ON-BOARD PROCESSING FOR ATTITUDE CONTROL OF APPLE

Abstract

APPLE, India’s first three axis stabilised communication satellite, was launched by the ARIANE launcher on June 19,1981. The communication payload operates in C-band (4-6 GHz) and facilitates experiments in communication technology and its applications. Attitude and Orbit control System (AOCS) of APPLE, whose on orbit performance is satisfactory despite the non deployment of one of the solar panels, is briefly described. Various functions on the Attitude Control Electronics (ACE) are described with details on processing schemes for Pulsewidth Pulse Frequency Modulator, Yaw error computation using hybrid SINE convertor, Magnetic torquer control and Thruster selection. Further, future trends in onboard processing for communication satellites are highlighted.