Simulating observations from the MODIS instrument with variable surface and atmospheric conditions

This paper describes the theoretical model for simulating Moderate-Resolution Imaging Spectroradiometer (MODIS) observations under varying environmental conditions. The model includes mathematical descriptions of the orbit of the Earth Observing System (EOS) AM platform, imaging process of the optical sensor, spectral response of the detectors, and realistic illumination and observation geometry for the scene being viewed. It includes a data base that supplies the model with variable surface and atmospheric conditions. Land surface elements are characterized with biome type, and reflectance is described using a time-dependent model bidirectional reflectance distribution function (BRDF). Ocean whitecap and Dun glint are dependent on National Meteorological Center (NMC) analysis wind speed and direction, and water leaving radiance is determined from chlorophyll concentration obtained from the Coastal Zone Color Scanner (CZCS). Cloud cover comes from the International Satellite Cloud Climatology Project (ISCCP) climatology data set. The mathematical descriptions and databases are implemented in a software package that produces data sets of calibrated MODIS data in the exact format that operational processing of real data will provide. The results are used in the test and development of MODIS data processing software.