In-orbit Calibrations of the Ultraviolet Imaging Telescope

The Ultra-Violet Imaging Telescope (UVIT) is one of the payloads in ASTROSAT, the first Indian Space Observatory. The UVIT instrument has two 375. mm telescopes: one for the far-ultraviolet (FUV) channel (1300-1800 angstrom), and the other for the near-ultraviolet (NUV) channel (2000-3000 angstrom) and the visible (VIS) channel (3200-5500 angstrom). UVIT is primarily designed for simultaneous imaging in the two ultraviolet channels with spatial resolution better than 1." 8, along with provisions for slit-less spectroscopy in the NUV and FUV channels. The results of in-orbit calibrations of UVIT are presented in this paper.