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Onwards to Uranus and Neptune!
Gladstoner
post Jan 19 2008, 08:54 AM
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nprev
post Jan 19 2008, 09:05 AM
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Uh...say what?! We haven't launched a Galileo follow-up, which would be easy compared to Uranus/Neptune recon mission(s) (to say nothing of orbiters, the technical hurdles of which have been extensively discussed). We are extremely lucky that Voyager 2 did succeed, else I suspect that none of us now living would have ever seen these planets up close in any respect.

Think I know what you mean, but frankly it seems that you're overestimating the impetus for doing such missions. Remember that there was actually a serious proposal floated to turn off Voyager 2 while it was enroute to Uranus as a cost-cutting measure; thank God it didn't happen.


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JRehling
post Jan 19 2008, 09:14 AM
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Gladstoner
post Jan 19 2008, 09:34 AM
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post Jan 19 2008, 10:18 AM
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QUOTE (Gladstoner @ Jan 19 2008, 01:34 AM) *
And the bean counter who considered switching off Voyager 2 before Uranus..... I hope he is now wrapping burrito supremes at Taco Bell.


No argument there! laugh.gif Still, the fact of the matter is that Uranus & Neptune are really off the radar screen right now, and have been for a considerable period of time. I don't like it either, but it is what it is. NH took advantage of an excellent launch opportunity to get to Pluto within a reasonable time to complete the initial recon of the major objects in the Solar System (Note: NO planet/ain't a planet comments welcomed!!! mad.gif I'm serious! Uh, would be remiss without mentioning Dawn as part of this effort as well), and I think that the vibe is to wait on Uranus & Neptune until a viable means to undertake a Cassini-style mission to each of them becomes available.


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Jyril
post Jan 19 2008, 10:26 AM
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Voyager 2 was only able to visit Uranus and Neptune because of the rare alignment of the planets which made the "Grant Tour" possible. No mission that could visit both ice giants is currently possible.


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Gladstoner
post Jan 19 2008, 11:00 AM
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Jyril
post Jan 19 2008, 02:22 PM
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One thing should be remembered when discussing about Uranus and Neptune systems: all the moons, including Triton have their axes almost coplanar to ecliptic meaning that parts of the moons are hidden from view for decades or more. The southern polar regions of Uranian satellites are now disappearing from view. If we sent a probe to Uranus today, it wouldn't see the same regions that Voyager 2 saw. On the other hand, having a probe there right now would have been perfect: currently the surfaces of the moons are fully visible because of the equinox. It'll take 40 years until the next time this is possible.


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mps
post Jan 19 2008, 02:50 PM
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QUOTE (Gladstoner @ Jan 19 2008, 01:00 PM) *
Instead, we currently have inferior vidicom images to play with, and probably will for the rest of our lives.

So, Gladstoner, would you cancel the next flagship mission, so that our grandchildren could see a little bit better quality images of Galilean moons or Titan? tongue.gif
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centsworth_II
post Jan 19 2008, 03:46 PM
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QUOTE (Gladstoner @ Jan 19 2008, 04:34 AM) *
Considering that New Horizons is on its way to Pluto, I would surely think that recon
missions to Uranus and Neptune would have at least as high a priority.

New Horizons just barely made it as a priority:

"The Bush Administration canceled it twice, NASA claimed its budget couldn't cover it
and Congress earmarked funds to be cut in mid-development; yet the trail-blazing
New Horizons Pluto-Kuiper Belt mission has survived....

It is a successor to a long line of planned Pluto missions, none of which ever left the
drawing board. New Horizons' immediate predecessor, the Pluto Express, got farther
than most, but in the summer of 2000 NASA canceled mission."

http://www.planetary.org/programs/projects/pluto/

Not exactly an example of the easy time a Uranus or Neptune mission would
have getting approved and flown, even if those planets had not yet been visited.
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nprev
post Jan 19 2008, 04:18 PM
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Come to that, Voyager itself was a scoped-down version of the Grand Tour, which IIRC would have also included Pluto had it been launched earlier.

There are many variables in UMSF, but none are so capricious (or, arguably, as influential) as budget environments. Still think that we were EXTREMELY lucky that the Voyagers flew at all.


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dvandorn
post Jan 19 2008, 04:57 PM
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You know, Nick, unlike a lot of the people here, you and I can recall when NASA and JPL were pushing hard to get the Grand Tour mission approved. I remember when it was first proposed in the late '60s, I remember when it was canceled, and I remember how elated I felt when its poor second cousin, a simple Jupiter/Saturn flyby, was "tweaked" into something approximating the original GT mission.

Also, IIRC, Voyager 2 could have been targeted for a Pluto flyby, thus completing the original GT mission plan -- but it would have lost its close flyby of Triton. The Pluto option was still possible after the Uranus encounter (though close to the limits of the remaining delta-V in the vehicle), but the craft was deteriorating (scan platform issues, among other things) to the extent that the decision -- and I think the right one -- was made to maximize science during the Neptune encounter.

When it came to deciding between doing as complete a recon of the Neptune system as possible with the healthiest spacecraft you could manage, or giving up Triton on the hope you'd still be operating well (or at all) when you got to Pluto, I think they did make the right decision.

-the other Doug


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nprev
post Jan 19 2008, 05:41 PM
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QUOTE (dvandorn @ Jan 19 2008, 08:57 AM) *
When it came to deciding between doing as complete a recon of the Neptune system as possible with the healthiest spacecraft you could manage, or giving up Triton on the hope you'd still be operating well (or at all) when you got to Pluto, I think they did make the right decision.

-the other Doug


smile.gif ...approaching geezerhood does have its advantages! I agree, oDoug, but IIRC (fading memory, not sure it's accurate), a Pluto flyby was off the table for both Voyagers after Saturn. V1 would have had to give up its close Titan encounter, and V2 would have had to have made some kind of ungodly close approach to Neptune, perhaps even within its atmosphere...in any case, not feasible.

Must confess that in my heart of hearts I'll always think of them as Mariners 11 and 12...the proud cumulation of an historic series of spacecraft that gave us the initial recon of the Solar System. (When you get to be a geezer, you get sentimental easily.. rolleyes.gif )


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Greg Hullender
post Jan 19 2008, 06:54 PM
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Nice account of the history of the Grand Tour project here:

http://history.nasa.gov/SP-4219/Chapter11.html

"Who killed Grand Tour? The demise of Grand Tour was less a simple case of its expensive price tag than its competition with other high-cost new starts (the shuttle and the space telescope) and Viking in a shrinking Federal and NASA budget. The smaller the budget became, and the more that costly programs competed for those shrinking funds, the more expensive each program appeared."

--Greg
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Gladstoner
post Jan 19 2008, 08:30 PM
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