Intercalibration of optical satellites - a case study with MOMS and SPOT

Abstract

The homogeneous test site of La Crau (South of France) was used for radiometric calibration of the MOMS camera onboard the Russian MIR-Station and of the HRV/HRVIR cameras on the SPOT 1 and SPOT 4 satellites. The test site has an extension of approximately 400 m x 400 m and is composed of pebbles which are sparcely covered with dry low vegetation. For the spectral characterization of the test site reflectance measurements with a field spectrometer and a field multichannel radiometer as well as multispectral images from a scanner onboard a low flying aircraft were obtained. To determine atmospheric optical parameters the direct transmission of the atmosphere was measured with sunphotometers and the ground spectrometer simultaneously with the overpass of the space cameras. With the measured reflectances and atmospheric parameters, the Modtran 3.5 [1] radiative transfer code was used to calculate the spectral radiance reaching the space cameras. The paper describes the measuring techniques and discusses the calibration results.