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Back to work, Post-hiatus but pre-entry
stevesliva
post Aug 31 2007, 01:26 AM
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QUOTE (dvandorn @ Aug 29 2007, 10:46 PM) *
One more time -- there have never, ever, even once, even just maybe, *ever* been any dust devils spotted anywhere near Opportunity. All of Oppy's cleaning events have come from straight-line winds.

Actually, thanks for saying it again. I hadn't made the connection yet, if you can believe that!
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Guest_Edward Schmitz_*
post Aug 31 2007, 09:44 PM
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QUOTE (dvandorn @ Aug 29 2007, 07:46 PM) *
One more time -- there have never, ever, even once, even just maybe, *ever* been any dust devils spotted anywhere near Opportunity. All of Oppy's cleaning events have come from straight-line winds.

-the other Doug

The absence of evidence is not evidence. We know next to nothing about the wind dynamics in Meridiani. The only evidence that we have come from pictures of the ground in a before and after state and power level changes on the rover. That's it. It seems a bit premature to declare that we know what is causing these cleaning events. I'm of the mind that it is not the result of dust devil activity. But at the same time, it seems reasonable to use the term 'dust devil' as a short hand for some kind of wind busrt of unknown origin.

It is my opinion that at best we can say it is unlikely that the cleaning events are the result of dust devils passing over the rovers.
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Pavel
post Aug 31 2007, 10:41 PM
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Wouldn't dust devil tracks be visible in Meridiani if there were dust devils there? It's not like the sand and the dust are too uniform in color in that region. Lack of the tracks is a pretty good proof that no dust devils have been present since the last major storm.
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BrianL
post Aug 31 2007, 11:48 PM
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Except for those really large dark tracks away from the rim where dust devils have swept them clean of dust.

wink.gif

Brian
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dvandorn
post Sep 1 2007, 01:00 AM
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I understand you're teasing, Brian, but, just for the record...

Dust devils are very specific weather phenomenah. The definition requires the formation of vortical wind structures large and energetic enough to raise surface dust into the air. Dust devils, again by definition, are visible as funnel-like or rope-like structures due to the dust entrained in their vortical structures.

Dust devils do not leave broad fan-like surface markings -- they tend to leave sinuous, worm-like tracks which do not vary in width by more than 20% to 30% along their lengths. The dust streaks emanating from Victoria begin at wind-stricture points along the crater wall and fan out to be several hundred percent wider by the time they fade to invisibility.

Calling every erosional or depositional wind event on Mars a dust devil is like calling any energetic wind event on Earth a tornado. It's an extremely poor, misleading, and just plain incorrect use of the term.

All that said, I'm really not as anal about this as it sounds. I just want to state the case clearly, and hopefully establish a level of terminology use on the forum that maintains us at an "impressively high level."

smile.gif

-the other Doug


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jvandriel
post Sep 1 2007, 12:48 PM
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Back in business again after the storm.

A panoramic view taken on Sol 1275 with the

R0 Navcam.

jvandriel
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ElkGroveDan
post Sep 1 2007, 04:12 PM
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QUOTE (dvandorn @ Aug 31 2007, 05:00 PM) *
Dust devils do not leave broad fan-like surface markings -- they tend to leave sinuous, worm-like tracks which do not vary in width by more than 20% to 30% along their lengths.

.. and they have a habit of tossing patio furniture into the pool.


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jamescanvin
post Sep 2 2007, 11:57 AM
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The L257 Duck bay image from yestersol (B1281)



As fredk pointed out, we have a dark band on the right edge of the left pancam probably due to dust. I'll need some new code to deal with the lower contrast in this area and so the mosaic is not great. I don't have the time to work on the problem at the moment so this'll have to do.

James


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algorimancer
post Sep 2 2007, 04:53 PM
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I had thought that the pancam head used a lens cover and tilted to point downward when not in use. If that's the case, why the dust on the lens? Was it so dusty that the occasional pics taken were sufficient exposure for the dust to accumulate? Or am I just remembering incorrectly?
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djellison
post Sep 2 2007, 04:57 PM
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It's not a particularly effective lens cover - it's not a good seal.

Doug
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mcaplinger
post Sep 2 2007, 05:19 PM
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QUOTE (algorimancer @ Sep 2 2007, 09:53 AM) *
I had thought that the pancam head used a lens cover and tilted to point downward when not in use.

AFAIK, the Pancam covers got pulled off at mast deployment and are now dangling from the head not doing anything. It's the MI that has a movable cover. The only way to limit dust on the Pancams is to point them down when not in use.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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Del Palmer
post Sep 2 2007, 05:59 PM
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I wonder if the need for Oppy to conserve power meant that it didn't always 'stow' the Pancam when not in use (the actuators would need to be heated at certain times of the day to allow it to be moved).


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Guest_Edward Schmitz_*
post Sep 2 2007, 08:43 PM
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QUOTE (dvandorn @ Aug 31 2007, 06:00 PM) *
I understand you're teasing, Brian, but, just for the record...

Dust devils are very specific weather phenomenah. The definition requires the formation of vortical wind structures large and energetic enough to raise surface dust into the air. Dust devils, again by definition, are visible as funnel-like or rope-like structures due to the dust entrained in their vortical structures.

Dust devils do not leave broad fan-like surface markings -- they tend to leave sinuous, worm-like tracks which do not vary in width by more than 20% to 30% along their lengths. The dust streaks emanating from Victoria begin at wind-stricture points along the crater wall and fan out to be several hundred percent wider by the time they fade to invisibility.

Calling every erosional or depositional wind event on Mars a dust devil is like calling any energetic wind event on Earth a tornado. It's an extremely poor, misleading, and just plain incorrect use of the term.

All that said, I'm really not as anal about this as it sounds. I just want to state the case clearly, and hopefully establish a level of terminology use on the forum that maintains us at an "impressively high level."

smile.gif

-the other Doug

I agree with your sentiment about establishing a high level of dialog.

By websters definition of dust devil - a small whirlwind containing sand or dust - it doesn't have to be very big. My major point from above is that not having evidence does not exclude dust devils as the causative agent. Our ability to monitor the wind activity in Meridiani is almost zero. The fact that we don't see surface prints could be due to the sensitivity of our instruments or that they just don't leave a visible trail. Dust devils on earth don't always leave a trail. That we haven't spotted any with the rovers may establish a upper limit on their frequencey but doesn't rule them out.

We've become very familiar with the behemoths that leave visible trails from space. This isn't necessarily the norm. I still am in the not very likely camp. I just don't see that it's been established that there is no D D activity in Meridiani.

I will concede that we shouldn't be calling phenomenon by the wrong name.
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Tesheiner
post Sep 3 2007, 08:27 AM
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I thought that we were just one step of entering VC, but after reading the latest MER update on TPS it seems that they are still planning to enter it by the other side of the bay.

QUOTE
"Opportunity is poised, literally with front wheels practically hanging over the edge of Victoria Crater, so we are right there at Duck Bay and very close to being ready to go in," said Squyres on his return from the Arctic. "We have a few tests we want to tick off before we go into the crater. But we're there."


QUOTE
On Sol 1278 (August 29, 2007), Opportunity bumped into a position right near the rim. Over the Labor Day weekend, the rover is slated to take new reconnaissance pictures of the planned entry point at Duck Bay, which is about 40 meters (131 feet) away. "We're a little concerned about what the dust storms might have done to change the terrain and the entry site," said Matijevic.
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djellison
post Sep 3 2007, 08:46 AM
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The plan was always the far side of Duck Bay. I've never seen anything to suggest that the choice of the best place to enter the crater has changed just because there has been a delay.

Doug
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