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

The homogeneous test site of La Crau (South of France) was used for radiome tric calibration of the MOMS camera onboard the Russian MIR-Station and of the HRV/HRVIR cameras on the SPOT I and SPOT 4 satellites. The test site ha s an extension of approximately 400 m x 400 m and is composed of pebbles wh ich are sparsely covered with dry low vegetation. For the spectral characte rization of the test site reflectance measurements with a field spectromete r and a field multichannel radiometer as well as multispectral images from a scanner onboard a low flying aircraft were obtained. To determine atmosph eric optical parameters the direct transmission of the atmosphere was measu red with sunphotometers and the ground spectrometer simultaneously with the overpass of the space cameras. With the measured reflectances and atmosphe ric parameters, the Modtran 3.5 radiative transfer code was used to calcula te the spectral radiance reaching the space cameras. The paper describes th e measuring techniques and discusses the calibration results. (C) 2001 Edit ions scientifiques et medicales Elsevier SAS.