Scintillations are observed during occultatlons of both stars and spacecraft by planetary atmospheres. Existing treatments of these scintillations ignore a major effect unique to occultatlons: the severe flattening of the Fresnel zone or source image by defocusing. Other large effects, due to "saturation" of the scintillation, have also been ignored. The deeper portions of atmospheric temperature and density profiles inferred from occultation data are seriously in error if other planets' atmospheres are as turbulent as our own. Thus, profiles obtained from entry probes (e.g., the Soviet Venera series) are probably more accurate than those from radio occultation (Mariner 5 and 10) data. Scintillation greatly reduces the information obtainable from occultation observations;much of the detail in published profiles is probably spurious. This paper gives an approximately - correct theoretical treatment that is a substantial improvement over published theories, and shows how a more accurate theory could be constructed. Some methods for a more accurate determination of atmospheric structure are proposed.
展开▼
