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abstract: 'We describe calibration data, and discuss performance of the photon-counting flight detectors for the Ultraviolet Imaging Telescopes on the Astrosat observatory. The paper describes dark current, flat field and light-spot images for FUV, NUV, and Visible band detectors at more than one wavelength setting for each. We also report on nominal gain and low-gain operations, full- and sub-window read rates, and non-photon-counting modes of operation, all expected to be used in flight. We derive corrections to the event centroids from the CMOS readout arrays, for different centroid algorihtms. We derive spatial resolution values for each detector and plots of point-source signal saturation for different flux levels. We also discuss ways to correct for saturation in extended object images.'
author:
- 'J. Postma'
- 'J.B. Hutchings'
- 'D. Leahy'
title: 'Calibration and performance of the photon-counting detectors for the Ultraviolet Imaging Telescopes (UVIT) of the Astrosat observatory[^1]'
---

Introduction and data
=====================

Astrosat is a multi-wavelength space observatory of the Indian Space Research Organisation (ISRO). The satellite is to be launched in 2012, and contains three pointed X-ray instruments and two UV-optical telescopes, all with fields of view that are aligned. There is also an X-ray scanning sky monitor. 