How will the Cassini mission end?

[aerogi]

Will the mission end the same way like the Jupiter mission? Or is there a possibility to let it 'crash' into Titan, to gain as much as possible data and pictures? Or letting it crash to Enceladus in one of those cracks might be an idea too, to have super close-up of the surface. Any other ideas, thoughts?

 

[vogon13]

They will not 'contaminate' Titan or Enceladus with a not totally sterile Cassini spacecraft.<br /><br />Most likely Cassini will be zorched in the upper atmosphere of Saturn.<br /><br />I could make a good case for blasting a crater in Cassini Regio on Iapetus to study how fast the 'stain' regenerates (by future missions).<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[efron_24]

if we are not in a hurry.. let Saturn give it an extra speed swing towards another planet... like uranus or Neptune.. There is much more to explore out there <div class="Discussion_UserSignature"> </div>

 

[centsworth_II]

Cassini's mission at Saturn will end when there is no more fuel or power. So there will be no fuel or power to go to another planet.<br /><br />I wonder if a suicide mission to the rings is out of the question.<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[absolutezero]

I do like efron's idea. I'm not knowledgable in this area or anything, but why couldn't NASA decide in another 2 years to leave Saturn and head towards Neptune? Is it simply not possible? Once we are in the orbit there isn't enough fuel to leave? Sure there is a million things to learn about the Saturnian system, but it would sure be nice to visit Neptune and Triton. <br /><br />Please bring me up to speed on why or why not this is a good idea?

 

[centsworth_II]

<font color="yellow">"Once we are in the orbit there isn't enough fuel to leave?"</font><br /><br />Correct! <div class="Discussion_UserSignature"> </div>

 

[qso1]

Once in Saturns orbit, Cassini would have to reach escape velocity again to go to Uranus or Neptune and there is simply not enough propellant aboard for that.<br /><br />I'm not sure what escape velocity is at Saturn but its probably 2 to 3 times that needed to escape Earths gravity or 50,000 mph plus. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[thalion]

IIRC, the Huygens probe itself was not thoroughly sterilized, I guess in anticipation that life on Titan was unlikely. Given that, I don't think they would mind crashing Cassini into the satellite.<br /><br />For my part, I think they'll either try to orbit Titan if they have enough fuel, or try the aforementioned dive-bomb through the rings. Or they just might want to try lots of risky satellite flybys, like flying past Mimas or Pandora at a few dozen kilometers. I think the "divebomber" option is the most likely, though.

 

[centsworth_II]

Both Cassini and the ring particles are orbiting Saturn. I wonder if there is a way for Cassini to enter the rings at the same velocity as the particles so destructive interactions are limited. In effect, for Cassini to become a ring particle among the ring particles. So rather than "dive bombing" the rings, a slow, careful entry into the rings. It probably still would be a suicide mission, but there may be a fairly long period of observation before.<br /><br />As far as "lots of risky satelite flybys" is concerned. Each flyby takes fuel to arrange. Since the mission is at an end due to lack of fuel there could be no "lots" of flybys. <div class="Discussion_UserSignature"> </div>

 

[CalliArcale]

Of course, it is also possible for missions to run out of *money* before they run out propellant. So a spacecraft with delta-vee to spare might still be deorbited. It happens with Earth-orbiting satellites. It's unlikely, though, given the fact that Cassini is the only Saturn orbiter and therefore singularly precious.<br /><br />Also, the craft won't run out of fuel before the end of the primary mission. I would expect that as they anticipate the end of the mission approaching, they'll perform increasingly risky flybys as there is less to lose at that point. But they will be limited by what's available, in terms of celestial mechanics. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[centsworth_II]

<font color="yellow">"...they'll perform increasingly risky flybys...</font><br /><br />I'm thinking that the only risky flybys would be ones involving Titan's atmosphere, Enceladus' plumes, or Saturn's ring particles. I don't think there should be risk in hitting a moon. (I think the planners' aim is better than that!) Are there risks I'm not thinking of? <div class="Discussion_UserSignature"> </div>

 

[mikeemmert]

I have noticed on the Wikipedia site on Enceladus that a close flyby of that moon had been planned for March 12, 2008. That flyby had been planned at an altitude of 25 km.<br /><br />I hear a lot about making more close flybys of Enceladus in view of the stunning discoveries there. I would advise against this. This would use up fuel. The primary mission ought to be completed before making risky new missions. If that's done, there might be enough fuel left over at the end of the primary mission to do something.<br /><br />Besides, until the complete survey is done, we really won't know exactly <i>what</i> to do. There might be some even more compelling discovery than the fountains of Enceladus, though it would be hard to imagine what that might be.<br /><br />The solution is to send another mission to Saturn. One with a real nuclear reactor, the new EU/Austrailian ion engines with 215 km/sec exhaust velocity, an Enceladus lander with a sink probe and a Titan zeppelin, plus a radar set with some <i>real</i> wattage. Launch with SDHLV.

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>hear a lot about making more close flybys of Enceladus in view of the stunning discoveries there. I would advise against this. This would use up fuel. The primary mission ought to be completed before making risky new missions. If that's done, there might be enough fuel left over at the end of the primary mission to do something. <p><hr /></p></p></blockquote><br /><br />Agreed. It would take one heck of an astonishing discovery to get them to change the primary mission, because of the risk of consequently missing other astonishing discoveries. Riskier flybys would not be attempted until later in the mission.<br /><br />What do I mean by a risky flyby?<br /><br />Well, it could be the obvious sorts of risks: dipping into Titan's atmosphere, or getting dangerously close to a moon. But I was thinking more of the kinds of flybys where there is a risk of losing access to other moons subsequently due to alterations in the spacecraft's trajectory, or of excessive propellant expenditure in correcting any post-encounter errors. Or, perhaps most exciting, a foray into the rings themselves.<br /><br />Some have suggested an impactor mission to get really close-up pics. This would be very challenging. I'm not sure whether Cassini is technically capable of it. It would have to be transmitting pictures as it acquires them, and it would have to be able to point its camera at the target while also pointing its high gain antenna at Earth. (Cassini lacks a scan platform; to orient its camera, it must slew its entire structure.) <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[spacechump]

<i>The solution is to send another mission to Saturn. One with a real nuclear reactor, the new EU/Austrailian ion engines with 215 km/sec exhaust velocity, an Enceladus lander with a sink probe and a Titan zeppelin, plus a radar set with some real wattage. Launch with SDHLV.</i><br /><br />Sure...that would be great! Why don't you chalk up the several billion it would take to get such an ambitious mission off the ground!?

 

[mikeemmert]

That's right. I'm asking the taxpayers to cough up a lot of money. <br /><br />This will keep America Great.

 

[centsworth_II]

Here's the big three as I see It for the grande finale:<br /><br />One: A dive into Saturn. Cassini would be able to return a constant stream of data to the end, unlike Galileo (with its antenna problems) as it plunged into Jupiter. But would the data returned during a suicide dive into Saturn return new information that could not be obtained any other way?<br /><br />Two: A merge into one of the rings. Is it conceivable that individual ring particles could be imaged before Cassini was destroyed? It would be interesting to see the decision process for which ring to enter. It would be similar to deciding a landing site on Mars. <br /><br />Three: Is there a moon small enough to allow a near zero gravity landing, a Hayabusa-like approach? It would be amazing to settle Cassini onto such a tiny moon.<br /><br /> <br /> <div class="Discussion_UserSignature"> </div>

 

[absolutezero]

I have a question, not sure if there is an answer or not, but what would Saturn look like if say we were flying in an air plane through it? For example, on earth, if we are in an airplane and were at 30,000 feet, I could either see miles and miles with some clouds or if its really cloudy I can barely see the tips of the wings. <br /><br />On Saturn, if I looked out the window of the plane would I be able to see great distance or would I barely be able to see the wing tip? Is the clouds that thick there?<br /><br />If Cassini were to take the plunge into Saturn, would it be able to return any pictures of that descent? The Galileo probe did not return pictures of its decent right?

 

[centsworth_II]

<font color="yellow">"On Saturn, if I looked out the window of the plane would I be able to see great distance or would I barely be able to see the wing tip?"</font><br /><br />I'm no expert but from looking at Cassini images of Saturn's cloudbands and storms it looks like there are clear areas that can extend deeply in spots between upper level clouds. So it may be similar to the plane analogy in that while inside a cloud you would see nothing but you could exit into a space between cloud bands and see -- all the way to the next cloud. <div class="Discussion_UserSignature"> </div>

 

[spacechump]

<i>That's right. I'm asking the taxpayers to cough up a lot of money.<br /><br />This will keep America Great. </i><br /><br />I wouldn't want to put all my eggs in one basket with a mission like that. Something that expensive with that many science objectives would be devestating to the exploration program if such a considered mission failed. It's best to tier the missions out so that the chance of success is much greater for any one science objective. I'm all for exploratory missions to such places. I just think a all-in-one mission is the answer.

 

[robnissen]

"That flyby had been planned at an altitude of 25 km."<br /><br />Is that really correct. Usually the flybys don't get much closer than about 500 KM. It would be great if they got that close, expecially if they were 25 kms from the south pole. But is that really accurate?

 

[centsworth_II]

The 25km is correct but don't expect great pictures. It's in the dark and Cassini will (as I understand) not be able to get blur-free images at that altitude and speed. Study of the atmosphere (and plumes) and gravitational field will probably profit much more than imagry from that close pass.<br /><br />For much more than you could ever care to know about it, check out the thread at the link below, featuring two old favorites from this forum, Volcanopele and AlexBlackwell.<br /><br />http://www.unmannedspaceflight.com/index.php?showtopic=2306&st=0 <div class="Discussion_UserSignature"> </div>

 

[robnissen]

Thx for the link. Very interesting thread.

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>Two: A merge into one of the rings. Is it conceivable that individual ring particles could be imaged before Cassini was destroyed? It would be interesting to see the decision process for which ring to enter. It would be similar to deciding a landing site on Mars.<br /><br />Three: Is there a moon small enough to allow a near zero gravity landing, a Hayabusa-like approach? It would be amazing to settle Cassini onto such a tiny moon. <p><hr /></p></p></blockquote><br /><br />The two of these proposals actually have a similar problem. Cassini is presently in an elliptical orbit around Saturn which does not coincide with the orbit of any of the moons. That is intentional; such an orbit gives it the best ability to survey the entire Saturn system. But it means that a Hayabusa/NEAR style landing or a resting site in the rings would require significant changes to the orbit. The orbit is being changed throughout the mission, in a carefully planned serious of encounters with massive Titan. But I don't think the apokrone is going to change very much. For either mission end, you'd have to maneuver Cassini such that its orbit were circularized and virtually identical to whatever body it was targetting, so that the landing could be performed as gently as possible. Otherwise, it won't be a landing but rather a high-speed impact. For the ring scenario, if the orbit isn't circularized, Cassini won't stay inside the rings (unless of course it smacks into a ring particle and is destroyed). <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[centsworth_II]

<font color="yellow">"The two of these proposals actually have a similar problem...."</font><br /><br />OK, that pops my bubble on a ring merge or soft landing. Thinking about the Saturn plunge though, I wonder if it could be drawn out into an aero-braked, degrading orbit rather than a plunge. Could Cassini's orbit be given one last adjustment that sets it grazing Saturn's atmosphere so it would eventually burn up, but not before making several (or many) passes yielding additional science. <div class="Discussion_UserSignature"> </div>

 

[CalliArcale]

It might depend on the radiation environment that close to Saturn. Certainly with Jupiter that would not be an option; it would fry the probe before very many passes could be completed. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>