Calibration of VELC detectors on-board Aditya-L1 mission

Abstract

Aditya-L1 is the first Indian space mission to explore the Sun and solar atmosphere with seven multi-wavelength payloads, with Visible Emission Line Coronagraph (VELC) being the prime payload. It is an internally occulted coronagraph with four channels to image the Sun at 5000 Å in the field of view 1.05 - 3 R, and to pursue spectroscopy at 5303 Å, 7892 Å and 10747 Å channels in the FOV (1.05 - 1.5 R). In addition, spectropolarimetry is planned at 10747 Å channel. Therefore, VELC has three sCMOS detectors and one InGaAs detector. In this article, we aim to describe the technical details and specifications of the detectors achieved by way of thermo-vacuum calibration at the CREST campus of the Indian Institute of Astrophysics, Bangalore, India. Furthermore, we report the estimated conversion gain, full-well capacity, and readout noise at different temperatures. Based on the numbers, it is thus concluded that it is essential to operate the sCMOS detectors and InGaAs detector at −5◦ and −17◦ C, respectively, at the spacecraft level.