Cool Helene images up Options

[remcook]

Looking at the latest raws, expecting to see Titan, I saw this:

http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=116647

That's pretty close!

[Floyd]

Best pictures to date. These were from 36,000 km, on October 23 we will an even closer encounter at 25,000 km.

[peter59]

Images of Titan and Helene are underexposed again. Starting from this image of Dione taken on June 18, 2007, images are mostly underexposed. Why ? What is wrong ?

[djellison]

Don't draw a conclusion on the exposure from the raw JPGS. More likely is a bad stretching algorythm during the processing from data to JPG. There are too many links in the chain to assume a dark JPG is indicative of anything wrong with the operation of the camera.

Doug

[Ant103]

I want to know : how do they stretch images from Raw to Jpg? What is the reason? They can't simply convert the raw data to jpg without apply a logarithm?

[ugordan]

The great majority of Cassini's images have a 12 bit dynamic range whereas jpegs only have 8. There's also the fact low contrast targets such as Titan would be... well, low contrast without stretching. In a way, histogram stretching maximizes the amount of information present in the raw pages while having a neat side-effect of disallowing any meaningful analysis to everyone but the imaging team.

I second Doug's opinion the algorithm is messed up rather than a problem with the camera. It started around the time those T33 images were supposed to show up and never have (also that Kodak moment with Enceladus and Mimas in front of Saturn).

[Phil Stooke]

This is going to be a fabulous stereo pair between the start and end of the sequence...

Phil

[Phil Stooke]

Here it is...

Phil

[ugordan]

Interesting how it has a much more cratered appearance than in previous coverage (which, admittedly was pretty unrevealing high phase).

[Ian R]

Phil's great stereo pair seems to show a massive crater at the top of the image. I wonder, is this the same feature that is prominent in the low-resolution Voyager picture?

[Phil Stooke]

Yes, I believe it is. Also seen in some other views in this thread:

http://www.unmannedspaceflight.com/index.php?showtopic=3082

Phil

[Exploitcorporati...]

This is in response to Emily's request for suggestions regarding the irregular satellite size comparison on PS weblog. Mimas is included for scale as the smallest of the (roughly) spherical icy moons. I picked images of Prometheus and Pan within the ring plane because they seem to have a bit more detail. A key is included for visitors. The image scale here is approximately 330 meters per pixel.





Rude Commentary: To put this politely, gosh, I sure hope they can get better views of Prometheus some time...

[Big_Gazza]

EC, you da man! (figuratively speaking..) Your work never fails to impress!

I've never seen that image of Pan before, showing the same accumulation of fine grained ring material as does Atlas. Far from being a unique feature of Atlas, such could easily be common for large-ish moonlets embedded within, or skirting the edge of a dense ring system. I wonder if there are any high-res image sequences planned for Daphnis in the Keeler Gap?

[ugordan]

I've never seen that image of Pan before, showing the same accumulation of fine grained ring material as does Atlas.

EC, am I right in assuming the dark band over Pan is actually the outer edge of the A ring in front of the moon and not actually a dark feature on the moon?

[pat]

Uhm, Pan appears to be too small in this wonderful rocks family portrait. The latest radii(km) appear to be

Atlas 22.8 19.0 9.6
Pan 17.6 17.3 11.5

Peter Thomas' latest figures as per the SPICE PCK kernel cpck_rock_19Apr2007_merged.tpc

Pan is only marginally smaller than Atlas. Atlas is a little more than 1/3 the size of Prometheus and Pandora which seems about right in the portrait.