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Last updated on April 18, 2014 at 1:21 EDT
VIMS Image of Cryovolcano
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VIMS Image of Cryovolcano

November 17, 2009
Two high-resolution images were taken during a 25-minute period that ended just before closest approach. Because the spacecraft was moving at 5.8 kms-1 (about 20 000 kmh-1) relative to Titan, image motion compensation was required so as to point to the same location on Titan's surface.

Two images were acquired of the same area 20 min apart. The non-referenced images are presented in a and b, and the georeferenced images are displayed in c and d. The first image (a and c) has a relatively long integration time of 240 ms per pixel. Slight changes in the spacecraft pointing during the observation have distorted the raw image (a).

Information about Cassini's attitude allowed scientists to retrieve the exact location of each pixel and to reconstruct the image (c). Note that the lines were not contiguous. The altitude of the spacecraft varied from 11 000km to about 5 000 km, with a spatial resolution of 5.5 kmpixel-1 to 3.0 kmpixel-1.

The second image was taken with a 80-ms integration, and was centred on the same reference point (b and d). Because the spacecraft had moved closer to the surface, the resolution varied from 2.6 kmpixel-1 to 1.8 kmpixel-1.

The dominant feature is a bright circular structure (8.5°, -143.5°) with two elongated wings extending westwards. The short-integration-time image (d) is put on top of the long-integration image where interpolation has been performed to fill the gaps between the lines. This allowed scientists to check that the circular feature has not moved between the two shots.