KazSTSAT (Kazak Science and Technology Satellite)
SSTL (Surrey Satellite Technology Ltd.) of Guildford, UK and Ghalam LLP of Astana, Kazakhstan have agreed that SSTL's new X50 platform design will deliver KazSTSAT, a small collaborative satellite mission announced under a contract signed in July 2013.
Ghalam LLP is a joint venture between JSC "National Company Kazakhstan Garysh Sapary" (KGS) and EADS Astrium. Under the contract, SSTL and the Ghalam team will jointly develop the "SSTL-X50" platform using heritage SSTL platform design and payload equipment including an SSTL EarthMapper payload designed for global commercial wide-area imaging, as well as flying a number of jointly-developed equipments and payloads, a novel imaging instrument, and a new on-board computer. The new platform will be designed to provide over 50 W orbit average power to a 50 kg payload mission and it is intended that the platform and some of the new technologies will be used on future Kazak missions. 1) 2) 3)
Under a joint development program, 14 Kazakh engineers will work alongside SSTL engineers to design and build the KazSTSAT spacecraft. In addition to the SLIM-6 imager, KazSTSAT will fly a number of Ghalam LLP developed payloads, and will join the Disaster Monitoring Constellation (DMC), which provides daily images for applications including global disaster monitoring. Environmental testing will take place at a new Ghalam LLP test facility being established in Astana, Kazakhstan.
The KazSTSAT mission is a collaboration between Ghalam LLP of Kazakhstan, SSTL, and UK based DMCii, an image processing company. In April 2015, the UKSA (UK Space Agency) announced some funding support through the IPSP ( International Partnerships Space Program) to aid in the development of an autonomous and collaborative Mission Operations system in partnership with Ghalam LLP to handle the high volume of Earth observation data that will be downloaded from the spacecraft's SSTL SLIM6 Imager, enabling the full research and commercial data provision of the mission to be realized. 4)
Some background: 5)
Over the last three decades, SSTL have delivered over 40 small satellites for a range of applications including Earth Observation, Communications, Navigation, Science and Technology Demonstration. Schedule, price and reliability are very important factors for all customers, and increasingly commercial spacecraft operators are considering groups of satellites working as part of a constellation. SSTL has been involved with a number of such constellations in various capacities, including DMC (Disaster Monitoring Constellation), RapidEye, Kanopus, FormoSat-7/COSMIC2 at spacecraft level, and at payload / subsystem level in ORBCOMM-SG, CYGNUS and the 22 Galileo FOC payloads. The production philosophy typically adopted for such batches of satellites to consider the closest existing product, modify this to the specific mission needs, build a proto flight unit, and then carry out a limited batch production run. As a result, the cost savings that can be achieved in batch production are often limited, as the base design was never optimized for such a batch production.
For individual spacecraft, the cost of the spacecraft production can also be prohibitive for science and technology demonstration missions, or restrict the feasibility of new business ideas in space. Increasingly, the labor costs involved in spacecraft production are dominating. SSTL has developed a concept for spacecraft manufacture which has so far not been used elsewhere in the space industry, which removes some of these limitations and cost drivers. This is targeted at improving production cost, speeding up mission delivery, and maintaining and improving reliability.
Figure 1 shows the SSTL missions and their respective launch dates. Because many of the same subsystems are used on several different spacecraft busses and mission, there is regular and significant opportunity in SSTL to batch build spacecraft equipments and so make economy of scale cost savings - even across different spacecraft for different customers, providing they are produced at roughly the same time. There are then also some cost savings in sharing staff and facilities. For instance, in the AIT/EVT (Assembly, Integration and Test/Environmental Test) phase, spacecraft can be processed at around the same time using the same test setup, for instance sharing a Thermal Vacuum chamber. For most missions, SSTL already gains these benefits. Nevertheless there is a fundamental limit on the amount of savings that can be achieved without a significant investment in building equipment for stock and permanent test setups, due to the fact that the avionics were designed considering conventional 20th century space industry practices, namely handcrafted production, human inspection, one-off and bespoke setup and test, and manual harness integration.
Figure 1: SSTL historical parallel spacecraft production (image credit: SSTL)
In order to provide further significant improvements in price and schedule for constellations of spacecraft, as well as on individual satellites, it is necessary to consider alternative approaches. An SSTL internal R&D program was started in 2011, with its main objective to improve performance to cost ratios even further, by exploiting new commercially developed technologies, protocols and processes in order to offer improved performance of current SSTL small satellite platforms at a similar or lower mass, but with significantly reduced schedule and price. This internal development program heavily leverages the investment made in other industries in batch manufacture of highly reliable products, and has resulted in the "X-Series" spacecraft.
The SSTL-X50 series of spacecraft are the first mission products. The series were released in 2013, and the first spacecraft using this class bus is already under contract and in production. Initially implemented on a high performance 50 kg class platform, the SSTL X50, the X-series core architecture and avionics will be implemented in all SSTL's small platforms over the next three to five years, thereby lowering the cost and improving delivery times for all X-series platforms.
SSTL has developed the new SSTL-X50 satellite platform to provide a smaller, lighter, flexible spacecraft with enhanced systems capabilities and quality. With a mass range of 50 -100 kg, the compact, highly integrated design baselines flight-proven heritage with next-generation "Fireworks" avionics to incorporate fully dual redundant subsystems and scaled core platform services such as power, structure, data processing, communications and high-precision attitude control. 6)
Figure 2: Two views of the KazSTSAT microsatellite with the EarthMapper payload (image credit: SSTL)
A block diagram of the SSTL-X50 ‘EarthMapper' configuration is shown in Figure 3, compared with a block diagram for a more complex X-series spacecraft configuration. The 'Card Frame' based architecture at the heart of all of the X-Series platforms has been developed with maximum flexibility and modularity in mind. A number of standard building block "cards" deliver the main platform functions such as power conditioning, TT&C, on-board processing and storage. The card-frame can be configured in an expandable arrangement to deliver the platform performance required by different payloads and associated mission classes. The ADCS (Attitude Determination and Control Subsystem) provides arcsecond attitude knowledge from star cameras, data storage of a minimum of 256 GB (Ref. 5).
Figure 3: System block diagrams (configurable common building blocks) for simple SSTL-X50 microsatellites (left) and more complex X-series spacecraft (right) like the SSTL-X300-S1 minisatellite series (image credit: SSTL)
Figure 4: Enlarged block diagram of the KazSTSAT-X50 platform (image credit: SSTL) 7)
The new platform design allows SSTL to take advantage of automated batch avionics manufacturing and test processes, and aids rapid assembly and integration of the spacecraft, bringing customers the benefit of shorter order to orbit timescales and reduced fixed-price costs.
The expected advantages of the new platform compared to similar heritage platforms include:
• Larger on-board payload data storage capacity
• Several orders of magnitude more powerful OBC that may potentially be used for heavy on-board processing of the payload data, as well as for some advanced star tracker and GPS functionalities
• Higher supported payload mass
• Higher orbit average power available to the payload.
Different size platforms can employ the new avionics mostly through duplication of modules to increase storage, computer and power capability. The first of these to be realized is KazSTSAT for Ghalam LLP, which is an "SSTL-X50" - 50 kg class platform.
KazSTSAT will be based on the SSTL-X50 EarthMapper variant and will carry an SSTL SLIM-6 imager, providing 17.5 m resolution multispectral imagery on a swath width of ~600 km for global wide-area imaging.
RF communications: The S-band is used for TT&C transmissions. X-band downlink for payload data transmission at 80 Mbit/s, onboard data storage capacity of 256 GB. Data compression ratio: Lossless up to 2.5:1, lossy 4:1 or higher. S-band is used for TT&C.
Table 1: Specification of the KazSTSAT microsatellite
Status of the KazSTSAT development:
• The payload data system was delivered for the KazSTSAT mission in November 2015. Spacemetric (Spacemetric Ltd., Farnborough, UK, a subsidiary of Spacemetric AB, Sollentuna, Sweden) has delivered a Keystone System for the KazSTSAT mission being developed jointly by SSTL and Ghalam LLC of Kazakhstan. The SSTL SLIM6 sensor has been modified for the KazSTSAT mission to specifications defined by DMC International Imaging Ltd (DMCii), the commercial distributor of imagery from the DMC satellites. This medium-resolution imager now provides Coastal Blue, Blue and Red-Edge channels in addition to the Red, Green and NIR (Near Infrared) channels of the previous DMC missions. Spacemetric is responsible for physical sensor modelling of the new instrument and has incorporated this capability into the Keystone software. After launch, the sensor parameters will be refined through an in-orbit calibration. 8)
• Start of AIT in August 2015.
• CDR (Critical Design Review) in May 2015.
• The end of Phase C in April 2015.
Launch: A launch of the KazSTSAT microsatellite is scheduled for Q1 2018 on a SpaceX Falcon-9 vehicle. 9)
Orbit: Sun-synchronous orbit, reference altitude of 542 km, inclination = 97º, LTAN (Local Time on Ascending Node) at 10:30 hours.
Sensor complement (EarthMapper, RadMon)
The Ghalam LLP developed instrument RadMon will be added when descriptions are available.
EarthMapper is a global imaging system providing full coverage of the Earth's land area in 5 days. The EarthMapper instrument is of SLIM6 (Surrey Linear Imager Multispectral 6 channels - but 3 spectral bands) heritage, flown on the Deimos-1 and UK-DMC-2 missions (launch July 29, 2009). The instrument consists of two bore‐sighted instrument banks. The design provides for a nadir-viewing, three-band multispectral scanning camera capable of providing mid-resolution image information of the Earth's surface.
SLIM6 employs the pushbroom imaging technology using two cameras per band (mounted in a double-barrel cross-track configuration - or in two banks) thus providing a dual (slightly overlapping) swath with a combined swath width of ~ 600 km with a spatial resolution 17.5 m GSD (Ground Sampling Distance) at nadir. 10)
The imager comprises six lens and sensor pairs, configured in two banks as part of an overall optical bench assembly. The banks are mounted angled away from nadir by approximately 13º, to double the swath width, but with a small overlap of approximately 5% to aid image stitching. The FOV (Field of View) from each bank is 26.6º.
Applications: Suitable for a wide variety of commercial, environmental and security applications. EarthMapper continuously images the sunlit land mass and is particularly suited to applications requiring a high temporal revisit rate. Typical examples include:
• Agricultural monitoring
• Flood monitoring
• Water quality
• Disaster management
• National and urban mapping.
Table 2: Parameters of the SLIM6 (SLIM6) instrument
The upgraded SLIM6 consists of two bore‐sighted instrument banks. The SLIM6 design provides for a nadir-viewing, three-band multispectral scanning camera capable of providing mid-resolution image information of the Earth's surface.
Figure 5: Schematic illustration of the SLIM6 configuration (image credit, SSTL)
The architecture of the KazSTSAT features a highly distributed nature with the main ground station, Spacecraft Operations Center, and main Mission Planning System located in three different geographical locations in Svalbard, Astana and Guildford. On top of that, there are provisions for backup ground station and MOC in Astana. Some of the customers are also expected to receive their imagery directly to their ground stations. All this have driven an innovative architecture and design of the components of the ground segment. 11)
The ground segment of the KazSTSAT mission is going to be based on a standard SOC (Spacecraft Operations Center) and MOC (Mission Operations Center) configurations.
The experimental part consists of the ground station based on SDR (Software Defined Radio). Connection to the remote ground stations will employ Ethernet over IP (Internet) that would be LAN transparent for both SOC and the SDR ground stations. The MOC (Mission Operations Center) will include new distributed Mission Planning System and image processing software.
S-band uplink and downlink chains:
Modern SDR technology is now mature enough to be used in commercial grade applications, including ground stations. The use of Ettus Research SDR's significantly reduces the cost of a GSN (by an order of magnitude) and visibly simplify the GSN (Ground System Network) architecture. Ettus Research B200 is considered as baseline, this model has sufficient bandwidth for the S-band uplink and downlink purposes (19.2 kbit/s CPFSK and 38.4 kbit/s BPSK/QPSK ½ k=7 respectively). Software composed of bespoke C++ and Python modules combined with the GNU-Radio environment is running on a medium level SDR host computer (Intel Core i5, 8 GB RAM, 250 GB SSD) running Ubuntu Linux which more than sufficient for the purpose.
As all the processing after a direct RF conversion stage is performed in in-house developed software, this configuration is easily modified for any uplink and downlink modulation, coding, randomization, and rate combinations.
The imagery is downloaded from the satellite using the Saratoga protocol which is IP-based and requires an uplink connection for sending negative acknowledgement and other types of IP packets. This requires full de-encapsulation of the X-band IP traffic in real time. For this mission a new configuration of a ViaSat-800 or Omnisat-G3LT X-band receiver interfaced via an Ethernet output port with a PC running a custom soft-ware suite is going to be employed. The X-band receivers are performing demodulation and FEC decoding, while an in-house software suite is dealing with the re-output receiver protocol, V.35 descrambling, HDLC de-encapsulation, and NRZ decoding. After de-encapsulation the IP packets are transferred to the standard IP-stack and either forwarded to the Ethernet interface, or consumed by the Saratoga-Win application, running locally on the same PC.
Figure 6: Top: Comparison between a typical standard S-band ground station architecture: Bottom: the KazSTSAT GSN based on the SDR technology (image credit: Gahlam LLP)
1) "SSTL signs contract for collaborative mission with Kazakhstan," SSTL, July 1, 2013, URL: http://www.sstl.co.uk/Press/SSTL-signs-contract-for-collaborative-mission-with
2) "First mission for SSTL's new X50 platform will be for Kazakh customer," SSTL, Jan. 14, 2014, URL: http://www.sstl.co.uk/News-and-Events/2014-News-Archive/First-mission-for-SSTL-s-new-X50-platform-will-be
3) "KazSTSAT: The Mission," SSTL, URL: http://www.sstl.co.uk/Missions/KazSTSAT/KazSTSAT/KazSTSAT--The-Mission
4) "First round of international space partnerships announced," UKSA, March 26, 2015, URL: https://www.gov.uk/government/news/first-round-of-international-space-partnerships-announced
5) Alex da Silva Curiel, Andrew Cawthorne, James Penson , Martin Sweeting, "Production engineering a low cost video imaging constellation," 10th IAA Symposium on Small Satellites for Earth Observation, Berlin, Germany, April 20-24, 2015, paper: IAA-B10-0501, URL of presentation: http://www.dlr.de/iaa.symp/Portaldata/49/Resources/dokumente/archiv10/pdf/0501_x50_daSilvaCuriel.pdf
6) "Introducing the next-generation technology X-Series Missions," SSTL, URL: http://www.sstl.co.uk/Products/EO---Science-Platforms/SSTL-X50-series
7) M. Moldabekov, M. Nurguzhin, V .Ten, S. Murushkin, H. Lambert, A. da Silva Curiel, D. King, H. Kadhem, G. Taylor, M. Sweeting, "First results and next steps in Kazakhstan Earth Observation missions in cooperation with SSTL," 10th IAA Symposium on Small Satellites for Earth Observation, Berlin, Germany, April 20-24, 2015, paper: IAA-B10-0804, URL of presentation: http://www.dlr.de/iaa.symp/Portaldata/49/Resources/dokumente/archiv10/pdf/0804.pdf
8) Ian Spence, "Payload data system delivered for KazSTSAT mission," Spacemetric, Nov. 10, 2015, URL: http://www.spacemetric.com/news/2015/11/10/payload-data-system-delivered-for-kazstsat-mission
9) Information provided by Vladimir Ten of Ghalam, Astana, Kazakhstan.
10) "SSTL-X50 EarthMapper," URL: http://www.sstl.co.uk/getattachment/Products/EO-Platforms/SSTL-X50-series/SSTL-X50-Earthmapper-tech-spec.pdf
11) Vladimir Ten, Alexandr Bychkov, Mikhail Murushkin, Aigul Anarbayeva, Sergey Murushkin, "New technology developments for the ground segment of the KazSTSAT mission," Proceedings of the 11th IAA Symposium on Small Satellites for Earth Observation, Berlin, Germany, April 24-28, 2017, paper: IAA-B11-1309P
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 (firstname.lastname@example.org).