Long Term Monitoring of GOME/ERS-2 On-fly Calibration Parameters

Abstract

In this paper, we present results from a study on seasonal dependence of the BSDF. Our study can be divided in two parts. First, we closely follow a method used previously in the GDAQI project. Here the main problem in the analysis is removed by smoothing the data over wavelength. It is found that the BSDF as function of illumination angle is not the expected parabola, but has a plateau (channels 1 & 2) or even a pronounced dip (channels 3 & 4) at the angle where maximum reflectivity was expected. In the second part we derive a BSDF for each wavelength, which can only be done for channels 1,3,4 but not for channel 2. This leads to the surprising result that the seasonal dependence of the BSDF is not, as expected, a smooth function of wavelength, but shows large (up to 2%) etalon-like variations with wavelength.