HR: 10:20h
AN: P22B-01 INVITED    [Abstracts]
TI: Topography of Titan from Cassini RADAR Stereo Data
AU: * Kirk, R L
EM: rkirk@usgs.gov
AF: U.S. Geological Survey, 2255 N. Gemini Dr., Flagstaff, AZ 86001, United States
AU: Howington-Kraus, E
EM: ahowington@usgs.gov
AF: U.S. Geological Survey, 2255 N. Gemini Dr., Flagstaff, AZ 86001, United States
AU: Stiles, B W
EM: bryan.w.stiles@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109, United States
AU: Hensley, S
EM: scott.hensley@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109, United States
AU: Mitchell, K L
EM: karl.l.mitchell@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109, United States
AU: Cassini RADAR Team, T
AB: The RADAR instrument onboard the NASA/ESA Cassini spacecraft uses 2.17 cm microwaves to see through the hazy atmosphere of Saturn's giant satellite Titan, forming a synthetic aperture image strip up to 5000 km long with 300-1400 m resolution during a single flyby. To date, 14 such image strips have been acquired, covering a total of 22% of the surface and revealing a strikingly diverse surface shaped by many of the same processes as Earth. Since late 2006, each new image has overlapped previous coverage, providing a stereoscopic view of 5% of Titan's surface. These image overlaps can be analyzed to provide information about Titan's topography at a resolution of a few km horizontally and one hundred to several hundred meters vertically, yielding more detail than any other available source except radarclinometry (shape from shading). Stereo analysis is made challenging by speckle noise and by the link between viewing geometry and illumination: image pairs with the greatest stereo convergence angle would give the most precise height measurements but differ most in illumination and are hardest to compare. We have therefore applied a combination of both manual feature measurements and automated image matching to produce both spot estimates of local relief and digital topographic models (DTMs) of areas where the image quality is suitable. Work to improve the efficiency and geometric rigor of these methods is ongoing at both USGS and JPL. Results to date reveal relief of 1 to1.5 km between the large hydrocarbon seas of the north polar region and surrounding mountains, and 300 to 600 m in caldera-like features containing smaller lakes. These stereo heights agree closely with collocated "SARTopo" elevation estimates obtained by comparison of the overlap between neighboring beams in a single image (Stiles, et al., this conference). The relief near the lakes and seas provides an indirect constraint on the probable depth of those bodies, and hence of Titan's reserves of liquid hydrocarbons (Mitchell et al., this conference). Topography of the extensive longitudinal dunes at low latitudes, and of the presumptive topographic obstacles that divert the dunes, is more subtle and has been difficult to quantify with stereo.
DE: 5460 Physical properties of materials
DE: 5462 Polar regions
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
DE: 6281 Titan
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting