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MSL landing sites
ElkGroveDan
post May 22 2011, 12:09 AM
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QUOTE (nprev @ May 21 2011, 02:55 PM) *
I believe that it does have to be decided before launch, since MSL will be on a direct trajectory to Mars just like the MERs, Phoenix, and Pathfinder.

My understanding is that it WILL be decided before launch but that there is also an ability to re-target the landing site in-flight, though it does start to affect the size and shape of the ellipse as time goes by.


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nprev
post May 22 2011, 12:55 AM
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Dig it. I suspect that retargeting is far from the most desired course of action, though; not only would it cost considerable enroute consumables, it would also decrease landing precision as you described, Dan.


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Greg Hullender
post May 22 2011, 01:31 AM
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QUOTE (centsworth_II @ May 21 2011, 01:53 PM) *
The remaining factor is how long Curiosity can drive. She has more power than Opportunity, but it takes more power just to move that hulk. It may end up being a wash, with Curiosity not consistently outdoing Opportunity's best pace. It will be interesting to see how long Opportunity holds on to her Mars distance record.

Curiosity will be active at night (and in the shade too). Of course they might not want to drive at night :-) but does Opportunity really manage to drive from dawn to dusk or is it only some fraction of daylight? Also, I'd expect Curiosity can do at least some science at night that Opportunity is forced to stop for during daylight hours.

Add all these factors together, and I expect either a) Curiosity manages maybe 2x the speed of Opportunity or cool.gif Curiosity goes places Opportunity couldn't attempt.
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infocat13
post May 22 2011, 01:34 AM
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one of the presenters with, I believe a Gale crater paper,presented a proposed route along with the geology to be found at each elevation.
Gale
if indeed all of these sites have compelling scientific merit, then there is one more factor to be considered,
The impact of images returned to the public imagination!
I remember watching on TV the Apollo 8 mission, and the earth rise photographs.The Gale creator presenter promised a compelling scenery, perhaps it is this consideration that should be added to the final decision.
the public so engaged might very well influence future decisions on planetary exploration.if all 4 candidates are scientificly compelling and are equaly safe for landing, Is my landing elipse safer then yours? then pick one that holds promise to excite the public imagination to ask for more funding smile.gifsmile.gif for future exploration.
Hubble is an example of such a machine that excites the public imagination.
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djellison
post May 22 2011, 03:51 AM
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QUOTE (Greg Hullender @ May 21 2011, 05:31 PM) *
Curiosity will be active at night (and in the shade too).


Oh, the oft repeated and oft corrected myth. Curiosity will have a power budget just like MER. Just because it's got an RTG doesn't mean it's awake 24/7. It'll be asleep at night, just like MER. What MSL will be doing at night is recharging its batteries. Moreover, in shade - it'll be colder than average and thus require even more actuator heating (already a significant power budget burden)

The RTG renders the power supply more reliable. It doesn't render it infinite.
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djellison
post May 22 2011, 04:02 AM
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QUOTE (ilbasso @ May 21 2011, 02:18 PM) *
Given the investment in the MSL platform and that there's just one shot at getting the science from her, prudence would seem to dictate putting her as close as possible to the priority targets of interest within the constraints of EDL etc. and not assuming that just because she's designed to last 2 years, she will necessarily have that long.


Again - if that's the case, send a lander. We've spent a fortune making a mobile vehicle...yet you're advocating not using it. It's like dangling keys infront of the science team, but not letting them use them. Moreover, again, all the landing sites have good stuff within their ellipses, and Mawrth would require driving just like the wrongly titled 'go to' landing sites.
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Greg Hullender
post May 23 2011, 01:27 AM
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QUOTE (djellison @ May 21 2011, 08:51 PM) *
Moreover, in shade - it'll be colder than average and thus require even more actuator heating (already a significant power budget burden)

Except that the RTG is generating much more heat than power. Even if it's charging its batteries, it ought to have a lot more heat available than the other rovers ever did. I'd expect getting rid of that heat would be a big problem. I'm surprised if it'd need to actually use electric power to heat anything.

Of course, I've been surprised before . . .


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djellison
post May 23 2011, 01:42 AM
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QUOTE (Greg Hullender @ May 22 2011, 06:27 PM) *
I'm surprised if it'd need to actually use electric power to heat anything.


Then be surprised. Mobility heating represents a significant portion of the daily power budget. Indeed some previously considered landing sites were expected to be so cold that there would be significant no-drive periods as the mobility heating requirements would be so bad, they were unsustainable. This is covered in earlier landing site selection meeting documentation.
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djellison
post May 23 2011, 02:08 AM
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QUOTE (ElkGroveDan @ May 21 2011, 05:09 PM) *
My understanding is that it WILL be decided before launch but that there is also an ability to re-target the landing site in-flight


Yup - by the 3rd landing site meeting, they had established that they could target any site between 30N and 30S by targeting at TCM1.
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Eluchil
post May 23 2011, 04:31 AM
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Come to think of it it really is TCM1 not launch that is the drop dead date. Though the decision will be made and announced before then I am sure. At launch the space-craft is targeted slightly away from Mars so that the third stage of the rocket doesn't hit the planet. It's too big to sterilize and everything that hits Mars has to be relatively clean of bacteria according to the Planetary protection guidelines. Thus it's only with TCM1 that the spacecraft is aimed directly at Mars at all giving a fairly wide choice of landing sites from any single launch profile.
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centsworth_II
post May 23 2011, 04:48 AM
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"...a pump system similar to a car's radiator. The pump circulates temperature-regulating fluid through the rover's body with 200 feet of tubes.
.... On Mars, the pump must run constantly, and if it failed, the rover would die." ohmy.gif

Oh, great. One more failure mode to worry about.
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centsworth_II
post May 23 2011, 05:20 AM
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I get the impression that following the MSL's progress through it's mission will have the same temporal feeling as following the MER missions. The MSL will not move from spot to spot any faster. And there will always be energy restraints placed on how fast science can be done at any one spot. Of course MSL can move into much more challenging terrain than MER and do a lot more science, but I think we will experience the same level of "are we there yet" and "when will we be moving on" feelings as we do with MER.

MSL produces about four times as much energy as the MERs, but it weighs over four times as much. The science payload, I'm sure, uses at least four times as much energy as the MER payload on average. So the energy budget restrictions for roving and science should be about the same for MSL as for MER.

Attached Image

http://www.usatoday.com/tech/science/space...4-13-mars_N.htm
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elakdawalla
post Jul 22 2011, 08:09 PM
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This topic has been split at the point that the downselection to Gale was made. Discussions of Gale Crater as the MSL landing site are now here.


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