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Garrie S. Mushet Camilla Colombo, Colin R. McInnes

1 st November 2012. 23rd International symposium on Spaceflight Dynamics Pasadena, CA. Autonomous Control of a Reconfigurable Constellation of Satellites on Geostationary Orbit with Artificial Potential Fields. Garrie S. Mushet Camilla Colombo, Colin R. McInnes. Overview.

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Garrie S. Mushet Camilla Colombo, Colin R. McInnes

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  1. 1st November 2012 23rd International symposium on Spaceflight Dynamics Pasadena, CA Autonomous Control of a Reconfigurable Constellation of Satellites on Geostationary Orbit with Artificial Potential Fields Garrie S. Mushet Camilla Colombo, Colin R. McInnes

  2. Overview Introduction/background to the problem Model of constellation system Development of the artificial potential field controller Demonstration of controller Parameter analysis of constellation and controller performance Overview of possible applications Conclusions Image From: http://www.kidsnewsroom.org/elmer/infocentral/space/html/universe/solar_system/planets/mars/surface/atmosphere/atmosphere.html 1st November 2012 Garrie S. Mushet 2

  3. Introduction In many space applications, constellations offer a number of advantages compared to single-satellite platforms, such as in Earth observation, space science and telecommunications Reduced costs associated with the use of a great number of smaller and less massive satellites, which are becoming increasingly viable due to advances in miniaturisation of space technology Greater system reliability and robustness – mission not dependent on the longevity and operational efficacy of a single satellite Massively distributed constellations with reconfigurability are proposed – but autonomy is needed as ground operations would be prohibitively complex This work presents a possible control method for such constellations Image From: http://www.kidsnewsroom.org/elmer/infocentral/space/html/universe/solar_system/planets/mars/surface/atmosphere/atmosphere.html 1st November 2012 Garrie S. Mushet 3

  4. Constellation Model Image From: http://www.kidsnewsroom.org/elmer/infocentral/space/html/universe/solar_system/planets/mars/surface/atmosphere/atmosphere.html 1st November 2012 Garrie S. Mushet 4

  5. Constellation Model Dynamics Satellite trajectories are propagated according to the Gaussian form of the variation of Keplerian elements equations – continuous low thrust form Image From: http://www.kidsnewsroom.org/elmer/infocentral/space/html/universe/solar_system/planets/mars/surface/atmosphere/atmosphere.html 1st November 2012 Garrie S. Mushet 5

  6. Constellation Model Dynamics But with some simplifying assumptions: • Only tangential thrusting available • Orbits remain quasi-circular • No out of plane motion • Numerical and analytical solution to these equations used in this work Image From: http://www.kidsnewsroom.org/elmer/infocentral/space/html/universe/solar_system/planets/mars/surface/atmosphere/atmosphere.html 1st November 2012 Garrie S. Mushet 6

  7. Constellation Model Validation of Assumptions Typical symmetrical maneuver used in this work simulated using full Gauss equations Eccentricity remains close to 0! Image From: http://www.kidsnewsroom.org/elmer/infocentral/space/html/universe/solar_system/planets/mars/surface/atmosphere/atmosphere.html 1st November 2012 Garrie S. Mushet 7

  8. Controller Artificial Potential Field Controller Designed to have a minimum value corresponding to desired state – minimised phase angles and altitude errors According to Lyapunov Stability theory, derivative must be negative definite for convergence Image From: http://www.kidsnewsroom.org/elmer/infocentral/space/html/universe/solar_system/planets/mars/surface/atmosphere/atmosphere.html 1st November 2012 Garrie S. Mushet 8

  9. Controller Artificial Potential Field Controller Following control law is proposed to best facilitate convergence of the system: Target longitude for each satellite offset slightly to maintain minimum separation distance Satellites assigned to targets based on initial proximity Image From: http://www.kidsnewsroom.org/elmer/infocentral/space/html/universe/solar_system/planets/mars/surface/atmosphere/atmosphere.html 1st November 2012 Garrie S. Mushet 9

  10. Demonstration 90 satellites, 3 targets: Image From: http://www.kidsnewsroom.org/elmer/infocentral/space/html/universe/solar_system/planets/mars/surface/atmosphere/atmosphere.html 1st November 2012 Garrie S. Mushet 10

  11. Parameter Analysis Conducted parameter analysis to understand constellation behaviour in terms of and convergence time as number of satellites and number of targets is varied Number of Satellites = 100, 150, 200, 250, 300, 350, 400 Number of Targets = 1, 2, 3, 4, 5 Performed for 3 different maximum thrust regimes representing different classes of response times Every target required 20 satellites to converge above its longitudinal position Image From: http://www.kidsnewsroom.org/elmer/infocentral/space/html/universe/solar_system/planets/mars/surface/atmosphere/atmosphere.html 1st November 2012 Garrie S. Mushet 11

  12. Parameter Analysis • Clearly an intrinsic advantage in having a higher number of satellites • As number of satellites increases, Delta V requirement reduces significantly, with reduction becoming more prominent as the number of targets is increased • With 5 targets, 40% saving in Delta V and 60% reduction in convergence time on average between 100 and 400 satellites. Savings expected to increase as number of satellites increases further Image From: http://www.kidsnewsroom.org/elmer/infocentral/space/html/universe/solar_system/planets/mars/surface/atmosphere/atmosphere.html 1st November 2012 Garrie S. Mushet 12

  13. Applications • Parameter study displays results for three different orders of magnitude of acceleration • Result is three classes of Delta V requirement and convergence time, and by extention, operational life-time • Each class corresponds to different possible mission applications • High Delta v, low convergence time – telecommunications response to peaks in demand associated with pre-planned events – e.g. Olympics • Low Delta v, high convergence time – disaster response • In all cases more satellites -> better performance Image From: http://www.kidsnewsroom.org/elmer/infocentral/space/html/universe/solar_system/planets/mars/surface/atmosphere/atmosphere.html 1st November 2012 Garrie S. Mushet 13

  14. Conclusions/Future • A simple method of controlling constellations of small satellites in GEO with the capability of reconfiguring to meet changes in demand has been demonstrated • Feasibility of the control law has been demonstrated with simple test cases • Parameter analysis has provided understanding of the constellation performance and suggested multiple mission concepts • Basis for future work has been formed – future work will investigate 3D eccentric orbits with relevant perturbations including solar radiation pressure and the J22 effect. Work will be extended to multiple-ring constellations. • In all cases more satellites -> better performance Image From: http://www.kidsnewsroom.org/elmer/infocentral/space/html/universe/solar_system/planets/mars/surface/atmosphere/atmosphere.html 1st November 2012 Garrie S. Mushet 14

  15. Thank You! garrie.mushet@strath.ac.uk

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