HR: 0800h
AN: P41B-0939    [Abstracts]
TI: Mapping Grazing Incidence X-band Martian Surface Echoes From MGS Occultations
AU: * Gunnarsdottir, H M
EM: hrefna@stanford.edu
AF: Stanford University, 350 Serra Mall, Stanford, CA 94305 United States
AU: Linscott, I R
EM: linscott@stanford.edu
AF: Stanford University, 350 Serra Mall, Stanford, CA 94305 United States
AU: Simpson, R A
EM: rsimpson@magellan.stanford.edu
AF: Stanford University, 350 Serra Mall, Stanford, CA 94305 United States
AU: Tyler, G L
EM: len.tyler@stanford.edu
AF: Stanford University, 350 Serra Mall, Stanford, CA 94305 United States
AB: Since data collection with Mars Global Surveyor began in 1998, over 15,000 radio occultation experiments have been recorded. A by-product of over half of these occultations is a transient grazing incidence Martian surface echo, which changes linearly in frequency at a rate between -2 Hz/sec and -37 Hz/sec with respect to the 8423 MHz (3.56 cm wavelength) carrier signal. The echoes are mostly concentrated at latitudes <-65° and >60°, although there is also sparse coverage of other regions. We have processed echoes from 1999 to 2003 and mapped their intensities on both Mars Orbiter Laser Altimeter (MOLA) topographic maps and USGS geological maps of Mars, revealing some distinct bright and dark radio reflective areas. Since the angle of incidence is >89° from vertical, considerable shadowing is observed around craters. At higher latitudes, echoes in the northern hemisphere are generally stronger than in the southern hemisphere. We expect this is due to the northern plains being less cratered, and thus smoother, than the south. Bright and dark areas appear to be associated with geological features.
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
DE: 6225 Mars
DE: 6964 Radio wave propagation
DE: 6974 Signal processing (0674)
SC: Planetary Sciences [P]
MN: Fall Meeting 2005