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Unmanned Spaceflight.com _ Cassini general discussion and science results _ Targeted Tethys Flyby To Be Added In September?

Posted by: BruceMoomaw Mar 26 2005, 03:25 AM

Apparently they are very seriously considering it, at the cost of one targeted Titan flyby during the primary mission -- although it isn't clear yet just how close they may come, as compared to the original untargeted flyby of 33,000 km:

http://saturn.jpl.nasa.gov/news/sig-event-details.cfm?newsID=555

The decision will be made tomorrow. If they go, there will be targeted flybys of Tethys, Hyperion and Dione within a month of each other, and of Rhea only about a month later.

Posted by: volcanopele Mar 26 2005, 06:27 AM

noTitan flyby would be lost as far as I know. If we were to lose a flyby, I guarantee I would have heard about this tweak far before a status report. I think they are just wanting to limit the amount of Delta-v that is used to achieve this encounter.

Posted by: BruceMoomaw Mar 26 2005, 10:35 AM

Yeah, that is an alternative interpretation of the passage, which just says that the delta-V should be kept below "10 m/sec or about the equivalent of one Titan flyby". It should also be remembered that, even before this, Cassini's primary tour included one very nice untargeted flyby within (I believe) about 10,000 km of Tethys (plus even closer untargeted flybys of Epimetheus and Rhea).

Posted by: Bjorn Jonsson Apr 2 2005, 03:51 PM

From the latest Cassini status report:

QUOTE

At the Mission Planning Forum, the decision was made to proceed with the trajectory adjustment that will reduce the non-targeted Tethys flyby altitude from about 32,000 km to 1500 km, and to reduce the targeted Hyperion altitude from 1000 km to 500 km. There were pros and cons for the science that could be obtained with and without the change, but the consensus was that there was an overall improvement with the change. The cost for making the change is around 7 to 8 m/sec.

Posted by: BruceMoomaw Apr 2 2005, 04:25 PM

A rather busy period. The Tethys flyby will be on Sept. 24, Hyperion only 2 days later, and the only targeted Dione flyby only 15 days after that.

Posted by: tedstryk Apr 2 2005, 09:35 PM

Wow....I'm marking my calendar

Posted by: BruceMoomaw Apr 3 2005, 01:20 AM

I forgot to mention that Cassini's closest flyby of Telesto -- within 10,000 km -- comes only 2 1/2 hours after the Dione flyby. Nor should we forget the second targeted (and third close) Enceladus flyby on July 14, and the fact that Cassini makes its closest primary-mission flyby of Mimas (45,000 km) on Aug. 2. (The Rhea flyby is Nov. 26.) Oh, yes: Cassini's second-closest flyby of Telesto -- 19,000 km -- is on Christmas. All in all, a very busy period moonwise -- after which all the smaller moons will be totally ignored until mid-2007, with the focus entirely on Saturn, the rings and Titan.

Posted by: tedstryk Apr 3 2005, 01:14 PM

Actually, although I don't know that Cassini will take advantage of them, there will be some decent flybys in 2006. They might offer some interesting perspectives from Cassini's new orbit. Especially the 9-9-06 flyby of Enceladus - only 40,000. If it is coming in from a polar angle, or at least one appreciably different from the targeted flybies and T3, it could be very worthwhile.

Atlas

9-9-06 -- 85,000

Enceladus

9-9-06 -- 40,000
11-9-06 -- 95,000

Telesto

7-24-06 -- 49,000

Dione

11-21-06 -- 73,000

Helene

2-25-06 -- 71,000
8-17-06 -- 49,000

Rhea

3-21-06 -- 87,000