Collision Risk Mitigation for Deimos Imaging Low Thrust Satellites

Abstract

A collision risk mitigation strategy is proposed for DEMOS-1 and DEIMOS-2 in order to ensure mission survivability, although taking into account several constraints coming from the platform. Due to the fact that both satellites are equipped with low-thrust electric propulsion systems, the achievable delta-V is too low to be able to separate the satellite enough from the incoming object along the radial direction. The strategy consists of a single collision avoidance maneuver that has to be made several hours before the Time of Closest Approach in order to achieve the suitable in-track separation from the expected collision location. The propulsion system characterization provides a deeper insight of that. The internal procedure implements a constant monitoring of hazardous events, assessing conjunction characteristics and sharing trajectory information with the 18th SPace Control Squadron (SPCS). It provides a scheme to be followed when meeting certain conditions, mainly the time to closest approach and collision probability. In this process, the automatic generation of risk assessment reports and reception of alarms by email are essential for the Flight Dynamics Team to be warned of new important events at any time of the day. The safety of the post-maneuver trajectory must also be granted by analyzing the close approaches foreseen after any orbit control maneuver and before executing it. This paper goes through the risk mitigation procedure especially dedicated to Deimos Imaging's low-thrust satellites when maneuvering for collision avoidance or orbit control purposes. I. Nomenclature Delta-V= velocity variation PC = collision probability as computed by Deimos Imaging