Well, as exciting as this new development is, I can't help but think that there may be some rather awkward questions levelled at the rover team regarding how long this wheel may have been operational.

I can't believe that wheel is turning. Of all the unexpected things.

It's pretty odd. But I don't think Galileo tried to open the HGA, ever, after it arrived at Jupiter. Maybe not the best analogy because it was too busy trickling info back to earth, but it would seem you eventually stop trying, especially if the trying is risky and takes time.

I do bet they're ticked they didn't try it when they failed to drive onto home plate. Other than that... Hindsight's 20-20. I bet they'd now try it every time the going got rough with that dragging wheel.

Good to see the RF moving again, but very frustrating knowing that it has probably been working for years. Unfortunately it now would be better to have a working RR than a working RF. Too bad they didn't try the low voltage test on the RF at the beginning of the extraction attempt while they still had a functional RR. Since the RR is burried so deap, dragging the RR through all that soil will be very difficult and indeed no forward extraction motion is seen in the latest animation. Is 'full speed ahead, straight forward' still the best option? Spirt seems to just be sinking futher. Hopefully there is a good rock for the RF to bite into burried deeper under the wheel...

Updated the animation to make it a little bit slower.

http://www.unmannedspaceflight.com/index.p...st&p=152003

As far as trying the RF wheel earlier, we've been told that that entailed a real risk of doing serious damage to other parts of the rover. So unless the situation was truly dire (like it is now), they decided it wasn't worth the risk. For example, when they failed to get back up on HP, they still had other route options. But I have to say I do wonder if it was possible to test the RF wheel with a voltage low enough to be safe, as Paolo asked a while ago.

But imagine if they tried the wheel three years ago and it worked, and they drove to G/VB but discovered nothing of interest - all of the interesting science was lying underground waiting for a dragging dead wheel to unearth it.

And trying the RF wheel at the start of the extraction process may not have made much difference, since the RR didn't do much driving before it died. Getting out of Troy would not have been easy, even with six functioning wheels.

As far as strategy goes, one idea now would be to steer to the right and drive forwards. A functioning RF now makes that possible. The idea would be to pivot around the dead and buried RR wheel, and get as many wheels as possible out of Scamander and into better traction. I'm unsure if that would mean doing some climbing, though, which wouldn't be easy.

Tyrone, Silica Valley, Troy, ...
The story behind HP perhaps would be never known without the science taken on these places.

I'm not saying this figured into their reasoning, but one consideration might be that it is more acceptable for the rover to die of natural causes than to die as a result of a risky operator intervention. The exception might be a calculated risk that is explained very very well.

Outstanding news...Way to go, Spirit team.

I'm holding my breath as I wait to see what happens next.

Do we know anything about the RR wheel. I've been studying the rear hazcams, but cannot tell if it turned or not.

I 'd dismissed the possibility of that wheel ever turning again!!!!

This is a good lesson in terms of mental complacency. When I reflect on my own thinking it makes me realize,in general, just how easy it is to make assumptions without being aware of it.

Amazing!!!!!

The wheel-dragging DEFINITELY made all the difference when it comes to the science return at Gusev, we have to remember that. Let´s just rejoice at this crazy new development instead of second-guessing our amazing JPL team. Hindsight is 20-20. Also, this topsy-turvy story is truly in the spirit of Spirit, our troublesome firstborn rover who always had to fight hard for whatever it earned.

Or by intentionally trenching from time to time, as they have been known to do.

Brian

I cannot avoid thinking whre could we be if that wheel was known to be working but!
But we have come a long way nevertheless...things can only get better...let us focus on the extricating process, then...past and future of the astounding MER mission will be our debate...well...the past maybe not...

Lots of info in the latest Spirit update. Highlights:

Spirit was designed to last 90 sols and maybe a little more. We are at 2100+ (23 times X 90 sols).

The grounding issue on the motor drive electronics board is a serious problem (... speaking as a humble electrical engineer, 30+yrs)

Ground should always be 0 volts. Since they are seeing excursions of -5 to -24V on the ground, it indicates a problem with a connection (opening, loose. -etc) or a funky component (a drive transistor or like devices) or something else. The ground issue may also explain why the RF wheel stopped working years ago and then again today. The JPL engineers have access to the schematic diagrams and can start a fault analysis (i.e. if this part is failing this way, it would explain these readings). since the number of parts is probably several hundred (and the number of inter-connections between the parts is higher than that ), and how each part can fail is large, the resulting 'fault tree' is broad and leafy. (I wish I had access to those schematics!)

The analysis is driven by the engineering visibility into the circuits by measuring voltages and currents at certain points. If they have installed many points to measure it is very easy. if you have just a few it becomes harder. The rover was designed to do a 90 Sol job so the the number of engineering measuring points are at the edges of the electronics (motor resistance, currents), as opposed to the middle of the circuits (i.e. what is this group of components in the middle of the electronics board doing). This means the fault analysis is harder.

The environment that the rovers operate in is very hard on electronics and the multitude of mechanical connections from the electronics 'warm box' (a relatively nicer environment) to the motors (a severe environment) is large.

I bring this up to tamp down speculation on how hard to drive the rover or how to steer -etc over the next few days/weeks. The analysis will occur in little baby steps of try this, measure that, until a way to use the 'ground compromised' drive electronics can be discerned.

A looming milestone is May 2010 when solstice occurs. and you and I know that the JPL team will be scrambling with passion and creativity each and every day as they march up to that event.

...of course, the rover could be free in a few days and this message will be moot...

This is one of the most singularly exciting and suspenseful missions of all time, and we all have a front row seat ... every day!

Cheers

That is true, I now sit down in the evening with a cup of hot cocoa in anticipation of reading this board and other sites. Like the ultimate soap opera!

My girlfriend was watching Aliens the other day and one of the soldiers in the APC on descent to the surface has an intermittent helmet camera, so he bangs his head on the bulkhead. GF says "hey! Maybe those mars guys can smash the arm into the rover!" Fix them electrical problems that seem to be coming and going. The moment was just so ridiculously funny!

Anyways, my armchair analysis says this is a mechanical problem; like a screw holding a grounding cable, or a cracked solder joint, or to a lesser extent and possibility a connector. I would imagine most connectors are double spring loaded to keep tension on the metal contacts.

We could play what-if till the cows come up.

Not using a wheel known to be dead, when further usage could endanger it's motor controller bed-fellows was the right thing to do at the time.

The only appropriate time to reverse that decision would be an in extremis situation, where the risk of damage to other components is worth the chance of finding the wheel working once more, which is what we have now. It may even transpire that the wheel has given is all it can already and may never turn again.

Trying to second guess a decision making process with 3 years of hindsight is, to be honest, silly.

I checked the tracking web this morning and found the pattern of imaging sequences corresponding to another driving sol today i.e. sol 2118. Might it be?

It is of GREAT value to me helping understand the issue, thanks a lot.

And thanks also to Oersted for his uplifting "spirit"

Regarding today's drive: 1.5mm forward, 3mm down.

The fhaz shows that the RF did move again today (2118):
http://qt.exploratorium.edu/mars/spirit/fo...86P1235R0M1.JPG
http://qt.exploratorium.edu/mars/spirit/fo...92P1214R0M1.JPG
So whatever happened at the end of the 2117 drive wasn't fatal. Perhaps an intermittent problem.

I'm not sure the rover gods are with us. Gain of RF in exchange for loss or RR is a poor deal. The RF wheel was sitting on the surface and could be dragges (or pushed) reasonably well with the other 5 wheels. The RR wheel is almost totally burried and will be most difficult to pull out of the sand--I think that is why we are sinking more than translating forward. Lets hope the RR comes back to life and we have 6 wheels for at least long enought to get free.

Think positive...the RF digs in, grabs a nice rock, pulls Spirit out. Then we go mountain climbing again with all SIX wheels .

Or they try a different approach. Right now I think they're still checking the right wheels as much as trying to extract Spirit. If the electrical problem is understood, perhaps they'll be able to come up with a workaround that restores use of the RR. If not, pivoting forwards and to the right around the RR might be another approach to prevent it from holding us back.

Is the electrical problem possibly a buildup of static electricity on the rover chassis? After 5 years in the cold dry Martian climate, I can imagine a significant static charge may have built up. If so, is there any way to discharge it? In any event, anything we can learn about the electrical issue with Spirit may be useful if a similar issue later develops with Opportunity. That is one of the benefits of having two rovers.

I would think that the rover would be grounded to the surface, so I would guess "no".

Grounding to the surface (through a light-weight mobility system) on Mars is difficult. A radioactive source that can create an ion path helps. My recollection from Pathfinder was that the Sojourner APXS was going to be used first if there was ever going to be contact between Sojourner and Pathfinder. That is also a concern (ie, a solvable problem, but something that needs attention) for future sample return operations. I'm not sure how conductive the IDD is vs. the mobility system, but I imagine the APXS and Mossbauer (plus contact plate) use has kept the static build up under control.

Definitely an understatement. AFAIK, there is no guaranteed ground path between the rover chassis and Mars. The rover has a number of small "lightning rods" that help to discharge it (see http://www.nasa.gov/centers/glenn/moonandmars/mer.html ), but I could imagine that potential differences of a few volts could still be sustained. There may be a detailed description of the power bus grounding architecture of MER on the web someplace, but I don't have time to look for it right now. It doesn't sound to me like the current issue has much if anything to do with any potential difference between the rover and Mars anyway.

Make sure you've checked Scott's blog here: http://twitter.com/marsroverdriver latest 5 or so entries are very interesting indeed.

"# With RR failed(?) and RF working(???), Squyres has proposed that there's a law of conservation of working wheels on Spirit. ;-) #FreeSpirit 2:32 PM Dec 16th from web "

Here is the approximate predicament of Spirit on Sol 2013... [[ 2113 ]]
(adaptive contrast and a try at re-focusing the MI...)
Click to view attachment
cheers

(edit: thanks James!)

I presume you meant Sol 2113?

Another drive attempt on sol 2120. Again the RF moved, but it didn't appear to move much - just a fraction of a wheel circumference. Of course they're still testing the wheels here, so they may have intended only such a small motion of the RF. Here's an animation of the 2120 fhazcams:
Click to view attachment
I could see no movement around the RR wheel.

So is this January review of Spirit's progress still on or has the change in the status of the front and rear wheels changed that?

Interesting that the RF moved slowly but constantly over about half an hour. I'm wondering if that was intentional. My guess would be yes.

Unless Spirit has "restless wheel syndrome."

--Greg :-)

Let's give Steve a chance!
Which one among the 6 weels will you choose not to use in the actual situation?

http://www.space.com/missionlaunches/09122...wheel-spin.html

Not very optimistic

"I don't know if we're going to get it out frankly," Arvidson told SPACE.com.

Well, let's wait and see, Santa might make a detour to the red planet
Colleagues of mine were amazed to see between 50-thousand and 100-thousand views on UMSF rover-related topics !!!

If there's one thing I've learned about the MERs, it's that it's never a safe bet to count them out. The fat lady ain't even warming up to sing yet for Spirit.

I think Arvidson's latest comments simply echo the view they have had for some time, which is cautiously pessimistic.

Dr. Arvidson seems more positive in todays piece:

http://www.space.com/scienceastronomy/0912...ars-spirit.html

Interesting drive on sol 2122, lasting almost an hour. Looks like maybe the LF wheel came up a bit at the end. I really can't speculate whether this drive was good, bad or neutral - I'm just looking forward to the next news update.

Yeah I noticed that too.

Is the RF wheel not spinning anymore?

(animation)

It looked to me like the RF turned just a little bit, and I'd still speculate that they're commanding it to turn slowly to help with leverage without digging in. Maybe.

More importantly, looking at the sequence again, just at the end: there was some real forward movement coinciding with the LF wheel raising slightly. And it looks like Spirit's left side actually rose a tiny bit at the end, instead of sinking for once. I'd say I'm cautiously excited about that... but still waiting to hear something official.

The RF turned a bit between the first and second frames of 2122. I can't see any motion after that. Of course we don't know what they commanded the RF to do.

One cheer, for sure: definitely forward movement. I think though that the left side is still sinking, despite the LF wheel coming up for air. At best it recovered part of the sinking from earlier in the same drive.

Thanks for the animation Hungry.

For sure: overall the left side sank more than it rose. And what's going on with the rear wheels still seems pretty alarming. Not out of the woods yet; not even close.

I mostly agree. I also saw more soil coming from front of LF going underneath. (?)

It is hard to tell exactly what happened. A little bit of forward motion at the end and the LF certainly rose a tad. But it seems to me that the the vehicle tilted slightly to the left rear. If the LR sank deeper then perhaps, just perhaps it sank far enough to get some traction from a deeper layer which would explain the terminal forward lurch. One can only hope.