OPS-SAT LEOP and Commissioning: Running a Nanosatellite Project in a Space Agency Context

OPS-SAT is a 3U CubeSat launched by the European Space Agency (ESA) on December 18, 2019. It is the first nanosatellite to be directly owned and operated by ESA. The spacecraft is a flying platform that is easily accessible to European industry, institutions, and individuals, enabling rapid prototyping, testing, and validation of their software and firmware experiments in space at no cost and no bureaucracy. The spacecraft is equipped with a full set of sensors and actuators including a camera, GNSS, star tracker, reaction wheels, high speed X band and S band communication, laser receiver, software defined radio receiver, and a 800 MHz processor with a reconfigurable FPGA at its heart. Conceived to break the “has not flown, will not fly” cycle, OPS-SAT has spearheaded many firsts. One of the reasons for the success of CubeSats is that they have changed the rules on who can access space; opening a world that used to belong to a few governmental and commercial players to smaller and newer ones. This is also true within space agencies as well as outside them. It would have been unthinkable just a few years ago for an ESA center, whose prime job is to control ESA satellites, to specify, design and launch a mission with the sole aim of improving mission operations. However, it was never going to be easy. This paper describes the events of the OPS-SAT mission starting from a few weeks before launch, when some last-minute non-compliances almost stopped the mission, through the LEOP and to the end of commissioning. During the whole process many challenges had to be overcome and it took ten months to complete commissioning compared to the initially planned three months. Problems started in the first pass, no UHF packets were received from the spacecraft and bad communications plagued the mission for many months. However, during this time a great deal of progress had already been made thanks to the ingenuity of the Flight Control Team (FCT) and the supporting industry. Given the unpredictable and short uplink possibilities a framework evolved whereby commissioning of the payload was done using the experimenter infrastructure rather than the flight control infrastructure

MO Services and CFDP in Action on OPS-SAT

OPS-SAT is a 3U CubeSat launched by the European Space Agency (ESA) on December 18, 2019. It is the first nanosatellite to be directly owned and operated by ESA. The spacecraft is a flying platform that is easily accessible to European industry, institutions, and individuals enabling rapid prototyping, testing, and validation of their software and firmware experiments in space at no cost and no bureaucracy. Conceived to break the “has not flown, will not fly” cycle, OPS-SAT has spearheaded many firsts in both space and ground segments. For instance, its uplink rate is four times higher than any ESA spacecraft; it employs never before flown communication protocols, and it implements new ESA patents. Proven and standard approaches to space operations are difficult to break away from in a sector that epitomizes risk-averseness. This is particularly true with how packet telemetry and telecommand are addressed using the Packet Utilization Standard (PUS). OPS-SAT has set aside PUS in favor of a standard that is currently being defined by the Consultative Committee for Space Data Systems (CCSDS), that is, MO Services and the File Delivery Protocol (CFDP)’s file-based operations. OPS-SAT is the first in-orbit demonstration of fully MO-based on-board software and ground implementations. With over 220 experiment proposals submitted, a robust file transfer and management system greatly reduces the complexity and cost of operating multiple on-board software instances that must reliably deliver results back to experimenters. This paper details the design, implementation, and operations of the MO Services and CFDP on OPS-SAT. It presents the benefits of developing, deploying, and maintaining the MO/MAL ground infrastructure with OPS-SAT as a case study. Lessons learned as well as recommendations from the spacecraft’s flight-proven experience in adopting and operationalizing the standard are presented as invaluable feedback for future missions as well as for CCSDS ongoing development of the standard

Image and radio-frequency data compression for OPS-SAT using FAPEC

OPS-SAT is an ESA technology demonstration cubesat which includes a colour camera, a Software Defined Radio (SDR) receiver and a powerful ARM processor. One of the experiments executed there is FAPEC, a high-performance and versatile data compression software. Among others, it features image compression and linear prediction coding algorithms, suitable for multi-band and baseband radio-frequency (RF) samples, respectively. Since its deployment on-board OPS-SAT in late 2020, FAPEC has allowed for downloading a large set of Earth Observation images. Recently, thanks to ESA Open Space Innovation Platform funds, these two algorithms from FAPEC are being improved to get better compression ratios and speeds, add video compression capabilities, and higher quality levels in case of lossy compression. A smart lossy approach is being developed for radio-frequency data, identifying the time segments with signal presence and quantizing noise-only samples to further reduce the size. In order to identify the really useful files to be downloaded from the satellite, on-board data analysis capabilities are being developed as well. In this work we present in-orbit results, recent developments and preliminary results obtained with the new algorithms on real data.Peer ReviewedPostprint (published version

On-board Images to Characterize a CubeSat\u27s ADCS

ADCS for nanosatellites in the New Space sector are frequently offered as Commercial-Off-The-Shelves (COTS) systems. However, when the COTS datasheet and the actual performance in flight differ dramatically, there are few means to assess the discrepancies. Here, we update on the current operations with a flying nanosatellite to assess the attitude stability during inertial pointing mode, based on the analysis of on-board images of the sky. The satellite is OPS-SAT, a 3-unit CubeSat owned and operated by ESA. The imager is directed to the -Z longitudinal axis and the star tracker and a Sun sensor are oriented in the transversal (X,Y) plane. After a trial and error process, a complex processing revealed many stars in the captured images, that could also be identified. It demonstrates that the inertial pointing did not reach the expected performance and, moreover, it provides a fine assessment of the actual pointing and its jitter and drift. This information was fundamental in assessing the possible improvements in terms of sensors’ alignments, operations and on-board systems. The latest results are presented, as the operations are still on-going. Such assessments were possible with low-sensitivity sensors and poor stability, demonstrating that a commissioning process of the ADCS in flight is needed and feasible

Recovery From File System Corruption on the OPS-SAT-1 Experimental Processor

Recover from radiation and wear induced faults on a spacecraft’s non-volatile memory: Regain communication with the processing platform. Identify the root cause of the issues. Develop mitigation strategies against further corruption. Return to nominal state

Implementing the New CCSDS Housekeeping Data Compression Standard 124.0-B-1 (Based on POCKET+) on OPS-SAT-1

The number of telemetry parameters available in a typical spacecraft is constantly increasing. At the same time, the bandwidth available to download all that information is rather static. Operators must therefore make hard choices between which parameters to downlink or not, in which different situations, and at which sampling rates. This tradeoff is more problematic for missions with higher communication latency beyond LEO. Since 2009, The European Space Agency’s European Space Operations Center (ESA/ESOC) has been promoting the compression of housekeeping telemetry as a solution to this problem. Most spacecraft housekeeping telemetry parameters compress extremely well if they are pre-processed correctly. Unfortunately, most spacecraft record telemetry packets in flat packet stores so accessing different packets within them is too CPU and memory intensive for flight computers. Using traditional compression schemes such as zip or tar are not compatible with the traditional “fire and forget” mode of operation i.e., occasional packet losses are expected. This would render entire compressed files unusable. ESOC invented an algorithm called POCKET+ to solve this problem. It is implemented using very low-level processor instructions such as OR, XOR, AND, etc. This means that it can run with low CPU usage and, more importantly, with a short execution time. It is designed to run fast enough to compress a stream of incoming packets as they are generated by the on-board packetiser. The output is a smaller stream of packets. The compressed packets can be handled by the on-board system in an identical fashion to the original larger uncompressed packets. Robustness with respect to the occasional packet loss is built into the protocol and does not require a back channel. In 2018, POCKET+ was proposed to the CCSDS data compression working group and after extensive research by other agencies the core idea has been Evans 2 36th Annual Small Satellite Conference incorporated into a proposed new standard for “Robust Compression of Fixed Length Housekeeping Data.” The second supporter for the mission is CNES, supported technically by the University of Barcelona (UAB). Both CNES and UAB have suggested changes that make POCKET+ even more powerful. POCKET+ is already flying on OPSSAT, a 3U CubeSat launched by the European Space Agency on December 18th, 2019. The mission has updated the Onboard Software (OBSW) and ground control software to be compliant with the latest POCKET+ standard. The standard is set to be available for an ESA review. This paper describes the latest algorithm and how it is implemented on OPS-SAT, including how the same core software has been successfully deployed in two completely different scenarios/environments. One compresses files offline and then uses a transport protocol with a completeness guarantee; the other compresses a packet stream in real-time and uses the classic transport protocol where completeness is not guaranteed. The results show that compression ratios between eight and ten are usual for the OPSSAT mission. Improvements made during the development of the planned CCSDS standard for “Robust Compression of Fixed Length Housekeeping Data” are also presented

Evaluating the new CCSDS mission planning and scheduling standard: how TGO and EnMAP could have benefitted from an interoperability standard for the exchange of mission planning and scheduling information

Work on the CCSDS Mission Planning and Scheduling (MPS) standard is currently nearing completion. This paper starts with providing a thorough introduction to the standard and then assesses how the upcoming MPS standard could potentially improve the interoperability of actual space missions. In this respect it will provide an evaluation of how the standard could potentially be applied in two missions currently in orbit, ESAs Mars Trace Gas Orbiter (TGO) and DLRs Earth Observation mission EnMAP. In the meantime, an additional evaluation of ESAs OPS-SAT mission has become available and has been included in the paper. As part of the analysis, first the most relevant interfaces of each mission will be described. It is then discussed how these interfaces could potentially be mapped onto CCSDS MPS service operations. Finally, it is assessed what would be the advantages of this new approach and where project-specific challenges remain. In addition, shortcoming will be identified, either with the MPS standard itself or in general with related CCSDS standards that are applicable to the mission ground segment