Calibration of Spectropolarimetry package for Visible Emission Line Coronagraph (VELC) on board Aditya-L1 mission

Abstract

Visible Emission Line Coronagraph (VELC) is the prime payload on board Aditya-L1 mission. One of the unique capabilities of VELC is the coronal magnetic field measurements from space. To achieve this, VELC performs dual beam spectropolarimetric observations in coronal emission line centered at 10747Å. Spectropolarimetric channel of VELC consists of different polarimetric components such as quarter waveplate (QWP), polarising beam displacer (PBD) and half waveplate (HWP). Calibration of individual components is essential to ensure that they meet the performance requirements of the payload. This work discusses the details of the calibration tests carried out to evaluate the performance of different polarimetric components of VELC and the results obtained.