Calibration procedures for the CHASE/HIS science data

TL;DR

This paper details the calibration procedures for the CHASE/HIS solar observation data, enabling accurate scientific analysis of high-resolution H-alpha spectroscopic measurements from the Sun.

Contribution

It introduces comprehensive calibration methods for CHASE/HIS data, improving data quality for solar eruption and plasma dynamics studies.

Findings

Calibration procedures enable accurate wavelength and intensity measurements.

Data correction methods improve the reliability of solar spectroscopic data.

Higher-level data products are ready for scientific research.

Abstract

The H{\alpha} line is an important optical line in solar observations containing the information from the photosphere to the chromosphere. To study the mechanisms of solar eruptions and the plasma dynamics in the lower atmosphere, the Chinese H{\alpha} Solar Explorer (CHASE) was launched into a Sun-synchronous orbit on October 14, 2021. The scientific payload of the CHASE satellite is the H{\alpha} Imaging Spectrograph (HIS). The CHASE/HIS acquires, for the first time, seeing-free H{\alpha} spectroscopic observations with high spectral and temporal resolutions. It consists of two observational modes. The raster scanning mode provides full-Sun or region-of-interest spectra at H{\alpha} (6559.7-6565.9 {\AA}) and Fe I (6567.8-6570.6 {\AA}) wavebands. The continuum imaging mode obtains full-Sun photospheric images at around 6689 {\AA}. In this paper, we present detailed calibration procedures for the CHASE/HIS science data, including the dark-field and flat-field correction, slit image curvature correction, wavelength and intensity calibration, and coordinate transformation. The higher-level data products can be directly used for scientific research.