Some definitions used commonly in end-to-end simulators, and in BIBLOS:
End-To-End Simulator (E2ES) simulates the acquisition of the instrument on board of the spacecraft, applying a forward model, and the processing on ground of the data, applying the retrieval algorithms.
And E2ES can be divided into two parts:
- The Instrument Data Simulator – simulates the acquisition of the energy by an instrument of board of the spacecraft, to the conversion to digital numbers (binary values). The Instrument Data Simulator includes the Geometry, Scene Generator and Instrument Modules.
- The Ground Processor Prototype – simulates the processing and retrieval done on ground to obtain the Level-2 products from the raw data received from the Spacecraft’s instrument. The GPP includes the Level-1 Processing and Level-2 Retrieval Modules. The goal of the GPP is to test and validate the calibration and retrieval algorithms that will later be used in the operational phase to obtain the products.
Level-1 Processing (L1) starts from the uncompressed image (binary image) and applies several layers of calibration, geolocation and error correction. The successive steps of products in the L1 processing chain are called L1A, L1B, L1C..
Level-2 Retrieval (L2) derives the environmental variables (e.g., ocean wave height, soil moisture, ice concentration) at the same resolution and location as the Level 1 source data, [Ref].