DEGREE PROJECT IN VEHICLE ENGINEERING, SECOND CYCLE, 30 CREDITS STOCKHOLM, SWEDEN 2021 Autonomous orbit control coupled with on-board risk management CLÉMENT LABBE KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ENGINEERING SCIENCES 2 Abstract Many satellites have an orbit of reference defined according to their mission. The satellites need therefore to navigate as close as possible to their reference orbit. However, due to external forces, the trajectory of a satellite is disturbed and actions need to be taken. For now, the trajectories of the satellites are monitored by the oper- ations of satellites department which gives appropriate instructions of navigation to the satellites. These steps require a certain amount of time and involvement which could be used for other purposes. A solution could be to make the satellites autonomous. The satellites would take their own decisions depend- ing on their trajectory. The navigation control would be therefore much more efficient, precise and quicker. Besides, the autonomous orbit control could be coupled with an avoidance collision risk management. The satellites would decide themselves if an avoidance maneuver needs to be considered. The alerts of collisions would be given by the ground segment. In order to advance in this progress, this internship enables to analyse the feasibility of the implementation of the two concepts by testing them on an experiments satellite. To do so, tests plans were defined, tests procedures were executed and post-treatment tools were developed for analysing the results of the tests. Critical computational cases were considered as well. The tests were executed in real operations conditions. Keywords Tests, Autonomous Orbit Control, collision risks, station-keeping, control indicators 3 Sammanfattning Manga˚ satelliter har en referensbana definierad enligt deras uppdrag. Satelliterna behover¨ darf¨ or¨ navigera sa˚ nara¨ deras referensbana som mojligt.¨ Pa˚ grund av externa krafter stors¨ dock satellitbanan och atg˚ arder¨ maste˚ vidtas. For¨ narvarande¨ overvakas¨ satellitbanorna av satellitavdelningar pa˚ marken vilka ger lampliga¨ instruk- tioner for¨ navigering till satelliterna. Dessa steg kraver¨ en tid och engagemang som skulle kunna anvandas¨ for¨ andra andam¨ al.˚ En losning¨ ar¨ att gora¨ satelliterna autonoma. Satelliterna skulle da˚ kunna ta sina egna beslut beroende pa˚ deras bana. Navigeringskontrollen skulle darf¨ or¨ vara mycket mer effektiv, exakt och snabbare. Dessutom kan den autonoma banregleringen kopplas till riskhantering for¨ undvikande av kollision med rymdskrot och andra satelliter. Satelliterna skulle sjalva¨ avgora¨ om en undvikande manover¨ maste˚ overv¨ agas.¨ Varningar om kolli- sioner skulle ges av marksegmentet. For¨ att ga˚ vidare i denna utveckling analyserar detta arbete genomforbarheten¨ av implementeringen av olika koncept for¨ undanmanovrar¨ genom att testa dem pa˚ en experimentsatellit. For¨ att gora¨ detta definierades test- planer, testprocedurer utfordes¨ och efterbehandlingsverktyg utvecklades for¨ analys av testresultaten. Kritiska berakningsfall¨ togs fram. Testerna utfordes¨ under verkliga driftsforh¨ allanden.˚ Nyckelord Tester, autonom bankontroll, kollisionsrisker, manovrer,¨ kontrollindikatorer 4 Acknowledgements First, I would like to thank my supervisor, Jer´ omeˆ THOMASSIN, who has accompanied me all along my in- ternship. He guided me and was always available when I had questions even during the COVID situation. We had deep discussions on technical aspects related to the topic of my thesis but also on common life issues. He was very comprehensive to my misfortune of finding an accommodation when I arrived in Toulouse. Thank you also to Sophie LAURENS who can be considered as my second supervisor. I had the opportu- nity to work closely with Franc¸ois TOUSSAINT as well, and two other interns, Chiara RUSCONI and Anthony SURIVET. We had a lot of meetings all together. Everybody was deeply involved in the project which facili- tated the work progress of each of us. I thank also all the members of the Flight Dynamics department who took their time to answer me and to give me explanations related to their field of study. I add thanks to all the other interns, Dexter QUINCY JONES, Yohan BRUNET, Guido MAGNANI, Marcos ROJAS-RAMIREZ, Chiara RUSCONI and Anthony SURIVET with who I spent amazing moments, I enjoyed the lunches and the laughs during the breaks. I want also to thank my family and my friends who encouraged me all along this internship. They gave me motivations and support especially during the moments of confinement. I finally thank all the people who contributed to my internship report, as for their advice as for their re-reading. 5 Contents 1 Introduction 10 1.1 OPS-SAT . 10 1.2 CNES involvement . 11 1.3 Objectives and goals of the thesis . 11 1.4 Structure of the report . 11 2 Background 12 2.1 Reference frames . 12 2.1.1 Geocentric inertial equatorial coordinates system IJK . 12 2.1.2 Celestial intermediate reference frame (CIRF) . 12 2.1.3 Local orbital frame (TNW) . 13 2.1.4 Local orbital frame (QSW) . 13 2.2 Set of orbital parameters . 13 2.3 Dynamical problem . 13 3 Method 20 3.1 ASTERIA . 20 3.1.1 Control system . 20 3.1.2 Working principle . 21 3.1.3 Control strategy . 22 3.2 CROCO . 26 3.2.1 CDM . 26 3.2.2 Collision risks calculation . 28 3.3 ASTERIA and CROCO interactions . 31 4 Tests preparation 33 4.1 ASTERIA . 33 4.1.1 AOC configuration . 33 4.1.2 Reference orbit . 34 4.1.3 Propulsive system . 34 4.1.4 Maneuver slots . 34 4.1.5 Solar flux data . 36 4.1.6 Change of the ASTERIA code . 37 4.1.7 ASTERIA analysis tools . 37 4.2 CROCO . 40 4.2.1 CROCO configuration . 40 4.2.2 Management of the CDMs . 41 4.2.3 CROCO analysis . 42 4.3 Tests implementation . 43 4.3.1 Solutions proposed to overcome the GPS system problem . 43 4.3.2 Time consideration . 43 4.3.3 First tests seen from the satellite’s point of view . 44 4.3.4 Second tests seen from the satellite’s point of view . 44 4.3.5 Third tests seen from the satellite’s point of view . 45 4.3.6 Fourth tests seen from the satellite’s point of view . 45 6 CONTENTS 4.3.7 Fifth tests seen from the satellite’s point of view . 46 4.3.8 Sixth tests seen from the satellite’s point of view . 46 4.3.9 Seventh tests seen from the satellite’s point of view . 46 4.3.10 Preparation of the supply files . 47 4.3.11 Data management . 48 5 Results analysis 50 5.1 Cross-validation . 50 5.2 AOC with risk management analysis . 54 5.3 CDM analysis . 55 5.3.1 Filtering analysis . 55 5.3.2 Propagation analysis . 56 5.3.3 Analysis of the impact of the covariance definition of the primary object . 58 6 Conclusion 61 7 List of Figures 2.1 Geocentric inertial equatorial coordinates system IJK . 12 2.2 Orbital parameters . 14 2.3 Change of frames . 17 3.1 Control system . 21 3.2 Predictability horizon . 21 3.3 Control strategy: semimajor axis maneuvers . 23 3.4 Eccentricity correction vs semimajor axis correction . 24 3.5 Control strategy: inclination maneuvers . 25 3.6 Inclination change maneuvers . 25 3.7 CDM transmissions from JSpOC to the O/O (Owners/Operators) . 27 3.8 Propagation of a covariance and a state from the TCA given by the original CDM to the potential risks found . 28 3.9 Interactions between ASTERIA and CROCO . 31 3.10 Shift strategy drawback . 32 4.1 OPS-SAT frame . 35 4.2 The worst case scenario considered for solar glares avoidance maneuvers . 35 4.3 VTS visualisation: case of solar glares . 36 4.4 Current solar flux evolution (from 01/10/2019 to 10/12/2020) . 37 4.5 Past solar flux evolution (from 10/12/1996 to 10/12/1997) . 37 4.6 Acquisition of the previous nodes list . 39 4.7 Preparation of the slots file . 47 4.8 Preparation of the file of secondary objects . 48 5.1 Difference of results between the simulator and the code implemented in the MNF . 51 5.2 Difference of results between the simulator and the code implemented in the MNF with no maneuvers in the provided GPS data . 52 5.3 Difference of coordinates in.