Autonomous Mode of Spacecraft Operations - GSAT-1 Experience

摘要

GSAT-1 was launched by first GSLV-D1 flight on l8th April 2001 from Satish Dhawan Space Centre, India. Short fall in the launcher-provided orbital velocity and spacecraft specific propulsion anomalies led to an orbit with a 23 hour period, with a drift rate of about 13° per day. To test and verify many of the new technological payloads, we had to devise means of maintaining satellite health without RF contact for long durations of nearly two weeks between satellite visibility over GSAT-1 TTC station Hassan. The problem was compounded with solar array drive assembly failure to track the sun. After detailed data analysis proper logics were devised and implemented by suitably updating onboard attitude and orbit control(AOCC) software. Proper power and thermal system configurations were arrived at. The autonomous mode of operations covered normal sun-lit period as well as special events such as lunar shadow and eclipse season. The Spacecraft functioned successfully for over a year to enable the verification of the new technology and survived two eclipse seasons.