View Full Version : Titan's Purple Halo

2005-Dec-23, 08:34 PM
SUMMARY: Cassini took this beautiful image of Titan with its orange surface shining against the purple halo of its atmosphere. The photograph was made by using separate blue, green and red spectral filters and then combining this with an ultraviolet image. This image was taken by Cassini's narrow-angle camera on the May 5, 2005, at a distance of approximately 1.4 million kilometers (900,000 miles) from Titan.

View full article (http://www.universetoday.com/am/publish/titan_thin_halo.html)
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2005-Dec-25, 01:08 AM
A fine picture, but why aren't all Cassini's pictures in color?

Hugo Drax
2005-Dec-28, 12:33 PM
read the FAQ for Cassini's raw images - link (http://saturn.jpl.nasa.gov/faq/raw-images.cfm)

Cassini's cameras consist of one megapixel CCDs with a large collection of filters that enable images to be taken using specific wavelengths of light. Colour images are made by combining three separate exposures (red, green, and blue).

Colour images are of limited interest/use because they require separate exposures (= more resources) and often don't reveal much. Titan's surface is completely obscured in colour/visible light images (it is just an orange sphere), so an infra-red filter (CB3) is used to peer through the atmosphere (latest Titan image (http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1935) at date of posting)

2006-Jan-03, 08:17 PM

Every picture of Titan's limb has demonstrated a benign outer atmosphere, many images show distinct vertical layering. This is consistent with a very cold planet, but completely inconsistent with the high positive and negative shear winds ~(+/-30m/s) that the ESA used to model Huygens' descent.