Reducing uncertainty in the AIRS radiometric calibration

Thomas S. Pagano; Evan M. Manning; Steven E. Broberg; Hartmut Aumann; Margie Weiler; Larrabee Strow

doi:10.1117/12.2320906

7 September 2018 Reducing uncertainty in the AIRS radiometric calibration

Thomas S. Pagano, Evan M. Manning, Steven E. Broberg, Hartmut Aumann, Margie Weiler, Larrabee Strow

Proceedings Volume 10764, Earth Observing Systems XXIII; 107640N (2018) https://doi.org/10.1117/12.2320906
Event: SPIE Optical Engineering + Applications, 2018, San Diego, California, United States

Abstract

The Atmospheric Infrared Sounder (AIRS) radiometric calibration coefficients convert the counts measured from the instruments A/D converters (Level 1A) to SI traceable radiance units (Level 1B). The calibration equations are based on how the instrument operates and follow a simple second order relationship between counts and radiance. Terms are included to account for nonlinearity of the detectors, emissivity and temperature knowledge of the on-board calibrator (OBC) blackbody and radiometric offset due to coupling of the polarization of the scan mirror with the spectrometer. In this paper, we re-derive the radiometric calibration equation with a little more rigor and account for the view angle of each of the 4 space views. We then derive new polarization coefficients from the 4 space views over the mission and use them re-derive the coefficients for blackbody emissivity and nonlinearity. We then compare new coefficients (Version 7k) with the latest operational version of the AIRS radiometric calibration coefficients (Version 5). The AIRS Version 5 coefficients were sufficiently adequate that an update has never been made since AIRS launch in 2002. However, it can be seen, when we compare to the Cross-track Infrared Sounder (CrIS), that better agreement is made in Version 7. The impact of the new coefficients is highest at cold scene temperatures and very warm temperatures.

Conference Presentation

Citation Download Citation

Thomas S. Pagano, Evan M. Manning, Steven E. Broberg, Hartmut Aumann, Margie Weiler, and Larrabee Strow "Reducing uncertainty in the AIRS radiometric calibration", Proc. SPIE 10764, Earth Observing Systems XXIII, 107640N (7 September 2018); https://doi.org/10.1117/12.2320906

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