Calibration and performance of the photon-counting detectors for the Ultraviolet Imaging Telescopes (UVIT) of the Astrosat observatory

TL;DR

This paper details the calibration procedures and performance evaluation of photon-counting detectors used in the UVIT instruments on Astrosat, including their operational modes, resolution, and saturation correction methods.

Contribution

It provides comprehensive calibration data and performance analysis for UVIT photon-counting detectors, including new correction techniques for event centroids and saturation effects.

Findings

Measured spatial resolution for each detector.

Derived correction methods for event centroid errors.

Analyzed saturation effects in extended images.

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 algorithms. 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.