This report discusses one application of a flight software design for a spacecraft in which the software executes from a database that can be managed by systems engineering. This report gives an overview of how such a software design can be developed and implemented. It also discusses why this approach is beneficial to the systems engineering program.

A Command and Data Handling (C&DH) system is being developed as part of a series of CubeSat missions being built at The University of Texas at Austin’s Texas Spacecraft Laboratory (TSL). With concurrent development of four missions, and with more missions planned for the future, the C&DH team is developing a system architecture that can support many mission requirements. The presented research aims to establish itself as a reference for the development of the C&DH system architecture so that it can be reused for future university missions. The C&DH system is designed using a centralized architecture with one main flight computer controlling the actions and the state of the satellite. A Commercial Off-The-Shelf (COTS) system-on-module embedded computer running a Linux environment hosted on a custom interface board is used as the platform for the mission software. This design choice and the implementation details of the flight software are described in detail in this report. The design of the flight software and the associated hardware are integral components of the spacecraft for the current missions in the TSL which, when flown, will be some of the most operationally complex CubeSat missions attempted to date. / text

With the increasing number of satellites operating in orbit and the development of nanosatelliteconstellations, it has become more and more arduous for operators to keep track of every satellitestate, and perform corrective or avoidance manoeuvres. That is why CNES, the French space agency,is developing new algorithms, which aimed at making satellites more self-su cient. More especially,these algorithms are in charge of autonomous orbit control, collision risk calculations and satellitestatus monitoring. In this thesis, we present the architecture of these three algorithms and how theyinteract between them to deal with the autonomous control of a satellite. In addition, this paper studiestheir integration within the OPS-SAT nanosatellite, which is an in-orbit demonstrator developed bythe European Space Agency (ESA) and opened to worldwide experimenters. By analysing the dataused by the numerical propagators, the size of the input configuration files sent to the nanosatellitewas optimised. Thanks to this optimisation, the size of telecommands sent during each OPS-SATflyby above the ESOC ground station meets the requirements. Due to some issues encountered with the nanosatellite’s GPS, a solution was found to update thecurrent orbit on-board, and thus allow the proper algorithms’ operation. This thesis also introduceshow the tests were carried out in order to validate these algorithms, both on flat-sat and on the realsatellite. The results demonstrate that their integration on the OPS-SAT numerical environment issuccessful, meaning that the algorithms and their dependences are correctly packaged, sent and uploaded,and that they work as expected. Their execution time are of course longer due to the limitedcalculation capacity of the on-board computer, but are still compatible with real operations, except forthe collision risk computation, which can exceed the orbital period depending on the initial conditions.Finally, the thesis presents the process of real operations for one of the three algorithms developed byCNES, the di culties encountered and the solutions considered. / Med det ökande antalet satelliter i omloppsbana och utvecklingen av nanosatellitkonstellationer hardet blivit mer och mer krävande för operatörer att hålla reda på varje satellits tillstånd och utförakorrigerande eller undvikande manövrar. Det är därför som CNES, den franska rymdorganisationen,utvecklar nya algoritmer som syftar till att göra satelliter mer autonoma. Närmare bestämt ansvarardessa algoritmer för autonom omloppsbanereglering, kollisionsriskberäkningar och satellitstatusövervakning.I detta examensarbete presenterar vi arkitekturen för dessa tre algoritmer och hur de interagerarmellan sig för att hantera den autonoma styrningen av en satellit. Dessutom studeras deras integrationinom OPS-SAT-nanosatelliten, som är en demonstrator i omloppsbana som utvecklats av Europeiskarymdorganisationen (ESA) och öppnad för globala experiment. Genom att analysera de datasom används av de numeriska propagatorerna optimerades storleken på de ingångskonfigurationsfilersom skickades till nanosatelliten. Tack vare denna optimering uppfylls storlekskraven på telekommandonsom skickas under varje passage av OPS-SAT ovanför ESOC-markstationen. På grund av vissa problem med nanosatellitens GPS hittades en lösning för att uppdatera den aktuellaomloppsbanan ombord och därmed möjliggöra korrekt funktion av algoritmerna. Detta examensarbeteintroducerar också hur testerna genomfördes för att validera dessa algoritmer, både på en s.k. flat-satoch på den verkliga satelliten. Resultaten visar att deras integration i den numeriska miljön OPS-SATär framgångsrik, vilket innebär att algoritmerna och deras beroende är korrekt förpackade, skickade ochuppladdade och att de fungerar som förväntat. Deras exekveringstid är naturligtvis längre på grundav den inbyggda datorns begränsade beräkningskapacitet, men är fortfarande kompatibel med verkligaoperationer, förutom beräkningen av kollisionsrisk, som kan överstiga omloppsperioden beroende påde initiala förhållandena. Slutligen presenterar rapporten processen för verkliga operationer för en avde tre algoritmerna som utvecklats av CNES, svårigheterna och de lösningar som övervägs.

This work describes the process of the design of a flight software for a space-qualified device, outlines the development and testing of the SW, and provides a description of the final product. The flight software described in this work has been developed for the project Demise Observation Capsule (DOC). DOC is a device planned to be attached to an upper stage of a launch vehicle and observe its demise during atmospheric re-entry at the end of its mission. Due to constraint on communication time during the mission and the need to maximize the amount of transferred data, a custom communication protocol has been developed. / Demise Observation Capsule