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Beautiful images jccwrt and James Sorenson

Apologies for the poor stitching in my version. False color and enhancement to emphasize particular features. Any ideas on what caused the massive soil disturbances in the otherwise smooth hillside?

I'm not seeing any disturbance care to point it out in the photo? I see rover tracks and gravity tumbles.

I guess it must be the gravity tumbles, by the sound of it. Is that a commonplace phenomenon?

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This is one of the disturbed areas.

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This is parallel-eye stereo of part of the area.

Perhaps you are referring to the horizontal band of bedrock dominating the upper left third section in this sol4743 image? From this tricky perspective, especially if like me you grew up in mudslide country where such formations are common, the eyes might suggest the resemblance of this to the tongue of a soil slump feature, but my take is it's a major bedrock layer preserved by, well, the lack of gravity tumbles, the erosion of the surrounding soil leaving it in high relief, and a small sampling of rocks from the bedrock layer doing gravity tumbles to litter the base of the section.. but the uncanny resemblance to some sort of mudslide tongue (or whatever you call that) from this viewpoint did strike me as well, almost like a wave coming down!

Long baseline stereo (visually matched from images on different Sols).

Parallel-eye:
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Cross-eye:
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My on-again off-again stitching has always been on a slow learning curve, especially with all the different tools I have downloaded since the beginning of this mission
Here is the first stitch that I felt good enough about to share (after 4744 sols!)
Two whole images in one.... (whew)

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http://www.planetary.org/explore/space-top...nce-valley.html

Monthly MER Report from The Planetary Society.
It seems this winter may be challenging from an energy point of view.

great article! thanks for linking it. I had always been curious about the linear feature running from the plains up to the valley edge, that shows up as a sort of thin rusty line in the HIRISE images linked in the story, Crumplers view, and especially this one, but couldn't imagine it being a relic of a water erosion channel, if thats ineed teh features in question, in which case the idea seems to not be out of the question, this early on at least, as suggested about those sol4747 images, of which the below crosseye and parallel view provides some terrain relief, whether it be a remnant channel from a spillover lake, or evidence of wind-scoured faulting, or something else entirely..
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As usual, I'm future-tripping 😅 Are they postulating a return up Perseverance Valley after the downward trek, or do they envision continuing to the crater floor?

To the crater floor, south, and up again further south.

Phil

I was just looking at the overview map of the path that Opportunity has covered -- over the plains and along the crater rim -- which led me to thinking that we really need to get down on the crater floor. That is potentially a whole new realm of geology, and if the plains were historically wet (at least in the subsurface), perhaps something even more interesting was going on within the crater.

Incidentally, I'm surprised that nobody has posted some large stereo panoramas of the long-baseline surveys of the "channel". Just at the moment, looking over what I've seen so far, I'm having one of those "the emperor has no clothes" feelings. But the HiRISE imagery is very persuasive.

https://mars.nasa.gov/mer/mission/status.html#opportunity

Seems to be an issue with the left front steering actuator. Hope this doesn't affect the exploration plans.

The plan was to try to straighten the LF wheel on 4754 but I see no sign of movement in the hazcams...

hope this is not the beginning of the end

These things way outlived their life I sort took advantage of that fact.

here's a rough widebase anaglyph of sol4749 x sol4754 stitches. interesting how its almost as if a lake shoreline feeds the channel narrowing towards the rim in these images, which hadn't seemed as apparent until now. also attaching the full sol4754 stitch as well with lightened leftmost image and scaled 50% to fit post limit.
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Nice, the channel is obvious. I'm wondering whether what appears as a lake shoreline is actually the upper portion of the channel wrapping around and heading off to the right. The overhead view hints at something to that effect.

The Pancam L2 view on Sol 4737-4744.

Jan van Driel

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We are now close enough to the Winnemucca edge to get good stereo separation in the above parallel eye image. Note the overhanging rock at the edge and the tapered form beneath it. Stalactite?

I don't see any real sign of an overhang, just a shadow - compare with this view:
http://merpublic.s3.amazonaws.com/oss/merb...KPP2596L2M_.JPG

I made my first MERB RGB images from Sol 4759...

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I think Oppy could still move if she drives backwards and steers the left and right rear wheels to the right(the excact opposite direction than the front wheels).What do you think?

Scott Maxwell and I did some quick testing with the SSTB in 2008 or 2009 with the LF wheel toed-in and it was still driveable going straight. Changing direction reliably, that would be more challenging. *I* haven't give up hope on that actuator tho.

Paolo

If all else fails, would it be possible to exploit a terrain effect to straighten the wheel?

The team would have to find the perfect spot (a rock?), and maneuver against it perfectly... a tricky problem!

We have donated all the suitable rocks to our sister Curiosity. We would have needed a formation that would act sort of like a vice, insert the wheel there and rotate the vehicle. We unintentionally ended in a vice situation before with Curiosity and we tried (and succeeded) to avoid getting the wheel stuck there.

Even if we could find a suitable setup nearby, manage the impossible and set the wheel there, would you really send the command to turn the vehicle around? There's a 1500:1 gear ratio on the gearbox. I would be afraid to bend the strut, or at least damaging the drive actuator!

Not trying to be blunt, but we in ops need to be really careful not to make more damage and completely disable the vehicle. This should not discourage anyone to provide suggestions. I will read them all.

Paolo

This is just a shot in the dark, but is there any way to leverage the mechanism used to deploy the wheels on landing?
Perhaps raise only the left-front wheel slightly so it offers less resistance to movement, if this is possible?

Please pardon my naivete. I don't have a good knowledge of the rover mechanisms.

If that were possible, they would probably have done it for Spirit.

No - it latched into place, it can't go back.

Could you orient the rover body so that the offending actuator gets maximum heating and cooling throughout a Martian day? Maybe that will loosen up whatever is stuck. Perhaps even try intentionally moving it in and out of the Sun during the day.

Try driving the wheel over a pointy rock, applying pressure on different parts of the wheel so that the actuator get wiggled a little. Not just forwards and backwards, but inboard/outboard edge of the tire too. Rock doesn't have to be tall, just high enough out of the bedrock that different pressure is applied to the wheel/actuator joint. Do it back and forth a few times to try loosening it.

Similar to Marsophiles idea, but instead of locking the wheel in place against two rocks, drag and push it over a pointy rock so that the wheel catches & skitters across the rock. It shouldn't be stuck, per se, but it should be pulling and pushing across the rock so that the treads hold and then release, vibrating the assembly.

How does the distance driven by the test bed compare to the distance on Spirit and Oppy? Has the test bed run into any similar issues with its actuators?

But how can you know whether those actions will make the situation worse rather than better? They can't be tested very accurately on Earth given limited knowledge of the exact geometry, positioning accuracy of the wheel on the rock, hardness or friability of the rock etc. I would be more inclined to run through the full range of engineering solutions - heaters, varying current applied to the actuator, driving forwards and backwards. Things that can be tested in the Mars Yard.

Phil

I'm sure Paolo would do the least risky attempts first, and only the more risky ones after a risk analysis or simulation done on the Test Bed. Perching on a rock shouldn't be too dangerous (I'm not talking a rock the size of the wheel, just one large enough that the force is localized on the tire - so maybe 1/4 wheel height), but trying to drag the wheel across I agree could be dangerous. But since everything can be done with small stepper motor steps, it's not like the drivers are going to gun the engine the first try. The Test Bed can tell us if it's even possible to move the wheel sideways across a rock, it might not work geometrically. Again, I'm not saying pin the wheel to the rock, just let the friction naturally grab and release the wheel as it goes over the rock.

I'm also curious about the Test Bed drive distance vs the rovers because the dust in the Martian environment might be similar to the Lunar dust that gave the Apollo astronauts such fits because it was so fine, dry, and abrasive. Could be that dust is reaching the gearbox or actuator? There might be something to learn about gaskets for future rovers - magnets to keep dust away from actuators or something, like this article proposed for Lunar dust. https://www.sciencedaily.com/releases/2008/...80924191552.htm Perhaps for future requirements a lunar dust analog endurance test could be done against actuators to determine how well they can keep the dust from eroding the gaskets and reaching the actuators.

The recent conversation on the Opportunity General Health includes a pretty thorough Paolo overview of the situation with respect to drive motors and actuators. Well worth the read for any that haven't seen it. For a system designed for a mission success criteria of 90 sols and 700 metres the performance of the mobility systems has been outstanding and I think that the engineering team can sit back and bask in the plaudits of we mere mortals.

Indeed there are rocks in shadow. They show up best (but still faint) in blue light.
Two-D images can give a misleading perspective. Here is a parallel-eye 3D.
(From Sol 4761 images brightened to show detail.)

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For those who prefer Xeye, here it is:

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Xeye underestimates depth perception for distant objects (but is better for close objects).
Here is a comparison with the image Fredk pointed to (bottom image).

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The new (top) image is from a slightly lower angle.

This R1 from Sol 4759, where the rocks are illuminated, tells a different story.
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It looks like it was just shadows as Fredk said.

I'm not sure this thread is the most appropriate one for this discussion, I will let the admins move or delete the offending post(s).

After the initial tests I'm not sure we know where the problem is, whether it is close to the motor, or the wheel. I would say that only after we have a reasonable idea we will come up with a solution (if it exists).

All the suggestions so far are good but unfortunately we have pretty severe restrictions due to power and volatile storage (cold and hot temperature testing). We also have to get ready for Conjunction and Winter 8 while providing meaningful means to explore Perseverance Valley.

I don't think anyone has kept track of the odometer on the testbeds but I would be surprised if it was a significant percentage of either Oppy or even Spirit. We typically use it to do small-motion tests (a few meters at most) and the tether is pretty short.

The torque at the output of the gearbox is so strong that any attempt to force a stall by manually locking a wheel was fruitless. So on the one hand we would need to apply a very strong force to do anything significant, and on the other hand one could cause more damage. So if you won't see us try more crazy things, please understand that we rather drive a crippled vehicle than a lander.

Not sure what flavor of lemonade we will make this time (maybe Orange Crush?), but we thought it was almost impossible to use the IDD after Joint 1 became unreliable. I'm sure we will learn how to drive this thing (again!). There's still some of us that remember how to drive a-la-Spirit.

Paolo

I appreciate that safety is paramount, but if the rover ever did need to find a vise-like terrain configuration, it could perhaps create its own by doing a "wheelie" in soft soil, as it has done many times before.

Indeed we have some motion this morning!
http://merpublic.s3.amazonaws.com/oss/merb...KVP1242R0M_.JPG
http://merpublic.s3.amazonaws.com/oss/merb...KWP1242R0M_.JPG

Not sure what you mean. Wheelies to me refer only to extreme bogie positions, so either mid or rear wheels in air while the other is in contact with the surface. Even in these cases, the shift in CG position would not have a significant impact on the front wheel.

Paolo (who is really happy about the LF wheel being straight)

here is a GIF of the wheel movement :
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No doubt LATE in the morning. We're into the melodramatic teenage years now.

From Crumpler's latest post:

And a sketch of a proposed route over the next couple of weeks:

Details of the LF wheel in the latest update:


I'm sure they tried this (and many other things) with the RF.

Testing on Mars was quite limited instead. There was much discussion but given the small toe-in value of the RF helped in settling into the decision not to use that actuator again.

Paolo

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Right, just below the solar panels. I don't think we have seen bluish-white material on the rover deck before. Pesky Birds!

Could be just a specular reflection, though an odd one.

Congrats Paolo on the recovery. Maybe on future rovers a grad student project would leave an actuator set inside a dustbox running continuously to look at potential lifetime failures. Can't complain about the endurance so far though. Keep on Opportunity!

http://www.planetary.org/explore/space-top...ains-ankle.html

Monthly MER Update from the Planetary Society (guest blog by A.J.Rayl).
May "toe-dip" into Perseverence Valley before Solar Conjunction.

The Pancam L2 view on Sol 4775-4777.

Jan van Driel

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Here we go.

Maybe the ejecta from this small crater will be of interest.
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crop from Phil's route map

Centsworth...
I agree, if you are exploring a 3 billion year old stream-bed on a dusty planet, and you don't have a shovel (other than your front wheels ) , look for a small impact crater

[quote name='PDP8E' date='Jul 9 2017, 10:51 AM' post='236462']
.... and you don't have a shovel (other than your front wheels )

Hey, don't put some weird ideas in their head! ;-)

Paolo