Determining Titan's spin state from Cassini RADAR images

Astronomical Journal
By: , and 



For some 19 areas of Titan's surface, the Cassini RADAR instrument has obtained synthetic aperture radar (SAR) images during two different flybys. The time interval between flybys varies from several weeks to two years. We have used the apparent misregistration (by 10-30 km) of features between separate flybys to construct a refined model of Titan's spin state, estimating six parameters: north pole right ascension and declination, spin rate, and these quantities' first time derivatives We determine a pole location with right ascension of 39.48 degrees and declination of 83.43 degrees corresponding to a 0.3 degree obliquity. We determine the spin rate to be 22.5781 deg day -1 or 0.001 deg day-1 faster than the synchronous spin rate. Our estimated corrections to the pole and spin rate exceed their corresponding standard errors by factors of 80 and 8, respectively. We also found that the rate of change in the pole right ascension is -30 deg century-1, ten times faster than right ascension rate of change for the orbit normal. The spin rate is increasing at a rate of 0.05 deg day -1 per century. We observed no significant change in pole declination over the period for which we have data. Applying our pole correction reduces the feature misregistration from tens of km to 3 km. Applying the spin rate and derivative corrections further reduces the misregistration to 1.2 km.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Determining Titan's spin state from Cassini RADAR images
Series title Astronomical Journal
DOI 10.1088/0004-6256/135/5/1669
Volume 135
Issue 5
Year Published 2008
Language English
Publisher American Astronomical Society
Contributing office(s) Astrogeology Science Center
Description 12 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Astronomical Journal
First page 1669
Last page 1680
Other Geospatial Titan
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