Minimize ISS: CATS

ISS Utilization: CATS (Cloud-Aerosol Transport System) / CRS-5 Dragon flight

Overview   CATS   Launch   Mission Status   References

The NASA CATS investigation uses a LIDAR (Light Detection and Ranging) remote sensing instrument, designed to provide measurements of atmospheric clouds and aerosols. The impact of clouds and aerosols (e.g., pollution, dust, smoke) on a global scale with regards to energy balance and climate feedback mechanisms is not yet fully understood. A better understanding of cloud and aerosol coverage and properties is critical for understanding of the Earth system and its associated climate feedback processes.

The CATS LiDAR obtains range-resolved information which can be used to assess the climate impacts of clouds and aerosols on a global scale. The orbit of the ISS (International Space Station) is particularly suited to measurements of this kind, because the ISS passes over and along many of the primary aerosol transport paths within the atmosphere. The ISS orbit also permits study of diurnal (day to night) changes due to the effects of aerosols and clouds in the atmosphere – something other Earth Science satellite cannot readily obtain given their orbits. 1) 2) 3) 4) 5)

CATS is a three wavelength (1064, 532, 355 nm) elastic backscatter lidar with HSRL (High Spectral Resolution Lidar) capability at 532 nm. Depolarization measurements will be made at all wavelengths. The primary objective of CATS is to continue the CALIPSO aerosol and cloud profile data record, ideally with overlap between both missions and EarthCARE. In addition, the near real time data capability of the ISS will enable CATS to support operational applications such as air quality and special event monitoring. The HSRL channel will provide a demonstration of technology and a data testbed for direct extinction retrievals in support of ACE mission development.

The CATS mission goals are:

A) Extend CALIPSO data record for continuity of Lidar climate observations

- Continue record of vertically resolved aerosol and cloud distributions and properties

- Improve our understanding of aerosol and cloud properties and interactions

- Improve model based estimates of climate forcing and predictions of future climate change

B) Improve operational aerosol forecasting programs

- Improve model performance through assimilation of near‐real‐time aerosol and cloud data

- Enhance air quality monitoring and prediction capabilities by providing vertical profiles of pollutants

- Improve strategic and hazard warning capabilities of events in near‐real‐time (dust storms, volcanic eruptions)

C) NASA Decadal Mission Pathfinder: Lidar for the future ACE (Aerosols, Clouds, Ecosystems) Mission

- Demonstrate HSRL aerosol retrievals and 355 nm data for ACE mission development

- Laser Technology Demo/Risk Reduction: high repetition rate, injection seeding (HSRL), and wavelength tripling (355 nm).

The CATS lidar will provide range‐resolved profile measurements of atmospheric aerosol and cloud distributions and properties at three wavelengths (355, 532, and 1064 nm). Retrieved properties include: layer height and thickness, backscatter, optical depth, extinction, depolarization, and discrimination of aerosol type and cloud ice/water phase. CATS operates in one of six science modes to meet mission goals, utilizing various configurations of two high repetition rate lasers and four IFOV (Instantaneous Field of View).


Figure 1: The CATS mission will help extend the CALIPSO data record to ensure continuity of lidar climate observations (image credit: NASA)


Figure 2: Artist's rendition of CATS collecting a swath of data from the ISS (image credit: NASA, Ref. 5)



CATS (Cloud-Aerosol Transport System) instrument:

The CATS instrument is designed and developed at NASA/GSFC (PI: Matthew McGill). The project was initiated in April 2011. The accommodation parameters of the lidar instrument are:

• Lidar, multiwavelength (1064, 532, 355 nm)

• Mass: 494 kg

• Power < 1 kW

• Data rate: ~2 Mbit/s via HRDL (High Rate Data Link).


Figure 3: Photo of the CATS instrument in the laboratory (image credit: NASA/GSFC) 6) 7)

Table 1: General specification of CATS operational science modes

Legend to Table 1:

• CATS utilizes two lasers. Laser 1 and Laser 2. Laser 2 has three internal configurations: 2a, 2b, and 2c. The laser output for each configuration is given in Table 1.

• Science modes 4, 5, 6 all utilize Laser 2c directed to one of three IFOVs. Thus they are not separate, independent backup modes for Mission goals A) and B). If Laser 2 were to fail then all these modes fail.

• Science modes 1 and 3 provide inherent redundancy for Mission goals A) and B).

• Science mode 2 does not provide depolarization measurements at 532 nm, and thus does not map directly to CALIPSO. As a result, this mode only partially supports Mission goal A).


Figure 4: Illustration of the CATS measurement configuration in horizontal and vertical direction (image credit: NASA/GSFC)

Legend to Figure 4: FFOV (Forward FOV), AFOV (Aft FOV), LSFOV (Left Side FOV), RSFOV (Right Side FOV).

CATS laser 1 is used in science mode 1, and is derived from proven technology employed onboard CALIPSO and flown on the NASA CPL (Cloud Physics Lidar). CATS Laser 2 is an injection seeded laser with three operational configurations. Configuration 2a emits 532 and 1064 nm narrow line width laser pulses necessary for HSRL observations required in science mode 2. Configuration 2b employs a THG (Third Harmonic Generation) to emit 355 nm laser pulses required for science mode 3. Configuration 2c is a backup for laser 1 if it fails, and is used to provide laser power for backup science modes 4, 5, and 6. All receiver pathways are fiber coupled. Photon counting detectors are utilized for all wavelengths. The HSRL receiver uses a Fabry Perot interferometer at 532 nm. Likewise, only one view path has filters and detectors selected for 355 nm observations. Table 2 describes the laser and receiver configurations, and corresponding science modes for CATS.

Table 2: Specification of the laser and receiver configurations and corresponding operational CATS science modes


Figure 5: Two cut-away views of the CATS instrument showing the internal payload components (image credit: NASA)

Legend to Figure 5: A 60 cm diameter telescope occupies the main portion of the volume. Two lasers (for redundancy and for tech demo purposes) are mounted on either side of the telescope. The PIU (Payload Interface Unit) provides the connection to the JEM-EF. Power, data, and coolant fluid pass through the PIU to the payload. 8) 9)


Figure 6: Illustration of the CATS instrument, a standard JEM-EF volume (image credit: NASA)


Figure 7: Instrument parts are labeled in this diagram of the CATS payload (image credit: NASA, Ref. 5)

CATS science: The impact of clouds and aerosols (e.g., pollution, dust, smoke) on global energy balance and climate feedback mechanisms is not yet fully understood. Obtaining a better understanding of cloud and aerosol coverage and properties is critical for understanding the Earth's systems and their climate feedback processes.

An important aspect of CATS science will be to provide real-time observations of aerosol vertical distribution to serve as inputs to global aerosol transport models. Current models tend to agree on total aerosol loading, but tend to disagree on the vertical distribution of the loading and the type of aerosols present. To begin to determine how much of the total aerosol load can be attributed to natural sources (e.g., dust) and how much can be attributed to human-induced sources (e.g., pollution), it is important to know how the aerosols are distributed through the atmosphere. In particular, the vertical distribution of aerosols is highly important, because their effects differ depending on whether the aerosol layer is below, mixed with, or above cloud layers. As mentioned earlier, aerosol–cloud interactions currently comprise the largest source of uncertainty in studies of climate forcing, so it is critical to ascertain the correct vertical distribution of aerosols.


Figure 8: Example of lidar profile data from the airborne CPL (Cloud Physics Lidar) instrument (image credit: NASA)


Figure 9: CATS observations: raw data (image credit: NASA)


Figure 10: High repetition rate side effect: SPS (Simultaneous Pulse Signals), image credit: NASA


Launch: The CATS primary payload was launched on January 10, 2015 at 09:47 UTC on the SpaceX CRS-5 (Commercial Resupply Service-5) to the ISS from the Cape Canaveral Air Force Station (Falcon-9 V1.1 vehicle). 10) 11) 12)

• SpaceX successfully launched their commercial Falcon 9 rocket and Dragon cargo ship on a critical mission for NASA bound for the space station this morning, Jan. 10, while simultaneously accomplishing an unprecedented hard landing of the boosters first stage on an ocean-floating "drone ship" platform in a very good first step towards the bold company goal of recovery and re-usability in the future. 13)

- A secondary goal of SpaceX was to conduct a history-making attempt at recovering the Falcon 9 first stage (42 m toll and 3.66 m in diameter) via a precision landing on an ocean-going landing platform known as the "autonomous spaceport drone ship." SpaceX CEO Elon Musk quickly tweeted that good progress was made, and as expected, more work needs to be done.

- This was an experiment involving re-lighting one of the first stage Merlin engines three times to act as a retro rocket to slow the stages descent and aim for the drone ship. The first stage made it to the drone spaceport ship, but landed hard.


The oft delayed launch of the SpaceX Falcon 9 rocket on the CRS-5 cargo resupply mission for NASA to the International Space Station (ISS) has been reset to January 10, 2015. 14)

The Dragon spacecraft is loaded with ~2360 kg of cargo, including 1680 kg of scientific experiments, technology demonstrations and supplies, including critical materials to support 256 science and research investigations that will take place on the space station during ISS Expeditions 42 and 43.

Due to the launch failure of Orbital's Cygnus Orb-3 spacecraft on Oct. 28, 2014, the student researchers from across America, are being given a second chance and will have their reconstituted experiments re-flown on the impending SpaceX CRS-5 mission launch, thanks to the tireless efforts of NASA, NanoRacks LLC, CASIS (Center for the Advancement of Science in Space), SpaceX and the Student Spaceflight Experiments Program (SSEP) which runs the program. The 17 student student experiments are known collectively as the "Yankee Clipper" mission. 15)

- The main science payload is CATS (Cloud-Aerosol Transport System)

- The mission also delivers an IMAX camera for filming during four increments and tools that will be used in future spacewalks to prepare the station for the installation of the new international docking adapters.

Several small satellites will also be carried aboard the Dragon for deployment from the ISS:

- These include a pair of Flock-1d' satellites rapidly assembled to replace some of the spacecraft lost in a launch failure of Orbital Sciences' Antares rocket last October. - Flock-1 satellites are 3U CubeSats operated by Planet Labs for commercial Earth imaging from low orbits. The satellites have short operational lifespans and typically decay from orbit around six months after launch.

- Brazil's AESP-14 CubeSat (1U) is also aboard the Dragon. The satellite, developed by Brazil's ITA (Instituto Tecnológico de Aeronáutica) in collaboration with INPE (Instituto Nacional de Pesquisas Espaciais), will be used to study plasma bubbles in the ionosphere.

- The SERPENS nanosatellite, a 3U CubeSat operated by a group of Brazilian universities, is also believed to be aboard the mission. This spacecraft will be used for technology development, testing communications systems in orbit.

If all goes as planned, Dragon will arrive at the station approximately two days after liftoff. - After 4 ½ weeks at the space station, the Dragon spacecraft will return with over1630 kg of cargo and packaging, including crew supplies,hardware and computer resources, science experiments, space station hardware and trash. Dragon is expected to return to Earth for a parachute-assisted splashdown off the coast of southern California.

Orbit: The near-circular orbit of the ISS is at a nominal altitude of ~400 km with an inclination of 51.6º.

The 51.6° inclination ISS orbit covers significant aerosol source and transport regions, and areas of important aerosol-cloud interaction. The precessing orbit also captures the full diurnal cycle, allowing for studies that are not possible with CALIPSO in the sun-synchronous A-Train orbit.


Figure 11: Illustration of the ISS orbit on a world map (image credit: NASA)


CATS will be installed on the JEM-EF (Japanese Experiment Module-Exposed Facility) of JAXA; the objective is to demonstrate the utility of state-of-the-art multi-wavelength laser technology to study aerosol distribution and transport in the atmosphere.


Figure 12: Photo of the JEM-EF complex on the ISS (prior to CATS installation) - the payloads are robotically attached to the JEM-EF using using "plug-in" ports (image credit: NASA, JAXA)


Figure 13: CATS data communications and processing system (image credit: NASA)

The CATS mission has a 6 month operational requirement, and a 3 year goal — with SOMD/ISS (Space Operations Mission Directorate/International Space Station).


Figure 14: Overview of Earth science instruments on the ISS (installed or planned) in the second decade of the 21st century (image credit: NASA) 16)



Mission status:

• On April 21, 2016, the CATS instrument observed dust, smoke and urban pollution across central India. As shown in the attenuated backscatter image (Figure 15) in Plot 1, the aerosol layer reached to heights of 5 km. Optical property retrievals from the lidar signals result in an extinction product (Plot 2), and the OD (Optical Depth) product (Plot 3) with total aerosol (OD) product (Plot 3) shown in red. The MODIS aerosol optical depth retrieval at 0.66 µm is shown in the map. Although the wavelength of CATS (1.064 µm) is somewhat larger, the overall horizontal distribution of OD strenghts are similar. 17)


Figure 15: CATS image of the week acquired on April 21, 2016 (image credit: NASA)


Figure 16: Comparison of CATS observations with MODIS/Aqua data on April 21, 2016 (image credit: NASA)

• March 3, 2016: The most frequently observed CATS aerosol types between 0-2 km are shown for August-September 2015 (Figure 17). CATS identifies dust and dust mixtures over Saharan and Arabian source regions, smoke over the Central African biomass burning region, and marine aerosols over the Atlantic, Southern and Indian Oceans. 18)

- The version 1 CATS aerosol typing has heritage from the CALIOP (Cloud-Aerosol LIdar with Orthogonal Polarization) instrument aerosol typing algorithm flown on the CALIPSO mission of NASA.


Figure 17: Aerosols over Africa (image credit: NASA)

• On February 18, 2016, the CATS instrument observed smoke and high clouds near Madagascar.


Figure 18: Optical properties analysis of the CATS observed data (image credit: NASA)

Legend to Figure 18: As shown in Plot 1, the CATS algorithm identifies the smoke layer (orange) and cirrus layers (dark blue). The optical property retrievals from the lidar signals result in a particulate backscatter product (Plot 2), extinction product (Plot 3), and ice water content product inside ice cloud only (Plot 4).

• July 25, 2015: When it comes to seeing what's going on in the atmosphere after dark, CATS (Cloud-Aerosol Transport System) has an advantage. From a perch on the outside of the ISS (International Space Station), CATS recently observed part of a plume streaming from Raung Volcano, even though the plume was not apparent in imagery from other spaceborne instruments. 19)

- Mount Raung, a stratovolcano on the Indonesian island of Java, has erupted at least 13 times in the past 25 years, according to the Smithsonian Global Volcanism program. The most recent bout of activity began in June 2015 and prompted authorities to temporarily close airports in neighboring Bali due to concerns about volcanic ash. In the daytime, Raung's ash plume is clearly visible in natural-color imagery acquired on July 14, 2015, and again on July 21. Viewing the plume at night, however, poses a bigger challenge.

- Shortly after midnight (Java time) on July 12, part of the plume could be detected by satellite sensors observing in the longwave infrared (thermal) portion of the electromagnetic spectrum. The top image was acquired with the VIIRS (Visible Infrared Imaging Radiometer Suite ) on the Suomi NPP satellite. Warmer areas appear light grey and white (mostly land and ocean), while cooler areas appear dark (high clouds and the volcanic plume). The plume spreads toward the south and cools high in the atmosphere, which is why it appears dark. But eventually the aerosols composing the plume are too diffuse to be visible even in the thermal image.

- The red line (Figure 19) shows where, less than an hour after Suomi NPP passed over, CATS scanned a vertical slice through the atmosphere (bottom image). The instrument sends pulses of laser light down through the atmosphere and measures the light scattered back up to the instrument. Even though the volcanic aerosols were relatively diffuse in the area, even that faint puff of ash showed up at altitudes of 5 km and below. Darker red areas on the CATS image depict where the atmosphere reflects more light — areas where the plume is optically thicker.


Figure 19: CATS nightview image of the Raung Volcanic Plume, acquired on July 11, 2015 (image credit: NASA, Jesse Allen)

• June 9, 2015: CATS continues to operate in Mode 2 (532 & 1064 nm backscatter), with near continuous operation since March 25. Several recent events have been captured in the CATS data, including ice clouds from Hurricane Blanca on June 4. Initial data release of the Mode 1 Level 1B data from Feb. 10 through March 21 will occur Friday June 12, with browse images available here at the CATS website, as well as links to the data files (Ref. 20).


Figure 20: Hurricane Blanca, acquired with CATS on June 4, 2015 (image credit: NASA)

• May 1, 2015: CATS has been operating primarily in Mode 2 (532 & 1064 nm backscatter) since March 25, and will continue to operate in this mode. Several recent events have been captured in the CATS data, including the plumes due to the eruption of the Calbuco volcano in Chile (Figure 21). The team will continue to refine the calibration for all the data since operation began in February. Initial data release of the Mode 1 data from Feb. 10 through March 10 will likely occur in the coming months. 20)


Figure 21: Calbuco volcano eruption, Chile, April 22-25, 2015 (image credit: NASA)

• March 12, 2015: The CATS laser was turned off on March 10 in preparation for Soyuz spacecraft activities. On March 12, the CATS team successfully turned on the second laser to test operation at all three wavelengths (355, 532, 1064 nm). The team will continue to monitor the operation of the second laser and perform instrument check-outs. 21)

• Feb. 26, 2015: From Saharan dust storms to icy clouds to smoke on the opposite side of the continent, the first image from NASA's newest cloud- and aerosol-measuring instrument provides a profile of the atmosphere above Africa. 22)

- The CATS image (Figure 22) shows a profile of particles in the atmosphere over a swath of Africa, from 30 º North to 30 º South, as the space station flew over it in the early morning of Feb. 11.

- Over northern Africa, particles – likely dust kicked up by Saharan windstorms – reach heights of 4 -5 km, said John Yorks, the science lead for CATS at Goddard. As the space station approached the equator, the instrument picked up higher atmospheric particles – thin, wispy ice clouds as high as 16 km above the surface. South of the cloudy tropics, aerosols appeared closer to the ground, likely smoke from biomass burning. The results from CATS can also be combined with images of Earth from instruments like the MODIS (Moderate Resolution Imaging Spectroradiometer), flown on the Terra and Aqua satellites.


Figure 22: This first CATS image, acquired over northern Africa, shows clouds, dust and smoke from fires, as well as topography returned by the instrument (image credit: NASA)

- The CATS team is calibrating the data from the two wavelengths on the primary laser operating at 532 nm and 1064 nm. The backup laser on CATS has three wavelengths. The different wavelengths reflect differently when they hit aerosols, so comparing the returns from multiple wavelengths allows the scientists to distinguish dust from ice, smoke or other airborne particles.

- Before receiving data plots like the one over Africa, the team aligned the telescope pointing. They used motors to adjust optics inside the instrument during nighttime segments until they got the strongest signal, indicating that the telescope's field of view aligned with the reflected laser photons.

- Data from CATS will help scientists model the structure of dust plumes and other atmospheric features, which can travel far distances and impact air quality. Climate scientists will also use the CATS data, along with data from other Earth-observing instruments, to look at trends and interactions in clouds and aerosols over time.

- The CATS team is moving forward with calibration and improving computer programs to identify types of aerosols, and by April hopes to be able to provide a data product to aerosol monitoring groups three hours after the data are collected, and provide products to the public within 12 hours (Ref. 22).

• Feb. 16, 2015: The CATS laser was turned off on February13 in preparation for the ATV undocking. The CATS laser was turned back on Feb. 15 and operated for over 24 continuous hours through Feb.16. Currently, the CATS laser is off in preparation for the Progress docking on Feb. 17, but will be turned back on around 18:00 UTC on Feb. 17. 23)

• Feb. 11, 2015: SpaceX's Dragon spacecraft departed the space station with 1676 kg of science cargo Feb. 10, 2015, for a 7:44 p.m. EST (Feb. 11, 2015 for a 00:44 UTC) parachute-assisted splashdown in the Pacific, 259 miles southwest of Long Beach, California. 24)

- The Dragon spacecraft will be taken by ship to Long Beach, where some cargo will be removed and returned to NASA. Dragon will then be prepared for a return trip to SpaceX's test facility in McGregor, Texas, for processing.

- Among the returned investigations were printed parts and hardware from the first technology demonstration of 3-D printing in space. The 3-D printer demonstration used relatively low-temperature plastic feedstock on the space station. The test phase ended with a printed ratchet wrench made with a design file transmitted from Earth to the printer.

- Dragon also returned samples, hardware and data from several biology and biotechnology studies performed on the station. The Advancing Membrane Protein Crystallization by Using Microgravity investigation explored the production of high-quality crystals of the cystic fibrosis protein and other closely related proteins. Because many medically relevant proteins are difficult to crystallize on Earth, researchers attempt to grow them in space to help determine their shape and structure with the hope of improving drug therapies for cystic fibrosis, a genetic disorder that causes severe damage to the lungs and digestive system.

• Feb. 5, 2015: Ground controllers sent commands to enable the laser as part of the CATS checkout procedure. Previously, laser firing attempts were disabled due to the payload experiencing multiple occurrences of resets in a controller card. CATS operations have resumed. 25)

• On Jan. 22, 2015, robotic flight controllers successfully installed NASA's CATS (Cloud Aerosol Transport System) on the exterior of the ISS through a robotic handoff — the first time one robotic arm on station has worked in concert with a second robotic arm. CATS will collect data about clouds, volcanic ash plumes and tiny airborne particles that can help improve our understanding of aerosol and cloud interactions and improve the accuracy of climate change models. 26)

- CATS had been mounted inside the SpaceX Dragon cargo craft's unpressurized trunk since it docked at the station on Jan. 12, 2015. Ground controllers at NASA/JSC (Johnson Space Center) in Houston used one of the space station's robotic arms, namely Dextre (Special Purpose Dexterous Manipulator), to extract the instrument from the capsule. The NASA-controlled arm passed the instrument to a second robotic arm — like passing a baton in a relay race. This second arm, the JEM/RMS (Japanese Experiment Module/ Remote Manipulator System), was controlled by JAXA (Japanese Aerospace Exploration Agency). The Japanese-controlled arm installed the instrument to the Space Station's Japanese Experiment Module, making CATS the first NASA-developed payload to fly on the Japanese module.

- After installation, CATS was powered on and is currently sending health and status data back to NASA/GSFC (Goddard Space Flight Center) in Greenbelt, Maryland, where the instrument's data will be analyzed, as the team begins their checkout procedures.


Figure 23: The Japanese robotic arm installed the CATS experiment assembly on the JEM/Kibo-EF (Exposed Facility). The SpaceX Dragon commercial cargo craft can be seen at the right center of the image (image credit: NASA TV)

• On Jan. 12, 2015, the CRS-5 Dragon capsule of SpaceX was captured by the crew aboard the ISS. Dragon was successfully berthed and bolted to the station's Harmony module a few hours later. Working at the robotics work station inside the seven windowed domed cupola, Expedition 42 Commander Barry "Butch" Wilmore of NASA, with the assistance of Flight Engineer Samantha Cristoforetti of ESA, successfully captured the Dragon spacecraft with the station's Canadian-built robotic arm at 10:54 UTC. 27)


Figure 24: The Canadarm2 has the SpaceX Dragon in its grips on Jan 12, 2015 (image credit: NASA TV)



Post-launch flight test 5 of SpaceX:

Aiming to one day radically change the future of the rocket business, SpaceX CEO Elon Musk has a bold vision unlike any other in a historic attempt to recover and reuse rockets set for the CRS-5 flight with the goal of dramatically reducing the enormous costs of launching anything into space. Towards the bold vision of rocket reusability, SpaceX dispatched the "autonomous spaceport drone ship" sailing at sea towards a point where Musk hopes it will serve as an ocean going landing platform for the first stage of his firms Falcon -9 rocket after it concludes its launch phase to the ISS (International Space Station). 28)

No one has ever tried such a landing attempt before in the ocean says SpaceX. The company has conducted numerous successful soft landing tests on land. And several soft touchdowns on the ocean's surface. But never before on a barge of size 90 m x 50 m, a floating platform in the ocean. The 18 m wide span of the rocket landing legs must not only land within the 50 m wide barge deck, but must also deal with large ocean swell and GPS errors. The fifth flight of the over-ocean controlled descent test series will be the first orbital flight to test the grid fin aerodynamic control surfaces that were previously tested in a low-altitude, low-speed test flight on the F9R Dev1 prototype vehicle earlier in 2014. The grid fins, plus gimbaling the engines, are projected to improve the landing accuracy to 10 m. — However, the absolute overriding goal of the CRS-5 mission is to safely deliver NASA's contracted cargo to the ISS.

In the CRS-5 (Commercial Resupply Service-5) flight, SpaceX will attempt a precision landing of a Falcon-9 first stage for the first time, on a custom-built ocean platform known as the autonomous spaceport drone ship. While SpaceX has already demonstrated two successful soft water landings, executing a precision landing on an unanchored ocean platform is significantly more challenging. 29)

The odds of success are not great — perhaps 50% at best. However this test represents the first in a series of similar tests that will ultimately deliver a fully reusable Falcon 9 first stage. Returning anything from space is a challenge, but returning a Falcon-9 first stage for a precision landing presents a number of additional hurdles. At 14 stories tall and traveling upwards of 1300 m/s, stabilizing the Falcon-9 first stage for reentry is like trying to balance a rubber broomstick on your hand in the middle of a wind storm.

To help stabilize the stage and to reduce its speed, SpaceX relights the engines for a series of three burns. The first burn—the boostback burn—adjusts the impact point of the vehicle and is followed by the supersonic retro propulsion burn that, along with the drag of the atmosphere, slows the vehicle's speed from 1300 m/s to about 250 m/s. The final burn is the landing burn, during which the legs deploy and the vehicle's speed is further reduced to around 2 m/s.

To complicate matters further, the landing site is limited in size and not entirely stationary. The autonomous spaceport drone ship is 90 m x 30 m, with wings that extend its width to ~50 m. While that may sound huge at first, to a Falcon-9 first stage coming from space, it seems very small. The legspan of the Falcon-9 first stage is about 18 m and while the ship is equipped with powerful thrusters to help it stay in place, it is not actually anchored, so finding the bullseye becomes particularly tricky. During previous attempts, SpaceX could only expect a landing accuracy of within 10 km. For this attempt, SpaceX is targeting a landing accuracy of within 10 m.



Figure 25: SpaceX Falcon-9 first stage rocket will attempt a precision landing on this autonomous spaceport drone ship, out at sea, soon after launch of the CRS-5 mission (image credit: SpaceX)

A key upgrade to enable precision targeting of the Falcon-9 all the way to touchdown is the addition of four hypersonic grid fins placed in an X-wing configuration around the vehicle, stowed on ascent and deployed on reentry to control the stage's lift vector. Each fin moves independently for roll, pitch and yaw, and combined with the engine gimbaling, will allow for precision landing – first on the autonomous spaceport drone ship, and eventually on land.


Figure 26: Illustration of the deployed hypersonic grid fins on the Falcon-9 first stage (image credit: SpaceX)

The attempt to recover the first stage will begin after stage separation, once the Dragon spacecraft is safely on its way to orbit. The concept of landing a rocket on an ocean platform has been around for decades but it has never been attempted. Though the probability of success on this test is low, SpaceX expects to gather critical data to support future landing testing.

A fully and rapidly reusable rocket — which has never been done before — is the pivotal breakthrough needed to substantially reduce the cost of space access. While most rockets are designed to burn up on reentry, SpaceX is building rockets that not only withstand reentry, but also land safely on Earth to be refueled and fly again. Over the next year, SpaceX has at least a dozen launches planned with a number of additional testing opportunities. Given what we know today, The SpaceX team believes it is quite likely that with one of those flights we will not only be able to land a Falcon 9 first stage, but also re-fly the first stage.


First stage landing:

SpaceX CEO Elon Musk reported that huge strides towards [rocket] reusability were achieved, following the flawless launch of his firms Falcon 9 rocket on a critical resupply mission to the space station for NASA, which also had a secondary objective of recovering the boosters first stage via an unprecedented precision guided landing on an ocean-going "drone." 30)

Despite making a ‘hard landing' on the vessel dubbed the ‘autonomous spaceport drone ship,' the 42 m tall Falcon 9 first stage did make it to the drone ship, positioned some 200 miles offshore of the Florida-Carolina coast, northeast of the launch site in the Atlantic Ocean. The rocket broke into pieces upon hitting the barge.

The drone ship, along with pieces of the rocket, was towed back to the Port of Jacksonville, FL, in the afternoon of Jan. 11.


Figure 27: The SpaceX ‘autonomous spaceport drone ship' being towed into the Port of Jacksonville, FL on the St. Johns River, on 11 Jan 2015 with possible pieces of the SpaceX Falcon 9 first stage under tarps (image credit: Spaceflight Now) 31)

Engineers plan to add more hydraulic fluid to the rocket for an upcoming launch, which will try to perform the recovery experiment again. If SpaceX succeeds, engineers will inspect the rocket to see what work is required to refurbish for another flight. The ultimate goal is to make the Falcon 9 rocket reusable, an achievement SpaceX says would reduce the cost of space launches.

• On January 16, 2015, SpaceX released new photos (Figure 28) and video of the daring and mostly successful attempt by Space X to land their Falcon 9 booster on an ocean-going drone ship. 32)

- The history making attempt at recovering the Falcon 9 first stage was a first of its kind experiment to accomplish a pinpoint soft landing of a rocket onto a miniscule platform at sea using a rocket assisted descent by the first stage Merlin engines aided by steering fins.

- Prior to the landing attempt, the first stage Falcon 9 booster ran out of hydraulic fluid and thus hit the barge.


Figure 28: Photo of the descending rocket hitting hard at an angle of ~45º, smashing legs and engine section (image credit: SpaceX, Elon Musk)


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12) "SpaceX CRS -5Mission Press Kit," SpaceX NASA, December 2014, URL:

13) Ken Kremer, "SpaceX Successfully Launches Cargo Ship to Station and Hard Lands Rocket on Drone Ship," Universe Today, Jan. 10, 2015, URL:

14) Ken Kremer, "SpaceX Launch and Historic Landing Attempt Reset to Jan. 10," Universe Today, January 9, 2015, URL:

15) Ken Kremer, "Student Scientists Get Second Chance to Fly Experiments to ISS Aboard Falcon 9 After Antares Loss," Universe Today, Jan. 6, 2014, URL:

16) Julie A. Robinson, William L. Stefanov,"Earth Science Research on the International Space Station," Committee on Earth Science and Applications from Space (CESAS) Space Studies Board National Academies of Science, Engineering, Medicine, 29 March 2016, URL:

17) "CATS Images of the Week," NASA, April 28, 2016, URL:

18) "Aerosols over Africa," NASA, CATS image of the week, released on March 3, 2016, URL:

19) "Nighttime View of the Raung Volcanic Plume," NASA Earth Observatory, July 25, 2015, URL:


21) "CATS Status Update," NASA, March 12, 2015, URL:

22) Kate Ramsayer, "Africa, From a CATS Point of View," NASA, Feb. 26, 2015, URL:

23) "CATS status update," NASA, Feb. 16, 2015, URL:

24) Joshua Buck, Dan Huot, "Critical NASA Science Returns to Earth aboard SpaceX Dragon Spacecraft," NASA, Release 15-019, Feb. 10, 2015, URL:

25) "ISS Daily Summary Report," NASA, Feb. 5, 2015, URL:

26) Kasha Patel, "NASA's CATS Installed on ISS by Robotic Handoff ," NASA, January 23, 2015, URL:

27) Ken Kremer, "SpaceX Dragon Captured at Station Loaded with Critical Supplies and Science," Universe Today, January 12, 2015, URL:

28) Ken Kremer, "Drone Ship at Sea Preparing for Bold SpaceX Rocket Recovery Landing Attempt," Universe Today, Jan. 05, 2015, URL:

29) "X marks the spot: Falcon 9 attempts ocean platform landing," SpaceX. Dec. 16, 2014, URL:

30) Ken Kremer, "Huge Rocket Recovery Strides Accomplished, SpaceX Drone Ship Back in Port," Universe Today, Jan. 11, 2015, URL:

31) Stephen Clark, "Photos: SpaceX's rocket landing platform back in port," Spaceflight Now, Jan. 11, 2015, URL:

32) Ken Kremer, "Elon Musk Releases Dramatic Imagery of Mostly Successful Falcon 9 1st Recovery Attempt, Hard Landing on Drone Ship," Universe Today, Jan. 16, 2015, URL:

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 (

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