Mitigate collision risk: different approaches for different missions

Le résumé fourni par la source

CNES operates nine "Mini-Micro" spacecrafts.CNES' flight dynamics team is responsible for these satellites' station-keeping as well as for the mitigation of collision risks with space debris.CNES' CAESAR department is dedicated to collision risks detection, monitoring and collision probability calculation.When the probability of collision is higher than a given "maneuvering" threshold, CAESAR alerts the operational flight dynamics team.The avoidance maneuver consists in a tangential maneuver at the opposite (180°) of the collision point in order to increase the radial crossing distance between the satellite and the debris, and thus, to lower the collision probability under an acceptable value.Due to their missions, these satellites have very different constraints and maneuvering abilities:• MICROSCOPE has a propulsive system based on cold gas, with low power.Initially the propulsive system was designed only to compensate for atmospheric drag for mission needs.Using such a propulsive system to mitigate close approaches requires long duration thrusts and so, longer notice time • JASONS, SMOS and CALIPSO spacecrafts, based upon the PROTEUS platform, have powerful thrusters, but they have different mission constraints: On JASONS, mission requires station-keeping within a narrow control box (+/-1km) and, in order to correctly perform their mission, JASONS are not allowed to exit their window, even temporarily.Therefore, the magnitude of a common Risk Mitigation Maneuver (RMM) leads to an almost immediate exit of such a narrow station-keeping window; On SMOS the constraint on the exit is as strong as on both JASONS, but the window is 10 times larger (10km vs. 1km).So, in most cases, a common RMM does not lead to an immediate exit; 1 Flight Dynamics Operations Engineer, Division of Satellite and Flight Dynamics Operations for Applications and European missions.2 Flight Dynamics Operations Engineer, Division of Satellite and Flight Dynamics Operations for Applications and European missions.3 Flight Dynamics Operations Engineer, Division of Satellite and Flight Dynamics Operations for Applications and European missions.4 Flight Dynamics Operations Engineer, Division of Satellite and Flight Dynamics Operations for Applications and European missions.

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