Retrospective Proposals for the Orbital Correction of GSAT0201 & GSAT0202

Abstract

On August 22, 2014, the first two Full Operational Capacity satellites of the Galileo constellation were launched from Kourou on a Soyuz ST-B rocket. Shortly after the insertion into the final orbit, the on-board telemetry showed the achieved orbit was different from the target highly inclined circular orbit, due to a failure in the Fregat upper stage attitude control system. This anomaly precluded nominal operations in the Galileo constellation, as well as introducing limitations in the use of several of on-board subsystems. A recovery campaign took place in the winter of 2014 to change the two satellites’ trajectories, so to reduce the entity of operative constraints and provide better communication with the ground segment. With no dedicated orbital thruster available, attitude thrusters were used effectively to modify and enhance the orbit and recover from a multi-system failure, making reinsertion in a GNSS constellation possible. This work investigates, by means of a numerical model, the best combination and sequence of maneuvers that could have been implemented in the recovery campaign to satisfy most proposed drivers with the given \(\Delta v\) budget. The results show that different final orbits with the same resonance but lower eccentricity could have been achieved.