Holy moly are these back-to-back flybys of Rhea and Helene going to ROCK!!!! Jason's http://ciclops.org/view/6221/Rev127?js=1 has all the details. Wispy terrain high-res mosaic -- close look at putative impact sites of former ring particles -- MIMI attempt to confirm presence of Rhea ring -- Imaging of pretty much all of Helene using Saturnshine to illuminate sub-Saturn hemisphere on approach, sunshine on anti-Saturn hemisphere on departure -- departure shots will be against Saturn as a backdrop -- C/A shots will use skeet shoot technique derived for Encelauds -- etc. etc. --
I can't wait!! Thanks Jason for the preview!!!
The CICLOPS Looking Ahead article for Rev127 (February 22-March 12) is now online, detailing the upcoming targeted flybys of Rhea and the trojan moon, Helene. In the case of Rhea, Cassini will fly within 100 km of the surface in order to confirm the presence of a set of narrow rings at that satellite. Images will be acquired of portions of the trailing hemisphere wispy terrain and the equator.
However, the flyby I am looking forward to the most is that of Helene on March 3 @ 13:41 UTC, with an altitude of 1,817 km. In preparation of this encounter, I have created an animation in Celestia showing the views of Helene from the ISS narrow-angle camera (missing some on the third trigger, since there were 48...and I'm tired):
I'm loving the ring-plane orbits with all these icy moon/rock encounters - lots more to come in the next few months. Thanks VP for the detail included in the looking ahead articles - always very informative, and appetite-whetting.
I must admit I'm a little surprised that that the the 'skeet-shoot' technique is being employed at Helene, but delighted nonetheless - it'll be very intriguing to see how 'smooth' the moon is at a few tens of metres resolution.
Hi,
just to http://ciclops.org/view/6221/Rev127?js=1:
I think not. A search of the SM-7_all.doc (posted here on UMSF somewhere) did not have the word Iapetus. If I recall correctly, it would have taken too much fuel to get into that orbit. If you go to the Cassini site, click Mission Overview, then Saturn Tour Dates. About 10 lines down on that page is a link http://saturn.jpl.nasa.gov/mission/saturntourdates/saturntourdates2010/ for a more complete list of the planned tour dates in 2010. From there you can get to activities for each remaining year of the mission.
Looking forward to this one as well.
If Helene is like Calypso, be great to get high resolution of 'striated' terrain. Plus the Rhea "ring" impactors.
Glorious!!!
Craig
Do we get some close ups of the intriguing equatorial stains ??
I am greatly interested in the 'stuff' orbiting Rhea too. Is it organized more like the asteroid belt (variety of inclinations and eccentricities), or more like the Saturnian rings (more planar and circular orbits)? And perhaps we can pin down the periods of the orbiting 'stuff' and see if there is a correlation to the Rhean period about Saturn.
Also, is more material within or outside the Rhean Roche limit . . . .
here are some nice perspective views of Rhea, target of the 100km pass next week.
they are based on stereo imaging of these regions acquired back in 2008. The first shows the western half
of the 6 km deep and 370 km wide Tirawa impact basin. The second shows the now
infamous blue equatorial streaks attributed to impact of Rhea's ring on to the surface. The frames
are from two Rhea flyover videos (too large to upload here) now on youtube (www.youtube.com/galsat400).
The Blue Streak movie shows one of these streaks lying across the top of a battered topographic ridge,
a common occurrence for these features consistent with a ring origin. The paper describing these
and the other Saturn ice moon color features has now been submitted for publication!
more details at http://stereomoons.blogspot.com
and http://www.youtube.com/galsat400
So,
about 75 images are http://saturn.jpl.nasa.gov/photos/raw/index.cfm?start=1&storedQ=2201417.
Here a quickout:
Hi Adam,
Tried your link, but I can't get it to leave earth for an observer point. What am I doing wrong?
I am not sure if MIMI data can confirm the disk/rings scenario. What MIMI data may tell us is whether the structures that will be observed during the flyby in electrons and ions, under a much different geometry compared to the two previous flybys, are consistent with that exciting scenario (or not). Consistent observations under much different geometries, may strengthen the initial interpretation, but definitely not prove it.
I think proof can only come from imaging observations (or maybe other, more direct methods than those based primarily on charged particle data).
Quick, dirty gif of a mutual event with Dione and ... Rhea?
(That guess is based off what I found in Celestia I suspect it's Cassini trajectory is out of date.)
I am not sure if this would be compression artifacts or just maybe a quirk of the pixel geometry due to the differing colors, but some of the ridges and crater rims in the lower portion of the RH image in post 6 seem to have very fine crenelation (for lack of a better word).
http://blogs.jpl.nasa.gov/?p=62 with a fantastic movie made by Cassini navigator Brent Buffington that shows each of the activities performed during Rhea flyby.
http://saturn.jpl.nasa.gov/video/videodetails/?videoID=207
Animation of Helene flyby just uploaded to youtube (may take 30-60 minutes to finish processing, so be patient):
http://www.youtube.com/watch?v=0aVbvAojQlw
Only 4 hours and 4 minutes until Helene closest approach!
Rhea images have started coming down:
http://saturn.jpl.nasa.gov/photos/raw/rawimagedetails/index.cfm?imageID=214324
http://saturn.jpl.nasa.gov/photos/raw/rawimagedetails/index.cfm?imageID=214340
http://saturn.jpl.nasa.gov/photos/raw/rawimagedetails/index.cfm?imageID=214348
http://saturn.jpl.nasa.gov/photos/raw/rawimagedetails/index.cfm?imageID=214356
http://saturn.jpl.nasa.gov/photos/raw/rawimagedetails/index.cfm?imageID=214378
Handstitched mosaic of Rhea. Image sequence N00152147,51,55,59,67,75,83,91 taken on March 02, 2010 and received on Earth March 03, 2010.
No, it's a real crack.
Really neat images!
First Helene images arriving:
http://saturn.jpl.nasa.gov/photos/raw/rawimagedetails/index.cfm?imageID=214390
Looks like the pointing is off
Well, Helene's surface certainly appears smooth as expected:
http://saturn.jpl.nasa.gov/photos/raw/rawimagedetails/index.cfm?imageID=214400
It will be interesting to see the closeups...
I guess this will be the highest resolution view of Helene for a while, then...
http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS58/N00152244.jpg
Nope this beats it:
http://saturn.jpl.nasa.gov/photos/raw/rawimagedetails/index.cfm?imageID=214417
I imagine that some careful compositing, a la Tempel 1, might make for some beautiful mosaics with patches of high resolution. The varied perpectives of the lower-resolution global frames are very nice too.
Looks to me there's too much rotation to pull off a Deep Impact impactor-camera-type mosaic.
Cripes - now we've got gullies on Helene...
Phil
Phil, that sent a chuckle among the HiRISE people here
It just shows the standard we've come to expect from this mission that we're a tad disappointed with the images at closest approach. I'm sure the pointing commands for the follow-up flyby will be tweaked based on the results from this one, with even more spectacular results. Kudos to the Cassini team for the double-header flyby.
Incidentally, I wonder how difficult in comparison it will be to image Methone in a couple of years time. The flyby is a similar range, but Cassini will be travelling faster, and Methone is a tenth the size of Helene....
Have we had all the Rhea images now, and if so has anybody found signs of the possibly ring related equatorial marks?
Well, the issue might have been not so much the pointing, but our understanding of the position of Helene... mean, we were pointed where we planned it, but Helene was not where we expected it to be. High resolution images such as these presumably will also be used to help refine our knowledge of the orbit of Helene.
One of the better global raws, rotated so the large crater is at the top, and with a bit of shadow/highlight enhancement:
Ah yes, you're right, I overlooked the rim of that (relatively) huge crater.
Darkside of Helene.
Combination from five raw images.
Approximately 2× magnified.
Nice machi! You brought out some gullies/streaks in the lower left there.
They all remind me of that closeup of the crater in Stickney on Phobos.
Welcome to UMSF Frank.
In this montage, the two views to the right are wide-angle shots of Helene which I presume were taken during the unsuccessful skeet-shoot sequence, while the left-most view is a NAC frame taken as Cassini was receding from the moon with Saturn providing a backdrop:
Nice montage Ian R!
I send another two views of Helene.
First image is higher resolution combination of the darkside (from 4 images).
Second is highest resolution image of Helene (global image is WAC frame). Resolution of this image is aproximately 20 meters per pixel (my rough estimate).
Lots of linear features on the crater rim, the results of landslides I assume. If a landslide was occurring while you were observing Helene, at ~0.001g, could you tell it was happening?
Very nice work indeed, Machi. Here's my attempt to link together all of the medium-resolution views of this moon, using some of its more prominent surface features:
Here's another attempt of making sense of the many different views of this little moon:
This is really awesome. One thing that I think would add to it is if you could trace in different colors the longitude lines on the simulated views that mark 0 (sub-Saturn), 90, 180 (anti-Saturn), and 270. That's something I wish the rings node viewer did automatically, but it doesn't. It'd really help me orient myself. What do you think?
I always love images of this kind!
Glad you got a kick out of my little experiment Emily; I went ahead and added the coloured meridians to the simulated views as per your suggestion (see my original post).
I enjoyed your latest blog entry elucidating the possible reasons why the skeet-shoot encounter didn't entirely go to plan. For the UMSF folks who haven't seen or read it yet, you can find the article here:
http://www.planetary.org/blog/article/00002383/
Interestingly, this isn't the first time that a non-targeted flyby of Helene has produced some poorly-framed views; the of images taken in November 2008 show the moon right at the edge of the frame, slowly moving out of sight as the sequence progresses:
http://saturn.jpl.nasa.gov/photos/raw/rawimagedetails/index.cfm?imageID=174939
http://saturn.jpl.nasa.gov/photos/raw/rawimagedetails/index.cfm?imageID=175050
Ian.
Fascinating how Helene can probe the mass ratio of Dione to Saturn for us.
At first glance, one might think whatever the initial trajectory of Helene was as it morphed into the Trojan relationship (assuming it did not form there) would swamp any subtle effects like the mass ratio effect. I concede I tend to think of these Trojan objects in a 2 dimensional realm as they 'wobble' about the actual Trojan point, where as in reality, objects like Helene would be exhibiting 'wobbles' in inclination too, making for three dimensional excursions in it's 'average' alignment with Dione and Saturn.
Taking this a step further, that initial orbit of Helene prior to dropping into the Trojan relationship (again, assuming it had one) would be even harder to discern now.
Just wanted to add to the chorus of approval of your montage Ian - stirling stuff!
Rhea encounter...
" At a science meeting Friday (03/05/10?), we talked about a few of the preliminary results. Some of the magnetospheric and plasma science instruments teams reported that they’re seeing some really interesting and surprising results! So stay tuned to hear more about those!"
Amanda Hendrix
http://blogs.jpl.nasa.gov/?p=64
Craig
It sounds interesting all right, but don't get too excited yet.
Saturn's immediate neighborhood is a very dynamic place, and without knowing the specifics there are a great many less spectacular possible explanations for unusual magnetic/plasma observations. Let's wait & see.
I think Rhea has been underappreciated. I'm looking forward to hearing more!
Evidently, Cassini did not impact anything too big near Rhea . . . .
I notice that the best narrow-angle shot of Helene from the March flyby has been released:
http://photojournal.jpl.nasa.gov/catalog/PIA12723
I've rotated the TIFF, so that north is up, and generated an enhanced version that highlights the small-scale surface features:
Of minor interest, I'm sure, is a video of the Helene flyby I put together ages ago, quickly forgot about and then rediscovered only recently:
http://www.youtube.com/watch?v=SP1fnh4vsKQ&fmt=43
Very nice - thanks!
Phil
An oxygen-carbon dioxide atmosphere has been observed at Rhea.
http://news.nationalgeographic.com/news/2010/11/101125-saturn-moon-oxygen-atmosphere-discovered-science-space
And a rather shocking interpretation of this,
http://io9.com/5699149/saturns-moon-rhea-may-have-a-breathable-atmosphere
At least the comments are (mostly) quite properly skeptical; nobody's buying it.
This site's audience seems far more informed than the author of that piece of tripe.
EDIT: Just sent a blistering e-mail to the editor-in-chief of that site; let's see if it does any good.
Deep breathes, nprev, deep breathes...... just don't do that on the surface of Rhea.
Craig
Grr. (I'm cool, Craig, I'm cool!) Article's still up as of 26 Nov/1743 GMT, no retractions, no corrections.
Must be a US site, nobody's watching the store during the (informal) holiday here. No reply to my e-mail from last night, either.
I will maintain robotic vigilance (that's the best kind, of course) over this issue
Dropping the S/N for a sec for an artistic interpretation of the latest news.
I'm curious what the presence of the atmosphere means for those strange readings that was originally interpreted as a ring.
the discovery of Rhea's "atmosphere" is now on Science: http://www.sciencemag.org/content/330/6012/1813.abstract
Image of Helene from March 3, 2010 flyby using "super-resolution" technique and PDS images:
That's an "oooo!!!" That's an "ahhhhh!" Like WOW, Mike!
And I can't help but add "groovy".
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