Cover Page/Proposal Summary

ROSS-99    NRA 99-OSS-01

Date Due: 5/3/99

We propose new research into the radio occultation method for study of planetary atmospheres, with the goals: (i) of delineating the role of atmosphere propagation ducts and related phenomena in limiting the usefulness of Abelian inversion for recovery of atmospheric structure; (ii) refinement and improvement of coherent backprojection or other wave optic techniques as a means of implementing wave solutions to the occultation inverse problem, thereby mitigating the effects of diffraction signatures in low altitude occultation observations; (iii) determining an optimal approach, including choices of wavelength and the proper weighting of frequency and intensity data types, for determination of atmospheric mixing ratios from occultation data, especially in instances of non-uniform mixing (e.g., variable CH4 in H2 + He); and (iv) determining and understanding the effects of orbital geometry in the reliability of occultation measurements conducted by mutually occulting vehicles. The results will be applicable to improved analyses of data presently in hand, from Voyager, Magellan, and Galileo, to data currently being gathered by MGS, to future observations planned for Cassini Orbiter, and to the concepts and detailed designs of future occultation investigations. This work builds on a very productive period during the past few years which yielded the first steps in understanding the role of ducts in occultation experiments, an intermediate solution employing coherent backprojection to obtain sub-Fresnel scale vertical resolution and simultaneously sort occultation multipath signals, a rigorous solution to the form of the Abelian retrieval kernel, and a comprehensive theory of systematic errors in occultation observations.