Characterizing Spectral Channels of Visible Emission Line Coronagraph of Aditya-L1

TL;DR

This paper presents an optimization strategy for the slit width of India's VELC instrument on Aditya-L1, using synthetic spectra to maximize SNR and inform observation planning of the solar corona.

Contribution

It introduces a synthetic profile-based method to optimize slit width for VELC, considering instrument and coronal conditions, enhancing observation quality and planning.

Findings

Optimal slit width identified as 50 microns for VELC.

SNR estimates guide future observation strategies.

Analysis of CME effects on spectral observations included.

Abstract

Aditya-L1 is India's first solar mission with Visible Emission Line Coronagraph (VELC) consisting of three spectral channels taking high-resolution spectroscopic observations of the inner corona up to 1.5 Rsun at 5303 \AA, 7892 \AA, and 10747 \AA. In this work, we present the strategy for the slit width optimization for the VELC using synthetic line profiles by taking into account the instrument characteristics and coronal conditions for log(T) varying from 6 to 6.5. The synthetic profiles are convolved with simulated instrumental scattered light and noise to estimate the signal-to-noise ratio (SNR), which will be crucial to design the future observation plans. We find that the optimum slit width for VELC turns out to be 50 microns providing sufficient SNR for observations in different solar conditions. We also analyzed the effect of plasma temperature on the SNR at different heights in the VELC field of view for the optimized slit width. We also studied the expected effect of the presence of a CME on the spectral channel observations. This analysis will help to plan the science observations of VELC in different solar conditions.