29-30 August 2007 Icy Satellites (rev 49), Last stop on the road to Iapetus |
29-30 August 2007 Icy Satellites (rev 49), Last stop on the road to Iapetus |
Aug 9 2007, 10:40 PM
Post
#1
|
|
SewingMachine Group: Members Posts: 316 Joined: 27-September 05 From: Seattle Member No.: 510 |
CICLOPS' Rev 49 Looking Ahead page is up. Highlights include a fourth monthy Voyager-class encounter with Tethys with 500m resolution over Odysseus (finally!)
Detailed mosaics of Rhea's prominent ray crater and points west are on tap for Old Scabby's second closeup. This should be a really cool periapsis passage to tide us over until the 10th of September. -------------------- ...if you don't like my melody, i'll sing it in a major key, i'll sing it very happily. heavens! everybody's all aboard? let's take it back to that minor chord...
Exploitcorporations on Flickr (in progress) : https://www.flickr.com/photos/135024395@N07/ |
|
|
Sep 5 2007, 12:57 AM
Post
#61
|
|
Solar System Cartographer Group: Members Posts: 10191 Joined: 5-April 05 From: Canada Member No.: 227 |
My trick - select the area containing truncated lines. Do a select color range to get the almost or all black pixels. Move the selection area (not the pixels, just the selection) up one line so it's over the good lines. Copy and paste, and move down over the bad lines. Then repeat, moving the selection down a line, copying and pasting and moving it up a line.
Now I have three layers. Original with black lines, and over the black lines, one copy of the line above, one copy of the line below. The top one I make 50% transparent so the "line fill" is an average of the line above and the line below. Flatten and serve with a glass of red wine. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
|
|
Sep 5 2007, 02:23 AM
Post
#62
|
|
Senior Member Group: Moderator Posts: 3233 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
Another way is to use a boxfilter to null the pixels affected by the truncation. Then use low pass filter with a box size of samp=1, line=3 to have each nulled pixel be an average of the good pixels above and below it...
-------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
|
|
Sep 5 2007, 07:36 AM
Post
#63
|
|
Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
Wow, great Rhea mosaic there, Emily!
-------------------- |
|
|
Sep 15 2007, 03:13 PM
Post
#64
|
|
Member Group: Members Posts: 207 Joined: 6-March 07 From: houston, texas Member No.: 1828 |
Crater Chains:
Ive noticed there are a lot of these long linear features as well on Tethys, Rhea, and Iapetus, and yes even Dione. Ive started doing some fits to them and most do line up as radials to big basins, tho not always the biggest one such as Odysseus. Smaller basins and craters produce such secondary impact chains. We see something similar associated 100-km size craters on Callisto. It is when they fail to line up that they get interesting. that is why the big chains on Callisto must be tidally split comets, since there are no basins they can be linked to. ill have more to say on all this later but am currently working on the paper so have to focus on that. i note that the theory of disruption predicts that there will be no split comets at Saturn, due to its very low density..... cheers, paul -------------------- Dr. Paul Schenk, Lunar and Planetary Institute, Houston TX
http://stereomoons.blogspot.com; http://www.youtube.com/galsat400; http://www.lpi.usra.edu/science/schenk/ |
|
|
Sep 15 2007, 03:18 PM
Post
#65
|
|
Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
i note that the theory of disruption predicts that there will be no split comets at Saturn, due to its very low density..... I'd like to know more about this. Does Jupiter break up comets in the vicinity of its "surface" or much farther out? If the former's the case I can understand how Saturn's density plays in, but if the latter - does a less dense object behave differently than a dense one (given same mass) at great distance, i.e. do they both not act as point gravity sources? -------------------- |
|
|
Sep 15 2007, 04:46 PM
Post
#66
|
|
Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
Crater Chains: i note that the theory of disruption predicts that there will be no split comets at Saturn, due to its very low density..... How about a plunge through the rings, especially at a low angle? Could that not disrupt a comet? Ugordan you're right about planets acting more or less as point masses, so I guess the theory Dr Shank mentions envisages Jupiter's disruptions happening pretty close in. The most uncertain parameter in any such theory must be the cohesive strengths of the comets. I wouldn't be surprised if there is a huge spread, and you might only need a few atypical ones at long intervals to produce the observed alignments on the moons. Therefore I'm a bit wary of the prediction quoted, even without the rings issue. Interesting. I look forward to reading that paper - maybe here??? |
|
|
Sep 15 2007, 06:44 PM
Post
#67
|
|
Member Group: Members Posts: 207 Joined: 6-March 07 From: houston, texas Member No.: 1828 |
i have to admit im short in the theory department. im only interested if they land someplace!
this all goes back to shoemaker-levy 9 days, now almost 15 years ago. breakup requires passage within about 1.5 jupiter radii of the surface of the planet, and something similar for saturn, except the density plays in somehow. the articles by asphaug, benz and others back in the mid-1990s tell all, otherwise start with the Schenk paper in Icarus in 1996 which includes such references. i dont have a copy with me at the moment, alas! cheers, paul -------------------- Dr. Paul Schenk, Lunar and Planetary Institute, Houston TX
http://stereomoons.blogspot.com; http://www.youtube.com/galsat400; http://www.lpi.usra.edu/science/schenk/ |
|
|
Sep 15 2007, 07:43 PM
Post
#68
|
|
Senior Member Group: Members Posts: 1887 Joined: 20-November 04 From: Iowa Member No.: 110 |
|
|
|
Sep 15 2007, 08:07 PM
Post
#69
|
|
Member Group: Members Posts: 241 Joined: 16-May 06 From: Geneva, Switzerland Member No.: 773 |
Did someone try to make the Saturn-shine mosaic of Rhea ?
Marc. |
|
|
Sep 15 2007, 08:52 PM
Post
#70
|
|
Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
i have to admit im short in the theory department. im only interested if they land someplace! Well, I'm sure this is obvious to you but for others who may be interested I'll just expand on the point I made in my last post. Any comet which is going to collide with one of Saturn's inner moons after being disrupted at Saturn has to have been orbiting pretty close to the ring plane in the first place. That particular subset of comets is precisely the one with the biggest chance of a lengthy and damaging encounter with the rings. Saturn's low density means that its surface is further out than the radius at which the gradient of it's gravitational field is deemed sufficient to disrupt a comet (based on certain assumptions about the material strength of comets). I suggest that an encounter with the rings presents a viable alternative mechanism whereby a comet in the right kind of orbit could be disrupted and then form a crater chain, streak or whatever on an icy moon. In fact it could well be that for the special case of comets orbiting in their respective planet's equatorial plane Saturn (plus rings) is better at disrupting them than Jupiter. |
|
|
Sep 15 2007, 09:25 PM
Post
#71
|
|
Senior Member Group: Members Posts: 1585 Joined: 14-October 05 From: Vermont Member No.: 530 |
If anyone is still interesting in looking at Rhea the closeup images that were mangled have been replaced by much improved versions. Unless you consider those phase angles that make the concave look convex to be "mangled." This may motivate me to actually download some photos to invert them. |
|
|
Sep 16 2007, 10:18 PM
Post
#72
|
|
Senior Member Group: Members Posts: 1645 Joined: 5-March 05 From: Boulder, CO Member No.: 184 |
Alan - glad to see the raw image improvements. I had sent in an email to the link on raw images page on Sept 2 about the raw images stretching issue. I received a nice reply on Sept 10 saying they were about to fix the stretching and would retroactively reprocess the S33 images. This was caused in June as an inadvertant side effect of stretching improvements they were implementing.
They thanked me for "catching" this. I wonder how many others had reported it to them (either internally or externally). -------------------- Steve [ my home page and planetary maps page ]
|
|
|
Sep 17 2007, 04:24 PM
Post
#73
|
|
Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
You also have to wonder whether or not the whole fiasco was indeed a simple error. After all, we know that many people on the Cassini imaging team have been less than happy about feeling "forced" to release real-time images.
I'm not a big fan of paranoid speculation, truly... but I can just see a few specific people snickering to themselves and gloating, "Just let those &^%#@! UMSFer's try and scoop us to our pretty processed images with THIS stuff!" -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
|
|
|
Sep 17 2007, 04:36 PM
Post
#74
|
|
Founder Group: Chairman Posts: 14433 Joined: 8-February 04 Member No.: 1 |
I don't believe the conspiratorial stuff for a second I'm afraid. I know the head of Cassini outreach personally, and she wouldn't take that sort of nonsense - believe me.
The UMSF admin team (Well, Bjorn and Emily) asked about it and it got fixed shortly thereafter. Doug |
|
|
Sep 17 2007, 05:09 PM
Post
#75
|
|
Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
Oh, trust me, I don't seriously believe there was anything like that going on. Just that some peoples' public statements on the general subject could lead the conspiracy-minded to that kind of conclusion.
The lesson, I guess, is that when you go on record as having a given minority view, and you could possibly have some influence on future events surrounding related issues, you have to be more careful than normal to avoid even the appearance of wrongdoing... But, as I said, I'm not seriously suggesting anyone actually messed up the raws in order to make then unusable by amateurs. Just that the appearance of wrongdoing is invited, and could be pursued by the conspiracy-minded, because some people have aired such views. Actually, on the larger conspiracy front, I'm a little surprised that the Hoaxland crowd never jumped on the image quality issues by screaming "What are they trying to hide?????!!!!!" -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
|
|
|
Lo-Fi Version | Time is now: 10th June 2024 - 12:25 PM |
RULES AND GUIDELINES Please read the Forum Rules and Guidelines before posting. IMAGE COPYRIGHT |
OPINIONS AND MODERATION Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators. |
SUPPORT THE FORUM Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member. |