The 4A model has a long history of validation within the frame of the international radiative transfer community (WMO/IRC). Hyperspectral sounders such as AIRS/Aqua and IASI/MetOp have led to even more extensive validations campaigns. Results are regularly presented and discussed in international Working Groups and in the open literature.
- 4A/OP is the reference radiative transfer code software at CNES for several satellite missions: IASI, IASI-NG, MicroCarb and MERLIN. It is also used for other missions as IIR/Calipso, GOSAT, SEVIRI… or for ground-based measurements (TCCON…).
- 4A/OP is widely used for the calibration and validation activities, including calibration of CALIPSO/IIR imager, spectral calibration and inter-calibration of IASI instruments on-board MetOpA, B, C. It is part of the LMD and CNES activities within the frame of the WMO/GSICS community.
- 4A/OP is widely used for sensitivity studies, for the selection of relevant spectral channels/windows, within the preparation of future instruments (IASI-NG), or for the processing of operational satellites.
- In the SWIR domain, 4A/OP is part of the MicroCarb ground segment for the level1 to level2 processing.