Calibration of VELC detectors on-board Aditya-L1 mission

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 \(\varvec{R}_{\odot }\) ${\mathit{R}}_{\odot }$ , and to pursue spectroscopy at 5303 Å, 7892 Å  and 10747 Å  channels in the FOV (1.05 - 1.5 \(\varvec{R}_{\odot }\) ${\mathit{R}}_{\odot }$ ). 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 \(\varvec{-5^\circ }\) $\mathbf{-}{\mathbf{5}}^{\mathbf{\circ }}$ and \(\varvec{-17^{\circ }}\) $\mathbf{-}{\mathbf{17}}^{\mathbf{\circ }}$ C, respectively, at the spacecraft level.