Analysis of MetOp/HIRS instrument self-emission and its impact on on-orbit calibration

Tiejun Chang; Changyong Cao

doi:10.1117/12.897463

3 October 2011 Analysis of MetOp/HIRS instrument self-emission and its impact on on-orbit calibration

Tiejun Chang, Changyong Cao

Proceedings Volume 8176, Sensors, Systems, and Next-Generation Satellites XV; 81760X (2011) https://doi.org/10.1117/12.897463
Event: SPIE Remote Sensing, 2011, Prague, Czech Republic

Abstract

This paper presents the self-emission models for infrared radiometers and analyzes the interrelationship between instrument self-emission, detector nonlinearity, and intercept and gain variations using both MetOp/HIRS prelaunch and post-launch data. HIRS has 19 infrared channels and 1 visible channel. The warm filters and other components makes the self-emission the majority of the total radiance detected. The thermal-equilibrium condition in pre-launch thermal vacuum allows us to evaluate the self-emission using a simplified model. It was found that the self-emission contributions at the detectors are in the range of 95% to 97%. A more comprehensive self-emission model is developed for the post-launch instrument by considering its thermal complexity, and the model is used to analyze the on-orbit instrument self-emission. The self-emission contributions are found in the range of 96% to 99% post-launch, and the difference between the pre-launch and post-launch is discussed. The on-orbit calibration of the HIRS infrared channels is performed every 40 scan lines using instrument responses to the views of the internal calibration target and cold deep space. The twopoint calibration provides a slope and an intercept for each channel. The instrument self-emission variation makes both coefficients deviate from their calibration value, and if uncorrected, can lead to errors in Earth radiance retrieval. The quantifications of these variations provide guidelines for on-orbit calibration algorithm improvement. Potential applications of both pre-launch and post-launch self-emission models to other infrared radiometers and sounders, and the impact assessment in general, are also discussed.

Citation Download Citation

Tiejun Chang and Changyong Cao "Analysis of MetOp/HIRS instrument self-emission and its impact on on-orbit calibration", Proc. SPIE 8176, Sensors, Systems, and Next-Generation Satellites XV, 81760X (3 October 2011); https://doi.org/10.1117/12.897463

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