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Posted by: Phil Stooke Aug 17 2006, 01:19 AM

Tomorrow - best view yet, less than 50,000 km. I hope we get a view of a different part of the surface than we've seen before.

Phil

Posted by: volcanopele Aug 17 2006, 04:30 PM

While this would allow for our highest resolution observations of Helene, this encounter is at relatively high phase, with phase angles between 112 and 121 degrees. Not sure if we have a chance at Saturn-shine which would increase our coverage and improve these images usefulness for shape modelling.

Posted by: Bart Aug 18 2006, 10:22 PM

According to the latest Cassini Significant Events report, there was Helene imaging this week.

http://saturn.jpl.nasa.gov/news/sig-event-details.cfm?newsID=684
(Way down at the bottom)

Bart

Posted by: Holder of the Two Leashes Aug 19 2006, 03:40 AM

Raw pictures of Helene are up now on the JPL Cassini web site.

Edit: Also some pics of Mimas, and some impressive ones of Dione. The Helene pictures (only two so far) just show mostly a rough outline, mostly the night side was seen. Some detail along the lit edges.

Posted by: volcanopele Aug 19 2006, 04:45 AM

Nice to see some great images of everyone's favorite space apple. That peak on the night side is certainly very intriguing. Some great saturn-shine Dione as well:

http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=80828

Posted by: ugordan Aug 19 2006, 12:02 PM

Helene in stretched color:

As the raws go, the color is probably not right, but no significant color variations are visible either.

Rhea stretched color mosaics processed to match approximately true color, taken at around 160 000 km (left) and 190 000 km (right):
http://img291.imageshack.us/my.php?image=rhea3wz7.jpghttp://img105.imageshack.us/my.php?image=rheaoq6.jpg

EDIT: Fixed the orientation of Rhea images, north is now correctly located upwards in both mosaics. I'm unsure whether north direction is correct for the Helene image.

Posted by: Phil Stooke Aug 19 2006, 04:23 PM

Quite a nice orbit! The rhea color pics are very nice, ugordan.

Here are two composites of the Helene images. There is faint saturnshine, which should look a lot better when these images come out on PDS. Too bad we don't have one longer exposure, as in the Dione set, to make the dark side glow.

Phil

1. Three views during the flyby. There's quite a bit of rotation to provide stereo viewing.

2. These three plus the previous Cassini image and the Voyager view.

Posted by: tasp Aug 19 2006, 05:18 PM

Lumpy little son of a gun.


Is there a way to calculate a surface roughness RMS coeffecient for all these interesting objects?

Seems like it was Calypso (or was it Melpomene?) was almost eerily smooth.

Maybe the Trojans have different historys from the ring edgers?

Posted by: volcanopele Aug 19 2006, 06:36 PM

Thanks Phil! I'll take a look at these on Monday. hopefully some detail can be pulled out of these but certainly the dark limb may still be helpful for shape modellers. Looking at these, Helene appears to be very oddly shapped, or at least very lumpy.

Posted by: David Aug 19 2006, 07:44 PM

What a gorgeous object! That's what tiny moons and asteroids used to look like, back in the day -- all spiky and craggy. It's nice to find at least one thing that matches the imaginations of the science fiction illustrators!

Posted by: Phil Stooke Sep 15 2006, 07:01 PM

Cassini's recent view of Helene was the subject of a nice release today:

http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=2273

Here I've stretched the Saturnshine areas even more to pull out everything that might be visible. It really shows the value of even high phase imaging of these little things.

Phil

CRedit: NASA/JPL/Space Science Institute

Posted by: Ian R Sep 15 2006, 08:06 PM

Phil,

Is it my imagination, or is there a long scarp-like feature visible in the Saturn-shine, near the right limb?

Also, which hemisphere of the moon are we looking at here? North or South?

Ian.

Posted by: Phil Stooke Sep 15 2006, 08:47 PM

No, it's not your imagination. There is a scarp or possibly groove-like feature there.

I think this looks down on the north side of the moon, but volcanopele might know better.

I'm looking forward to the PDS release of the previous Helene sequence, which also has good Saturnshine.

Phil

Posted by: ugordan Sep 16 2006, 11:49 AM

It's possible the PDS release will allow even more to be visible as the brightness was clipped here to 8 bits from 12 bit data.

Posted by: volcanopele Sep 16 2006, 05:05 PM

From the two images stretched to show features in sunlight perhaps, but these images weren't exposed to show a great amount of detail in Saturn-shine, and I don't think there is much there beyond what is in the right-most image.

Posted by: ugordan Jan 4 2007, 01:43 PM

Reviving an old thread... The Helene pics recently hit the PDS so I had a whack at them. Below's a RGB composite and a very brightened up view showing yellow saturnshine faintly illuminating the moon's dark side.

Compare this to what Phil managed to pull out from the badly artifacted raws. The green ghost image is likely an internal reflection in the filter somewhere, I've seen it in other images when massively brightened. Magnified 2x.

Lastly, here's a simple attempt to join the two (don't laugh):