Mapping Distortion of Detectors in UVIT Onboard AstroSat Observatory
  Ultraviolet Imaging Telescope (UVIT) is one of the payloads onboard AstroSat, India's first multi-wavelength Astronomy mission. UVIT is primarily designed to make high resolution images in wide field, in three wavelength channels simultaneously: FUV (130 - 180 nm), NUV (200 - 300 nm) and VIS (320 - 550 nm). The intensified imagers used in UVIT suffer from distortions, and a correction is necessary for these to achieve good astrometry. In this article we describe the methodology and calculations used to estimate the distortions in ground calibrations. 
V. Girish, Shyam N. Tandon, S. Sriram, Amit Kumar and Joe Postma
astro-ph.IM