Coherence-polarization phenomena in remote sensing

The importance of polarization phenomena in remote sensing by electromagnetic means is discussed briefly. With active sensor systems using microwave or laser sources the radiation is very likely to be coherent and plane polarized. Both intuition and measurement point to anticipated differences in the scattering functions of particles and surfaces interacting with incoherent and with coherent radiation. Polarization is one important aspect of these scattering functions that we have undertaken to investigate in the laboratory. Data selected from our measurements on silica beach sand, Haleakala volcanic ash, and magnesium carbonate have been used to point out significant differences in polarization, depolarization, and photometric functions related to the geometry of incidence and observation. Filtered tungsten light (λeff=0.48 µ, λeff=0.54 µ, λeff=1.0 µ) results are compared with He-Ne laser (0.6328 µ) results on the same photometric-polarimetric analyzer, and possible explanations are offered. A very interesting aspect of the magnesium carbonate data is the marked deviation from the cosine law reflection that makes it such a useful photometric reflection standard for incoherent light.