The Scene Generator Module is in charge of simulating the observed scene, the energy arriving to the instrument detector elements. The simulation chain of the Scene Generator Module starts from the geo/bio-physical variable that is the target of the mission (the soil moisture, the salinity of the oceans, the chlorophyll, etc.). The electromagnetic radiation has a different response depending on the terrain properties and the environment (atmosphere, clouds, etc.). To model this response a Radiative Transfer Model (RTM) is applied to the input geo/bio-physical map. The RTM calculates either the reflectance (the reflected energy at Top-Of-Canopy, the TOC image), or directly the Top-of-Atmosphere image (TOA), which includes the propagation of the electromagnetic radiation through the atmosphere. Clouds also have an impact on the propagation of the energy.
The composing Blocks of the Scene Generator are the following:
- The Resampling Block interpolates the input map in bio/geo-physical variable or TOC to the observation area.
- The Class Map Block classifies the landcover type of each pixel (vegetation, ocean, coastal area, urban area, etc.)
- The Forward Model Block calculates the reflectance or reflectivity, depending on the Radiative Transfer Model and the landcover type of each pixel. The Atmosphere and Clouds Simulator applies the atmospheric radiative transfer model to the reflectance (Top-of-Canopy image), in order to calculate the Top-of-Atmosphere image
The simulation flow of the Scene Generator Module is shown in the diagram below: