Cape York - Northern Havens, Sol 2780 - 2947 Options

[CosmicRocker]

I'd suspect a "bit of settling, too. I don't see any rotation of the wheel, but it is easy to imagine a weak rock fragment eventually failing under the load of the wheel over time; with or without encouragement.

[kungpostyle]

Happy Martian solstice!

[PaulM]

Happy Martian solstice!

[Matt Lenda]

I'd've thought that a wheel performing a steering or driving movement without being commanded would be very unlikely, but I also know nothing about the architecture. My thinking was more along the lines of a bit of settling, maybe prompted by an IDD movement or even a wind gust. We are on a pretty good slope here. Maybe the LF wheel was perched on the edge of a miniature cliff, in an unstable position, and finally worked its way down?

I'd say this is our current best theory. We rather facetiously suggested local meteor strike and Mars quake -- "just to be complete".

There are actually several other mysteries floating in and around the same time frame. For instance, that the apparent movement occurred near in time to a IDD joint stall seems significant, but we can find no mechanism (physical or otherwise) that could do such a thing. Certainly no one theory describes everything we've seen so far.

The problem is that when you're not expecting anomalies, you're not recording data or taking pictures every moment to document them!

We're now kicking ourselves in the foot for not recording our attitude as finely as we could haven when we stopped for the winter a few months ago. If we had done so, it would helped in the analyses that our downlink folks and RPs have been doing. Oh well. Still driving a car on Mars, still pretty cool.

-m


EDIT: Say, anybody got a blinking GIF of two hi-res front hazcams that show the apparent movement? I've got one from this side of the fence at JPL which I'm not allowed to use in my blog (have to pretend I'm a layman!)...

[stevesliva]

With the way the suspension works, can the middle wheel sinking push the front wheel down harder? Could it be the middle wheel that was precariously perched?

[elakdawalla]

EDIT: Say, anybody got a blinking GIF of two hi-res front hazcams that show the apparent movement? I've got one from this side of the fence at JPL which I'm not allowed to use in my blog (have to pretend I'm a layman!)...

Happy to oblige. Here's two, one just a stupid animation of the two full frames, the other a detail in which I've aligned the rocks to remove that component of the apparent motion and adjusted levels to match.

Attached thumbnail(s)

 

[Hungry4info]

For what it's worth, an animation showing multiple wheel movements and some IDD inspection.

Attached thumbnail(s)

 

[Matt Lenda]

Happy to oblige. Here's two, one just a stupid animation of the two full frames, the other a detail in which I've aligned the rocks to remove that component of the apparent motion and adjusted levels to match.

Bingo! Thanks, added to recent blog post...

For what it's worth, an animation showing multiple wheel movements and some IDD inspection.

Curious -- what sols are each frame? You seem to have spotted the second movement of the wheel the team is currently looking at...

-m

[fredk]

There was movement of the LF wheel between 2899 and 2901 - the frames are listed at this post.

[ElkGroveDan]

Dang. That one of Emily's really makes it look related to the arm movement. If this was an eight year old machine operating outdoors on Earth I'd be looking for crossover voltage from abrasion in the cable bundles, but surely that can't be the case in these environs. I would assume the team are looking at internal circuitry issues then?

[fredk]

If it's linked to the IDD movement, that doesn't mean it's an electrical problem. An IDD movement would shift the centre of mass of the whole rover (slightly), which may have been enough to precipitate the LF wheel "over the cliff", or to crumble a little piece of bedrock sticking up under the LF, or whatever. A sort-of "local marsquake", so to speak.

[djellison]

There's no reason to suggest any current went to the wheel motor - it didn't turn - and there are brakes on the wheel drive motors anyway that would have to be disengaged I believe.

Take the combo of moving the arm around (quite a lump on the end of a long stick), strong winds with large solar arrays, and on a rocky slope, it's easy to see how the rover could just nudge ever so slightly.

Indeed - up at the summit of Husband Hill, Craig Covault's article about 'Rocky Martian High' talks about concerns in moving the arm whilst on a slope that might cause the rover to move slightly.

[centsworth_II]

Dang. That one of Emily's really makes it look related to the arm movement....

Looks can be deceiving. The second image shows the arm and wheel in new positions but that does not mean they moved to those positions at the same time..

[ElkGroveDan]

There's no reason to suggest any current went to the wheel motor - it didn't turn - and there are brakes on the wheel drive motors anyway that would have to be disengaged I believe.

I was envisioning a brief tug on the steering actuator rather than a wheel turn, but now that I think of it your suggestion sounds just as likely, perhaps more so.

[eoincampbell]

Is this serious enough for a testbed rover comparison ?