Calibration of Fourier Transform Spectrometer with Blackbody Temperatures Optimally Determined

Spectral responsivity calibrating of Fourier Transform Spectrometer (FTS) is essential for eliminating its systematic error in a ground-based solar observation system. Conventionally the calibration is being done by the three-temperature blackbody method, which gives a spectral responsivity curve of the FTS under calibration in addition to the respective temperatures of the blackbody. It is an advantage that the method does not require pre-information on the blackbody temperatures. However, a combination of three temperatures remains a question in terms of the calibration accuracy. In this paper, the method is applied to a high level of radiance calibration at a wavenumber range from 2000 cm-1 to 8000 cm-1. We propose a technique which determines an optimal combination of the three temperatures in the blackbodies to improve the calibration accuracy of the FTS. Experiments were carried out using four arbitrary combinations of blackbody temperatures settings and an optimal combination of the temperature settings. The result deviation of the optimal combination is less than 0.5% and 3% for measured temperature and spectral radiance respectively, which is better than the arbitrary temperature combinations. (paper)