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Getting Unstuck in West Valley
fredk
post May 12 2009, 02:29 AM
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We may have the same scenery for quite a while. From the latest release:
QUOTE
The rover team... has suspended driving Spirit temporarily while studying the ground around the rover and planning simulation tests of driving options with a test rover... "Spirit is in a very difficult situation," JPL's John Callas... said Monday. "We are proceeding methodically and cautiously. It may be weeks before we try moving Spirit again."

In the past week, the digging-in of Spirit's wheels has raised concerns that the rover's belly pan could now be low enough to contact rocks underneath the chassis, which would make getting out of the situation more difficult.
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alan
post May 12 2009, 02:51 AM
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I've been seeing this listed on the tracking site recently

01904 p2568.22 0 0 0 0 0 0 pancam_light_disturbed_soil_L6R1
01904 p2569.22 0 0 0 0 0 0 pancam_undisturbed_soil_L6R1
01904 p2570.22 0 0 0 0 0 0 pancam_dark_disturbed_soil_L6R1

Watching for signs of wind gusts?

By the way with the new found energy and the apparent decrease in activity why isn't the backlog of images being downloaded?
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RoverDriver
post May 12 2009, 03:06 AM
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QUOTE (alan @ May 11 2009, 07:51 PM) *
I've been seeing this listed on the tracking site recently

01904 p2568.22 0 0 0 0 0 0 pancam_light_disturbed_soil_L6R1
01904 p2569.22 0 0 0 0 0 0 pancam_undisturbed_soil_L6R1
01904 p2570.22 0 0 0 0 0 0 pancam_dark_disturbed_soil_L6R1

Watching for signs of wind gusts?
...


No. We are trying to gather mechanical properties of the soil under the wheels. Actually where the wheels are buried. We have observe from the RHAZ that although the wheels have churned up the soil pretty badly, the left side soil is bright in color while the RR wheel has churned up dark material. We believe the dark toned material could provide more traction than the light tone material. We will try to replicate the soil properties in the testbed, evaluate which strategies might work better and go from there. The situation is compound by the issue of high-centering. We are not sure we are high centered, but if we are not, we are cose to it. There is a single frame NAVCAM taken on sol 1870 which shows the terrain the rover is currently sitting. By comparing that NAVCAM frame with the NAVCAMS taken from the current location we are trying to figure out exactly where the rover is and determine if we are high-centered. The last fly in the ointment is that during the last executed drive (sol 1899) the LM wheel stalled. We do not have a cause yet, could be a rock stuck in the wheel well, could be bedrock underneath the wheel, could be an actuator problem.

This is a pretty big mess: embedding event + high-centered vehicle + stalled wheel. Since I have been asked to lead this investigation, you know why I won't be posting much during the next few weeks.

Paolo


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nprev
post May 12 2009, 05:17 AM
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Oh, boy. sad.gif Thanks for the update, and good luck, Paolo. We're rooting for you!


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alan
post May 12 2009, 05:45 AM
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My guess for the location of the wheels.
Attached Image


Also identified are the original location of the rock that was flipped after being dragged and one that appears to have gone missing during all the churning.

ETA:
the pancam site has a color image of this location,
http://marswatch.astro.cornell.edu/pancam_..._L257_pos_5.jpg
(about a third of the way up and a third of the way to the right from the lower left corner)
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Guest_Sunspot_*
post May 12 2009, 07:20 AM
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Looks like some people think we may be here for the rest of the mission.
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RoverDriver
post May 12 2009, 09:47 AM
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QUOTE (alan @ May 11 2009, 10:45 PM) *
My guess for the location of the wheels.


Good guess!

QUOTE
ETA:
the pancam site has a color image of this location,
...
(about a third of the way up and a third of the way to the right from the lower left corner)


I believe this PANCAM is at a higher elevation than our current location.

Paolo


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RoverDriver
post May 12 2009, 10:33 AM
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QUOTE (Sunspot @ May 11 2009, 11:20 PM) *
Looks like some people think we may be here for the rest of the mission.


Hmm... maybe it is a language barrier, but I do not understand the point of your remark.

Paolo


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djellison
post May 12 2009, 10:49 AM
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He's being the worst kind of pessimist...a pessimist who also thinks everyone else is pessimistic.
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alan
post May 12 2009, 01:24 PM
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QUOTE (RoverDriver @ May 12 2009, 04:47 AM) *
I believe this PANCAM is at a higher elevation than our current location.

Paolo

???

Do you mean it was taken from a higher position (its from the edge of Homeplate) or that the location is wrong?

Perhaps my explanation of the specific location in the image wasn't clear. I've circled what I meant in this image.

Attached Image


I can clearly see the two flat rocks which were run over during the drive on sol 1871(arrowed)
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ElkGroveDan
post May 12 2009, 01:24 PM
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Here's a wild thought that would be more a later move of desperation. I'm not certain what kind of mass ratios we are dealing with but would it make sense to extend the arm and IDD to slightly shift the CG, and add to the traction/load on a preferred wheel or wheels?


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charborob
post May 12 2009, 01:59 PM
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Seeing how the rovers are so vulnerable to getting stuck in soft ground, I wonder if that possibility had been taken into account when designing the rover wheels. With hindsight, it might have been better to equip the rovers with large balloon-type wheels, allowing them to "float", so to speak, over the sand. Maybe it would have caused other problems (storage space for big wheels, less traction?).
I can't help thinking about MSL, which seems to be equipped with somewhat similar wheels, although wider to account for the higher mass. I hope the experience gained with the MERs will be put to good use on MSL. We know there are sand traps on Mars. Lets hope MSL doesn't suffer the same fate as the MERs, getting stuck all over the place. (OK, the MERs aren't getting stuck all over the place, but you see what I mean.)
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MahFL
post May 12 2009, 02:00 PM
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If anyone on the planet Earth can get us out, it is Paolo !

wheel.gif wheel.gif wheel.gif wheel.gif wheel.gif wheel.gif wheel.gif huh.gif
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SpaceListener
post May 12 2009, 04:18 PM
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I still believe we can rescue Spirit. The things that must be studied carefully are about the relieve of the soil around the Spirit. We must take the advantage of the help of gravity direction to be unstuck. According to Alan's picture, I am not able to see precisely about the inclination of the surface. As the rule of thumb, the lower land, has softer soil than the higher ones. The picture has show that the left side, close to the slope, the surface is very smooth but I doubt it would be a firm soil.

Is Spirit capable to turn around by 90 degree to change the scape route toward left side (close to the slope) toward the Braun hill?

Maybe, lower soil, has another kind of layer, a firmer soil which might help to improve the traction?
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Stu
post May 12 2009, 04:18 PM
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Is this roughly the right position?

http://cumbriansky.files.wordpress.com/2009/05/stuck.jpg


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