On-board calibration radiance error correction for MetOp/AVHRR IR channel

Tiejun Chang; Xiangqian Wu

doi:10.1117/12.929619

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15 October 2012 On-board calibration radiance error correction for MetOp/AVHRR IR channel

Tiejun Chang; Xiangqian Wu

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Proceedings Volume 8510, Earth Observing Systems XVII; 85100L (2012) https://doi.org/10.1117/12.929619
Event: SPIE Optical Engineering + Applications, 2012, San Diego, California, United States

Abstract

The increasing need for accuracy in Advanced Very High Resolution Radiometer (AVHRR) radiance products requires a precise calibration of the instrument response. One concern is the error in the on-board calibration radiance, which combines the on-board black body (BB) imperfection effect and the temperature measurement error. The BB imperfection effect includes the radiance reduction due to the non-perfect BB (emissivity less than 1) and the reflection of the instrument and Earth scene environment through the BB. In addition, discriminating the temperature measurement error and BB imperfection is difficult due to insufficient on-board measurement information. In this work, an effective emissivity is used to analyze the on-board BB calibration radiance. The error in the effective emissivity is evaluated using an intercomparison approach, from the difference in radiance retrieved by AVHHR IR channels and the spectral radiance measured by the Infrared Atmospheric Sounding Interferometer (IASI) on the same satellite, MetOp-A. Two AVHRR IR channels (channels 4 and 5) are covered by the IASI spectrum and homogenous Earth scenes with brightness temperatures close to the on-board BB temperature are selected to evaluate the calibration radiance error. It is found that this error is 0.30% for channel 4 and 0.33% for channel 5. The correction of the calibration radiance provides the possibility to correct the errors due to other effects, such as the offset and nonlinearity in instrument response. The Earth scene brightness temperature dependent bias will be discussed and the source of the error will be discussed.

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Tiejun Chang and Xiangqian Wu "On-board calibration radiance error correction for MetOp/AVHRR IR channel", Proc. SPIE 8510, Earth Observing Systems XVII, 85100L (15 October 2012); https://doi.org/10.1117/12.929619

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