Understanding the possible effect of scan mirror contamination in the AIRS instrument

R. Chris Wilson; Evan Manning; Thomas Pagano; Hartmut Aumann; Steven Broberg

doi:10.1117/12.2568798

20 August 2020 Understanding the possible effect of scan mirror contamination in the AIRS instrument

R. Chris Wilson, Evan Manning, Thomas Pagano, Hartmut Aumann, Steven Broberg

Proceedings Volume 11502, Infrared Remote Sensing and Instrumentation XXVIII; 115020G (2020) https://doi.org/10.1117/12.2568798
Event: SPIE Optical Engineering + Applications, 2020, Online Only

Abstract

AIRS has provided highly stable and accurate radiances since 2002. Stability at the 2 mK/yr has been demonstrated relative to the sea surface temperature (SST) in the 8-12 micron window channels. However, there is evidence of a larger trend in the shortwave channels: 8mK/yr when viewing clear ocean at about 300K, about 200 mK/yr when viewing 220K DCC at night in the tropical oceans, but a trend of less than 20 mK/yr for Dome C at 220K. Under these conditions, the 8-12 micron window channels show trends of less than 20 mK/yr. This study proposes that the trends in the shortwave channels are the result of a wavelength dependent contamination of the scan mirror and the on-board calibration (OBC) blackbody. Scattered light from nearby scenes while viewing DCCs causes the large apparent radiometric trend in the shortwave channels and can be removed via spatial linear regression. An experiment that assumes the OBC blackbody emissivity has slightly decreased is tested to explain the smaller trends. The emissivity experiment results show similar stability drifts at 1231 cm^-1 but not to other window channels. The emissivity decrease may explain some of the stability drift, but other unknown physical mechanisms are likely as well.

Conference Presentation

Citation Download Citation

R. Chris Wilson, Evan Manning, Thomas Pagano, Hartmut Aumann, and Steven Broberg "Understanding the possible effect of scan mirror contamination in the AIRS instrument", Proc. SPIE 11502, Infrared Remote Sensing and Instrumentation XXVIII, 115020G (20 August 2020); https://doi.org/10.1117/12.2568798

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