Solar observation with the Fourier transform spectrometer I : Preliminary results of the visible and near-infrared solar spectrum

TL;DR

This paper reports preliminary results of solar spectrum observations using a Fourier transform spectrometer in visible and near-infrared wavelengths, validating the method and setup for future solar magnetic field measurements.

Contribution

It introduces a novel experimental setup and data analysis method for solar spectrum observation with FTS, demonstrating good agreement with standard spectra in the visible and near-infrared ranges.

Findings

Good consistency with solar spectrum atlas from 0.45-2.2 μm

Validated the observation and data analysis methods

Provided experience for future solar magnetic field measurements

Abstract

The Fourier transform spectrometer (FTS) is a core instrument for solar observation with high spectral resolution, especially in the infrared. The Infrared System for the Accurate Measurement of Solar Magnetic Field (AIMS), working at 10-13 $\mu m$, will use a FTS to observe the solar spectrum. The Bruker IFS-125HR, which meets the spectral resolution requirement of AIMS but just equips with a point source detector, is employed to carry out preliminary experiment for AIMS. A sun-light feeding experimental system is further developed. Several experiments are taken with them during 2018 and 2019 to observe the solar spectrum in the visible and near infrared wavelength, respectively. We also proposed an inversion method to retrieve the solar spectrum from the observed interferogram and compared it with the standard solar spectrum atlas. Although there is a wavelength limitation due to the present sun-light feeding system, the results in the wavelength band from 0.45-1.0 $\mu m$ and 1.0-2.2 $\mu m$ show a good consistence with the solar spectrum atlas, indicating the validity of our observing configuration, the data analysis method and the potential to work in longer wavelength. The work provided valuable experience for the AIMS not only for the operation of a FTS but also for the development of its scientific data processing software.