Martin A. Slade

High‐resolution stratospheric dynamics measurements with the NASA/JPL Goldstone Solar System Radar

We have used, for the first time that we are aware of, the NASA/JPL Goldstone planetary radar to study the Earths atmosphere. With its high bandwidth and power, we were able to achieve a height resolution of 20 m, which is significantly better than the usual 150-m resolution for stratospheric radars. Here we discuss the observation of a very thin scattering layer that persisted over several hours at the same height just above the tropopause. We question the assumption of turbulent radar scatter based on the available evidence, and also investigate the two-minute oscillation observed in the vertical velocity.

An improved map of the lunar south pole with earth based radar interferometry

NASApsilas long-term exploration goals include a return to manned missions to the Moon that will culminate in a permanent manned station on the Moon. Prior to embarking on such a mission, a series of precursor unmanned robotic missions are required to ascertain the best locations for manned exploration or a permanent lunar base. These precursor missions will consist of both orbital missions, such as the Lunar Reconnaissance Orbiter (LRO) and missions for which probes will be landed on the lunar surface. The south polar region of the Moon has attracted much recent attention due to the possibility of significant amounts of frozen water being trapped in permanently shadowed regions in craters in that region. In order to better plan and determine the optimal landing sites for such probes, as much a priori information as possible on the lunar south polar region is desired. Of particular importance from a landing survivability and accessible exploration region perspective is knowledge concerning the lunar topography. This paper will discuss processing of recently acquired radar interferometric data from Earth-based radar, namely the NASA Goldstone Solar System Radar, into topographic maps.

Valley systems on Tyrrhena Patera, Mars: Earth-based radar measurements of slopes

Abstract Eight new topographic profiles across the Martian volcano Tyrrhena Patera have been obtained between latitudes 20.0° and 25.1°S from radar data collected by the JPL Goldstone Radar System in 1988. These profiles, which have a reproducible accuracy of better than 150 m, show the volcano to rise ∼1.5 km above the plains of Hesperia Planum to the east, and to have an average height-to-diameter ratio of ∼1:340. The maximum slopes of the flanks appear to be ∼3.0°. The slopes on the northern flanks of Tyrrhena Patera (0.2 to 3.0°) bear little correlation with the width (1.7 to 5.2 km) or depth (∼200 to 300 m) of valley systems found in that area. This suggests that erosion by gravity-driven flows was not responsible for valley formation and that other factors, such as spatial or temporal variations in the volume of ground water released by sapping, or strength differences in the materials comprising the surface units of the volcano, controlled the geometry and locations of the valleys.

Radar Imaging of the Planets Using the Very Large Array

We have used the VLA to make images of the planets which are continuously illuminated by the high power planetary radar transmitter on the 70 meter antenna at Goldstone, CA. That instrument is capable of transmitting up to 460,000 watts of continuous power near 8.5 GHz. Radar imaging experiments became possible after the installation of the 8.5 GHz receivers on all VLA antennas by NASA for the encounter of the Voyager spacecraft with Uranus. A similar radar may be configured with the Australia Telescope (array) at Narrabri and the Goldstone 70 m at S-band which may be important for experiments on Venus whose atmosphere strongly absorbs at X-band. Highly successful experiments have been carried out at the VLA on Mercury, Venus, Mars, Saturn’s rings and Titan, the giant satellite of Saturn.

Alsep-Quasar VLBI: Complementary Observable for Laser Ranging

The potential development of a high precision inertial reference frame composed of extragalactic radio sources (principally quasars) offers opportunities to perform both astronomical and geophysical studies at previously unrealizable levels of accuracy. A program of ALSEP-quasar differential VLBI is now being carried out at the Jet Propulsion Laboratory. The precision of these observations is comparable to lunar laser ranging, but the sensitivity is in right ascension and declination instead of in range. These high accuracy observations can be used to tie the lunar ephemeris to this new reference frame. Such a tie could be a valuable step in a validation phase of intercomparing VLBI and lunar laser ranging. The combination of this VLBI data with laser ranging can also be used in testing gravitational theories, improving the knowledge of lunar physical librations, and for refinement of the lunar gravitational field. Preliminary results of a covariance study on such a data set combination for 3 years of ALSEP-quasar data show a significant improvement in the solution parameters over laser ranging alone.