Saturn's bared mini-moons |
Saturn's bared mini-moons |
Guest_AlexBlackwell_* |
Mar 29 2006, 05:52 PM
Post
#1
|
Guests |
There is a new Cassini-related paper by Tiscareno et al. (and accompanying News and Views piece by Spahn and Schmidt) in the March 30, 2006, issue of Nature. See also the Editor's Summary: Propelled into the limelight.
|
|
|
Mar 30 2006, 02:27 AM
Post
#2
|
|
Senior Member Group: Admin Posts: 4763 Joined: 15-March 05 From: Glendale, AZ Member No.: 197 |
This kind of discovery is one of the reasons why I'm in favor of closer and closer ring dives as Cassini nears the end of it's mission, sort of the way they got bolder and bolder with Galileo near Io as its days were numbered.
(...assuming of course the orbital mechanics would allow it. I put away my slide rule long ago, so I'll leave it up to you guys who crunch numbers for a living.) -------------------- If Occam had heard my theory, things would be very different now.
|
|
|
Guest_Richard Trigaux_* |
Mar 30 2006, 09:30 AM
Post
#3
|
Guests |
This kind of discovery is one of the reasons why I'm in favor of closer and closer ring dives as Cassini nears the end of it's mission, sort of the way they got bolder and bolder with Galileo near Io as its days were numbered. (...assuming of course the orbital mechanics would allow it. I put away my slide rule long ago, so I'll leave it up to you guys who crunch numbers for a living.) With my opinion, the best "last" orbit for Cassini would be -periastron just grazing Saturn atmosphere -apoastron lower than Enceladus (to avoid biological contamination) -crossing the ring plane at periastron, just above saturn atmosphere, the place where there are the less particules (not stable in this place). -with a very lonw inclination, so that it will graze the rings throughout their width. Pros: -lower radioactivity -close view to the rings, perhaps possibility to separate larger particules -possibility to radar probe the rings and even Saturn itself -safe end of Cassini when out of fuel (such an orbit will soon lead to a crash on Saturn or into the rings, but avoids Enceladus). Cons: -Would need lot of fuel or moon assistance. Don't know if it is possible -if it is possible, the fuel consumed would be at the cost of an extended mission. |
|
|
Mar 30 2006, 05:55 PM
Post
#4
|
|
Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
With my opinion, the best "last" orbit for Cassini would be -periastron just grazing Saturn atmosphere -apoastron lower than Enceladus (to avoid biological contamination) [...] Cons: -Would need lot of fuel or moon assistance. Don't know if it is possible -if it is possible, the fuel consumed would be at the cost of an extended mission. It's totally impossible. Once you get apoapsis inside Titan's orbit, there are no more gravity assists to be had. And circularizing the orbit that deep in the gravity well would require a LOT of delta-v. Unless aerobraking at Saturn were possible, this cannot be done, and aerobraking at Saturn is a much more difficult than at Mars. |
|
|
Guest_Richard Trigaux_* |
Mar 30 2006, 06:22 PM
Post
#5
|
Guests |
It's totally impossible. Once you get apoapsis inside Titan's orbit, there are no more gravity assists to be had. And circularizing the orbit that deep in the gravity well would require a LOT of delta-v. Unless aerobraking at Saturn were possible, this cannot be done, and aerobraking at Saturn is a much more difficult than at Mars. The matter is not to circularise the orbit: it is impossible because the orbit would have to cross the rings. I rather speak of a very elliptic ellipse, which periastron is grazing Saturn atmosphere, or at least under the ring (the rings have no defined lower limit, but seeminly the particule density decreases with altitude). After, apoastron is where we can set in, probably near Titan, as it is, as you note, the only strong help for gravity assist. Of course it would be fine to set the apoastron below Enceladus. Such orbit is, for instance, grazing the ring on the north side on the descending branch; then it crosses the ring plane very close to Saturn (where it can do a radar probe of the atmosphere); after it climbs back to the apoastron, on the southern side of the rings. At both times it may have a much closer view of them than anything previously done. The only question is if Titan can deflect Cassini trajectory at nearby 90° to bring it on a trajectory toward Saturn. I noted that, on the programs, the planned orbits of Cassini have a lower and lower apoastron, so that its energy is decreasing. Maybe what is not possible today will be possible in two or three years. If the fuel is not already spent, of course. |
|
|
Lo-Fi Version | Time is now: 1st June 2024 - 10:43 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. |