  AstroSat is a multi-wavelength satellite launched on 2015 September 28. The
CZT Imager of AstroSat on its very first day of operation detected a long
duration gamma-ray burst (GRB) namely GRB 151006A. Using the off-axis imaging
and spectral response of the instrument, we demonstrate that CZT Imager can
localise this GRB correct to about a few degrees and it can provide, in
conjunction with Swift, spectral parameters similar to that obtained from
Fermi/GBM. Hence CZT Imager would be a useful addition to the currently
operating GRB instruments (Swift and Fermi). Specifically, we argue that the
CZT Imager will be most useful for the short hard GRBs by providing
localisation for those detected by Fermi and spectral information for those
detected only by Swift. We also provide preliminary results on a new exciting
capability of this instrument: CZT Imager is able to identify Compton scattered
events thereby providing polarisation information for bright GRBs. GRB 151006A,
in spite of being relatively faint, shows hints of a polarisation signal at
100-300 keV (though at a low significance level). We point out that CZT Imager
should provide significant time resolved polarisation measurements for GRBs
that have fluence 3 times higher than that of GRB 151006A. We estimate that the
number of such bright GRBs detectable by CZT Imager is 5 - 6 per year. CZT
Imager can also act as a good hard X-ray monitoring device for possible
electromagnetic counterparts of Gravitational Wave events.
