Spirit cleaner? |
Spirit cleaner? |
Jun 22 2007, 05:15 PM
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#31
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Senior Member Group: Members Posts: 4252 Joined: 17-January 05 Member No.: 152 |
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Jun 23 2007, 01:34 PM
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#32
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Senior Member Group: Members Posts: 2492 Joined: 15-January 05 From: center Italy Member No.: 150 |
Well, seriously, I think that now that power is up, they should try move fast the rover in order to maximize exploration in the incoming months! This because frankly I doubt Spirit will survive another winter... moreover, last mission extension is approaching to the end (around Sol 1350, if I recall) and, while another year extention is possible (and auspicable), with actual budget issue there is the risk of a commandend shutdown within 5 months from now!
-------------------- I always think before posting! - Marco -
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Jun 23 2007, 04:16 PM
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#33
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Founder Group: Chairman Posts: 14433 Joined: 8-February 04 Member No.: 1 |
While they have one mobile rover, it's unlikely the program will be shut down.
Spirit probably wont survive another winter - all the more reason to do the good science infront of us Doug |
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Jun 24 2007, 05:42 AM
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#34
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Senior Member Group: Members Posts: 1887 Joined: 20-November 04 From: Iowa Member No.: 110 |
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Jun 27 2007, 07:00 PM
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#35
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Member Group: Members Posts: 257 Joined: 18-December 04 Member No.: 123 |
All this cleaning might be timely but hopefully not fruitless, big storm a comin'....maybe.
http://www.space.com/news/070627_mars_storm.html -------------------- Turn the middle side topwise....TOPWISE!!
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Jun 27 2007, 07:19 PM
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#36
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
Well, isn't it almost a truism that semi-global and global dust storms on Mars tend to occur as the planet approaches and works through its equinoces? Those are the times when the most extensive atmospheric transfer between the poles occurs (as CO2 sublimates off the cap approaching summer and condenses onto the cap approaching winter), and so generates the greatest global winds.
We've survived regional storms since the MERs landed, we can only hope that this storm (and any others that may pop up over the next couple of months) will remain regional and not go semi-global or global. We could still see both rovers die within days of each other if a global dust storm of the extent, say, of the 1971 storm were to develop. Do note, though, that the rovers might well become cleaned by the more energetic winds to an extent that they *could* survive even a major dust storm. The HiRISE color image of the Viking 1 lander, for example, demonstrates that it is still primarily non-dust-covered, and we know it has endured several global dust storms. Depending on the rate of deposition vs. the rate of cleaning during such a storm, we might be able to get the rovers to advantageous slopes and weather a storm, as we have weathered Martian winters. -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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Jun 27 2007, 07:34 PM
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#37
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Member Group: Members Posts: 530 Joined: 21-March 06 From: Canada Member No.: 721 |
Depending on the rate of deposition vs. the rate of cleaning during such a storm Well, just in case this turns into a poll, I'm going to join the deposition camp now. Clean-sweeping burned me last time and I still haven't forgiven it. Don't even get me started on my feelings about the far side of the crater. Brian |
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Jun 27 2007, 09:09 PM
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#38
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Member Group: Members Posts: 809 Joined: 11-March 04 Member No.: 56 |
Do note, though, that the rovers might well become cleaned by the more energetic winds to an extent that they *could* survive even a major dust storm. Let's say we have the most optimistic scenario -- the dust in the wind gets blown by, and whatever dust is on the rover gets blown off -- how much would power drop, not from the dust on the rover, but the dust in the atmosphere? How long would the storm have to last before the rovers would become irrecoverable? |
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Jun 27 2007, 09:57 PM
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#39
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Dublin Correspondent Group: Admin Posts: 1799 Joined: 28-March 05 From: Celbridge, Ireland Member No.: 220 |
Assume for a moment that the dust on the panels has reduced efficiency to 75%. The numbers for in and around now for Spirit would be:
CODE Tau Whr/Sol Beam 0.9 730 38.0% 1.5 609 19.2% 2 529 12.5% 4 314 1.8% 6 198 0.3% So things would have to get very bad for this to be lethal right now. The highest Tau values we've seen so far are 1.84 for Opportunity (Sol 489) and 1.53 for Spirit (Sol 511) . On the plus side the drop in Tau reduces the power loss as a result of shade within Victoria. |
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Jun 27 2007, 10:15 PM
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#40
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Senior Member Group: Members Posts: 4252 Joined: 17-January 05 Member No.: 152 |
Those numbers are interesting. When the tau increases from 0.9 to 1.5, the direct sunlight ("beam") drops by almost half, while the total available power drops less than 20%. Unless I've missed a square root, that means that a lot of the attenuated direct sunlight eventually makes it to us as scattered light, ie the sky gets a lot brighter.
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Jun 27 2007, 10:26 PM
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#41
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Founder Group: Chairman Posts: 14433 Joined: 8-February 04 Member No.: 1 |
No - thats what happens, the direct drops, the indirect increases. For 'close ops' to a cliff, you'd want a clean rover, but a filthy sky
Doug |
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Jun 27 2007, 10:40 PM
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#42
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Dublin Correspondent Group: Admin Posts: 1799 Joined: 28-March 05 From: Celbridge, Ireland Member No.: 220 |
As Doug says that is what happens - as the dust levels rise the direct beam insolation falls off pretty rapidly in an exponential decay curve (~exp(-tau) ) but the diffuse light actually rises initially and only starts to drop after around Tau ~ 1.8. The exact detail is I used for the above is from the formulas from this paper by Applebaum and Landis http://ntrs.nasa.gov/archive/nasa/casi.ntr..._1994010257.pdf
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Jun 28 2007, 03:33 AM
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#43
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Member Group: Members Posts: 444 Joined: 1-July 05 From: New York City Member No.: 424 |
Fascinating to read in the Applebaum & Landis paper the discussion of dust accumulation ("There may be removal of dust by wind as well as deposition"), and the possibility of designing solar arrays that could "flap" to remove dust. See pp. 12-13.
How high are the values of Tau for the biggest Martian dust storms, like the one encountered by Mariner 9 in the first months of its orbital mission? TTT |
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Jun 28 2007, 04:07 AM
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#44
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
Or, more specifically, what was the greatest tau value recorded by the Viking landers when they endured major global dust storms? Each went through at least two major dust storms, and I know that *some* estimate of tau during those periods has been made.
Also, I know I've seen sequences of Viking lander images showing dust buildup after dust storms. I'd be interested in seeing those again, to get a feel for the kind of short-term buildup we may be looking at for our rovers. -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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Jun 28 2007, 04:09 AM
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#45
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Senior Member Group: Members Posts: 4252 Joined: 17-January 05 Member No.: 152 |
Spirit's Solar Power Levels Continue to Rise
Another cleaning has occured. Power has risen to 738 watt-hours!! |
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