MODIS, MOPITT)

Measurement Region

Measurement

Instruments used

Atmosphere

Cloud properties
Radiative energy flux
Tropospheric chemistry
Aerosol properties
Atmospheric temperature
Atmospheric humidity

MODIS, MISR, ASTER
CERES, MODIS, MISR
MOPITT
MISR, MODIS
MODIS
MODIS

Land surface

Land cover and land use change
Vegetation dynamics
Surface temperature
Fire occurrence
Volcanic effects

MODIS, MISR, ASTER
MODIS, MISR, ASTER
MODIS, ASTER
MODIS, ASTER
MODIS, MISR, ASTER

Ocean

Surface temperature
Phytoplankton and dissolved organic matter

MODIS
MODIS, MISR

Cryosphere

Land ice change
Sea ice
Snow cover

ASTER
MODIS, ASTER
MODIS, ASTER

Table 2: Overview of major physical process measurements of the Terra instruments


ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer):

ASTER is a Japanese instrument sponsored by METI (Ministry of Economy, Trade and Industry) and a cooperative project with NASA. The ASTER team leaders are Hiroji Tsu of ERSDAC (Japan) and Anne B. Kahle of JPL. ASTER management is provided by JAROS (Japan Resources Observation System Organization). ASTER was built by NEC, MELCO, Fujitsu, and Hitachi. A Joint US/Japan Science Team is responsible for instrument design, calibration, and validation. Previous instrument name: ITIR (Intermediate Thermal Infrared Radiometer).

Objective: Provision of high-resolution and multispectral imagery of the Earth's surface and clouds for a better understanding of the physical processes that affect climate change. Applications: studies of the surface energy balance (surface brightness temperature), plant evaporation, vegetation and soil characteristics, hydrologic cycle, volcanic processes, etc. 57) 58) 59) 60) 61) 62)

The ASTER instrument consists of three separate instrument subsystems; each subsystem operates in a different spectral region, has its own telescope(s), and is built by a different Japanese company. The subsystems are in the VNIR (Visible Near Infrared), SWIR (Shortwave Infrared) and TIR (Thermal Infrared) spectral regions. The VNIR and SWIR subsystems employ pushbroom imaging while the TIR subsystem performes whiskbroom imaging. ASTER is pointable in the cross-track direction such that any point on the globe may be observed at least once within 16 days in all 14 bands and once every 5 days in the VNIR bands. The absolute temperature accuracy is 3K in the 200-240 K range, 2K in the 240-270 K range, and 2 k in the 340-370 K range for TIR bands.

Total instrument mass=421 kg; power=463 W average, 646 W peak; data rate = 8.3 Mbit/s average and 89.2 Mbit/s peak; thermal control by 80 K Stirling cycle coolers, heaters, cold plate/capillary pumped loop, and radiators; pointing accuracy: for control = 1 km on ground (all axes), knowledge= 342 m on ground (per axis), stability=2 pixels for 60 seconds. shown in this figure.

Parameter

Band No

VNIR

Band No

SWIR

Band No

TIR

Spectral bands in µm

1

0.52 - 0.60

4

1.600 - 1.700

10

8.125 - 8.475

2

0.63 - 0.69

5

2.145 - 2.185

11

8.475 - 8.825

3N

0.76 - 0.86

6

2.185 - 2.225

12

8.925 - 9.275

3B

0.76 - 0.86

7

2.235 - 2.285

13

10.25 - 10.95

Stereoscopic viewing
capability along-track

8

2.295 - 2.365

14

10.95 - 11.65

9

2.360 - 2.430

 

 

Ground resolution

15 m

30 m

90 m

IFOV (nadir)

21.5 µrad

42.6 µrad

128 µrad

Data rate

62 Mbit/s

23 Mbit/s

4.2 Mbit/s

Cross-track pointing

±24º (±318 km)

±8.55º (116 km)

±8.55º (116 km)

Swath width

60 km

60 km

60 km

Detector type

Si (CCD of 5000 elements,
4000 are used)

PtSi-Si Schottky barrier linear array, cooled to 80 K (Stirling cooler)

HgCdTe
cooled to 80 K
(Stirling cooler)

Data quantization

8 bit

8 bit

12 bit

Radiometric accuracy

4%

4%

 

Table 3: ASTER instrument parameters of the three subsystems

The cooling capacity of the SWIR cryocooler is a nominal value of 1.2 W at 70 K; the measured power consumption is 43.5 W, which satisfies the requirement that it be less than 55 W. The cooling capacity of the TIR cryocooler is a nominal value of 1.2 W at 70 K; the measured power consumption is 50 W, which satisfies the requirement that it be less than 55 W. 63)

The VNIR subsystem, built by NEC Corporation, is a reflecting-refracting improved Schmidt design. VNIR features two telescopes, one nadir-looking with a three-spectral-band detector, and the other backward-looking with a single-band detector. The backward-looking telescope provides a second view of the target area in band 3B for stereo observations. Cross-track pointing is accomplished by rotating the entire telescope assembly. Band separation is through a combination of dichroic elements and interference filters that allow all three bands to view the same ground area simultaneously. Calibration of the nadir-pointing detectors is performed with two halogen lamps.

 

ASTER

TM on Landsat 4/5

Wavelength Region

Band No.

Spectral Range (µm)

Band No.

Spectral Range (µm)

VNIR

 

 

1

0.45 - 0.52

1
2
3

0.52 - 0.60
0.63 - 0.69
0.76 - 0.86

2
3
4

0.52 - 0.60
0.63 - 0.69
0.76 - 0.90

SWIR

4

5
6
7
8
9

1.60 - 1.70

2.145 - 2.185
2.185 - 2.225
2.235 - 2.285
2.295 - 2.365
2.360 - 2.430

5

1.55 - 1.75

7

2.08 - 2.35

TIR

10
11
12
13
14

8.125 - 8.475
8.475 - 8.825
8.925 - 9.275
10.25 - 10.95
10.95 - 11.65

6

10.4 - 12.5

Table 4: Spectral range comparison of ASTER and TM (on Landsat)

The SWIR subsystem, built by MELCO (Mitsubishi Electric Company), uses a nadir-pointing aspheric refracting telescope. Cross-track pointing is accomplished by a pointing mirror. The size of the detector/filter combination requires a wide spacing of the detectors, causing in turn a parallax error of about 0.5 pixels per 900 m of elevation. This error is correctable if elevation data (DEM) are available. Two halogen lamps are used for calibration. The maximum data rate is 23 Mbit/s. 64)

The TIR subsystem employs a Newtonian catadioptric system with aspheric primary mirror and lenses for aberration correction. The telescope of the TIR subsystem is fixed to the platform, pointing and scanning is done with a single mirror. The line of sight can be pointed anywhere in the range ± 8.54º in the cross-track direction of nadir, allowing coverage of any point on Earth over the platform's 16 day repeat cycle. Each channel uses 10 mercury cadmium telluride (HgCdTe) detectors in a staggered array with optical bandpass filters over each detector element to define the spectral response. Each detector has its own pre- and post-amplifier for a total of 50. The detectors are being operated at 80 K using a mechanical split-cycle Stirling cooler. - In scanning mode, the mirror oscillates at about 7 Hz with data collection occurring over half the cycle. The scanning mirror is capable of rotating 180º from the nadir position to view an internal full-aperture reference surface, which can be heated to 340 K. 65)

Overview of some ASTER instrument characteristics:

• The Visible Near InfraRed (VNIR) telescope subsystem features a backward viewing band (next to a nadir viewing band) for high-resolution along-track stereoscopic observation (two-line VNIR imager)

• Provision of multispectral thermal infrared data of high spatial resolution (8 to 12 µm window region, globally)

• ASTER provides the highest spatial resolution surface spectral reflectance, temperature, and emissivity data within the Terra instrument suite

• The instrument provides the capability to schedule on-demand data acquisition requests

• The VNIR and SWIR subsystems employ pushbroom imaging while the TIR subsystem performes whiskbroom imaging

• ASTER provides band-to-band registration of the 14 spectral bands, not only within each subsystem, but also among the three subsystems. Accuracies of 0.2 pixels within each subsystem and 0.3 pixels among different subsystems are achieved.

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Figure 85: Illustration of the VNIR and SWIR subsystems of ASTER (image credit: JPL)

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Figure 86: Illustration of the TIR subsystem of ASTER (image credit: JPL)


CERES (Clouds and the Earth's Radiant Energy System):

The CERES instrument of NASA/LaRC was built by Northrop Grumman (formerly TRW Space and Technology Group) of Redondo Beach, CA (PI: Bruce Wielicki). Objective: Long-term measurement of the Earth's radiation budget and atmospheric radiation from the top of the atmosphere to the surface; provision of an accurate and self-consistent cloud and radiation database (input to WCRP international programs like TOGA, WOCE, and GEWEX). Retrieval of cloud parameters in terms of measured areal coverage, altitude, liquid water content, and shortwave and longwave optical depths. Specific science objectives are: 66) 67) 68) 69)

• For climate change analysis, provide a continuation of the ERBE record of radiative fluxes at the top of the atmosphere (TOA), analyzed using the same algorithms that produced the ERBE data.

• Double the accuracy of estimates of radiative fluxes at TOA and the Earth's surface.

• Provide the first long-term global estimates of the radiative fluxes within the Earth's atmosphere.

• Provide cloud property estimates that are consistent with the radiative fluxes from surface to TOA.

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Figure 87: View of one CERES radiometer and location of instruments on the Terra spacecraft (image credit: NASA/LaRC)

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Figure 88: Observation geometry of the CERES instruments on Terra (image credit: NASA/LaRC)

The CERES instrument assembly (of ERBE heritage) consists of a pair of broadband scanning radiometers (two identical instruments), referred to as FM-1 (Flight Module-1) and FM-2; one instrument operates in the cross-track mode for complete spatial coverage from limb to limb; the other one operates in a rotating scan plane (biaxial scanning) mode to provide angular sampling. The cross-track radiometer measurements are a continuation of the ERBS mission. The biaxially scanning radiometer provides angular flux information to improve model accuracy. A single cross-track CERES instrument is flown on TRMM (Tropical Rainfall Measuring Mission), while the dual-scanner instrument is flown on Terra (EOS/AM-1) and Aqua (EOS/PM-1).

The CERES instrument consists of three major subassemblies: 1) Cassegrain telescope, 2) baffle for stray light, and 3) detector assembly, consisting of an active and compensating element. Radiation enters the unit through the baffle, passes through the telescope and is imaged onto the IR detector. Uncooled infrared detection is employed.

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Figure 89: Schematic view of the CERES instrument (image credit: NASA/LaRC)

Instrument parameters (2 identical scanners): total mass of 100 kg , power = 103 W (average, 2 instruments), data rate = 20 kbit/s, duty cycle = 100%, thermal control by heaters and radiators, pointing knowledge = 180 arcsec. The design life is six years. CERES measures longwave (LW) and shortwave (SW) infrared radiation using thermistor bolometers to determine the Earth's radiation budget. There are three spectral channels in each radiometer:

- VNIR+SWIR: 0.3 - 5.0 µm (also referred to as SW channel); measurement of reflected sunlight to an accuracy of 1%.

- Atmospheric window: 8.0 - 12.0 µm (also referred to as LW channel); measurement of Earth-emitted radiation, this includes coverage of water vapor

-Total channel radiance in the spectral range of 0.35 - 125 µm;. reflected or emitted infrared radiation of the Earth-atmosphere system, measurement accuracy of 0.3%.

Limb-to-limb scanning with a nadir IFOV (Instantaneous Field of View) of 14 mrad, FOV = ±78º cross-track, 360º azimuth. Spatial resolution = 10-20 km at nadir. Each channel consists of a precision thermistor-bolometer detector located in a Cassegrain telescope.

Instrument calibration: CERES is a very precisely calibrated radiometer. The instrument is measuring emitted and reflected radiative energy from the surface of the Earth and the atmosphere. A variety of independent methods used to verify calibration: 70)

• Internal calibration sources (blackbody, lamps)

• MAM (Mirror Attenuator Mosaic) solar diffuser plate. MAM is used to define in-orbit shifts or drifts in the sensor responses. The shortwave and total sensors are calibrated using the solar radiances reflected from the MAM's. Each MAM consists of baffle-solar diffuser plate systems, which guide incoming solar radiances into the instrument FOV of the shortwave and total sensor units.

• 3-channel deep convective cloud test

- Use night-time 8-12 µm window to predict longwave radiation (LW): cloud < 205K

- Total - SW = LW vs Window predicted LW in daytime for same clouds <205K temperatures

• 3-channel day/night tropical ocean test

• Instrument calibration:

- Rotate scan plane to align scanning instruments TRMM, Terra during orbital crossings (Haeffelin: reached 0.1% LW, window, 0.5% SW 95% configuration in 6 weeks of orbital crossings of Terra and TRMM)

- FM-1 and FM-2 instruments on Terra at nadir

Instrument heritage

Earth Radiation Budget Experiment (ERBE)

Prime contractor

Northrop Grumman (formerly TRW)

NASA center responsible

LaRC (Langley Research Center)

Three channels in each radiometer

Total radiance (0.3 to 100 µm); Shortwave (0.3 to 5 µm); Window (8 to 12 µm)

Swath

Limb to limb

Spatial resolution

20 km at nadir

Instrument mass, duty cycle

50 kg/scanner, 100%

Instrument power

47 W (average) per scanner, 104 W (peak: biaxial mode) both scanners

Data rate

10 kbit/scanner

Thermal control

Use of heaters and radiators

Thermal operating range

38±0.1ºC (detectors)

FOV (Field of View)

±78º cross-track, 360º azimuth

IFOV

14 mrad

Instrument pointing requirements (3σ)
Control
Knowledge
Stability


720 arcsec
180 arcsec
79 arcsec/6.6 sec

Instrument size

60 cm x 60 cm x 57.6 cm/unit

Table 5: CERES instrument parameters

The international CERES Science Team includes scientists from NASA, NOAA, US universities, France (CNRS), and Belgium (RMIB).

Data: A key element in the success of CERES, beyond the development of an instrument, is the development of data analysis and interpretation techniques for producing radiation and cloud products that meet the scientific objectives of the project.


MISR (Multi-angle Imaging SpectroRadiometer):

The MISR instrument was designed and developed by NASA/JPL (PI: D. J. Diner). Objective: provision of multiple-angle continuous sunlight coverage of the Earth with high spatial resolution (multidirectional observations of each scene within a time scale of minutes). MISR uses nine CCD pushbroom cameras to observe the Earth at nine discrete viewing angles: one at nadir, plus eight other symmetrical views at 26.1º, 45.6º, 60.0º, and 70.5º forward and aft of nadir. Images at each angle are obtained in four spectral bands centered at 0.446, 0.558, 0.672, and 0.866 µm. Each of the 36 instrument data channels (i.e. four spectral bands for each of the nine cameras) is individually commandable to provide ground sampling of 275 m, 550 m, or 1100 m. The swath is 360 km; multi-angle coverage (repeat cycle) of the entire Earth in nine days at the equator, and in two days at higher latitudes. By design, MISR is an along-track nine-line camera system, offering multidirectional observations of each ground (or target) scene. 71) 72) 73) 74)

Camera

View angle

Boresight angle

Swath offset angle

Effective focal length

Df

70.3º forward

57.88º

-2.62º

123.67 mm

Cf

60.2º forward

51.30º

-2.22º

95.34 mm

Bf

45.7º forward

40.10º

-1.71º

73.03 mm

Af

26.2º forward

23.34º

-1.06º

58.90 mm

An

0.1º nadir

-0.04º

0.04º

58.94 mm

Aa

26.2º aftward

-23.35º

1.09º

59.03 mm

Ba

45.7º aftward

-40.06º

1.76º

73.00 mm

Ca

60.2º aftward

-51.31º

2.24º

95.33 mm

Da

70.6º aftward

-58.03º

2.69º

123.66 mm

Table 6: MISR as-built camera pointing specifications

Application: MISR provides global maps of planetary and surface albedo (brightness temperature), and aerosols and vegetation properties. Monitoring of global and regional trends in radiatively important optical properties (eg., opacity, single scattering albedo, and scattering phase function) of natural and anthropogenic aerosols.

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Figure 90: A camera of the MISR instrument with support electronics (image credit: NASA/JPL)

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Figure 91: Cut-away view of the MISR instrument (image credit: NASA/JPL)

MISR images are acquired in two observing modes: global and local. The global mode provides continuous planet-wide observations, with most channels operating at moderate resolution; some selected channels operate at the highest resolution for cloud screening and classification, image navigation, and stereo-photogrammetry. The local mode provides data at the highest resolution in all spectral bands and all cameras for selected 300 km x 300 km regions. In addition to data products providing radiometrically calibrated and geo-rectified images, global mode data will be used to generate two standard (level 2) science products: TOA (Top-of-Atmosphere)/Cloud Product and the Aerosol/Surface Product.

MISR on-orbit radiometric calibration is performed bi-monthly, using deployable white spectralon panels to reflect diffuse sunlight into the cameras, and a set of photodiodes to measure the reflected radiance. Additionally, vicarious calibrations using field and AirMISR data are done on six-month intervals. Geometric calibration of the cameras is done using ground control points.

Parameter

Description

Mission life

6 years

Global coverage time

Every 9 days, with repeat coverage between 2-9 days depending on latitude

Cross-track swath width

360 km common overlap of all 9 cameras, FOV = ±60º along-track and ±15º cross-track.

Nine CCD cameras

Named An, Af, Aa, Bf, Ba, Cf, Ca, Df, and Da where fore, nadir, and aft viewing cameras have names ending with letters f, n, a respectively and four camera designs are named A, B, C, D with increasing viewing angle respectively

View angles at Earth surface

0º, 26.1º, 45.6º, 60.0º, and 70.5º

Spectral coverage

Four bands centered at 0.446, 0.558, 0.672, and 0.866 µm (blue, green, red, and NIR)

Spatial resolution

275 m, 550 m, or 1.1 km, selectable in-flight

Detectors

CCDs, each camera with 4 independent line arrays (one per filter),1504 active pixels per line

Radiometric accuracy

3% at maximum signal

Detector temperature

-5 ±0.1º C (cooled by thermo-electric cooler) of focal plane

Structure temperature

5º C

Instrument mass, power

148 kg, 131 W peak and 83 W average

Instrument size

0.9 m x 0.9 m x 1.3 m

Data rate

3.3 Mbit/s average, 9.0 Mbit/s peak

Table 7: MISR instrument specification

Terra_AutoD

Figure 92: Illustration of the MISR observing concept from Terra (image credit: NASA/JPL)


MODIS (Moderate-Resolution Imaging Spectroradiometer):

MODIS is a NASA/GSFC instrument; prime contractor is Raytheon SBRS, Goleta, CA, formerly Hughes SBRS (Science team leader: V. Salomonson); MODIS algorithm development by an international team of scientists from USA, UK, Australia, and France; there are four discipline groups: Atmosphere, Land, Oceans, and Calibration. 75) 76) 77) 78)

The instrument is flown on the Terra and Aqua satellites (prime instrument). Objective: to measure biological and physical processes on a global basis on time scales of 1 to 2 days. Specific science goals are:

• To determine surface temperature at 1 km resolution, day and night, with an absolute accuracy of 0.2 K for ocean and 1 K for land

• To obtain ocean color (ocean-leaving spectral radiance) from 415 to 653 nm

• To determine chlorophyll fluorescence within 50% at surface water concentrations of 0.5 mg per cubic meter of chlorophyll a

• To obtain chlorophyll a concentrations within 35%

• To obtain information on vegetation and land surface properties, land cover type, vegetation indices, and snow cover and snow reflectance

• To obtain cloud cover with 500 m resolution by day and 1000 m resolution at night

• To obtain cloud properties and aerosol properties

• To determine information on biomass burning

• To obtain global distribution of atmospheric stability and total precipitable water.

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Figure 93: Artist's rendition of the MODIS instrument showing the 360º scan mirror (image credit: Hughes SBRS, NASA)

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Figure 94: Schematic view of the MODIS instrument (image credit: Raytheon SBRS, NASA)

Parameter

Value

Parameter

Value

Instrument type

Opto-mechanical design (whiskbroom scanner)

Data rate

10.6 Mbit/s (peak daytime), 6.1 Mbit/s (orbital average)

Scan rate

20.3 rpm

Data quantization

12 bit

Telescope

17.8 cm diameter off-axis, afocal (collimated) with intermediate field stop

Spatial resolution

250 m (bands 1-2)
500 m (bands 3-7)
1000 m (bands 8-36)

Size

1.0 m x 1.6 m x 1.0 m

Swath width, FOV

2330 km, 110º (1354 pixels in cross-track)

Mass

229 kg

Swath length/scan

10 km (10 pixels in parallel along track)

Power

162.5 W

Design life

6 years

Table 8: Some specification parameters of the MODIS instrument

MODIS is an optomechanical imaging spectroradiometer (whiskbroom type), consisting of a cross-track scan mirror (continuously rotating double-sided scan mirror assembly) and collecting optics, and a set of linear detector arrays with spectral interference filters located in four focal planes. To accommodate frequent infrared calibration (every 1.47 s), a 360º rotating paddle-mirror is centered within a scan cavity to provide the optical subsystem with sequential views of the five calibrators and the Earth.

The optical arrangement provides imagery in 36 discrete bands between 0.4 and 14.5 µm (21 bands within 0.4-3.0 µm range, 15 bands within 3-14.5 µm range). The spectral bands provide a spatial resolution of 250 m, 500 m, and at 1 km at nadir. MODIS heritage: AVHRR (POES), HIRS (POES), TM (Landsat), CZCS (Nimbus-7). In fact, the MODIS instrument is considered to be a next-generation AVHRR instrument, having 36 bands (AVHRR/3 has 6) and a spatial resolution of 250 m (AVHRR has 1 km).

A high-performance passive radiative cooler provides cooling to 83 K for the infrared bands on two HgCdTe FPAs (Focal Plane Assemblies). A new photodiode-silicon readout technology for the VNIR range provides unsurpassed quantum efficiency and low-noise readout with a very good dynamic range.

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Figure 95: Functional architecture of the MODIS instrument (image credit: Raytheon SBRS)

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Figure 96: Major elements of the MODIS instrument (image credit: NASA)

MODIS polarization sensitivity < 2% for the visible range out to 2.2 µm; the performance goal for SNR (Signal-to-Noise Ratio) and NEΔT (Noise-Equivalent Temperature Difference) values is 30-40% better than the required values in Table 9.; absolute irradiance accuracy of 5% for <3 µm and 1% for >3 µm; absolute temperature accuracy of 0.2 K for oceans and 1 K for land; daylight reflection and day/night emission spectral imaging; swath width of 2330 km at 110º FOV; scan rate = 20.3 rpm across track; instrument mass = 250 kg; duty cycle = 100%; power = 225 W (average); data rate = 6.2 Mbit/s (average), 10.6 Mbit/s (peak daytime), 3.2 Mbit/s (night); quantization = 12 bit. Instrument IFOV (spatial resolution) = 250 m (bands 1-2), =500 m (bands 3-7), = 1000 m (bands 8-36).

The observations are made at three spatial resolutions (nadir): 0.25 km for bands 1-2 with 40 detectors per band, 0.5 km for bands 3-7 with 20 detectors per band, and 1 km for bands 8-36 with 10 detectors per band. All the detectors, aligned in the along-track direction, are distributed on four focal plane assemblies (FPAs) according to their wavelengths: visible (VIS), near infrared (NIR), short- and mid-wave infrared (SMIR), and long-wave infrared (LWIR).

Primary Use

Band No.

Bandwidth
(µm)

Spectral Radiance
NESR
(W m-2 µm-1 sr-1)

Required SNR
(Required NEΔT
in K)

Spatial
Resolution at nadir

Land/Cloud
Boundaries

1
2

0.620 - 0.670
0.841 - 0.876

21.8
24.7

128
201

250 m

Land/Cloud
Properties

3
4
5
6
7

0.459 - 0.479
0.545 - 0.565
1.230 - 1.250
1.628 - 1.652
2.105 - 2.155

35.3
29.0
5.4
7.3
1.0

243
228
74
275
110

500 m

Ocean Color/
Phytoplankton/
Biogeochemistry

8
9
10
11
12
13
14
15
16

0.405 - 0.420
0.438 - 0.448
0.483 - 0.493
0.526 - 0.536
0.546 - 0.556
0.662 - 0.672
0.673 - 0.683
0.743 - 0.753
0.862 - 0.877

44.9
41.9
32.1
27.9
21.0
9.5
8.7
10.2
6.2

880
838
802
754
750
910
1087
586
516

1000 m

Atmospheric
Water Vapor

17
18
19

0.890 - 0.920
0.931 - 0.941
0.915 - 0.965

10.0
3.6
15.0

167
57
250

Surface/Cloud
Temperature

20
21
22
23

3.660 - 3.840
3.929 - 3.989
3.929 - 3.989
4.020 - 4.080

0.45
2.38
0.67
0.79

(0.05)
(2.00)
(0.07)
(0.07)

Atmospheric
Temperature

24
25

4.433 - 4.598
4.482 - 4.549

0.17
0.59

(0.25)
(0.25)

Cirrus Clouds

26

1.360 - 1.390

6.00

150

Water Vapor

27
28
29

6.535 - 6.895
7.175 - 7.475
8.400 - 8.700

1.16
2.18
9.58

(0.25)
(0.25)
(0.25)

Ozone

30

9.580 - 9.880

3.69

(0.25)

Surface/Cloud
Temperature

31
32

10.780 - 11.280
11.770 - 12.270

9.55
8.94

(0.05)
(0.05)

Cloud Top
Altitude

33
34
35
36

13.185 - 13.485
13.485 - 13.785
13.785 - 14.085
14.085 - 14.385

4.52
3.76
3.11
2.08

(0.25)
(0.25)
(0.25)
(0.35)

Table 9: MODIS spectral performance parameters

MODIS onboard calibration employs various techniques for comprehensive verification of spectral, radiometric and spatial measurements. They include: 79) 80) 81) 82)

• Spectroradiometric Calibration Assembly (SRCA)

- Spectral calibration of reflective channel channel bandpasses

- Verification of spectral band registration

- DC restoration on every scan using a direct view of space

- Lunar calibration via the space-view port as well as periodic rotations of the S/C to enable full scans across the moon through the active scan aperture

• Blackbody (BB) calibration of thermal bands on every scan (a v-groove blackbody)

• Solar Diffuser (SD) reference

• Solar Diffuser Stability Monitor (SDSM)

The spectral mode of the SRCA device consists of a light source, a grating monochromator, and a beam collimator. The light source is a SIS (Spectral Integration Sphere) with lamps distributed inside. By combining the use of the spectral filters mounted on the filter wheel assembly and the grating monochromator, the SRCA is capable of performing spectral characterizations of the RSB (Reflective Solar Bands) ranging from 0.41 to 2.2 µm. Its spectral calibration is referenced to the ground equipment (SpMA) with high accuracy.

Terra_Auto8

Figure 97: Schematic view of the SRCA device (image credit: NASA/GSFC)

The SD/SDSM system is used for the RSB calibration and BB for the TEB (Thermal Emissive Bands) calibration. The SRCA is primarily used for the sensor's spectral (RSB only) and spatial (TEB and RSB) characterization. The RSB calibration is reflectance based using a sensor’s view of diffusely reflected sunlight from a solar diffuser (SD) plate with a known bi-directional reflectance and distribution function (BRDF). Because of the solar exposure onto the SD plate, its reflectance properties slowly degrade on-orbit.

The Blackbody is located in front of and slightly above the Scan Mirror, which views the BB with every revolution. The BB assembly provides a full-aperture radiometric calibration source of the MWIR and LWIR bands to within 1 percent absolute accuracy. It provides known radiance levels and is also used in the DC restore operation (a space-view signal level provides the second level for all bands in the two-point calibration). In normal operation the BB is kept at the instrument’s ambient temperature (nominally 273 K), though it is possible to heat and control the BB to 315K. Twelve sensors below the assembly's surface monitor its temperature. Each sensor is calibrated to National Institute of Standards & Technology (NIST) traceable standards, and can determine the temperature of the assembly to within ± 0.1 K.

Terra_Auto7

Figure 98: View of the BB assembly (image credit: NASA/GSFC)

To maintain the calibration and data quality, a solar diffuser stability monitor (SDSM) is used in tandem with the SD to track its degradation or BRDF changes. The SDSM system has a small integration sphere (SIS) with a single input aperture and nine filtered detectors. Each filter has a narrow spectral bandpass so that the change in reflectance is effectively monitored at nine discrete wavelengths between 0.4 µm and 1.0 µm. A three-position fold mirror enables the detectors to view sequentially a dark scene, direct sunlight, and illumination from the SD (Solar Diffuser). The direct sunlight is attenuated via a two-percent transmitting screen to keep the radiance within the dynamic range of the SDSM’s detector/amplifier combination.

Terra_Auto6

Figure 99: The MODIS SD device (image credit: NASA/GSFC)

Terra_Auto5

Figure 100: The SDSM device (image credit: NASA/GSFC)

MODIS product overview: MODIS provides global coverage every 1 to 2 days. It provides specific global survey data, which includes the following (some standard data products):

• Cloud mask: at 250 m and 1 km resolution by day and at night

• Aerosol concentration and optical properties: at 5 km resolution over oceans and 10 km over land during the day

• Cloud properties: characterized by optical thickness, effective particle radius, cloud droplet phase, cloud-top altitude, cloud-top temperature

• Vegetation and land-surface cover, conditions, and productivity, defined as:

- Vegetation indices corrected for atmospheric effects, soil, polarization, and directional effects

- Surface reflectance

- Land-cover type with identification and detection of change

- Net primary productivity, leaf-area index, and intercepted photosynthetically active radiation

• Snow and sea-ice cover and reflectance

• Surface temperature with 1 km resolution, day and night, with absolute accuracy goals of 0.3-0.5ºC for oceans and 1ºC for land surfaces.

• Ocean color: defined as ocean-leaving spectral radiance within 5% from 415-653 nm, based on adequate atmospheric correction from NIR sensor channels

• Concentration of chlorophyll-a within 35% from 0.05 to 50 mg/m3 for case 1 waters

• Chlorophyll fluorescence within 50% at surface water concentrations of 0.5 mg/m3 of chlorophyll-a.


MOPITT (Measurement of Pollution in the Troposphere):

MOPITT is a Canadian sensor supported by CSA, built by COM DEV, Cambridge, Ontario (PI: J. R. Drummond, University of Toronto). The MOPITT instrument design is of MAPS (Measurements of Air Pollution from Space) heritage, flown on STS-2 (November 12.-14, 1981), then on STS-13 (October 5 -13, 1984), and then twice in 1994 (STS-59, STS-68). MOPITT is the first satellite sensor to use gas correlation spectroscopy (A technique to increase the sensitivity of the instrument to the gas of interest by separating out the regions of the spectrum where the gas has absorption lines and integrating the signal from just those regions. The specific wavelengths are located using a sample of the gas as a reference for the spectrum). By using correlation cells of differing pressures, some height resolution can be obtained. Thus MOPITT has multiple channels to provide height resolution, it also carries multiple channels to afford some redundancy. Definitions of acronyms in Table 10: LMC (Length Modulator Cell), PMC (Pressure Modulator Cell). 83) 84) 85) 86) 87) 88) 89) 90)

The CO profile measurements are made using upwelling thermal radiance in the 4.6 µm fundamental band. The troposphere is resolved into about four layers with approximately 3 km vertical resolution, 22 km horizontal resolution and 10% accuracy. Pressure Modulated Cells (PMCs) are used to view the upper layers whilst Length Modulated Cells (LMCs) are used for the lower troposphere measurements. By varying the cell pressures the modulators can be biased to view the different layers.

The MOPITT instrument contains four optical chains initiated by four scan mechanisms, which are split into eight independent channels. Each channel uses a technique known as correlation spectroscopy to perform the science measurements. This uses a sample of gas in the optical path. By performing synchronous demodulation of the detected infrared signal, the system functions as a complex filter, providing very good spectral resolution and good sensitivity by incorporating several molecular lines simultaneously.

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Figure 101: Isometric optical system layout of the MOPITT instrument (image credit: University of Toronto)

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Figure 102: Schematic illustration of the MOPITT instrument (image credit: University of Toronto)

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Figure 103: Schematic view of the correlation radiometry concept (image credit: NCAR, University of Toronto)

Terra_Auto1

Figure 104: Photograph showing the finished PMC for MOPITT (image credit: Oxford Physics)

Channel No

Cell type

Cell Pressure (kPa)

Center Wavelength (cm-1)

Spectral band constituent

1

LMC1

20

2166 (52)

CO thermal

2

LMC1

20

4285 (40)

CO solar

3

PMC1

7.5

2166 (52)

CO thermal

4

LMC2

80

4430 (140)

CH4 solar

5

LMC3

80

2166 (52)

CO thermal

6

LMC3

80

4285 (40)

CO solar

7

PMC2

3.75

2166 (52)

CO thermal

8

LMC4

80

4430 (140)

CH4 solar

Table 10: Channel definition of MOPITT

The instrument measures emitted and reflected infrared radiance in the atmospheric column. Analysis of these data permit retrieval of tropospheric CO profiles and total column CH4. Objective: study of how these gases interact with the surface, ocean, and biomass systems (distribution, transport, sources and sinks). Measurements are performed on the principle of correlation spectroscopy utilizing both pressure-modulated and length-modulated gas cells, with detectors at 2.3, 2.4, and 4.7 µm. Vertical profile of CO (carbon monoxide) and total column of CH4 (methane) are to be measured; CO concentration in 4 km layers with an accuracy of 10%; CH4 column abundance accuracy is 1%.

Swath width = 616 km, spatial resolution = 22 x 22 km; instrument mass = 182 kg; power = 243 W; duty cycle = 100%; data rate = 25 kbit/s; thermal control by an 80 K Stirling cycle cooler, capillary-pumped cold plate and passive radiation; thermal operating range = 25º C (instrument) and 100 K (detectors).

MOPITT is designed as a scanning instrument. IFOV = 1.8º x 1.8º (22 km x 22 km at nadir). The instrument scan line consists of 29 pixels, each at 1.8º increments. The maximum scan angle is 26.1º off-axis which is equivalent to a swath width of 640 km. - MOPITT data products include gridded retrievals of CH4 with a horizontal resolution of 22 km and a precision of 1%. Gridded CO soundings are retrieved with 10% accuracy in three vertical layers between 0 and 15 km. Three-dimensional maps to model global tropospheric chemistry.

The instrument is self-calibrating in orbit and performs a zero measurement every 120 seconds and a reference measurement every 660 seconds. The instrument operation is practically autonomous, requiring very little commanding to keep it within the mission profile at all times. 91)

Terra_Auto0

Figure 105: View of the MOPITT instrument (image credit: COM DEV)

MOPITT operations: MOPITT has suffered two anomalies since launch. On May 7, 2001 one of the two Stirling cycle coolers, which are used to keep the detectors at about 80 K, failed. The cooler fault compromised half of the instrument. After the fault, only channels 5, 6, 7, and 8 are delivering useful data. On Aug. 4, 2001 chopper 3 failed. Fortunately, it stopped in the completely open state, which permits to continue to use the data by adjusting the data processing algorithm accordingly.




EOS (Earth Observing System)

EOS is the centerpiece of NASA's Earth Science Enterprise (ESE). It consists of a science component and a data system supporting a coordinated series of polar-orbiting and low inclination satellites for long-term global observations of the land surface, biosphere, solid Earth, atmosphere, and oceans. 92) 93) 94) 95)

Background: The EOS program is a NASA initiative of the US Global Change Research Program (USGCRP). Planning for EOS began in the early 1980s, and an AO (Announcement of Opportunity) for the selection of instruments and science teams was issued in 1988. Early in 1990 NASA announced the selection of 30 instruments to be developed for EOS. Major budget constraints imposed by the US Congress forced the EOS program into a restructuring process in the time frame of 1991-92. In addition a rescoping of the EOS program occurred in 1992 leading to just half of the 1990 budget allocation (the HIRIS sensor was eliminated). The instruments adopted as part of the restructured/rescoped EOS program were chosen to address the key scientific issues associated with global climate change. This action reduced the required instruments to 17 that needed to fly by the year 2002 (six were deferred and seven instruments were deselected from the original 30). Furthermore, a shift occurred in the conceptual design of the EOS satellite platforms from “large observatories” to intermediate and smaller spacecraft that may be launched by smaller and existing launch vehicles. The EOS program experienced a further rebaselining process in 1994, due to a budget reduction of about 9%. This resulted in the cancellation of the combined EOS Radar and Laser Altimeter Mission (but rephasing the latter as two separate missions), deferring the development of some sensors and spreading the launch of missions by increasing the basic re-flight periods of missions from 5 to 6 years, and flying some EOS instruments on missions of partner space agencies (NASDA, RKA, CNES, ESA) in a framework of international cooperation. The EOS program includes instruments provided by international partners (ASTER, MOPITT, HSB, OMI) as well as an instrument developed by a joint US/UK partnership (HIRDLS).

The overall goal of the EOS program is to determine the extent, causes, and regional consequences of global climate change. The following science and policy priorities are defined for EOS observations (established by the EOS investigators working group and in coordination with the national and international Earth science community):

• Water and Energy Cycles: Cloud formation, dissipation, and radiative properties which influence the response of the atmosphere to greenhouse forcing, large-scale hydrology, evaporation

• Oceans: Exchange of energy, water, and chemicals between the ocean and atmosphere, and between the upper layers of the ocean and the deep ocean (including sea ice and formation of bottom water)

• Chemistry of the Troposphere and Lower Stratosphere: Links to the hydrologic cycle and ecosystems, transformations of greenhouse gases in the atmosphere, and interactions including climate change

• Land-Surface Hydrology and Ecosystem Processes: Improved estimates of runoff over the land surface and into the oceans. Sources and sinks of greenhouse gases. Exchange of moisture and energy between the land surface and the atmosphere. Changes in land cover

• Glaciers and Polar Ice Sheets: Predictions of sea level and global water balance

• Chemistry of the Middle and Upper Stratosphere: Chemical reactions, solar-atmosphere relations, and sources and sinks of radiatively important gases

• Solid Earth: Volcanoes and their role in climate change.

The original EOS mission elements (AM S/C series, PM S/C series, Chemistry S/C series) was redefined again in 1999. The EOS program space segment elements are now: Landsat-7, QuikSCAT, Terra, ACRIMSat, Aqua, Aura and ICESat.

Parameter

Terra (EOS/AM-1) S/C

Aqua (EOS/PM-1 S/C)

Downlink center frequency

8212.5 MHz

8160 MHz

EIRP

14 W

27.2 W

Bandwidth

26 MHz

15 MHz

Data modulation

OQPSK

SQPSK

Data format

NRZ-L

NRZ-L

I/Q power ratio (nominal)

1:1

1:1

Operational duty cycle

100%

100%

Antenna coverage from nadir

±64º

±64º

Antenna polarization

RHCP

RHCP

Data rate

13 Mbit/s

15 Mbit/s

Data protocol standard

CCSDS

CCSDS

Instrument data provided

MODIS

MODIS, AIRS, AMSU-A, CERES, HSB, AMSR-E

Table 11: Specification of Direct Broadcast (DB) service of Terra and Aqua satellites

EOS policy includes providing Direct Broadcast (DB) service to the user community; this applies to real-time MODIS data from the Terra spacecraft, as well as to the entire real-time data stream of the Aqua satellite. These data may be received by anyone with the appropriate receiving station, without charge. The broadcast data are transmitted in X-band. A 3 m antenna dish (minimum) should be sufficient for X-band data reception.


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The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (herb.kramer@gmx.net).

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