Analysis of the Rendezvous Phase of E.Deorbit Guidance, Communication and Illumination

Analysis of the Rendezvous Phase of e.deorbit Guidance, Communication and Illumination MSc Thesis Report 19 December 2014 J.A.F. Deloo Credits cover image: AGI (Analytical Graphics, Inc.) Analysis of the Rendezvous Phase of e.deorbit Guidance, Communication and Illumination by J.A.F. Deloo in partial fulfilment of the requirements for the degree of Master of Science in Aerospace Engineering at the Delft University of Technology, to be defended publicly on Tuesday January 13, 2015 at 2:00 PM. Student number: 4024478 Supervisor: Dr. ir. E. Mooij, TU Delft Thesis committee: Prof. dr. ir. P.N.A.M. Visser, TU Delft Ir. K. Cowan, TU Delft Ir. T. Soares, ESA An electronic version of this thesis is available at http://repository.tudelft.nl/. Delft University of Technology Abstract The aim of this thesis is to investigate a debris-remediation technique where a chaser performs a rendezvous with the debris, establishes a rigid-link connection, and actively de-orbits the debris. Remediation of the space environment becomes an increasing urgency, since the continuously growing space debris population in low-Earth orbit currently poses a serious threat for active satellites. Furthermore, on Earth a threat exists due to uncontrolled re- entry of the debris sooner or later. The thesis addresses various aspects of the rendezvous phase for the debris-remediation technique under consideration. Among others, the aim is to assess passive safety of the required manoeuvres in the rendezvous phase. Also, the thesis explores the possibility of continuous ground communication of the chaser during its final approach with the target. Finally, the thesis studies the illumination conditions. This includes sensor blinding, target face illumination and chaser solar-array illumination. ESA's satellite ENVISAT was used as design case. The safety aspects of the rendezvous manoeuvres were assessed by analysing the resulting trajectories after various thruster failures. For the analysis related to communication, the chain of core ESTRACK ground stations (located mainly in Europe) was considered. Furthermore, obstruction of the communication signal by the target was studied. Last, for the illumination conditions, obscuration of the Sun by target was taken into account. In the topic of passive safety, the results indicate that fly-around manoeuvres are preferred in the direction opposite to the natural orbital motion, as these are passively safe. On the other hand, manoeuvres on H-bar and fly-around manoeuvres along the natural orbital motion are found to be passively unsafe. It can be concluded from the communication analysis that the maximum duration of the uninterrupted window amounts up to more than half an hour, using the chain of core ESTRACK ground stations. However, the study on communication blockage shows that frequent communication gaps can occur, with the longest gaps being in the order of one minute in duration. In the field of illumination, it can be concluded that correct target illumination and sensor visibility cannot be guaranteed. Furthermore, the results show that the average solar-array area available during final approach varies between 35% and 75%, due to both incorrect pointing of the solar array by the chaser and obscuration by the target. iv Contents Preface vii List of Symbols ix Acronyms xii 1 Introduction 1 1-1 Background . 1 1-2 Scope of the Research . 2 1-3 Thesis Outline . 4 2 Research Context 5 2-1 Background . 5 2-2 The e.deorbit Mission . 6 2-3 Definitions . 9 2-4 Target Analysis . 11 2-5 Baseline Chaser . 16 3 Theoretical Background 19 3-1 Relative Orbital Motion . 19 3-2 Typical Rendezvous Manoeuvres . 21 3-3 Relative Perturbations . 30 3-4 Communication . 32 3-5 Illumination . 36 3-6 Analytical Hierarchy Process . 38 4 Research Methodology 43 4-1 Guidance . 43 4-2 Communication . 44 Analysis of the Rendezvous Phase of e.deorbit vi Contents 4-3 Illumination . 47 4-4 Research Overview . 48 4-5 Assumptions . 49 4-6 Software Description and Application . 53 5 Guidance 57 5-1 Close-Range Rendezvous Phase . 57 5-2 Target Characterisation Phase . 64 5-3 ENVISAT Rotation Scenario 1 . 67 5-4 ENVISAT Rotation Scenario 3 . 76 5-5 ENVISAT Rotation Scenario 2 . 90 5-6 Drag due to Residual Atmosphere . 100 6 Communication 107 6-1 Optimal Communication Windows . 107 6-2 Severity of Antenna Obstruction . 112 6-3 Communication Gaps . 113 7 Illumination 121 7-1 Illumination Conditions in 2021 . 121 7-2 Available Solar-Array Area . 123 8 Conclusions and Recommendations 131 8-1 Conclusions . 131 8-2 Recommendations . 135 Bibliography 139 Appendices 141 A Disturbance Torques and Relative Orbital Perturbations 143 A-1 Disturbance Torques . 143 A-2 Relative Orbital Perturbations . 145 B Transfer Options Trade-Off 147 B-1 Trade-Off Criteria . 147 B-2 Pairwise Comparison Matrices . 148 B-3 Sensitivity of Results to Trade-Off Criteria . 150 Preface This report represents my MSc thesis and results from 7 months of work. The MSc thesis serves as final work for my Master of Science degree in Space Flight at TU Delft. I performed my MSc thesis in the form of a graduate internship at ESTEC (ESA's site in Noordwijk, The Netherlands), where I worked on an active debris-removal mission. The topic of active debris removal is one that I have found intriguing since the start of my studies at TU Delft back in 2009. The first time I have had the opportunity to work on the topic was during my Bachelor graduation project where I designed, together with a group of students, a heavy space debris removal system. Next, I continued working on the subject during my Master with an internship at Airbus Defence and Space, where I developed a simulator for non-cooperative rendezvous. Finally, I was offered the possibility to perform this graduate internship within the Clean Space Initiative at ESTEC in the framework of e.deorbit. The e.deorbit mission aims to remove a large European object from low-Earth orbit. For successful completion of this thesis I have had help from many people and I would like to take the time to thank them all. First of all, I want to express my gratitude to Frederique Teston for his effort in finding me the opportunity to perform my thesis at ESTEC. Also, many thanks to Massimo Bandecchi for receiving me in his Systems and Concurrent Engineering Section and providing licences for various software (STK, MATLAB, CATIA). Next, I would like to thank Tiago Soares, my principle supervisor at ESTEC, for his support and comments during this period. The comments by the rest of ESA's e.deorbit team were also much appreciated. Furthermore, I would like to express my sincere appreciation to Guillermo Ortega and Sven Erb from ESA's Guidance, Navigation and Control Section for providing tools (LAREDO) and support to my thesis respectively. I want to thank all the CDF colleagues for the friendly environment they created, which made my stay at ESTEC a pleasant experience. From TU Delft, I want to thank Erwin Mooij for his excellent guidance during my thesis and for his effort to come to ESTEC several times. Analysis of the Rendezvous Phase of e.deorbit viii Preface List of Symbols Roman Symbols A Area (m2) A Criteria pairwise comparison matrix (−) a Semi-major axis (km) B Alternatives pairwise comparison matrix (−) CD Drag coefficient (−) −2 g0 Gravity on Earth (9.81) (m s ) H Orbit altitude (km) Isp Specific Impulse (s) i Orbit inclination (◦) ◦ Lnode Longitude of ascending node ( ) m Mass (kg) N Number of orbital revolutions (−) q_ Closing rate (m s−1) R Fly-around radius (m) RE Earth radius (km) r Orbital radius (km) r[x; y; z] Position (m) S Score matrix (−) s Score vector (−) T Communication time (s) T Orbital period (s) t Time (s) −1 V[Vx;Vy;Vz] Velocity (m s ) v Global score vector (−) w Weight vector (−) Greek Symbols α Azimuth (◦) α_ Fly-around angular rate (rad s−1) β Ballistic coefficient (kg m−2) −2 γ[γx,γy,γz] Acceleration (m s ) ∆x Change of quantity x (−) Spacecraft elevation angle (◦) η Nadir angle (◦) Analysis of the Rendezvous Phase of e.deorbit x List of Symbols λ Earth central angle (◦) θ Elevation (◦) µ Standard gravitational parameter (Earth: 398600.44) (km3 s−2) π Mathematical constant (3.141592645) (−) ρ Angular radius (◦) ρ Atmospheric density (kg m−3) σ Standard deviation (−) φ Fly-around angle (◦) ! Mean motion (rad s−1) Subscripts avg Average c Chaser com Centre of mass D Drag day Day f Final condition i Initial condition j Row number of matrix entry k Column number of matrix entry orb Orbit t Target tot Total x x-component y y-component z z-component Superscripts Superscripts denote the reference frame in which the variable is expressed (for those applicable). In this report the LVLH-frame is default. For the sake of brevity the superscript is not shown unless it is different from LVLH. Acronyms ADR Active Debris Removal AHP Analytical Hierarchy Process Airbus DS Airbus Defence and Space BoL Beginning of Life CAM Collision Avoidance Manoeuvre CDF Concurrent Design Facility CI Consistency Index CoM Centre of Mass CW Clohessy-Wiltshire EDRS European Data Relay System EoL End of Life ESA European Space Agency FoV Field of View GEO Geosynchronous Earth Orbit GNC Guidance, Navigation and Control HPOP High Precision Orbit Propagator KOS Keep-Out Sphere KT Kayser-Threde GmbH LAREDO LAunch, REndezvous and DOcking simulation tool LEO Low-Earth Orbit LoS Line of Sight LVLH Local Vertical, Local Horizontal MRD Mission Requirements Document NASA National Aeronautics and Space Administration SoW Statement of Work SRQ Sub-Research Question SSO Sun-Synchronous Orbit STK Satellite Tool Kit TAS Thales Alenia Space TBC To Be Confirmed TDRS Tracking & Data Relay Satellite TLE Two-Line Element TTC Telemetry Tracking and Command Analysis of the Rendezvous Phase of e.deorbit xii Acronyms Manoeuvre Acronyms CFMFA Closing Forced Motion Fly-Around FD Free Drift FM (Straight-Line) Forced Motion FMFA Forced Motion Fly-Around RIT Radial Impulsive Transfer SK Station Keeping TIT Tangential Impulsive Transfer Chapter 1 Introduction In this chapter the research is introduced.

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