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A.F.C. Haldemann (Jet Propulsion Laboratory, Caltech), K.W. Larsen (LASP, Univ of Colorado - Boulder), R.F. Jurgens, M.P. Golombek (Jet Propulsion Laboratory, Caltech)
The Goldstone Solar System Radar (GSSR) carried out Earth-based delay-Doppler radar observations of Mars with four receiving stations during the oppositions in 2001 and 2003, supporting Mars Exploration Rover landing site selection. This interferometric technique demonstrated radar mapping of Mars with a 5 km to 10 km spatial resolution. The data for both Gusev Crater and Meridiani Planum indicated smooth terrains, consistent with, but somewhat different from, previous lower spatial resolution Earth-based radar data. Now, with quantitative ground-truth roughness measurements by Spirit and Opportunity, along with THEMIS visible camera images, we can begin to reconcile these differing remote-sensing observations.
For Gusev crater, older \lambda=3.5 cm wavelength data did not directly sample the crater but were of nearby terrain of the same map unit as Gusev's floor. The reported Hagfors scattering model parameters were \thetarms=4.7±1.6 degrees, and \rho0=0.04±0.02. These quasi-specular parameters refer to roughness in the range 10 \lambda to 100 \lambda. The higher resolution data from 2003, averaged over the whole MER Gusev ellipse were \thetarms=1.3+1.0-0.5 degrees and \rho0=0.02±0.01. The \rho0 for the 5 km pixel where Spirit landed was like the average, but \thetarms=1.6+1.0-0.5. The roughness derived from stereo images from Spirits first 30 sols, available on the PDS, implies near-nadir scattering from 3 m scales is dominant. We examine the spatial coverage of the older data, as well as other radar data to reconcile the differing observations.
For Meridiani, GSSR made direct observations at 3.5 cm at both 5 km resolution and at 10\times150 km resolution in 2001. We will carry out our comparative analyses once rover navigation data beyond Eagle crater, obtained after Sol 58, are released to the PDS, and expect to have them for presentation at the meeting.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.