Bistatic UHF Radar Experiments at Mars Using the SRI 150-ft Dish and the Mars Odyssey Spacecraft

During the second half of 2005, three bistatic UHF radar campaigns are being conducted, using the Mars Odyssey spacecraft and the SRI-150 (46 m) dish in the Stanford foothills. The main purpose of these campaigns is to look for evidence of multi-path interference in the Martian surface echoes, in the hopes of detecting a subsurface interface. These echoes will also be used to infer general Martian surface properties, such as slope distribution and local scattering functions. To date, one campaign has been completed (August 1-5), one is in progress (September 5-9), and the third has yet to be conducted (October 31-November 4). Each of the five-day campaigns consists of up to 20 uplink experiments and 20 downlink experiments, where each uplink experiment is 20 minutes long, at a Doppler compensated frequency of 401.6 MHz (74.7 cm wavelength), with a transmit power of 3 kW to 30 kW, and each downlink experiment is 30 minutes long, at a Doppler compensated frequency of 437.1 MHz (68.6 cm wavelength), at 10 W. During the first campaign (August 1-5, 2005), four good uplink surface echoes were received by the 1-bit sampler on board Mars Odyssey. Two were in the northern hemisphere and two in the southern hemisphere, all at high latitudes, with some echoes reaching a maximum SNR of 15 dB. At least 10 additional good uplink echoes have been received in the second campaign, which runs from September 5-9, 2005. Due to the low transmit power of Mars Odyssey, the downlink surface echoes are considerably weaker, at only 3 dB SNR. Maximum echo strengths are expected during the third campaign starting on October 31, 2005, which begins the day after Mars' closest approach (0.46 AU) to Earth this year. The initial results from all three campaigns will be presented.