KazEOSat-1 (High Resolution Earth Observation Satellite), Kazakhstan
In 2009, EADS Astrium was selected by JSC (Joint-Stock Company «National Company «Kazakhstan Gharysh Sapary»), called the “Company” or simply KGS, charged with the development of Kazakhstan’s space program, on behalf of Kazcosmos (Kazakhstan National Space Agency) to develop an “Earth Observation Satellite System” consisting of two missions, namely a HR (High Resolution) and a MR (Medium Resolution) mission. KGS is a division of Kazcosmos, located in Astana, Kazakhstan. 1) 2)
The Company was created under the order of the Government of the Republic of Kazakhstan of March 17, 2005, No. 242 «About creation of the Joint-Stock Company «National Company «Kazcosmos» with the total share of the Government in the authorized capital. It was renamed on the basis of the order of the National space agency of the Republic of Kazakhstan on August 2, 2007, No. 32. 3)
The basic directions of the Company's activity are:
• participation in elaboration and realization of current, long-term inter-industrial programs in the field of space activity of the Republic of Kazakhstan
• implementation of space technologies directed onto solving social and economic problems of the Republic of Kazakhstan
• carrying out development activities in creation of space systems and complexes.
Figure 1: Photo of the KGS trainees at Astrium in Toulouse, France (image credit: KGS)
In October 2010, the partnership between Astrium and JSC NC Kazakhstan Gharysh Sapary (KGS), the national company charged with the development of Kazakhstan’s space program, has reached another major milestone with the signature of a contract for a Satellite Assembly, Integration and Test (AIT) Center in Astana. - Astrium and KGS signed the agreement during the visit of the President of the Republic of Kazakhstan, Mr Nazarbayev, to Paris on the 27th October, 2010. 8)
Under the contract Astrium will provide and install the various test equipment (mechanical, radiometric, thermal and acoustic facilities) at the new AIT Center. Astrium will also assist KGS in the construction of the AIT Center to ensure coordination with the test equipment. The signature follows a major contract signed in October 2009 by Astrium and KGS for the development of two Earth observation satellites.
The AIT Center will form part of the ‘Space City’ that the Kazakhstan space agency, Kazcosmos, is developing in Astana. The city will also include the ground segment for the two Astrium-built satellites, as well an administrative building and a museum dedicated to the country’s long space history.
The Earth observation system of the Republic of Kazakhstan is planned to reach an operational readiness by the end of 2014. 9)
The KazEOSat-1 spacecraft was built by Airbus Defence and Space (formerly Astrium SAS) of Toulouse, France. The spacecraft is based on the same product line as SPOT-6 and SPOT-7, and features the standard AstroSat-250 avionics. The hexagonal AstroSat-500 platform combines heritage with flexibility for customization. Through optimization of reuse, it helps to reduce program risk and to achieve reliable schedule and cost commitments. It ensures high quality and robustness due to continuous application of proven solutions and it guarantees continuity of engineering skills.
As part of the product line evolution, the HR satellite will be the first in the AstroSat HR family to be based on a gyroless attitude control scheme, i.e. accurate pointing and stability will be ensured through the sole use of new generation APS star trackers. 10)
Figure 2: Artist's rendition of the KazEOSat-1 spacecraft in orbit (image credit: EADS Astrium) 11)
The core of the AstroSat-250 electrical platform is the redundant OBC (On-Board Computer). The OBC includes processing, reconfiguration and timing functions while the complete I/O system is allocated in a separate physical unit, the RIU (Remote Interface Unit), which enables for mission customization. The backbone for the on-board communication is formed by two MIL-STD-1553 buses, one serving the platform one serving the payload. Optional SpaceWire interfaces allow for transmission of data at high rates between the OBC and e.g. special payloads.
The LEON3-FT (Fault Tolerant) microprocessor, namely the SCOC3 (Spacecraft Controller On-a- Chip), is being used as OBC. SCOC3 has been developed at EADS Astrium SAS; it is manufactured by Atmel.
A standard S-band TT&C system with full spherical coverage in uplink and downlink is used for satellite command reception and telemetry transmission. Ciphering functions are available either integrated within the OBC or in form of an add-on unit to the OBC called DCU (Data Control Unit).
Figure 3: Standard electrical architecture of the AstroSat-250 platform (image credit: EADS Astrium)
ADCS (Attitude Determination and Control Subsystem)): The enhanced 3-axis stabilization attitude control system is based on a set of 4 RW (Reaction Wheels) for fine-pointing with 3 MTQ (Magnetic Torquers) for off-loading. Actuation is provided by Astrium patented CMGs (Control Moment Gyros).
Attitude and orbit measurement is performed with a GPS and a Star Tracker (STR) for nominal operation, providing a pointing accuracy of up to 500 µrad (3σ) and a pointing knowledge of up to 30 µrad (3σ), depending mainly on STR accommodation and alignment accuracy. While standard precise attitude control is performed without the support of a gyro, an optional inertial measurement unit can be added for attitude control improvement. On-board orbit determination accuracies of < 10 m (1σ) are achieved, if the standard 1-frequency GPS design is applied. The 2-frequency GPS option provides on-board orbit determination accuracies of < 3 m (1σ).
Figure 4: Photo of the Hydra multiple head star tracker based on APS (CMOS) detector technology (image credit: EADS Sodern)
Safe mode attitude sensing is based on a Magnetometer (MAG) / Sun Sensor (BASS) system or optionally a Magnetometer / Coarse Earth Sun Sensor (CESS) system. This provides two optional Safe mode attitude control principles:
4) Sun oriented, magnetic field spin controlled, or
5) Earth oriented.
Propulsion system: A mono-propellant propulsion system (hydrazine) is implemented to allow for orbit maintenance and optionally for rapid rate damping during initial acquisition in case of the Earth oriented safe mode. Different tank sizes and thrusters configurations are available to cover specific mission needs.
Figure 5: Photo of the propulsion module (image credit: EADS Astrium)
EPS (Electrical Power Subsystem): The EPS is built around an unregulated 28 V Power Bus. GaAs triple junction solar cell based arrays, which are either composed of standard panels or have to be tailor designed to suit mission needs, are used for power generation. Power control and distribution functions are combined in the PCDU (Power Control and Distribution Unit).
For missions with a low power demand (~1200 W) and only slight variations in solar array illumination conditions, a standard PCDU with shunt regulation system is foreseen. Higher power demand can be satisfied with MPPT (Maximum Power Point Tracker) regulation based PCDU, which can be selected from a set of different peak power values. Sufficient FCLs and LCLs in different power classes are provided for platform and payload power distribution and protection. Furthermore, a comfortable amount of heater switches and redundant release actuators is available. Electrical energy is stored in Li-ion batteries, for which a large range of different capacities is available.
The AstroSat-250 software is based on a modular architecture with a standard mission and hardware independent core consisting of the RTEMS operating system and the Astrium CDHS (Core Data Handling System). A library of reusable hardware-and mission dependent software elements exists which can be used as basis for construction of individual mission customized software versions. The process of mission specific software customization and development is done in compliance with ECSS E-40 and Q-80.
An essential feature of AstroSat-250 is the robust standard FDIR (Failure Detection, Isolation and Recovery) concept, which is hierarchically structured and can easily be adapted to specific mission needs.
Payload data are being stored in Flash Memory technology based standard CoReCi (Compression Recording and Ciphering) units, available at various capacities ranging from 1 Tbit to ~ 10 Tbit. Options exist for inclusion of compression and encryption functions within the CoReCi. Several different standard algorithms are available for this purpose. 12)
Figure 6: Photo of the CoReCi system (image credit: EADS Astrium)
CoReCi implementation parameters for KazEOSat-1: 13)
- Modular architecture adaptable to various data rates and capacities
- Input data rate up to 1.4 Gbit/s
- Capacity 850 Gbit (EOL) with Flash technology
- Embedded Wavelet Image Compression with MRCPB algorithm
- Ciphering based on AES (Advanced Encryption Standard) algorithm with 127 x 128 bit ciphering keys
- Data Formatting according to CCSDS ESA Packet Telemetry Standard
- Instrument mass: 14 kg
- Power consumption 75 W during simultaneous data record / data compression / data replay.
CoReCi on SPOT-6 represents the first commercial use of Flash storage technology in an on-board PDHU (Payload Data Handling Unit).
RF communications: The standard for downlink of payload data is a 270 Mbit/s 2-channel cold redundant X- band. The data transmission system uses QPSK modulation. A single Isoflux antenna provides the necessary ground coverage. Optionally, other systems can be incorporated in case of higher downlink data rate needs. Encryption of downlink data can be implemented as option. A number of different basic mechanical standard configurations are available which can be used as foundation for mission customization in many typical applications. The TT&C data are transmitted in S-band.
Table 2: Main system parameters of KazEOSat-1
Figure 7: Photo of the KazEOSat-1 spacecraft in Astrium's clean room (image credit: Astrium SAS)
Figure 8: Photo of the assembled KazEOSat-1 spacecraft (image credit: Astrium SAS)
Launch: The KazEOSat-1 spacecraft was launched on April 30, 2014 (1:35:15 UTC) on a Vega vehicle (flight VV03) of Arianespace from the Guiana Space Center, French Guiana. Vega’s payload mass for this launch was 918 kg, of which 830 kg was the satellite. KazEOSat-1 was released into its designated orbit 55 minutes and 29 seconds after launch. 14) 15) 16)
Orbit: Sun-synchronous near-circular orbit, nominal altitude = 750 km, inclination = 98.54º, period = 100 minutes, LTDN (Local Time on Descending Node) = 10:30 hours.
• October 2014: The KazEOSat-1 mission is expected to be fully operational by the end of 2014.The main purposes of the high performance 1 m resolution system and the program in general are to provide the governmental and commercial users in Kazakhstan with regularly updated imagery of the country, and to build the national capability in design and development of satellites and ground segments for future missions through an extensive hands-on know-how technology transfer program. 17)
All the mission and system level requirements have been successfully verified during the 3 months of in orbit tests. The key mission requirements were:
- The in-orbit measured system end-to-end MTF minimum value across the field of view is more than 17%. Note that any higher system MTF would lead to noticeable aliasing artefacts, while the value of 17-20% may be considered optimal. The minimum SNRdiff over all CCD arrays is around 17, while in the standard L2 conditions the SNRL2 is above 140.
- Daily throughput capacity: 228, 000 km2 have been acquired and downlinked to the single ground station in Astana in 24 hours – the workplan was very close to the sizing scenario defined in the contractual specification. 100 stereo images taken in one day. 50 three-strip area images taken in one day.
- Geolocation accuracy: Approximately 1 m planimetric accuracy across the scene with ground control points. Better than 15 m (1D RMS) without ground control points.
- Low-light experiments: The large aperture diameter of the instrument and low levels of dark noise allows the use of the system at night time. Several images of the cities and towns at night have been taken and processed with in-house developed processing tools. It has been shown that useful imagery of a synthetic resolution of 5-20 m GSD can be produced even for relatively poorly illuminated areas. So the satellite can be used as one of the sources of high-resolution night time imagery.
• In July 2014, the KazEOSat-1 spacecraft completed the in-orbit test phase and reached operational readiness.
• May 2014: The KazEOSat-1 spacecraft is on orbit operating nominally. The spacecraft acquired the first images of Kazakhstan on May 5, 2014 (Figure 9). The commissioning phase of the KazEOSat-1 mission, performed by the joint Airbus DS and Kazakh team, will last for about 3 months during which the spacecraft is being operated from the launch control center in Toulouse, France. 18)
Figure 9: First image of Astana, the capital of Kazakhstan, acquired with KazEOSat-1 on May 5, 2014 with a 1 m resolution (image credit: KGS, Airbus DS)
Sensor complement: (NAOMI)
NAOMI (New AstroSat Optical Modular Instrument):
NAOMI is a high-resolution pushbroom imager designed and developed at Airbus DS (former EADS Astrium SAS): The instrument design is mainly driven by mission parameters and detector characteristics. The TDI (Time Delay Integration) mode in the Pan band enables to reduce the pupil size for a given GSD (Ground Sample Distance). The pupil diameter is no more sized to comply with SNR requirements which can be achieved by increasing the number of TDI stages and is only driven by the MTF (Modulation Transfer Function) requirement.
NAOMI 310 flight heritage: NAOMI is a copy of the imager flown on the AlSat-2 spacecraft of CNTS (Algerian National Space Technology Centre) with a launch on July 12, 2010; of SSOT of ACE (Agencia Chilena del Espacio - Chilean Space Agency) and the Chilean Air Force (FACh = Fuerza Aerea de Chile), Santiago, Chile with a launch on Dec. 17, 2011; VNREDSat-1A (Vietnam Natural Resources, Environment and Disaster-monitoring Satellite-1A) of STI-VAST (Vietnam) with a launch on May 7, 2013, and of SPOT-6 /-7, a commercial imaging constellation of Astrium's Geo-Information Services. The SPOT-6 spacecraft was launched on Sept. 9, 2012; the SPOT-7 spacecraft was launched on June 30, 2014. — However, unlike the previous missions the Korsch telescope for KazEOSat-1 had to be much bigger to comply with the performance requirements of KGS, namely ensuring the ground resolution of 1 m in panchromatic channel. One of the key requirements was the image quality formulated as MTF x SNRdiff > 2.8 at the end of the lifetime.
Figure 10: Photo of the NAOMI instrument for KazEOSat-1 (image credit: EADS Astrium)
The main building blocks of the instrument are: 19)
• A highly stable, light and compact telescope built in SiC material, with a simple thermal control.
• A focal plane, embedding TDI (Time Delay Integration) detector, a PAN CCD and four XS (multispectral) detectors equipped with strip filters and coupled with front end electronics. The TDI implementation exhibits an outstanding MTF (Modulation Transfer Function) service with an extremely low power consumption. This allows significantly loosening of optical requirements at the telescope level, while keeping the same overall optical quality at system level; in other words, the same optical quality can be reached from smaller and much lighter telescopes. Therefore more performance can be obtained from smaller satellites.
• Back-end electronics, including video Electronics, data storage and services adapted to the mission specifics. The modular video chains are capable of operating at different frequencies up to 15 Msample/s, so that the same hardware can be easily tuned to serve ground resolutions ranging from 0.5 m to say 10 m. The swath width can easily be adjusted by butting together several detectors and associated modular video chains, thus fulfilling the requirements of the most demanding customers.
The telescope is based on a Korsch combination, offering a simple, compact concept. The detector, space qualified, includes on the same die one TDI matrix of 7000 pixels for the panchromatic channel, and four lines of 1750 pixels for the multispectral bands. The detector exhibits excellent characteristics that significantly contribute to the instrument very high optical performance.
The optical assembly is based on a Korsch-type telescope including three aspheric mirrors and two folding mirrors.
Figure 11: Illustration of the optical concept of the Korsch telescope (image credit: EADS Astrium)
The detection chain is made of three main parts: the detectors, the Front End Electronics Module (F2EM) and the Video Electronics (MEV) which are part of the IEU (Imaging and Electronics Unit). The PAN + XS focal planes are the heart of the detection chain.
The focal plane is based on a customized high performance detector architecture developed by e2v for Astrium (proprietary architecture). It takes benefit of all the heritage and skills acquired in CCD architecture definition and in operating with the ultimate conditions of speed and performances. The result of this customization offers an unrivalled level of integration and performances. All the stringent constraints of dynamic range optimization and power consumption reduction have been mastered with less than 1 watt detector dissipation.
The Front-End Electronics Module (F2EM) encompasses all the functions to be implemented close to the detectors. Mounted inside the FPA (Focal Plane Assembly), it provides the detectors with all the necessary biasing and clocking signals and performs preamplification and transmission of the video signal to the MEV.
The MEV (Module Electronique Video) is the backend part of the NAOMI detection electronics. The MEV provides the F2EM with the primary power supplies and clocks necessary to front-end operation. The video signal from the F2EM is received, adapted and digitally converted to 12 bit in the MEV. The resulting data, rounded down to 10 useful bits, are then transmitted to the digital functions of the NIEU to be real-time processed and stored into the mass memory for further downlink.
Figure 12: PAN+XS focal plane architecture (image credit: EADS Astrium)
Figure 13: Overview of NAOMI detection chain (image credit: EADS Astrium)
The mission requirement of 1 m GSD in Pan has driven the diameter of the main mirror from 20 to 64 cm and the number of TDI stages to 8 . The FOR (Field of Regard) and the agility of the platform provides revisit of any area of the Republic of Kazakhstan within 3 days (Ref. 9).
Table 3: Specification of the NAOMI instrument
The same logic applies to the variable parameter of GSD in Table 3: The GSD is fixed for a particular mission (the ranges feature the values for different missions using a NAOMI instrument). For KazEOSat-1, the GSD for PAN = 1 m and for MS = 4 m.
Figure 14: Functional block diagram of the IEU including mass memory functions fitted to small platforms configuration (image credit: EADS Astrium)
Figure 15: NAOMI camera with three focal plane units:KazEOSat-1 instrument configuration (image credit: EADS Astrium)
Note: The image of Figure 15 corresponds not to the KazEOSat-1 FM of the NAOMI instrument; an updated image will be provided when available.
Mission: The KazEOSat-1 spacecraft is sun-pointing during portions of the sunlit orbit for power generation. The attitude is geocentric during imaging sessions (up to 35° off-nadir) and contacts with the ground segment. The maximum duration of imaging per orbit is 10 minutes, the average duration is 3 minutes. The maximum length of a strip imaging is 2000 km. The agility of the satellite allows performing one-pass 3-strip area and stereo imaging in one pass with the width of the synthetic mosaic scene of 60 km, and length 90 km, and stereo imaging (Ref. 9).
1) “Astrium signs major contract with Kazakhstan during President Sarkozy’s visit to Astana,” Oct. 6, 2009, URL:http://www.astrium.eads.net/node.php?articleid=3523
2) Dominique. Pawlak, Thomas Schirmann, “The New Generation of Astrium Earth Observation Optical Systems,” Proceedings of the Symposium on Small Satellite Systems and Services (4S), Funchal, Madeira, Portugal, May 31-June 4, 2010
4) Joost Elstak, Mark Taylor, Ian Praine, Alex Da Silva Curiel, Gérard Carrin, Gilles Laffaye, Christophe Pages, G. T. Murzakulov, M. R. Nurguzhin,. S.A. Murushkin, “A Million Square Kilometer Optical Satellite for Kazakhstan,” Proceedings of the 61st IAC (International Astronautical Congress), Prague, Czech Republic, Sept. 27-Oct. 1, 2010, IAC-10.B1.2.9
5) “Astrium signs strategic partnership agreement with Kazakhstan,” May 19, 2009, URL: http://www.astrium.eads.net/node.php?articleid=262
6) Information provided by Gerard Carrin of Airbus Defence and Space (former EADS Astrium), Toulouse, France.
7) Information provided by Alexander Mostovoy, Chief Manager of the International Cooperation Office of KGS
8) “Astrium to fully equip Kazakhstan’s Satellite Integration and Test Center,” Astrium, Oct. 27, 2010, URL: http://www.astrium.eads.net/en/press_centre/astrium-to-fully-equip-kazakhstan-s-satellite-integration-and-test-centre-.html
9) Talgat A. Musabayev, Meirbek M. Moldabekov, Marat R. Nurguzhin, Simbay T. Dyussenev, Sergey A. Murushkin, Bakhytzhan S. Albazarov, Vladimir V. Ten, “Earth Observation System of the Republic of Kazakhstan,” Proceedings of the 64th International Astronautical Congress (IAC 2013), Beijing, China, Sept. 23-27, 2013, paper: IAC-13-B1.2.3
10) Eric Beaufumé, Stéphane Castejon, Eric Maliet, Charles Koeck, “AstroSAT-300 : Next Generation Optical Earth Observation Systems,” Proceedings of the 4S (Small Satellites Systems and Services) Symposium, Port Petro, Majorca Island, Spain, May 26-30, 2014
11) Eric Maliet, Michel Siguier, Gérard Carrin, Ange Defendini, Didier Radola, “Applying satellite product lines to affordable Earth observation systems,” Proceedings of the 4S (Small Satellites Systems and Services) Symposium, Portoroz, Slovenia, June 4-8, 2012
13) Michael Stähle, Tim Pike, “ADCSS 2012 Astrium - Current and Future Mass Memory Products,” Proceedings of ADCSS (Avionics Data, Control and Software Systems) Workshop, ESA/ESTEC, Noordwijk, The Netherlands, Oct.23-25, 2012, URL: http://congrexprojects.com/docs/12c25_2510/09stahele_astriumfinal.pdf?sfvrsn=2
14) “Commercial liftoff for Europe's smallest launcher,” ESA, April 30, 2014, URL: http://www.esa.int/Our_Activities/Launchers/Commercial_liftoff_for-Europe_s_smallest_launcher
15) “UPDATE: Airbus + Arianespace + Republic of Kazakhstan...Success At Last, KazEOSat-1 Achieves Orbit (Launch | Earth Observation),” Satnews Daily, April 30, 2014, URL: http://www.satnews.com/story.php?number=714534250#
16) “Third Vega Lunch from the Guiana Space Center,” Arianespace, URL: http://www.arianespace.com/images/launch-kits/launch-kit-pdf-eng/VV03-launchkit-EN2.pdf
17) Talgat A. Musabayev, Meirbek M. Moldabekov, Marat Nurguzhin, Baglan Kaziev, S Murushkin, Bakhytzhan Albazarov, Gerard Carrin, Christophe Pages, Gilles Laffaye, Vladimir Ten, “First in-orbit results from KazEOSat-1: the high-resolution Earth observation mission of the Republic of Kazakhstan,” Proceedings of the 65th International Astronautical Congress (IAC 2014), Toronto, Canada, Sept. 29-Oct. 3, 2014, paper: IAC-14-B1.2.2
19) P. Luquet, A. Chikouche, A. B. Benbouzid, J. J. Arnoux, E. Chinal, C. Massol, P. Rouchit, S. de Zotti, “NAOMI instrument: a product line of compact & versatile cameras designed for high resolution missions in Earth observation,” Proceedings of the 7th ICSO (International Conference on Space Optics) 2008, Toulouse, France, Oct. 14-17, 2008
20) Information provided by Michel Pascal of Astrium Services, Toulouse, France
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).