Scanning Sky Monitor onboard AstroSat

Scanning Sky Monitor (SSM) onboard AstroSat is an X-ray sky monitor in the soft X-ray band (2.5 to 10 keV). SSM is designed with a large field of view to detect and locate transient X-ray sources and alert the astronomical community about interesting phenomena in the X-ray sky. SSM comprises position sensitive proportional counters with 1D coded mask for imaging. There are three detector units mounted on a platform capable of rotation which helps covering about 50% of the sky in one full rotation. AstroSat was launched in September 2015. Since then SSM has been observing the sky with its three Cameras mounted on a rotating platform. Although the theoretical sensitivity of SSM goes down to 30 mCrab, due to its really large Field of View which is about 2200 sq_deg per Camera unit, the X-ray sky seen by SSM is swamped with huge diffuse X-ray background along with background from other sources like the Earth in its FoV (whenever it comes in the FoV), the charge-particle background during ingress and egress of SAA, additional scattered background if the spacecraft elements come in the FoV etc. Detailed study of these background components has given a realistic judgement of the sensitivity and duty cycle for SSM. Also detailed calibration study has helped update the response of the instrument and bring out the best possible science with the instrument. Only bright sources have been reported by SSM with which a handful of Astronomer’s Telegrams were published with the SSM lightcurves for really bright transients. In addition, SSM data has been studied for additional objectives like rotation period of pulsars, different variability classes of the exotic source, GRS 1915+105 etc. The talk will discuss science results from SSM since the launch and also the details of the onboard calibration aspects of the instrument.