Three years of successful in-orbit calibration of the modular optoelectronic scanner (MOS) on the Indian IRS-P3 mission

Abstract

The Modular Optoelectronic Scanner MOS of the German Aerospace Center (DLR) has now been working about three years on board the Indian Remote Sensing Satellite IRS-P3 very successfully. It consists of three instruments: the spectrometer MOS-A (for atmospheric purposes with 4 spectral bands in the 02A absorption band from 757nm to 767 nm and a spectral FWHM of i -1.4 nm), the spectrometer MOS-B (for ocean, land and atmospheric purposes with 13 spectral bands between 400 nm and 1010 nm and a spectral FWHM of AX 10 nm) and the camera MOS-C (1 spectral band at 1.6 jim with a spectral FWHM of & = 100 nm). To meet the sophisticated radiometric and spectral requirements especially for ocean purposes, a 16 bit dynamic range and a qualified in-flight calibration concept including sun calibration and internal lamp calibration have been established. All three instruments have shown a remarkably high data stability and quality during the three years mission time. The highest changes of radiometric sensitivity of +7% were found in the SWIR-channels of MOS-B and the lowest changes of -1% in the MOS-A channels. Spectral shifts of center wavelengths could not be found. Small differences between the results of the two calibration methods are due to the fact that they do not cover the same optical components exactly. But this enables us to allocate the sensitivity changes to those components of the instruments which cause them. The measured in-orbit calibration values were used to update the calibration coefficients.