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When Phoenix Lands..
tedstryk
post Jan 24 2006, 06:05 PM
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I have been wondering about something....given the performance of the MERs, if one or both survive this winter, is it not conceivable that they could be operational when Phoenix lands? It would, I believe, be the first landing on anything but the moon with other landers (other than parts of the same mission) still operational.


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akuo
post Jan 24 2006, 06:12 PM
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Um, Viking? rolleyes.gif

Well ok, they are the same mission. It would speak a lot about the longevity of MERs.


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djellison
post Jan 24 2006, 08:53 PM
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I think there's some potential for functional, if not 'mobile' Rovers come '07. I certianly think they'll last thru to MRO's science orbit, and as such could do simultanious observations out and into the atmosphere.

But that's a long way away, and a hell of a lot could go wrong between then and now, I wouldnt put money on it, but I wouldnt be suprised.

Doug
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tedstryk
post Jan 24 2006, 09:39 PM
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QUOTE (akuo @ Jan 24 2006, 06:12 PM)
Um, Viking?  rolleyes.gif

Well ok, they are the same mission. It would speak a lot about the longevity of MERs.
*


If we are going to go the same mission route, Opportunity would be from the same mission as Spirit as well. But I was thinking about not-twin missions.


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Guest_BruceMoomaw_*
post Jan 24 2006, 10:09 PM
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Well, you know, we're within two months of having four working and scientifically productive (and non-redundant) Mars orbiters simultaneously. I think that's quite impressive enough.
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hendric
post Jan 24 2006, 10:28 PM
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QUOTE (tedstryk @ Jan 24 2006, 03:39 PM)
But I was thinking about not-twin missions.
*


This raised an interesting question: What's the success rate of twin missions vs one-shot?

Viking 1/2
Pioneer 10/11
Voyager 1/2
MER A/B
Mariner 1/2 (1 was destroyed during liftoff, so doesn't count)
Mariner 3/4/5 (3 was a shroud failure, so doesn't count)
Mariner 6/7

It's an interesting comparison, anyways.


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tedstryk
post Jan 24 2006, 11:33 PM
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QUOTE (hendric @ Jan 24 2006, 10:28 PM)
This raised an interesting question:  What's the success rate of twin missions vs one-shot?

Viking 1/2
Pioneer 10/11
Voyager 1/2
MER A/B
Mariner 1/2 (1 was destroyed during liftoff, so doesn't count)
Mariner 3/4/5 (3 was a shroud failure, so doesn't count)
Mariner 6/7

It's an interesting comparison, anyways.
*


Don't forget that Mariner 8/9 fit the same pattern, as Mariner 8 was a launch failure.


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centsworth_II
post Jan 26 2006, 06:44 AM
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If still alive, I wonder if one of the rovers could see the entry fireball of Phoenix. It would be a great way of calibrating the images of possible meteors seen by the MERs.
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djellison
post Jan 26 2006, 10:13 AM
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I doubt it - Phoenix's landing site is going to be a long long way from the rovers. It'd be like trying to see the Stardust re-entry from Cuba.

Doug
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helvick
post Jan 26 2006, 01:17 PM
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QUOTE (djellison @ Jan 26 2006, 11:13 AM)
I doubt it - Phoenix's landing site is going to be a long long way from the rovers.  It'd be like trying to see the Stardust re-entry from Cuba.

Doug
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Yep - if we assume that the potentially visible entry stage begins at around 120km altitude it will only be visible within a zone that spans at most +-15deg from the re-entry track. Since Phoenix is going to land at ~70deg N any martian surface observer would have to be norrth of around 55deg to have any chance of seing it.

I think that even if you adjust for obliquity and the fact that it's approaching mid summer at landing time the lowest latitude you could possible see anything from would be ~32 deg N in the very unlikely event that the initial atmospheric entry happens at local midnight. I might be wrong in my assumptions on this one but I suspect that if even if I am the reality would be even less favourable.
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djellison
post Jan 26 2006, 01:30 PM
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Remember - Mars is much smaller than earth, so the horizon is much closer as well, if the exact path of Stardust were replicated on Earth, those lines showing visibility at specific elevations would be much much closer to the entry track

Doug
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helvick
post Jan 26 2006, 01:53 PM
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QUOTE (djellison @ Jan 26 2006, 02:30 PM)
Remember - Mars is much smaller than earth, so the horizon is much closer as well, if the exact path of Stardust were replicated on Earth, those lines showing visibility at specific elevations would be much much closer to the entry track

Doug
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Doug - I based those numbers on calculating horizon distances with a Martian radius (3397km), 1deg ~ 59km.

The 120km altitude is just a pure guess - I'm assuming that "entry" starts somewhere around there but I don't know for sure where it would actually happen.
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djellison
post Jan 26 2006, 02:04 PM
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Can't remember off hand, but on the EDL live coverage, Wayne Lee mentions that atmospheric entry occured fairly high, but deceleration didnt occur for about another minute or so, and I'd only expect to be able to see a plasma trail etc after deceleration starts to occur. perhaps 75km?

Looking at this
http://atmos.nmsu.edu/PDS/data/mpam_0001/edl_ddr/edl_ddr.tab
and this
http://atmos.nmsu.edu/PDS/data/mpam_0001/e...dr/r_eacc_s.tab

The peak decel was at 30 - 40km

Doug
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Guest_BruceMoomaw_*
post Jan 26 2006, 11:11 PM
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In this connection, Pioneer 12's imaging photopolarimeter was actually used to try and photograph the firing of Magellan's orbital insertion motor, but saw nothing. A pity.
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Guest_AlexBlackwell_*
post Jan 26 2006, 11:31 PM
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QUOTE (BruceMoomaw @ Jan 26 2006, 11:11 PM)
In this connection, Pioneer 12's imaging photopolarimeter was actually used to try and photograph the firing of Magellan's orbital insertion motor, but saw nothing.  A pity.

IIRC, wasn't there also an effort by HST to image the Galileo Probe entry? I also remember (dimly) some talk about doing the same thing for the orbital insertion burns of MGS and/or MCO.
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