In orbit performance of UVIT over the 5 years

TL;DR

Over five years, UVIT demonstrated stable sensitivities, effective contamination control, and improved calibration and operational protocols, ensuring reliable in orbit performance despite challenges like charged particle hits.

Contribution

This paper provides a comprehensive analysis of UVIT's in orbit performance over five years, including calibrations, operational improvements, and handling of in orbit challenges.

Findings

UV sensitivities remained steady over 5 years

Calibration procedures were refined for greater accuracy

Operational protocols were optimized based on in orbit experience

Abstract

Over the last 5 years, UVIT has completed observations of more than 500 proposals with ~ 800 unique pointings. In addition, regular planned monitoring observations have been made and from their analysis various key parameters related to in orbit performance of UVIT have been quantified. The sensitivities of the UV channels have remained steady indicating no effect of potential molecular contamination confirming the adequacy of all the protocols implemented for avoiding contamination. The quality of the PSF through the years confirms adequacy of thermal control measures. The early calibrations obtained during the Performance Verification (PV) phase have been further revised for more subtle effects. These include flat fields and detector distortions with greater precision. The operations of UVIT have also evolved through in orbit experience, e.g. tweaking of operational sequencing, protocol for recovery from bright object detection (BOD) shutdowns, parameters for BOD thresholds, etc. Finally, some effects of charged particle hits on electronics led to opimised strategy for regular resetting. The Near-UV channel was lost in one of such operations. All the above in-orbit experiences are presented here.