Ultraviolet Imaging Telescope on AstroSat

Abstract

Solar coronagraph mimics total solar eclipse by blocking the solar disk and enabling the observation of extended coronal atmosphere of the Sun. Visible Emission Line Coronagraph (VELC), on-board Aditya-L1 space mission, is an internally occulted solar coronagraph capable of simultaneous imaging, spectroscopy and spectro-polarimetry close to the solar limb. This payload is designed to study the coronal plasma and heating of the solar corona. Studying development, dynamics and origin of coronal mass ejections and measurement of coronal magnetic fields over active regions are other important science goals. VELC is designed to image the solar corona at 500 nm with an angular resolution of 5 over a field of view (FOV) of 1.05–3 R o. It also facilitates simultaneous multi-slit spectroscopy at three emission lines, viz. Fe XIV (530.3 nm), Fe XI (789.2 nm) and Fe XIII (1074.7 nm) with a spectral resolution of 28 , 31 and 202 mÅ/pixel respectively, over an FOV of 1.05–1.5 Ro. The payload has a dual-beam spectro-polarimetry channel for magnetic field measurements at 1074.7 nm.