26 October 2007 Disturbances and their corrections in space observation with GOSAT Fourier transform spectrometer
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Abstract
GOSAT (Greenhouse Gases Observing Satellite) is a satellite to measure greenhouse gases from space with the Fourier Transform Spectrometer (FTS). It measures spectra of Earth-reflected solar radiations with high spectral resolution of about 0.2 cm-1, covering four spectral bands, including 0.76, 1.6, 2.0 and 14 micron wavelength regions. In first three bands, we have two detectors for measuring two components of polarization. For the acquisition of one interferogram, it takes 4 seconds or less, depending on the definition of measurement mode. Since the satellite moves in high speed, an image motion compensation mirror (IMC) works to continuously stare the same position on the Earth surface during this period of acquisition. For staring same position, the mirror is controlled by two-axis motors. Staring position could slightly fluctuate around the right position, making the position of the instantaneous filed of view (IFOV) vibrate with an amplitude of a few hundreds meters. Since the optical characteristics (such as the albedo) of the IFOV changes place-by-place, the intensity of IFOV could also change due to this fluctuation. The intensity of IFOV could also change due to the change of reflection angle, wind on the water surface, or other causes. During this period of the acquisition, the optical path length and Doppler shift caused by the satellite moving could also change. In this paper, we examine the effects of some of these kinds of disturbances to the signals of interferograms on resultant spectra and retrieval accuracies of CO2, and discuss about the correction method to the interferogram and spectra.
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Tadao Aoki, Tadao Aoki, Tatsuya Yokota, Tatsuya Yokota, Gen Inoue, Gen Inoue, Koji Nobuta, Koji Nobuta, Akira Kotani, Akira Kotani, } "Disturbances and their corrections in space observation with GOSAT Fourier transform spectrometer", Proc. SPIE 6748, Image and Signal Processing for Remote Sensing XIII, 674812 (26 October 2007); doi: 10.1117/12.736793; https://doi.org/10.1117/12.736793
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