Hay, Paolo! I saw and heard you today on NASA TV! Looked like you were having tons of fun dumping DE into the pit from the wheelbarrow and then raking it down...

You're a TV star, dude!

-the other Doug

I was not aware of that. What was I saying?

Paolo

Lipreading, it looks like... "Ah, Mr Ellison, I've been expecting you. I see you have met my little... `pets'! "

sorry if this post is on topic

Looking at the set up in the TB, I'm wondering about how it will account for the RF given that it is on "solid" ground and apparently higher . I realize the rover suspension system could be compensating for the tilt but would there not be considerable downward force from front to back effectively driving the RR (or perhaps the LR diagonally) into the ground ?

I'm guessing that no one wants to drop all 6 wheels into the mire but perhaps an attempt to drive the RF off it's "shelf" so that the forces are equal back to front? I'm not sure what that means when taken with the tilt of the whole thing.

We will b placing the RF wheel on a piece of plywood simulating the shelf. We'll see how that works out.

Paolo

How about its own little private sandbox of hard packed dirt to give the wheel something to drag through? Or does that just needlessly complicate things?

It was basically B-roll kind of stuff (the "interview" was of John Callas), but after dumping a bunch of DE into the pit, walking away, you were clearly heard saying "Whoof!" (I'd have to run the recording again to quote anything else; there was one point while TeeBee was being driven into the pit that you were calling off numbers, for instance, and you were laughing with the woman who was helping fill the pit, clapping your gloves and then, despite the facemasks, coughing like crazy from the DE dust that flew.)

The camera was right behind your head at one point -- I mean, I know scientists and engineers can get a little single-minded at times, but you have to have been aware of the cameras. Now you know what they do with the footage they're taking!

-the other Doug

Good News everyone!


“And we're not stuck.....Spirit is mobility impaired.”



http://www.planetary.org/news/2009/0630_Ma...ate_Spirit.html

Great update as usual from TPS; nobody does it like A.J.S. Rayl!

That pic of pallets of soil component material made me tired just looking at it. For a mad scientist, Paolo sure does work hard. Make those young pups do most of the heavy lifting, man; as one of my former USAF bosses put it, "Use them stripes, Sarge!"

Also, congrats to our esteemed Poet Dude Stu for inclusion of his Endeavour road sign for Oppy...really like that image!

You can see this short video here : http://www.jpl.nasa.gov/video/index.cfm?id=851
( JPL-"Free Spirit" website )

I was aware of the camera. They have been taping almost every barrel we dumped. I was curious of what exactly they selected.

Paolo

No stripes here. But if I didn't have the help from all the "young pups" I would be still there huffing and puffing.

Paolo

Paolo mentioned on another thread that the rover's wheels can be commanded independently. Can they be set to just roll freely without being powered? If so, could the tractionless wheels be set to spin freely and only the wheels with traction be commanded on?

That was answered before. The wheels can't roll freely. The gear ratio is too high.

Not to pick on you, but do you seriously believe that if we could actually do it we would not have done it already? The RF drive actuator was lost about 1200 sols ago. Someone in the MER team might have stumbled in this idea by then!

Also, you are suggesting to do it on the tractionless wheels, not on the RF, but since none of the other wheels have much traction, which wheel would do the driving?

Paolo

Obviously the one that's had a chance to rest for 1200 sols and is now ready to start working again.

07.01 navcams enhanced.

Click to view attachment

Paolo

How far down the list is a retest of the RF wheel right now? You mentioned it some time ago, but there was some risk associated with it...

Now that's what we refer to as a CLEANING EVENT!

Whoa!!!! Wonder if any before & after power data was recorded.

Forget power levels, check and see if there's a yellow brick road nearby. That was a direct hit. Wow, what luck! You couldn't get a better photo sequence if you were... um,... shooting this on a soundstage...

What sol was that? (The wind gust.)

Edit: Never mind. You must have done one heck of an enhancement because I can’t see much of anything in the originals.

http://qt.exploratorium.edu/mars/spirit/navcam/2009-07-01/

Not surprising that the latest status report goes up to sol 1952 and the straight-line wind event was on sol 1953.

Luckily the next update should be tomorrow.

So far down that I can't see it. Probably right around using the IDD to shovel rocks under the LF wheel. This was not asked too many times, and is not in the FAQ, might be a good addition, if the admins want to pick this up:

In order to save mass and reduce complexity, some of the actuators (~=motors) share motor controllers (electronics), for example IDD and mobility. This means that if an attempt at applying voltage to the RF wheel results in damage the motor controller we potentially lose the use of another actuator. In addition, given the fact we are not 100% sure about the type of fault we have on the RF actuator, sending power down a line that might be shorted some unknown place might ultimately send power to a device that might get damaged. When I talked to Jake Matijevic some time back he did not like the idea at all. I still think we might be able to send a voltage that is low enough not to cause damage but high enough to verify whether the motor is OK or not. I will try to talk to him again about this.

Paolo

Thanks for that

I figure you actually did this (sending power down the line) right after the wheel stalled to conclude it was dead? So the "risk" is that it in the meantime it has developed a short that could damage some other hardware if it is powered on as you said?

Do you know what other actuators are controlled by the RF wheels motor controller?

Yes we did send power down the line to determine the mode of failure but don't recall what we measured (short or open circuit). The rationale is that if we want to test the actuator we believe something might have changed and if so, we might be dealing with a loose wire.

No, I do not recall what actuator is shared with the RF. I would need to look it up. I will let you know.

[edit]
The RF drive actuator shares the motor controller with one of the IDD joints and the failure was an open circuit indicating that at some point along the wire there is a break in the cable or interconnects.
[/edit]

Paolo

RoverDriver said: ...FAQ, might be a good addition, if the admins want to pick this up

Done! There was a reference about trying the RF wheel already, but thanks for the extended answer which has been added to the FAQ.
I'll try to keep it uptodate as Q&A come along.

Is the electric motor of rover wheel attached inside of the wheel? There are many causes that the electric motor get stuck. Most of the cases might be due to dirty contact brush. As I remember that RF wheel stopped to work after going a very dusty surface. The ideal is that "someone" there is able to kick or try to rotate manually it in order to get rid any dirty dust of wheel. Spirit as alone there, the only way is to kick its wheel against any rock when she is back on business.

I'd even said CLEARING EVENT!

I figured it had probably been thought of, but I didn't see it mentioned in the freeing Spirit FAQ. Sorry.

Thank you guys for all your work on the FAQ! Great resource for all of us who don't have much time.

I'm not convinced it was one of those.

I can't say I see convincing evidence of rotation in those dust clouds, but there does appear to be evidence of front and back side dust clouds. I think that very well could have been a DD roaring over Spirit. Other DDs were evident in the background, indicating that it was an active sol for them.

BTW, thanks for that wonderful, enhanced animation, Fran. It was one of the most fascinating rover observations I've seen in quite a while. It often goes unsaid, but many thanks to those who had the foresight to program Spirit to watch for such wind events.

Awesome...It's almost as if Mars was in my back yard.

Possibly, the best way to tell on earth is the debris field. Not really an option in this case.

I'm sorry if this falls under the "stupid question" catagory:

From reading the mission updates for Opportunity, I thought prior to the RF failure on Spirit there were a series of sols with increased voltages indicating the actuator was drawing more power than normal because it was under stress. If the failure on Spirit was due to a broken connection, then perhaps wheel-resting to resdistribute lubricant on Opportunity is not accomplishing much?

Perhaps keeping a low and steady current could help anneal contacts in the wire/circuit (prevent failure on Opportunity and with amazing good fortune, restore the connection on Spirit)? Anneal might be too strong a word, but perhaps allowing the wire to warm keeps it more flexible and perhaps expand enough to restore a weak/broken connection?

Unfortunately we do not have clear indication of what is the source of high currents there, so we don't know how to fix it. We do know that there is clear evidence that rest seems to help to solve the problem temporarily.



On Spirit, we do not know where the open circuit is. It could be at any location along the wire, any connector or it could even be one of the brushes in the motor. We typically have heaters near actuators not on cables or connectors, so we could not actively warm them, but we could use them at different times of day. Still the hesitation in attempting to use the wheel again stems from the fact that the open circuit might also be due to a loose wire that potentially could contact unintended components, damaging the rover irreparably.

Unfortunately, there is only a limited set of things we can try to analyze a failure, and we have to be conservative whenever we have potential for permanent damage.

Paolo

Also, there seem to be sharp borders at either side. If it was a "straight line" wind, it was very narrow and well defined like a blast from an air gun. It looks like a DD to these untrained eyes.

Are any official odometry readings from the test bed rovers kept? Would the team expect the RF wheel problems on the test bed rovers eventually? Also, is that SSTB1 featured in the Roving Mars(IMAX) movie? (scene where SS shows the rover to school kids, and some other scenes). Apologies if this has been mentioned already but my search didn't seem to yield these topics.
Thanks in advance and good luck!
Eoin

Part of your question, Eoin, was answered in this post by Paolo.

Thank you fredk, did you use the search function to find that? Any quick tips on narrowing searches? The answers to the other parts are bound to be here too
Eoin

Not that I know of.



Possibly but the environment of the SSTB is quite different from Mars ;-)



No, that is the SSTB Lite.

Paolo

I remembered Paolo answering that question some time ago. So I searched for keyword "testbed" and member name "RoverDriver" for posts older than 2 months old, with "Show results as posts" selected under "Result Type". It showed up very quickly.

To these untrained eyes it looks like the very early stages of a dust devil in formation when the hot air is starting to punch up through the cooler layers immediately above and before rotation starts.

In my part of the world (Central Australia) we see quite a lot of these. Quite often rotation never starts and a line of dust blows onwards for short distances before dissipating or sometimes it goes on for a few kilometers. The disturbance shows itself through a jagged rough line of dust which has all the appearance and feel of a small squally wind front. Occasionally the front can be suprisingly broad - 100 meters or so. The pic that Fran posted really reminded me of these broad fronts.

Alaska sounded the most appropriate place to go for a ref!!
http://www.gi.alaska.edu/ScienceForum/ASF2/227.html
http://science.nasa.gov/headlines/y2005/14jul_dustdevils.htm

I have actually walked into the middle of a large dust devil on a calm day when it was almost stationary. About 10 metres wide - 300 metres high. I got to the centre after getting sandblasted by a wall of roaring sand (100kph?). The centre was completely calm - very clear air - about 6 metres wide. Could see right up to a point of blue sky at the top of the funnel. Kept walking along with it for a few minutes. I'll never forget the utter calm of the centre eerily contrasting to the tight wall of roaring sand whipping so close around it. Amazing!!

Whatever's happening here, it's been a fantastically good factor in taking time pressure off getting Spirit unstuck.

Too right. If she had to get stuck for awhile, Trojan is certainly proving to be a great place for it what with the unusual soil composition & favorable + interesting winds!

I understand that it is currently high summer in Gusev. It is concievable that Spirit may not be extracted over the whole of the next Earth year.

What I wondered is whether the soil in Gusev crater would become harder and so easier to drive through during the martian winter?

What prompted me to ask this question is the report around one year ago during the martian autumn that liquid salty water may have been present at the Phoenix landing site. I presume that driving a rover on frozen soil at the Phoenix landing site during a martian winter would be easier than driving a rover on damp soil at the Phoenix landing site during a martian summer.

I am of course assuming that my hypothetical polar rover would be far more resistant to cold than an MSL or MER rover.

Only after Spirit is alive again, the rover driver would be more aware of the tricks of land between the Troy to Von Braun hill. This is due to the fact that the RF is causing more troubles in driving on somewhat loose surface. The tracing path would be on the firmer surface, or close to bedrock as the preference path. By seeing the picture, it is rather hard to guess for the best route. Well, it is still to soon to talk about!

From what I've read, I've not seen anyone mention or realistically propose slush as a current day occurrence anywhere on Mars. Not to mention, it's taking this particular thread very off topic.

The question of the properties of dry soil as temperatures drop has already been addressed - see the entry on trying to drive at night in the extraction FAQ.

Just out of curiosity, how long has it been since any of the wheels have been moved?

Reason I ask is that it might be interesting to take another look with the IDD & see if any of the disturbed soil has begun to settle a bit--or has blown away, for that matter. If the direction & intensity of the wind was favorable there might be a bit of a venturi effect under Spirit (though of course not enough to free her by excavating the wheels.) Could provide some more insight into the various materials' properties, if we're lucky.

I think with the latest downlink all of the L2 images from the Calypso Pan are down in full. Someone want to check me on that?

Edit: Both L2 & R2 images are now down. Still waiting on L5 & L7.

Calypso panorama R2 (autostitched)
Click to view attachment