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Posted by: Decepticon Apr 10 2005, 02:37 PM

I'm already looking forward to the extended mission. And one target I hope gets a closer look at is Iapetus.

(And yes I understand money and fuel are issues when it comes to this.)


Close Ups of the that ridge would be very interesting. Along with some Radar Observations.

Another reason is to get as much mapping done on all the major moons.




What would you like to see in the extended mission?

Posted by: Jeff7 Apr 10 2005, 02:46 PM

Probably just a continuation of the primary mission - that's likely all we'd get anyway. We can't go visit another planet, like Voyager did, unless something came along and strapped a booster rocket on. Maybe they'll do some closer, riskier flybys of the moons as Cassini's death seems imminent.

Posted by: djellison Apr 10 2005, 02:53 PM

Cunning flybys and aerobraking into titanian orbit for me please

Doug

Posted by: cIclops Apr 10 2005, 03:01 PM

A fully functioning spacecraft and some images of the ring particles.

Posted by: Gsnorgathon Apr 10 2005, 06:29 PM

Well, here's the trick: "More of the same" would be great, and allow for a longer extended mission without damage to the spacecraft.

But there are some nifty things I'd like to see that are potentially hazardous, like closer imaging of Enceladus or the rings. I'd love to see meter-scale images of Enceladus, and it would be fabulous if Cassini could get close enough to the rings to resolve individual ring particles (where "particles" would presumably mean mean objects meters in diameter).

Orbiting Titan for more radar mapping would be fine with me, but is it even possible?

Posted by: Decepticon Apr 10 2005, 07:23 PM

I've seen topics about this on space.com and the argument was both ways. It looked more like "I'm Right Your Wrong" Thread.

I remembered reading before Orbit Insertion on the cassini web page that it was possible.

Posted by: cIclops Apr 10 2005, 08:43 PM

... another close look at Phoebe, is it a Kuiper belt object or not? and what are those "unidentified minerals"?

... and a really close flyby of Enceladus to sample some of that atmosphere with INMS

Posted by: Jeff7 Apr 10 2005, 08:50 PM

I have my doubts that Cassini would be able to image anything that close and small. But then, I don't have any good technical data on the focal length of the narrow angle camera onboard Cassini.

Posted by: Phil Stooke Apr 10 2005, 09:26 PM

I understand that Cassini is not sterilized to a high degree, and would probably not be put into Titan orbit for planetary protection reasons. If they are close enough in for extensive radar mapping there is a lot of drag from the atmosphere, so the orbit would decay fairly quickly, certainly long before we could have thoroughly characterized the organic chemistry with future missions. But lots more close passes (preferably with lots of additional radar coverage) plus other moon flybys should be easy to do.

Phil

Posted by: paxdan Apr 11 2005, 08:29 AM

The closest images of the rings during the primary mission has already occured, it was during orbital insertion. How close were they to resolving individual ring particles? The images in question that potentially show some fine structure are http://photojournal.jpl.nasa.gov/jpegMod/PIA06096_modest.jpg, http://photojournal.jpl.nasa.gov/jpegMod/PIA06094_modest.jpg and http://photojournal.jpl.nasa.gov/jpegMod/PIA06093_modest.jpg. I have a printout of the last image of the bending and density wave by my desk at work. Yeah, I would love to see some more ultra close-ups of the rings during the extended mission.

I can't remember where i read it, but i read that an option at then end of the mission was to raise cassini into a high orbit, and keep it active on a minimal program for decades. How long could the extended mission be, are we talking 20-30-40 years?

Some say the world will end in fire,
Some say in ice.
From what I've tasted of desire
I hold with those who favour fire.
But if it had to perish twice,
I think I know enough of hate
To say that for destruction ice
Is also great
And would suffice.

Robert Frost

So at the end of the extended mission do you want Fire (a glorious death, either in saturn or titans atmosphere, or a ring plane impact) or Ice, a long cold extended orbit till cassini goes cold.

Posted by: Jeff7 Apr 11 2005, 02:59 PM

I figure they'd probably sooner plunge Cassini into Saturn rather than Titan, like they did with Galileo. A ring plane impact would just dent the hell out of Cassini, but not really destroy it outright - unless they sent it in in a retrograde orbit.


Anyone know how much fuel is left in the main booster? Does that still get used for orbital adjustments, or does it rely solely on smaller thrusters for that?

Posted by: BruceMoomaw Apr 12 2005, 12:11 AM

Cassini manager Bob Mitchell has just informed me that the chance of aerobraking it into orbit around Titan is zilch: "With regard to aerocapture at Titan, I think it's a very safe bet to say that that isn't going to happen. I guess I wouldn't go so far as to say it's impossible, although I think it probably is, but since our speed relative to Titan is around 6 - 7 km/sec, it would take so many aerobraking passes to get captured that it just isn't a practical thing to consider."

Beyond that, he says the nature of an extended mission is (as I would suspect) completely up in the air: "There hasn't been any narrowing of the possibilities for an extended mission. Various of the scientists are forming their own opinions and
priorities, but as a group, nothing has been done."

I will add myself that some of the highest-priority things we want to do can be done from the relatively low-altitude polar orbit that Cassini will be in at the end of its primary tour -- both more protracted ring observations and adjustments of the periapsis to allow more close flybys of moons from Janus at least out to Hyperion, if we choose. The main problem with this is that Cassini would keep flying past the same side of Titan -- if we want really widespread surface coverage of Titan (which I take for granted we DO want at this point), we'll have to either keep adjusting the azimuth of the polar orbit or switch Cassini back to a low-inclination orbit.

Posted by: PaleBlueDot Apr 19 2005, 12:12 AM

if i rember correctly, i read a while back on cassini webpage that some other options for the extended mission could include a trip back to jupiter or uranus via multiple titan assists

Posted by: Marcel Apr 19 2005, 10:59 AM

That's exactly what i was thinking. Uranus would be my choice. But how can one escape from the saturnian system and later on brake in UOI with so little fuel left (how much is left actually ?) I bet a gravity assist from titan might help, but completely leave saturn needs a lot of fuel i'd say.

Posted by: Bjorn Jonsson Apr 19 2005, 02:46 PM

Escaping Saturn for a later planetary flyby isn't possible. If Cassini could escape Saturn orbit it would end up in an orbit similar to Saturn's.

Posted by: Jeff7 Apr 19 2005, 04:05 PM

Oh I imagine it would be possible. Of course, making enough orbits around Saturn, combined with engine burns at the right times would probably take a generation or two.
And by that time, the ROTG's would have long gone too cold to make any useful amount of power.

Posted by: volcanopele Apr 19 2005, 06:51 PM

I've heard nothing seriously discussed regarding anything more than what Bruce mentioned, simply continuing the tour for at least another 2 years. One of the initial goals I've heard discussed is to reduce the inclination of Cassini's orbit, since at the end of the nominal mission, Cassini is in a high orbit. the question has been whether to let the inclination drop naturally, or to use hydrazine to bring it back down faster. The fact that the natural inclination drop option seems to be favored suggests that mission planners are wanting to be conservative with the fuel left from the primary mission.

Posted by: Gilles Apr 21 2005, 04:32 PM

My first time on this chat... It looks great and it is very interesting...

From previous experiences, we know that something will come up in x many years that will require the assistance of any hardware we would have in space (they are still measuring solar flares with Voyager !).

My feeling would be to try to get as much as possible in the main portion of the project and then find a nice, cozzy orbit to station Cassini (this doesn't mean Cassini will remain idle, but at least it would increase the "mile per gallon" ratio).

Soon enough, something will come up where Cassini will be a most unique and valuable asset (if it is still useable and has enough fuel).

In a nut shell, let's keep our options open.

Posted by: Redstone Apr 21 2005, 10:43 PM

What is the feasiblity of passing through the Cassini division? Or the Encke gap? A periapsis lowering maneuver should make it technically possible, but I've no idea of the risk of impact when passing through the inner gaps in the rings. Failing that, a close flyby of Mimas (<1000 km) and the inner small moons would be something I'd like to see.

Posted by: Decepticon Apr 22 2005, 01:10 AM

^^No Way!

Any risk is to much.

Posted by: tedstryk Apr 22 2005, 03:18 AM

It is a shame the NASA brass didn't let Pioneer 11 fly inside the rings. This might be an option for very late in the mission, when the spacraft is about to die. Perhaps a course that takes it through the rings, and ultimately crashes into Saturn, sending data back all the way if it survives the ring plane passage.

Posted by: deglr6328 Apr 22 2005, 06:55 AM

but....., didn't it?

Posted by: BruceMoomaw Apr 22 2005, 10:31 AM

Nope -- Cassini flew through the ring plane twice in the gap between the F and G Rings. It DID come closer to Saturn than most of the rings -- but at the time it was just south (or was it north?) of their plane, and so got some very nice cross-sectional photos of them. It also got data on Saturn's fields and particles as good as Pioneer 11 could have gotten -- except that, unfortunately, there was a glitch in the magnetometer during that period that prevented it from getting direct magnetic measurements.

Posted by: BruceMoomaw Apr 22 2005, 10:34 AM

Nope -- Cassini flew through the ring plane twice in the gap between the F and G Rings. It DID come closer to Saturn than most of the rings -- but at the time it was just south (or was it north?) of their plane, and so got some very nice cross-sectional photos of them. It also got data on Saturn's fields and particles as good as Pioneer 11 could have gotten -- except that, unfortunately, there was a glitch in the magnetometer during that period that prevented it from getting direct magnetic measurements.

I have no objection to the NASA brasss overriding the desires of Pioneer 11's scientists, though -- they decided it was more important to have it scout that same zone between the F and G Rings to see if it was safe for Voyager 2 to fly through it, which was the only way it could reach Uranus and Neptune. Had Pioneer been destroyed by dust during that passage, Voyager would have been reaimed to a second close flyby of Titan like Voyager 1.

Posted by: Decepticon Apr 22 2005, 12:19 PM

Even if Pioneer did fly close to the rings, its imager was not the best for observing such small particles.

Posted by: tedstryk Apr 22 2005, 01:05 PM

True, Pioneer didn't have imaging capability worth squat. But it had great particle and fields instruments. I think they should have risked it.

Posted by: ljk4-1 Jan 5 2006, 05:52 PM

NASA Considering Extending Cassini Mission Through 2010

By Jefferson Morris

12/27/2005 08:57:09 AM

NASA is considering a two-year extension to the Cassini mission that would extend the probe's exploration of Saturn and its moons through 2010.

"NASA has given us some additional funding to study what the options would be" for the extra two years, said Bob Mitchell, Cassini program manager at the Jet Propulsion Laboratory in Pasadena, Calif. "About a year from now, I'm expecting that NASA will give us an [answer] one way or the other."

http://www.aviationnow.com/avnow/news/channel_aerospacedaily_story.jsp?id=news/CASS12275.xml

Posted by: antoniseb Jan 6 2006, 01:34 PM

Looking at the article, it says that Cassini might have enough hydrazene for a mission extension that doesn't involve a lot of fly-bys, but rather gives another two years or so of studying the rings (and perhaps Saturnian weather - my addition).

I suppose that would be a good thing to do... observe the rings as they move towards being edge on to the Sun. My gut feeling is that I'd really like to see a switch to Iapetus (from Titan) as the primary encounter target, but the low amount of fuel makes that unrealistic, and I suppose that there is really little that Cassini in particular can tell us more about that object's mysterious history.

Posted by: Cugel Jan 6 2006, 04:03 PM

That is not how I read it:



So we would get another 2 years of Titan flybys and some icy moons and after that... it's over. On the other hand, the 'uneventful' ring studying orbit could last much longer than 2 years, maybe even 10 years or so.

Posted by: tty Jan 6 2006, 05:04 PM

If NASA is willing to fund 10 more years of 'uneventful' research which I strongly doubt.

tty