Spectral signatures of micron-sized particles in the Shuttle optical environment

Solar-illuminated particulates surrounding the space Shuttle have been observed repeatedly in Shuttle missions. Even very low particulate loadings can interfere optically with measurements of earth limb emissions. Depending on wavelength and particle size, the important optical contributions can be scattering of solar radiation, scattering of earth radiation, and particle self-emission, all of which can exhibit significant spectral structure. We examine predicted particle brightnesses for ice particles as functions of wavelength through the visible and IR and as functions of particle size between the volume absorption and geometric scattering regimes. Predicted brightnesses are compared to expected atmospheric limb radiances in various spectral bandpasses to illustrate conditions in which earth limb sensors would be affected and the means for identifying particulate contributions.