Traceable Radiometric Calibration of the German Imaging Spectrometer Satellite Mission EnMAP

Abstract

The Remote Sensing Technology Institute (IMF) of the German Aerospace Center (DLR) operates a laboratory for the radiometric, spectral and geometric calibration of imaging spectrometers. Though, mainly used for the calibration of airborne sensors the laboratory is additionally used for the development and test of calibration techniques for the German satellite mission EnMAP. For the calibration of spectrometers in the spectral range from 380 to 2500 nm the self-monitoring radiance standard RASTA was developed which is calibrated by the National Metrology Institute of Germany (PTB). RASTA will be used as the radiometric standard for the laboratory calibration of EnMAP. Due to the limited size of the RASTA’s radiance field, EnMAP cannot be directly calibrated with it. Therefore, the calibration is transferred to an integrating sphere using a spectrometer. The non-uniformity of the integrating sphere’s light field is determined with high spatial and spectral resolution by an approach developed by DLR. To minimized errors introduced by the non-uniformity of the integrating sphere, a setup was developed which allows the determination of the spot actually measured with the spectrometer. This will guarantee that EnMAP measures the same spot of the sphere which is calibrated with the spectrometer