Physics
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.p33a1437d&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #P33A-1437
Physics
5405 Atmospheres (0343, 1060), 5464 Remote Sensing, 5494 Instruments And Techniques
Scientific paper
To design altimeter and interferometric SAR (InSAR) systems for measuring Venus' topography, the effects of Venus' atmosphere on the signals need to be investigated. These radar systems are envisioned to operate at X-band, and therefore, a model of Venus atmosphere permittivity profile at X-band is required and has been developed in this work. The effect of signal propagation through this atmosphere and its implication in designing the altimeter and the InSAR instruments are also investigated. The model was constructed for the complex dielectric constant of the atmosphere. Using relations between permittivity and polarization of polar material, the real part of the atmosphere dielectric constant was obtained by calculating the total polarization of the mixture of known atmospheric components including CO2, N2, H2O, SO2, H2SO4, CO, and OCS. The contribution of each atmospheric component to the mixture polarization was calculated based on given temperatures and component densities in the mixture. For each atmospheric component, the polarization was modeled as a function of frequency, temperature, and pressure based on available information in literature. Imaginary part of the atmospheric dielectric constant was calculated by superposing the measured absorptions of mixture components. The temperature and pressure dependences of absorption of each component were modeled according to measurement data and published information. Hence, based on several datasets inferred or directly measured from previous explorations of Venus, the complex dielectric constant profile has been constructed. The validity of the atmosphere permittivity model has been verified by comparing simulation results with measurement data of Venus atmosphere, e.g., from nadir refractivity and absorption measured by the Magellan mission for a portion of the profile. Using this simulated dielectric constant profile, the X-band electromagnetic wave propagation in Venus atmosphere has been modeled, in particular for phase delay and ground pixel center shift of prospective altimeter and InSAR systems. Sensitivity of those quantities to perturbations in atmospheric profile has been investigated as well. The results indicate that radar signal processing and image formation schemes can tolerate at least up to 10% uncertainty in our knowledge of the atmospheric permittivity profile, therefore holding promise that such systems can be successful in producing accurate surface topography for Venus.
Duan Xueying
Jordan Richard
Moghaddam Mahta
Smrekar Sue
Wenkert Daniel
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