Calibration of subsystems of visible emission line coronagraph

Abstract

Aditya-L1, India’s first mission with multiple science payloads is designed to study the solar dynamics. Aditya-L1 includes multiple payloads, the significant one being the Visible Emission Line Coronagraph (VELC). VELC is designed to study the solar corona from 1.05 Ro to 3R, which has never been achieved by any other space solar mission. It consists of four channels for observation, two spectroscopic, one spectropolarimetric and one imaging channel. VELC contains 38 optical elements including mirrors, lenses, diffraction grating, etc. These 38 optical elements are made into 17 optical assemblies. The performance of each of the elements must be tested and calibrated before they can be used in the payload. This report will go through all the procedures followed for calibration of polarization modulators, polarizing beam displacers and diffraction grating.