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Kilometer-High Waves Flow In Saturn's Rings
An anonymous reader sends along a Cosmos Magazine piece on the discovery by NASA's Cassini probe of vertical structures in Saturn's rings, 150 times as high as the rings are thick. The structures were seen because a once-every-15-years orientation of the rings caused vertical features to cast visible shadows. "NASA's Cassini probe has uncovered for the first time towering vertical structures in Saturn's otherwise flat rings that are attributable to the gravitational effects of a small moon. 'We thought that this vertical structure was pretty neat when we first saw it in our simulations,' said John Weiss, the paper's lead author at the Cassini Imaging Central Laboratory for Operations in the US city of Boulder, Colorado. 'But it's a million times cooler to have your theory supported by such gorgeous images. It makes you suspect you might be doing something right,' he added." Update: 06/17 19:29 GMT by KD : The CICLOPS team sent a note correcting the attribution of the quote; the linked article also had it wrong, and has since been corrected.
The Cassini site has a bunch of nice high resolution photos.
http://ciclops.org/view_event/110/Towering_Edge_Waves_Pop_Into_View
Go take a look. They're great!
I am involved with planning the Cassini mission and, in fact, helped plan the images in the current story.
Yet only now are we beginning to receive imagery of detailed ring structure.
You're starting from a mistaken premise. We've been getting detailed images of the rings for the entire mission. In fact, the highest resolution images of the rings to date (probably ever) occurred during orbit insertion at the very beginning of the prime mission.
Since the primary mission has ended it is apparent that obtaining detailed images of ring structure was never a priority.
Nope, rings is a major priority and drives the mission around 20%. (Depending on how you quantify that.)
All of the time has been spent on the moons, Saturn and relatively wide shots of the rings.
Again, blatantly false. Any time we're out of the equatorial plane of Saturn (as we are now and have been many times during the mission to date), we're studying the rings and the magnetosphere (and Saturn, but they tend to be a bit less insistent on this geometry). There are many close-ups of the rings available. Have you looked for them? They're all over at CICLOPS, if you do a search. Or even browse images, really.
Is resolving the ring constituents even feasible for Cassini?
No, we can't get close enough to resolve a 1-m body.
I can see from the flight schedule that close up passes of some sheppard moons will occur in 2010. Will attempts be made to image the detailed structure of the rings at this time?
Yes and no. At the time of flyby, we're in the ringplane and cannot see the rings very well at all. Near that time, I'm sure we'll take images of the rings. As we have always done.
I know the rings are largely particulate; a fog of ice particles.
Not the main rings, no. The main rings are ~30-cm to ~3-m bodies. And there is almost no way to get close enough to image these. It's not even a matter of risk, it's a matter of having to be far, far too close to what amounts to a solid wall of ring. And what good would imaging a few particles in one location do compared to destroying the spacecraft in the process? Apart from satisfying you need to see even closer up to the rings?
We have to apply for extended missions by putting together a plan and pitching what we're going to do. ("More of the same," is generally frowned upon, naturally.) If the mission is healthy and the plan seems reasonable, they'll approve it. From what I've seen (I'm still pretty young in the field), they tend to be pretty favorable to healthy missions, though, so odds seem good of extension. It's pretty much expected that missions will survive their prime missions since those tend to be conservative estimates for life expectancy.
Are the conservative estimates an example of the Scotty factor. In other words if the team is 90% confident that the mission will last 5 months do they then quote 3 to management - that way if they mission carks it after 4 then they are still covered? I would imagine even the scientists and engineers are very concerned about managerial aspect like project tracking and meeting specification now.
More to the point, how do they estimate such a difficult and unpredictable mission parameter anyhow? I mean somethings like battery life, wear and tear and so on must be quite well understood, but others like the stress of launch, damage, and the great "other" option must be much harder to predict.
It's not so much the Scotty factor as standard engineering procedure for years. If you're told to design an elevator to life 5 people, you make sure it can hold 10 just to be safe. If the design requirements from NASA say "Four years", you design for 6 or 8. You don't want to be penalized for early failure, after all.
And I don't know how the engineers estimate life expectancies, but most components aren't mission-enders. You worry mostly about things like fuel/reaction mass and power sources, first. These are relatively predictable. Other parts that fail generally seem to do so gradually. (Electronics degradation, the reaction wheels on Cassini, etc.) So while you wouldn't necessarily have predicted that a priori, you can track it once it starts to happen.