Abstract
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) onboard Terra platform, which was launched in 1999, has three separate subsystems: a visible and near-infrared (VNIR) radiometer, a shortwave-infrared radiometer, and a thermal-infrared radiometer. The ASTER VNIR bands have been radiometrically corrected for approximately 14 years by the sensor degradation curves estimated from the onboard calibrator according to the original calibration plan. However, this calibration by the onboard calibrator encountered a problem; specifically, it is inconsistent with the results of vicarious calibration and cross calibration. Therefore, the ASTER VNIR processing was applied by the radiometric degradation curves calculated from the results of three calibration approaches, i.e., the onboard calibrator, the vicarious calibration, and the cross calibration since February 2014. Even though the current degradation curves were revised, the inter-band and lunar calibrations show some inconsistencies owing to the different traceability in the bands by different calibration approaches. In this study, the current degradation curves and their problems are explained, and the new curves that are derived from the vicarious calibration with lunar calibration are discussed. The new degradation curves that have the same traceability in the bands will be used for future ASTER VNIR processing.
Highlights
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) onboard Terra platform, which was launched in 1999, has three separate subsystems: a visible and near-infrared (VNIR) radiometer, a shortwave-infrared (SWIR) radiometer, and a thermal-infrared (TIR) radiometer [1].The detector temperature of the SWIR radiometer started to increase owing to the degradation of the detector cooling system, which resulted in the progressive deterioration of product quality in 2007, and low-quality SWIR images have been acquired since May 2008 [2]
The VNIR and SWIR radiometers have onboard calibrators that consist of two halogen lamps with photodiode monitors for the onboard calibration [4]
In 2014, the radiometric correction of ASTER VNIR bands was once improved by the current radiometric degradation curves in the radiometric DB ver. 4 [17], compared to the previous DBs ver. 1 to 3
Summary
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) onboard Terra platform, which was launched in 1999, has three separate subsystems: a visible and near-infrared (VNIR) radiometer, a shortwave-infrared (SWIR) radiometer, and a thermal-infrared (TIR) radiometer [1]. Numerous studies have reported the cross calibration of ASTER and Moderate Resolution Imaging Spectroradiometer (MODIS) VNIR bands [7,8,9,10,11], but the trends in the cross-calibration results are not necessarily consistent [11]. The degradation curves produced by onboard calibration are inconsistent with the results obtained by vicarious and cross calibrations [16]. The degradation curves calculated from the results of three calibration approaches (i.e., onboard, vicarious, and cross calibrations) have been applied to the latest version of the radiometric DB The new degradation curves that have the same traceability in the bands have been selected to be used for the radiometric DB ver. The new degradation curves that have the same traceability in the bands have been selected to be used for the radiometric DB ver. 5 in the ASTER VNIR processing
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