Recently, the October 2005 non-targeted flyby data of this moon hit the PDS. I've been playing with color composites and the result somewhat surprised me. Unlike Prometheus, Pandora and Pan which all seem to have an orange-reddish tint to them, Telesto turns out whitish-blue. I first thought there'a an obvious error somewhere in my calibration pipeline (wouldn't be the first one), but I haven't been changing it recently and it was giving me consistent results for other targets.
The approximately natural color composite turns out distinctly bluish. Furthermore, the stretched color IR-GRN-UV composite is also much more subdued than similar composites of Prometheus/Pandora with similar phase angles. The other two appear much redder in stretched color. This suggests a much gentler drop in reflectance in the short wavelength range than with the other moons, so that's where the visible bluish color came from. The stretched color turns out similar to Calypso, for which CICLOPS released a http://ciclops.org/view.php?id=1495.
I've also checked the result VIMS gives out and although the spatial resolution is very poor, it too gives a bluish "true color" image. It's as though this moon is covered in very fine, clean icy particles, with very little dust contamination.
Have any previous spectra been published of this trojan moon suggesting the color? A quick google search comes out with nothing.
For illustration, here's the http://www.flickr.com/photos/ugordan/258907722/ I got.
Interesting find. Perhaps its color is related to the E-ring which IIRC extends out beyond Dione, although it must be very diffuse by then. I wonder if Helene is the same color.
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