MASTER RECOVERY SEQUENCER (MRS) FOR AUTONOMOUS ATTITUDE RECOVERY OF INDIAN MARS ORBITER

摘要

Mars Orbiter Mission (MOM) is India's first interplanetary mission to planet Mars with the Spacecraft designed to orbit Mars in an elliptical orbit. The Attitude and Orbit Control Subsystem (AOCS) of MOM is configured as a 3-axis body stabilized zero momentum system with four reaction wheels to provide a stable platform and Reaction Control System (Eight 22N thrusters and one 440N Engine) for orbit raising, Mars Orbit Insertion (MOI) and attitude control. It has high performance inertial measurement system, star sensor for fine pointing and Coarse Analog Sun Sensor for sun pointing. For such missions on-board autonomy becomes vital due to large round trip delay, limited visibility, limited uplink/downlink volume and constraints on the communication link due to limited field of view. First level of autonomy is achieved through sensor and actuator FDIR (Fault Detection Isolation and Reconfiguration) logics, which take care of individual failures. The next level of autonomy is achieved by the Master Recovery Sequencer (MRS). The MRS takes a global view of the available resources, battery power and decides on the optimum recovery path. In each recovery path a set of convergence and timeout logics are incorporated at various stages, failure of which leads to choose the next best option. At the end of successful recovery, power generation and ground communication through high gain antenna are ensured. The required pre-settings and data used during safe mode recovery are stored in EEPROM, which will be uplinked/ updated from ground periodically. Simultaneous/multiple failures are taken care of by prioritising the recovery operations. Various failure scenarios are simulated and successful recovery was achieved through MRS during ground testing. This approach gave good reliability of on-board software and helped in faster realization of AOCS.