7 October 2014 ASTER TIR onboard calibration over fourteen years
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Abstract
The ASTER Instrument is one of the five sensors on the NASA’s Terra satellite on orbit since December 1999. After 14 years on orbit, ASTER VNIR and TIR are still taking Earth images of good quality. The TIR radiometer has five bands from 8 to 12 μm with spatial resolution of 90 m. Each band has ten detectors. The detectors are cooled at 80 K precisely by using a Stirling cooler within 0.1 K. TIR is radiometrically calibrated by a single onboard blackbody. In the normal operation mode the blackbody is kept at 270 K, and once in 49 days the blackbody is heated up to 340 K for the gain calibration. The degradation at band 12 is largest and 48% and that at band 10 is smallest and 18%. One of the possible causes of the degradation is the contamination accretion by outgas of silicone SE9188 RTV used for TIR followed by the ultraviolet radiation. The absorption spectra of outgas of this silicon was measured at JAXA and the absorption spectra showed similar to the TIR degradation in the early days on orbit. ASTER science team is proposing the second lunar calibration at the end of terra mission for the estimation of the TIR optical characteristics. ASTER experienced first lunar calibration in April 2003 and many of the TIR bands were saturated. Due to the responsivity degradation the TIR dynamic range has extended to higher temperature. At least TIR four bands will not saturate in the next lunar calibration.
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Fumihiro Sakuma, Masakuni Kikuchi, Kenji Tatsumi, Hidehiko Ono, "ASTER TIR onboard calibration over fourteen years", Proc. SPIE 9241, Sensors, Systems, and Next-Generation Satellites XVIII, 92410N (7 October 2014); doi: 10.1117/12.2067082; https://doi.org/10.1117/12.2067082
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