Analysis on stray radiation of multi-spectral infrared remote sensor

The backward Monte Carlo method and the bidirectional Monte Carlo method were introduced to analyze the stray radiation of an infrared remote sensor. The formulae of radiation flux reaching the focal plane have been derived on the basis of spectral radiative transfer factors. After verifying the calculation reliability, a spaceborne multi-spectral infrared optical system was taken as an example, and the radiative propagation from the earth background to the focal plane which from its internal structure were simulated numerically. The effects of wall absorptance and temperature on the stray radiation have been analyzed. The investigation indicates that the bidirectional Monte Carlo method is flexible for analyzing the radiation transfer from the earth to the focal plane and the backward Monte Carlo method can be easily used to analyze the effects of inner thermal radiation. The results also show the significant influence of wall absorptance on the propagation of stray radiation outside viewing field, and the thermal emission of internal structure will become the main stray radiation at its temperature higher than 250 K.