KOMPSAT-2 (Korea Multi-Purpose Satellite-2) / Arirang-2
KOMPSAT-2 (also referred to as Arirang-2 by South Korea) was developed by KARI (Korea Aerospace Research Institute) to continue the observation program of the KOMPSAT-1 mission. The main mission objectives of the KOMPSAT-2 are to provide a surveillance capability for large-scale disasters by acquiring high-resolution imagery for GIS (Geographic Information Systems) applications. 1) 2) 3) 4) 5) 6)
Figure 1: Artist's rendition of the KOMPSAT-2 spacecraft (image credit: KARI)
The spacecraft design is based on the KOMPSAT-1 heritage making extensive use of existing hardware, software, tools, and facilities; it allows parallel integration of the payload, equipment, and propulsion modules. The KOMPSAT-2 bus structure consists of the five modules: SMS (Structure and Mechanisms Subsystem), TCS (Thermal ConTrol Subsystem), AOCS (Attitude and Orbit Control Subsystem), TC&R (Telemetry Command and Ranging) subsystem, EPS (Electrical Power Subsystem), PS (Propulsion Subsystem), and the FSW (Flight Software) element.
The AOCS provides three-axis stabilization (3-axis control with zero momentum bias system) with high accuracy for roll, pitch and yaw pointing. Star trackers, gyro reference assemblies, three-axis magnetometers, magnetic torquers and reaction wheels are used for attitude sensing and control. The pointing accuracy is < 0.025º in roll and pitch, and 0.08º in yaw. The pointing knowledge is 0.020º in roll and pitch, and 0.045º in yaw. The spacecraft platform offers a cross-track body-pointing capability through roll maneuvers (up to ±45º). The propulsion subsystem makes use of re-used components (hydrazine monopropellant thrusters with blowdown pressure-feed system, 73 kg propellant). 7) 8) 9)
Figure 2: Configuration of the KOMPSAT-2 spacecraft (image credit: KARI)
Figure 3: Block diagram of the AOCS with the various elements of the system (image credit: KARI)
A MIL-STD-1553B data bus interfaces most of the spacecraft bus and payload to the onboard computer (monitoring and control). A GPS receiver (Topstar 3000 of Alcatel) provides the onboard time, satellite position and velocity. 10) 11)
The spacecraft mass is 800 kg (including propellant), the S/C size is hexagonal: 1.85 m diameter x 2.6 m in height (6.8 m length in deployed configuration), the power is 955 W (EOL) provided by two solar arrays (GaAs cell technology). A super NiCd battery has a capacity of 30 Ah for eclipse phase support. The S/C design life is three years. EADS Astrium has been selected by KARI to support the platform development and manufacture of KOMPSAT-2.
Figure 4: Schematic illustration of KOMPSAT-2 elements (image credit: KARI)
Figure 5: The KOMPSAT-2 spacecraft in test phase (image credit: KARI)
Figure 6: Illustration of the OBC (image credit: KARI)
Figure 7: Illustration of the transponder (image credit: KARI)
Launch: The KOMPSAT-2 spacecraft was launched on July 28, 2006 with a Rockot-KM launch vehicle of Eurockot Launch Services from the Plesetsk Cosmodrome, Russia. 12)
Orbit: Sun-synchronous circular orbit, altitude = 685 km, inclination = 98.13º, period = 98.46 min, the mean local time of the ascending node is at 10:50 hours. Repeat cycle = 28 days. The KOMPSAT-2 orbit is identical to that of KOMPSAT-1 but with a different phase (180º apart).
RF communications: Onboard storage capacity of 96 Gbit (BOL) and 64 Gbit (EOL) for image data. S-band (TT&C) and X-band (payload data at 8.205 GHz downlink frequency) communications are provided for all data transmission to the ground (real-time and playback), the downlink data rate is 320 Mbit/s (QPSK modulation). Encryption of image data. The CCSDS communication protocols are implemented. The S-band data rates are: 2 kbit/s uplink and 1.5 Mbit/s downlink.
• The KOMPSAT-2/Arirang-2 mission is operational in January 2017 in its 11th year on orbit. 13)
Figure 8: KOMPSAT-2 image of a rural region near Lawrence, Kansas, USA, acquired on May 13th, 2016 (image credit: SIIS, KARI)
• The KOMPSAT-2 mission is operational in March 2016 and will be continued to the end of its lifetime for experimentation. There is still more than 40 kg of fuel onboard (initial value 72.5 kg), enough power margin, and no outstanding anomaly. 14)
• In October 2015, the MSIP (Ministry of Science, ICT and Future Planning) and KARI made plans about the future of the KOMPSAT-2 mission which is on orbit for more than 9 years. It was decided not to extend the KOMPSAT-2 mission any further for systematic observation services, but instead use it for research purposes until the end of its life cycle. Although KOMPSAT-2 was originally designed to have a life cycle of 3 years, this was extended three times (by two years each time, for a total of 6 years) by applying highly reliable satellite technology. As such, KOMPSAT-2 has successfully carried out its mission of obtaining images of the Korean Peninsula and other major areas of the world over a period of nine years. 15)
- From now on, KOMPSAT-2 will be used in next-generation satellite technology research without any further extension of its mission until the end of its life cycle, as its operation systems - such as its payload module, sensor, and earth station operation system (command transmission and satellite condition analysis) - are aged.
- KOMPSAT-2 was a milestone, since the basis for the development of Korean model was established and the foundation of space industrialization was laid by investing KRW (Korean Won) 263.3 billion from 1999 to 2006 to secure the design, fabrication, assembly, and testing capability led by Korean technology based on the experience in the joint international development of KOMPSAT-1.
- The satellite was designed and fabricated jointly by KARI and 29 Korean companies, while the payload was jointly developed with ELOP in Israel (20 technical professionals dispatched during 4 years).
- The development of KOMPSAT-2 resulted in 91.5% self-sufficiency (54 out of 59 key technologies secured) in terms of satellite design and 65.2% self-sufficiency (30 out of 46 key technologies secured) in satellite parts fabrication, thereby establishing the basis for Korean self-sufficiency in the space technology sector.
- By developing KOMPSAT-2, Korea became the 7th country in the world to own a 1m class high- resolution satellite, and successfully established a strategic milestone for cooperation and the sharing of satellite information.
- Over the past 9 years, KOMPSAT-2 has orbited the Earth some 46,800 times and communicated with the Earth around 26,000 times. It has acquired 75,400 images of Korea and 2,448,300 images of the rest of the world, thus playing a key role in building up the nation's image assets.
- Until mission end, KOMPSAT-2 will continue to operate alongside the other Korean satellites, KOMPSAT-3 (launched in May 2012), KOMPSAT-5 (launched in August 2013) and KOMPSAT-3A (launched in March 2015), all of which are currently in operation, in an effort to fulfill the demand for national satellite utilization. The MSIP plans are to support key technologies for the application in the private sector and to promote the relevant industries.
• The KOMPSAT-2 mission is operational in 2015.
Figure 9 was released by ESA on January 16, 2015 showing a portion of the shoreline of the Caspian Sea. The Caspian Sea is the largest landlocked water body in the world, with a surface area of 371 000 km2. It is bounded to the northeast by Kazakhstan, to the northwest by Russia, to the west by Azerbaijan, to the south by Iran, and to the southeast by Turkmenistan. The shallow northern section of the Sea has an average depth of about 5–6 m, although it fluctuates depending on variations in river flow and wind-driven currents. The water appears green in this image, indicating an algal bloom. 16)
- Caused by heightened levels of phosphorus – found in fertilizers, detergents and unfiltered sewage – finding its way into the water, these blooms deplete the amount of oxygen in the water. This causes a reduction in aquatic life and poses a threat to rich fisheries: the Caspian Sea is an important site for sturgeon, which yield roe (eggs) that are processed into caviar.
- The mineral-rich land of Kazakhstan's Mangistau region is visible along the bottom of the image. With large fossil fuel reserves and an abundant supply of other minerals and metals, Mangistau is sometimes called the ‘treasure peninsula' of Kazakhstan.
Figure 9: The shoreline of the northeastern Caspian Sea as acquired by KOMPSAT-2 on Sept. 26, 2012 (image credit: KARI, ESA)
• Nov. 28, 2014: Peru's Quelccaya glacier, located in the Cordillera Oriental of the Peruvian Andes (Figure 10), has been shrinking due to rising temperatures in the region, losing over 20% of its area since the 1970s. Downstream communities rely on this water source for drinking and electricity in this dry region, but some estimates show that the ice cap will vanish in a matter of decades, draining the water supply for millions of people. 17)
Figure 10: Peru's Quelccaya ice cap, the largest in the Tropics, acquired with KOMPSAT-2 on June 29, 2009 (image credit: KARI, ESA)
Legend to Figure 10: In the far upper-left corner of the image, one can see the Qori Kalis Glacier, the ice cap's main outlet. This glacier is retreating – and this retreat has accelerated in recent years – losing about 50% of its total length since the 1960s. As a result of the glacier's melting, a lake began to form in late 1980s and has grown over the years. -Other smaller lakes have also formed around the ice cap. Meltwater lakes are generally lighter in color through the presence of fine particles produced by the grinding of the ice over bedrock – called ‘rock flour'. When this ‘flour' turns the water white or cloudy, it is referred to as ‘glacial milk'. The false-color of this image makes vegetation appear bright red, and we can clearly see how vegetation grows mainly in the valleys and along the paths of water runoff.
• October 31, 2014: Egmont National Park on New Zealand's North Island is pictured in this satellite image of Figure 11. National parks protect forested areas from human activities that cause land degradation and deforestation. The boundary between protected and non-protected areas is often very clear in satellite images – as we see here between the green, densely forested area and surrounding agricultural landscape. 18)
The land here was first formally protected in 1881, within a 9.6 km radius of the mountain summit. With high rainfall and a mild coastal climate, the park is home to a lush rainforest, with some plants unique to the park. Halfway up the mountain slopes, the forest is sometimes called the ‘Goblin Forest' for its gnarled trees and thick moss.
The mountain at the center of the national park has two names: Mount Egmont and Mount Taranaki. Taranaki is the original name given by the indigenous Māori people, while the name Egmont was given by British explorer James Cook after John Perceval, 2nd Earl of Egmont in 1770. Many places in New Zealand have official dual names or, as in this case, alternate names in the original Māori and English (following colonization by the British).
The mountain is considered an active volcano, although it has been dormant for over 150 years.
Figure 11: KOMPSAT-2 image of the Egmont National Park, New Zealand, acquired on March 6, 2013 (image credit: KARI, ESA)
• October 10, 2014: The image of Figure 12, shows an area in the southern Darfur region of Sudan (Africa), just south of the city of Nyala. The Wadi Nyala flows diagonally across the image, surrounded by agricultural plots. To the north, we can see the straight line of the railway. The city of Nyala to the northwest (not pictured) was formerly a nomadic camp, but experienced a boom in commercial activity with the arrival of the railway in the 1950s. The population further increased as people moved to the town during times of drought and conflict. 19)
Satellite images can assist in identifying water resources and aid the sustainable growth of urban areas. During conflict, they can also be used to find suitable locations for refugee camps by identifying where water and other resources are available, and suitable terrain. In the upper-left section of Figure 12, one can see thousands of small structures of the Kalma camp, housing tens of thousands of internally displaced people who have fled the Darfur conflict.
As the war in Darfur continues, so do the hardships in the camp. Kalma saw a recent outbreak in hepatitis, claiming an estimated 150 lives and infecting another 500 people. Last month, violence broke out between security forces and camp residents protesting raids by government forces. A number of protesters were killed in the skirmish.
Figure 12: KOMPSAT-2 image of Southern Dardur, Sudan, acquired on Feb. 8, 2013, and featured in ESA's Earth from Space program (image credit: KARI, ESA)
• July 18, 2014: The KOMPSAT-2 image of Figure 13, released on July 18, 2014 in ESA's 'image of the week series', shows the eastern part of Mexico City. The area pictured lies within central Mexico's highlands plateau, called the Valley of Mexico. This valley (minimum altitude of 2000 m) was originally covered by the waters of Lake Texcoco, but over the centuries the water has been drained. The area that has not been built up is today used for hydraulic management and is made up of reservoirs and ponds such as the large, dark Nabor Carrillo lake pictured here. 20) 21)
The area receives more than 100 000 migratory birds each year that travel through the Central Migratory Flyway, and is a key resting, feeding and breeding ground for several species of shorebirds.
In contrast to the open space of the former Lake Texcoco, Mexico City is a densely populated metropolitan area (left and bottom). One can in in Figure 13 see the runways of the international airport on the far left. South of the airport is the Alameda Oriente recreational park with its somewhat spiral artificial lake. North of the airport, El bosque de San Juan de Aragón is another park and important green area.
City parks play a large role in the city's effort to alleviate air pollution. In the early 1990s, pollution was believed to cause hundreds of deaths each year. Air quality has improved in recent decades through a series of government efforts to cut emissions.
Figure 13: Image of the eastern part of Mexico City, Mexico, acquired by KOMPSAT-2 on December 21, 2012 (image credit: KARI, ESA)
• June 19, 2014: The KOMPSAT-2 image of Figure 14, released on June 19, 2014 in ESA's 'image of the week series', shows southeast Iran's Dasht-e Lut salt desert. The desert is often called the ‘hottest place on Earth' as satellites measured record surface temperatures there for several years. The highest land surface temperature ever recorded was in the Lut Desert in 2005 at 70.7ºC, as measured by NASA's Aqua satellite. 22)
The area pictured is surrounded by salt flats, visible on the left side of the image. The ridges dominating the image extend about 125 km.
Figure 14: Wind-carved ridges and furrows in southeast Iran's Dasht-e Lut salt desert, this image was acquired on Nov. 4, 2011 (image credit: KARI, ESA)
• June 5, 2014: The image from the Kompsat-2 satellite (Figure 15), acquired on January 9, 2011, shows islands of the Haa Alif Atoll in northern Maldive archipelago in the Indian Ocean. The Haa Alif Atoll contains 43 islands, 14 of which are inhabited and classified as 'island-class' constituencies. The Maldives are a member of the Alliance of Small Island States, they are one of the world's most vulnerable nations to the effects of climate change. 23)
As 2014 is the UN-designated International Year of Small Island Developing States, this year's theme focuses on the effects of climate change on small islands. Small islands and coastal areas are under threat from rising sea levels. An increase in global temperatures has accelerated the melting of glaciers and ice sheets. This influx of water together with thermal expansion is causing the global sea level to rise by about 3 mm a year.
‘Raise your voice, not the sea level' is the theme for today's World Environment Day.
Figure 15: The islands of the Haa Alif Atoll in the northern Maldives of the Indian Ocean, observed from KOMPSAT-2 (image credit: KARI, ESA)
• May 2014: The KOMPSAT-2 image of Figure 16 shows an area 13 km east of the city of Mafraq in northern Jordan. Sitting geologically between the Syrian Desert and the volcanic Hauran plateau, the area experiences a desert climate. The light-colored area in the image is the Zaatari Refugee Camp, measuring some 3 km across. Located just over 10 km from the border with Syria, the camp is currently home to over 100 000 people displaced by the conflict in the neighboring country. The image is featured in the ESA "Earth from Space video program" and was released on May 23, 2014. 24)
Figure 16: KOMPSAT-2 image of the Zaatari Refugee Camp, Jordan, acquired on June 5, 12013 (image credit: KARI, ESA)
• The KOMPSAT-2 spacecraft and its payload are operating nominally in 2014 (in its 8th year on orbit). Initially, the KOMPSAT-2 mission was planned to last for 3 years, but the operational life was extended already 3 times, as technical inspection proved it had no issues.
Figure 17: KOMPSAT-2 image of the Imja glacier in the Himalayas, acquired on January 14, 2013 (image credit: KARI, ESA)
Legend to Figure 17: The image,featured in the ESA 'Earth from Space video program', was release on March 14, 2014. It shows an area of the Himalaya mountain range in northeastern Nepal, about 8 km south of Mount Everest (not pictured). The range is also home to thousands of glaciers, including the Imja glacier in the upper-central part of this image. Studies have shown an increase in the rate of glacial retreat for Imja and many other glaciers in the region – and in the world. 25)
• In June and July 2013, the KOMPSAT-2 Data Processing and Calibration/Validation Team of KARI performed cross-calibrations of the KOMPSAT-2 MSC (Multi Spectral Camera) using satellite imagery taken by the EO-1/Hyperion instrument of NASA. In this study, the DN (Digital Number) value from each band of EO-1 Hyperion sensor, representing the spectral radiance at wavelength, was converted applying the Relative Response Function of MSC to the interpolated radiance from EO-1. 26)
Figure 18: Cross-calibration placement and numbering scheme (image credit: KARI)
This study was conducted in the following order as shown in Figure 18 : obtaining images; geometric correction; setting overlapping areas; calculating the mean DN of areas and radiance conversion factor of DN. The DN to radiance conversion factor of KOMPSAT-2 was calculated with the following formula, using the radiance converted from DN of KOMPSAT-2 and EO-1. The calculated factor was verified by applying SBAF to the radiance values measured with Landsat-7.
Legend to Figure 19: The city of Jeddah's seaport on Saudi Arabia's western coast is pictured in this image from the KOMPSAT-2 satellite, released on Feb. 7, 2014 on ESA's Earth from Space video program. The second largest city in the country, Jeddah has a population of over five million people. The city is a gateway to Islam's holiest city of Mecca, which lies about 60 km to the east, as well to the holy city of Medina, about 320 km north. Jeddah is also an important commercial hub, with its port located in the middle of an important shipping route between east and west. The Red Sea's coral reefs are visible off the coast. In fact, this is one of the few places along this coastline with a gap in the reef, enabling large vessels to approach the coast.
• KOMPSAT-2 is operational in 2013 (7th year on orbit) - and is expected to continue operations into the year 2014 (Ref. 30).
Figure 20: KOMPSAT-2 false color image of the Amazon river released on Oct. 18, 2013 and acquired on July 6, 2012 (image credit: KARI, ESA)
Legend to Figure 20: This KOMPSAT-2 image, featured on ESA's Earth from Space video program, shows the Amazon River in the heart of northern Brazil's rainforest. The false color makes land vegetation appear pink, while water appears green and dark blue. In the upper-right corner, we can see some sparse clouds. The shades of pink vary – the bolder color representing thick vegetation with lighter pink showing where trees were possibly cut down. In fact, in the upper-left portion of the image, there's a clear line between the two shades, showing where vegetation was cut. The white dots show man-made structures. With their unique view from space, Earth observation satellites have been instrumental in highlighting the vulnerability of the rainforests by documenting the scale of deforestation. 28)
About 70 km west of the area pictured is the city of Manaus – the capital of Amazonas state.
Figure 21: The 'treasure peninsula' of Kazakhstan (image credit: KARI, ESA)
Legend to Figure 21: This KOMPSAT-2 image was acquired on 24 November 2012 over southwestern Kazakhstan's Mangistau region east of the Caspian Sea. Along the top of the image we can see water and wetlands, with eroded areas at the top and on the right. The majority of the image is dominated by flatland covered with low-lying vegetation. The bright web of roads in the lower left section of the image is the Karakuduk oil field. The white squares in this ‘web' indicate where wells are located. One can also see buildings and other structures related to oil production. Kazakhstan – and in particular, the Mangistau oblast – has large fossil fuel reserves and an abundant supply of other minerals and metals. Because of this, Mangistau is sometimes called the ‘treasure peninsula' of Kazakhstan.
Figure 22: Rolling hills of farmland in the northwest United States are pictured in this image from the Kompsat-2 satellite, observed in Sept. 2012 (image credit: KARI, ESA)
Legend to Figure 22: The image was acquired over Washington state, the south and west areas of the image are in Walla Walla county, while the central-eastern-upper area is Columbia County. The area pictured is part of the Palouse region – an agricultural zone that mainly produces wheat and legumes. The rolling, picturesque landscape has sometimes been compared to Italy's Tuscany. Touchet River, known for its trout fishing, can been seen in the lower left. The diagonal line running next to the river is a road that connects the town of Prescott to the west to Waitsburg to the east. 29)
• In November 2012, KARI selected SI (Satrec Initiative) of Daejeon, Korea as the 'worldwide exclusive representative' for KOMPSAT imagery sales. This applies to imagery of KOMPSAT-2, -3 and -5 missions. KARI has chosen Satrec Initiative for its ability to develop international customers and data distribution network, as well as long experience in space industry. Satrec Initiative will deliver high quality image data to worldwide customers through collaboration with existing satellite operators, and in addition to that, building its own KOMPSAT data distribution network. 30)
• The KOMPSAT-2 spacecraft and its payload are operating nominally in 2012. The spacecraft is well past its design life of 3 years. 31)
Note: The follow-on KOMPSAT-3 (Arirang-3) mission was launched on May 17, 2012 from TNSC, Japan.
• The Namib Desert image of Figure 23, featured on the 'Earth from Space video program', was released by ESA on May 10, 2013, by ESA.
Figure 23: Korea's Kompsat-2 satellite captured this image over the sand seas of the Namib Desert (Africa) on 7 January 2012 (image credit: KARI, ESA)
Legend to Figure 23: The blue and white area is the dry river bed of the Tsauchab. Black dots of vegetation are concentrated close to the river's main route, while salt deposits appear bright white. Running through the river valley, a road connects Sossusvlei to the Sesriem settlement. At the road's 45th kilometer, seen at the lower-central part of the image, a white path shoots off and ends at a circular parking area at the base of a dune. This is Dune 45, a popular tourist stop on the way to and from Sossusvlei. In this image, there appears to be some shadow on the western side. From this we can deduce that the image was acquired during the late morning.
Figure 24: Sample image of Astana, Kazakhstan, observed with MSC (1 m Pan sharpened) on KOMPSAT-2 (image credit: KARI)
Figure 25: Sample image of Singapore, observed with MSC (1 m Pan sharpened) on KOMPSAT-2 (image credit: KARI) 32)
Figure 26: Uluru/Ayers Rock in the Australian outback, KOMPSAT-2 acquired this image on Sept.15, 2011 (image credit: ESA) 33)
• In January 2012, KOMPSAT-2 has been confirmed as an ESA Third Party Mission (TPM) for the next 2 years, and approved scientific users will have the possibility to order KOMPSAT-2 data from the archive up to a total of 3000 products. 34)
• In June 2011, an orbit correction maneuer was conducted to satisfy the POD (Precise Orbit Determination) accuracy requiresments of 2-3 m rms (1σ). 35)
• The KOMPSAT-2 spacecraft and its payload are operating nominally in 2011.
• The KOMPSAT-2 spacecraft and its payload are operating nominally in 2010. With a design life of 3 years, KOMPSAT-2 has successfully completed its nominal mission lifetime, and now its mission is extended for further services to the users. 36)
• Spot Image operates a multimission ground segment, referred to as HMA (Heterogeneous Mission Access), integrating SPOT seies missions (SPOT-4/ -5) along with FormoSat-2, KOMPSAT-2, and in the future also with Pleiades and SPOT-6/-7 (Astroterra) spacecraft data. 37)
Figure 27: Schematic view of HMA implementation at GEO-Information Services (formerly Spot Image), image credit: ESA
• KOMPSAT-2 is also an ESA TPM (Third Party Mission). In general KOMPSAT-2 observations over Europe shared between ESA (Cat-1 users) and Spot Image (commercial users). From 2008-2010 (and possibly beyond) ESA is offering the data for research and application development:
- Archived KOMPSAT-2 data since 2006 (on demand production)
- New KOMPSAT-2 data (on demand acquisition and production)
• The KOMPSAT-2 geometric accuracy verification was successfully evaluated from 2007 through 2008. The 121 test sites provided excellent condition for geometric verification due to its flat terrain and a very good grid infrastructure. 38) 39)
Figure 28: Pan-sharpened image of the government complex Putrajaya near Kuala Lumpur, Malaysia, April 2007 (image credit: KARI, SPOT Image distribution)
• KOMPSAT-2 completed its commissioning phase in late September 2006 and started its nominal operations phase in October 2006.
• In August, 2006, KOMPSAT-2 had provided its first images.
Figure 29: Sydney Olympic Park, Australia in Aug. 2006 (image credit: KARI, SPOT Image distribution)
• On Oct. 24, 2005, KARI has made Spot Image (France) exclusive distributor of imagery from the KOMPSAT-2 Earth observation satellite - except for customers from Korea, the United States, and the Middle East, which are being serviced by KAI Image Inc. of Korea.
Note: As of July 15, 2008, EADS's Astrium Services unit has acquired a majority stake (81%) in Spot Image (from CNES). - In January 2011, Astrium fully integrated Spot Image and Infoterra into the new GEO-Information business division. 40)
Sensor complement: (MSC)
MSC (Multi-Spectral Camera)
MSC is a joint development of KARI with ELOP (Electro Optics Industries Ltd. of Rehovot, Israel) and OHB-System, Bremen, Germany. The objective is to collect high-resolution panchromatic and multispectral imagery of the Earth's surface (simultaneous observation). ELOp of Elbit Systems refers to the camera as Uranus-MSC. 41)
MSC is an optoelectronic linear pushbroom instrument with a single nadir-pointing telescope. The Pan band has a spectral range of 500-900 nm, the four MS bands are in the 450-900 nm range. The GSD (Ground Sample Distance) of the Pan data is 1 m (GSD), the MS data has a GSD of 4 m. The swath width is 15 km. A FOR (Field of Regard) of ±30º in pitch and up to ±56º in the roll direction is provided through spacecraft body pointing. MSC has a duty cycle of 20%. 42) 43) 44) 45) 46) 47) 48) 49)
The EFL (Effective Focal Length) of the optics subsystem is 9000 mm for the Pan band, and 2250 mm for the MS bands.
Table 1: Overview of MSC performance parameters
The MSC consists of the following elements: EOS (Electro-Optical Subsystem), PDTS (Payload Data Transmission Subsystem), PMU (Payload Management Unit), and the interconnection harness.
• EOS itself comprises the optical module including optical components and optical structure, Pan FPA (Focal Plane Assembly), MS FPA, and two CEU (Camera Electronics Unit), CEU-Pan and CEU-MS. A Ritchey-Chretien telescope type with large aperture (60 cm diameter) is being used.
• PDTS consists of DCSU (Data Compression Storage Unit), DLS (Data Link System) including CCU (Channel Coding Unit), and QTX (QPSK Transmitter), and APS (Antenna Pointing System).
The PMU controls the overall MSC system, using dedicated communication channels (RS-422); it communicates with the spacecraft via the MIL-STD-1553B bus. MSC operations support includes programmable gain and offset to allow for in-flight adaptation of the instrument sensitivity to the landscape luminosity. Gains and offsets are selectable by command. In addition, MSC provides a calibration function. Actually, there are three different calibration functions: 1) the radiometric, 2) NUC (Non Uniformity Correction), and 3) the focus calibration function in order to use the image data accurately. 50) 51)
Figure 30: Block diagram of the MSC (image credit KARI)
Figure 31: Illustration of the MSC (image credit: KARI)
TDI (Time Delay Integration) techniques are being employed for panchromatic imagery up to level 32 to enhance the SNR and to support observations in low-light conditions. MSC features the support modes of a) automatic normal operation and b) of stereo imaging. The latter is being accomplished by the agility of the spacecraft, i.e. tilting the S/C either in roll (up to ±56º) and/or in pitch (up to ±30º).
The control parameters of MSC are:
• Line rate change: the CCD line rate can be changed in the range from 7100 to 2200 during stereo imaging to reduce the degradation of the imagery due to smear effects. Appropriate line rate setting is advantageous to minimize any degradation of the image quality.
• Gain and offset
• Number of sector for the recording of source data
• Compression ratio
• Encryption ratio
• Quantization table
Figure 32: Overview of MSC components (image credit: OHB-System)
Future: The KOMPSAT-3 project development started in 2004 at KARI for a projected launch in 2011 (Note: KOMSAT-3 was launched on May 17, 2012). The optical imager on this satellite will have a GSD (Ground Sample Distance) of 0.7 m.
Figure 33: Elop's MSC payload on KOMPSAT-2 (image credit: Tel Aviv University) 52)
Ground segment of KOMPSAT-2
Mission operations are performed at KMOC (Korea Aerospace Research Institute Mission Operation Center). The KGS (KOMPSAT Ground Station) is located at KARI, Daejeon, South Korea. In addition, there is a second ground station at ETRI (Electronics and Telecommunications Research Institute) in South Korea. Each site is comprised of MCE (Mission Control Element) and IRPE (Image Reception and Processing Element). MCE monitors and controls the satellite and provides mission planning. Mission control provides also operational orbit determination/prediction and the POD (Precise Orbit Determination) function. 53) 54) 55)
In the meantime, the KOMPSAT ground segment has become multi-mission facility to accommodate also the operations requirements of the future missions under development, namely KOMPSAT-5 (SAR payload, launch in late 2010) and KOMPSAT-3 (optical payload, launch in 2011). The final goal of multi-satellite operations is to reduce the operational cost while concurrently maximize the operational stability ensuring the safety of satellite and operational efficiency, i.e. do more with less. 56)
Figure 34: Architecture and operational flow of the MCE (Mission Control Element), image credit: KARI
Figure 35: The European ground segment of KOMPSAT-2 (image credit: SPOT Image) 57)
The MCE system consists of five subsystems:
- TTC (Tracking, Telemetry and Command Subsystem). TTC provides the S-band uplink and downlink communications interface with satellite, CCSDS command and telemetry processing and tracking capabilities.
- SOS (Satellite Operations Subsystem). SOS provides spacecraft command generation and execution, satellite state of health monitoring and housekeeping telemetry data processing. Use of TMAS (Telemetry Monitoring and Analysis System). 58)
- MPS (Mission Planning Subsystem). MPS provides satellite mission planning, incorporates user requests, prepares bus operation parameter including bus activity, defines and manages the configurations of the satellite, and prepares operating schedules. MPS is also referred to as MAPS (Mission Planning and Analysis Subsystem).
- FDS (Flight Dynamics Subsystem). FDS provides satellite flight dynamics operation support functions such as orbit determination, orbit prediction, and antenna pointing data generation for satellite tracking.
- SIM (Satellite Simulator Subsystem). SIM provides support functions rather than direct operational function such as anomaly resolution support and operating personnel training.
TMAS (Telemetry Monitoring and Analysis System): KARI developed TMAS capable of performing such tasks as telemetry processing, trend analysis and reporting activities automatically. This automation scheme considerably reduces the operational cost by eliminating many repetitive processes and allows operators to concentrate on special situations which require human intervention. The key functions of TMAS are as following: (Ref. 58)
- Telemetry receiving and archiving in accordance with contact schedule
- Telemetry limit violation check
- Trend Analysis based on the computation of daily statistics
- Report files generation and distribution to the MOT and the related engineering staff.
TMAS is composed of a common module and a mission-unique module. The common module includes the connection module, analysis module and report module. The mission-unique module includes the parsing module that consists of the database and the processing algorithm in accordance with the mission-unique processing scheme.
Figure 36: Architecture of TMAS (image credit: KARI)
The modular implementation of TMAS permits also the support of future missions such as KOMPSAT-5 and KOMPSAT-3, which are scheduled to be launched in 2010 and 2011, respectively.
MAPS predicts satellite orbital events that affect the satellite mission operations and generates a conflict-free pass plan of the satellite operations. MAPS was designed to make a plan of up to 20 imaging request per day. Since KARI contracted with SPOT Image in 1 June 2007, the amount of imaging acquisition requests has been on the increase. In order to meet the demands of lots of satellite mission planning activities, KARI developed a software called MPVS (Mission Planning Verification System) that is capable of verifying the results of mission planning. The development of MPVS is aimed at reducing operation risk and increase the efficiency of operations. 59)
The key functions of MPVS are aimed at verification about mission planning and command planning results created by MAPS. MPVS consists of the three main module, including: CSG (Contact Schedule Generation) module, MPV (Mission Planning Verification) module, and CPV (Command Planning Verification) module. The CSG module is to predict the ground contact time that is used for MPV and CPV. The MPV module is to verify the pass plan that is generated in the MAPS with the results of mission scheduling processing. The CPV module is to verify the command plan that will be uploaded to the satellite through SOS (Satellite Operations Subsystem).
Figure 37: Architecture of MPVS (Mission Planning Verification System), image credit: KARI
Contact schedule generation: MPVS requires the realistic and accurate ground contact time to check the constraints. The CSG module has the capability to generate the ground contact time considering several conditions such as the ground mask angle, operational limitations of the ground stations and the satellite. A user can flexibly configure the setup file in accordance with the change of operational condition concept. Figure 2 represents the architecture of CSG module.
Figure 38: Architecture of the CSG (Contact Schedule Generation) module (image credit: KARI)
MPV (Mission Planning Verification): KARI considers two basic mission planning activity types: One is named "Payload normal activity" that is related to the routine imaging activities. The other is named "Spacecraft activity" that includes all activities except for the routine imaging activities. For example, it includes the onboard data dump, ephemeris upload and orbit maneuver for the maintenance of satellite orbit, and parameter upload for the maintenance of payload. The automated verification using MPV is performed for the only "Payload normal activity" based on the SRF (Schedule Request File). The verification of "Spacecraft activity" can be done manually by users if needed.
Figure 39: Architecture of the MPV (Mission Planning Verification) module, image credit: KARI
FDS (Flight Dynamics Subsystem): The FDS supports operational orbit determination, precise orbit determination, precise orbit ephemeris generation, antenna pointing data generation, etc. KARI developed KOOPS (KOMPSAT's automated Operational Orbit Processing System) to support the various FDS tasks on a daily basis. KOOPS determines the orbit and evaluates its result using pre-defined criteria, and generates the orbit data automatically based on the execution schedule. The automated system integrates all of the components of several routine processes which are necessary for daily flight dynamics activities (Ref. 36).
The automation scheme in KOOPS, implemented for a multi-mission support, reduces considerably the operational risk and cost by eliminating many repetitive processes and allows engineers to concentrate on non-nominal situations which require human intervention. Additionally, the operational stability and efficiency of the flight dynamics supports are significantly enhanced.
Figure 40: Schematic view of KOOPS and its external elements (image credit: KARI)
• On the domestic scene (Korea) KAI Image Inc. is the commercial distributor of KOMPSAT-2 data. 60)
• SPOT Image S. A. (Toulouse, France) is the exclusive commercial distributor of KOMPSAT-2 imagery (except for customers in Korea, the United States and the Middle East) with data reception via its own acquisition stations.
Figure 41: Overview of ground segment data flow of KOMPSAT-2 (image credit: SPOT Image, Ref. 37)
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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 (email@example.com).