16 September 2011 MetOp/HIRS pre-launch characterization data reanalysis
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Instrument self-emission and nonlinear response play important roles in satellite thermal infrared radiometers, and can affect the accuracy of Earth scene radiance retrieval if uncorrected. This paper presents a simplified self-emission model for infrared radiometers and analyzes the interrelationships between the instrument selfemission, detector nonlinearity, and calibration intercept and slope variations using MetOp-A/HIRS prelaunch characterization data. HIRS is a traditional cross-track line scanning radiometer in the infrared and visible spectrum, including 12 long wave infrared channels (669-1529cm-1), 7 short wave infrared channels (2188- 2657cm-1), and 1 visible channel, with beamsplitters and a rotating filter wheel assembly consisting of 20 spectral filters separates individual channels. The warm filters and other in-path components generate selfemission which becomes the majority of the total radiance falling on the detector. The pre-launch TV data allow us to evaluate the self-emission using the simplified model. It was found that the self-emission contributions at the detectors are in the range of 95% to 97%. The self-emission fluctuates with the instrument temperature and causes the variation in instrument response, including the variations of intercept and the instrument gain. The quantification of these variations provides guideline for on-orbit calibration algorithm improvement. The selfemission model is improved and its impact on MetOp-A/HIRS on-orbit calibration and Earth scene retrieval are also assessed.
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Tiejun Chang, Tiejun Chang, Changyong Cao, Changyong Cao, } "MetOp/HIRS pre-launch characterization data reanalysis", Proc. SPIE 8154, Infrared Remote Sensing and Instrumentation XIX, 815418 (16 September 2011); doi: 10.1117/12.891916; https://doi.org/10.1117/12.891916

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