5. Optical interference signal

5.1 Optical ground signal

In the visible range, the parasitic optical signal is due to downward diffuse solar radiation, while in the thermal infrared (10 to 12 μm) it is due to thermal emission from atmospheric components (clouds, aerosols, absorbing gases such as H ₂ O, CO ₂ , CH ₄ , etc.). In the visible during the day, the parasitic signal can be very significant, whereas it is negligible at night outside large conurbations. In thermal IR, the spurious signal remains more or less the same intensity day...