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The end of MESSENGER's mission, What happens after March 2013?
Seryddwr
post Apr 21 2012, 10:08 AM
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I know nothing about either the technological constraints or the funding possibilities, but I was wondering if anyone knew what might happen to the probe once the extended mission at Mercury comes to an end. Is it definitely going to be decommissioned? Or is there a chance of sending it somewhere else? Is there sufficient propellant to allow it to break orbit using the LVA, and (say) conduct a flyby of an Aten or Apollo asteroid? I do not know how much delta-v would be required to do this, or even if there are any targets in favourable positions, but it would (to my untrained eye) be an excellent reuse of what has proven itself to be a very capable spacecraft.
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Paolo
post Apr 21 2012, 10:57 AM
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with all the oxidizer used during the latest orbit lowering maneuver, the remaining delta-v must be quite small. I guess the only realistic end of mission is a series of Sun-perturbed lower and lower orbits and a final impact on the surface of Mercury


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Paolo
post Apr 21 2012, 11:07 AM
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I have checked the biography of spaceflight mechanics guru Robert Farquhar, who worked on MESSENGER orbit design, and he does not discuss any end-of-mission scenario.
I remember reading somewhere that an option would be to lower the periapsis down to 25 km for close-up observations before crashing on the surface


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I'm one of the most durable and fervent advocates of space exploration, but my take is that we could do it robotically at far less cost and far greater quantity and quality of results.

James Van Allen
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Phil Stooke
post Apr 21 2012, 12:28 PM
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Impact on Mercury is the final act of Messenger's life. there's so much to see there, and only limited coverage at high resolution, that it would be very counter-productive to leave Mercury for a (say) 12 month cruise to an asteroid (even if it were possible, which it would not be with minimal fuel left).

Phil



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... because the Solar System ain't gonna map itself.
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Seryddwr
post Apr 21 2012, 12:50 PM
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Thanks both for your replies. It's sad in one way, but good in another - can't wait to see those very high-res images!
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Bill Harris
post Apr 21 2012, 09:19 PM
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I imagine that having perfected the Skeet Shooting Technique at Enceladus very nice hi-res low-altitude imagery of selected Mercurian targets are very do-able.

--Bill


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brellis
post Apr 22 2012, 01:56 AM
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Just for curiosity's sake, how far away from the sun could MESSENGER end up if it uses its last bit of fuel towards such a goal? It sure took a lot of gas to get it into Mercurial orbit. Could it be placed in some kind of safe solar orbit for the sake of future planetary historians?
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Phil Stooke
post Apr 22 2012, 03:17 AM
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Most likely it could do no more than limp into a solar orbit close to Mercury's, which would be inherently unstable and end up with an impact anyway. Better to target it and get a few close-ups.

Phil



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Paolo
post Apr 22 2012, 09:54 AM
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digging in my library I have found this, from Aviation Week (26 July 2004, p59)

QUOTE
As the flight winds down, Farquhar hopes the orbit can be reduced even lower to 15 mi. for extremely high-resolution imaging before Messenger crashes onto the surface to end the mission nearly a decade after its launch.


I have also checked the special issue of Space Science Review dedicated to MESSENGER, but I have found nothing on end-of-mission plans.


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I'm one of the most durable and fervent advocates of space exploration, but my take is that we could do it robotically at far less cost and far greater quantity and quality of results.

James Van Allen
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stevesliva
post Apr 24 2012, 12:12 AM
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Any proposals they have for end of mission likely depended on remaining fuel and analysis of how well their solar-sailing techniques work. And because there are no planetary protection requirements at Mercury, no one has forced their hand yet.

That said, there seems to be little other mention out there other than what Paolo dug up.
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jasedm
post Apr 24 2012, 08:33 PM
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No chance of Messenger spiralling sunwards I suppose, and snapping some solar limb movies on the way in ???
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djellison
post Apr 24 2012, 10:38 PM
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Given that it took a very large MOI burn to get IN to Mercury orbit - I would have thought it's fairly obvious that they're not getting out again.
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JRehling
post Apr 24 2012, 10:56 PM
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Moving into a gravity well is just as hard as getting out.

You've all seen those spiral wishing wells for coins:

http://farm4.static.flickr.com/3449/328365...e235f0e17_o.jpg

Moving in or out of a gravity well requires propulsion in proportion to the local slope, which gets steepest at the center. A minimum-energy trajectory from Uranus to Neptune would require little impulse. Going from Mercury to the Sun would require more propulsion than any other two-body cruise in the solar system. Going from Earth to the Sun would require more energy than from the Earth to any other object in the universe. (Of course, a cruise from Earth to another galaxy would take a long TIME, but not as much energy as a cruise to the Sun.)

This is a key reason why it took so long to follow up on Mariner 10 and why Messenger utilized so many gravity assists.

Moreover, there's nothing much that Messenger could do in solar observation that a much bigger earthbound telescope can't do better from three times further away.

Finally, the planet itself has a nontrivial escape velocity. It's only slightly less than Mars's.

There's one intriguing science target left for Messenger, and that's Mercury itself.
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Eutectic
post May 5 2012, 05:42 PM
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QUOTE (jasedm @ Apr 24 2012, 02:33 PM) *
No chance of Messenger spiralling sunwards I suppose... ???

Even if Messenger were not orbiting Mercury, because of the planet's high orbital velocity around the Sun, getting much closer to the star would take significant energy. Mercury's orbital velocity is about sixty percent higher than the Earth's. At the other end of the speed scale, Neptune orbits at less than twenty percent of Earth's velocity. So if you wanted to drop straight into the Sun, it would be almost nine times easier to do so from Neptune than from Mercury, which is pretty counter-intuitive. The way to spiral in from Mercury would be to use the solar wind for drag...
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Explorer1
post May 6 2012, 05:24 AM
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I doubt the camera is even designed to image the sun without being wrecked.
Though sunrise from Mercury orbit would be quite a sight (and without protection, one's last).
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