Innovations in the AOCS of AstroSat spacecraft

AstroSat is India’s first mission dedicated to space-based Astronomy and carries a complement of instruments sensitive over a wide spectral region covering visible, ultraviolet, soft X-ray and hard X-ray bands. The spacecraft platform provides the required stability, pointing, power, thermal control, and interface requirements. Among the critical functions of the Attitude and Orbit Control System (AOCS) were, manoeuvre the spacecraft from one target source to another in an optimal way while avoiding the sun, compensate for the rotational disturbance torque created by the scanning of the SSM payload on the other payloads, primarily the UVIT payload, provide for calibration of all the payloads, which involved manoeuvring through 2-dimensional target patterns. All the above novel control functions, along with the routine house-keeping operations, were designed, developed, and tested extensively on ground, before declaring them as flight-worthy. The payload performance and the resulting science are a testimony to the excellent performance of the on-board Control System.