Detector electronics for visible emission line coronagraph payload of Aditya-L1

Abstract

Accurate solar observation plays a vital role in space weather prediction. Aditya-L1, ISRO’s first solar observatory mission, carried a Visible Emission Line Coronagraph (VELC) instrument. This instrument provides observations very close to the solar limb with internal occultation. We provide design and development details of detector electronics for continuum, two spectroscopic channels and one spectro-polarimetry channel of the VELC instrument. The developed hardware with imaging detectors (sCMOS in visible and InGaAs in near-infrared spectral region) has very high sensitivity (noise equivalent signal = 0.2 photon/s/pixel). The instrument has onboard intelligence for detection of coronal mass ejection events. Photon-noise-limited detector electronics are developed and qualified for all four channels. Dark noise of ≈1.2e− with dark signal ≈0.035e−/p/s was achieved. Detector electronics cater to very high input dynamic range >120 dB. Stringent contamination control protocols were evolved and implemented during all stages of development. The uniqueness of the VELC instrument is that it makes observations very close to the solar limb (1.05 R) as well as magnetic field measurements and has simultaneous spectroscopic and imaging capability.