A Novel Method for Fault Tolerance Intelligence Advisor System (FT-IAS) for Mission Critical Operations

In Communication and inter-planetary missions, satellites are placed in elliptical parking orbits (EPO). This is followed by a series of maneuvers which subsequently positions the spacecraft in the de-sired Orbit. Liquid Apogee Motor (LAM) mode is a thruster firing mode used for orbit raising with the help of sensors such as Dynamically Tuned Gyroscopes (DTG), Digital Sun Sensors (DSS), Star Sensors (SS) and actuators such as thrusters. In the LAM mode, the output from the selected sensor is used to update the spacecraft attitude and this is compared with the desired attitude steering profile to derive the error in the attitude. The controller then corrects the spacecraft attitude error along the three axes. Presently, in the absence of sensor data during LAM mode, the burn is terminated by the on-board software logic and the spacecraft is normalized by ground intervention. But during mission critical operations, like in interplanetary missions, this logic fails to meet the mission requirements since there is no other opportunity to carry out the burn. In this context, a new fault tolerant intelligence approach is required. This chapter discusses the design and implementation of a new logic introduced in on-board software, to overcome LAM termination, in case of failure of sensor data updates. It also highlights the recovery time for various combinations of sensor failures.