The other day a local museum sponsored a MER lecture entitled "Mars Exploration Rovers: 1389 Days into a 90 Day Mission." The lecture was presented by Dr. David Mittlefehldt of NASA's Johnson Space Center. While much of the presentation covered things MER fans here are familiar with, I did learn some new things. Specifically with regard to Spirit, one of the maps he showed had two WH3 locations on it: WH3a and WH3b. I had to quickly sketch them, so my reproduction may not be precise. The attached map shows their approximate locations on a recent JPL location map.
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By the way, did anyone notice the terrific navcam stereo images of Tartarus that came down today? The stereo view really provides an excellent impression of it's depth. Attached below is the anaglyph directly from MMB.
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The anaglyph makes it appear as if Spirit came very close to a nasty drop off.
A few more wheel widths and....

Astro0

Stuck in a rut and having a depression... poor girl!

Today, sol 1392, was yet another driving sol; the seventh in a row! I don't remember last time Spirit -- well, actually the rover drivers -- did such a thing. Does anybody has the numbers on hand?

Today's move was about 6.5m ENE, according to the tracking web info, and here's the latest navcam mosaic. I don't know if they still plan to stop or pass by the sites 7 and 8 pointed on the official route map (here), but just in case I've circled them on the mosaic.
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Short of having a 'Sarlac' at the bottom, Tartarus was a close call for our little Spirit.
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Astro0

I was updating my Spirit's route map to include the so called "WH3 - Winter Haven #3" on the map, and seaching for it on older images I found that Alan already posted some ones here on this same thread. I looked for the navcams taken during sols 766 and 767, which are the closest ones to the planned WH3, and stitched this mosaic below.
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Now, each time I look to this picture I ask myself: "where will Spirit be parked?"
Correct me if I´m wrong but I see this place as another sand trap.

The drifts I see are on a fairly steep slope. Traversing them going down the slope, I assume they will avoid the rocks by driving towards the 767 position, shouldn't be too much of a problem. The problems the rovers have had so far with sand traps have occurred when going upslope.

The problem I see is that those drifts look to be of "fluffy" sand deposited by wind, meaning that it would be very easy to loose traction on the back wheels due to dragging the broken one, even on a downslope. Off course, it's just an opinion.

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On another topic, today (sol 1393) was planned as driving sol however the downlinked pictures show no movement at all (site/drive counters are still the same as yestersol).

SFX of Spirit at WH3:



with link to sol 766 RAD panorama.

This is my best guess. Spirit will back down the slope? Maybe stop a little higher up the slope to get more tilt?

I'm sure the SFX gurus ( guruae?) can create a better image, but I thought I would try -- since, as Tesheiner pointed out, there was no movement tosol.

If might be better to go sideways with the lame wheel on the high side, that would take a lot of weight off it and put more weight on the three good down slope wheels. That would give the option of moving in both directions to maneuver into a favorable position. If they got straight down the slope there will be no going back once they are committed.

Forgive me if this was discussed elsewhere:

Have they considered running a wheel up on one of the rocks to tilt the panels even more? Maybe that would knock some more dust off too.

Quote: "I'm sure the SFX gurus ( guruae?) can create a better image..."

Only if we can get the new version of the Rover model you are using.
Is this another of Doug's creations or something new.
I recall that the last one was posted somewhere on UMSF.
Could we pleeeease have the latest version? Pleeeeease.

Astro0

I assume they'll be backing down the slope. Once they're on it - there's no way they'll be able to drive back up again. If I pick up, rattle, drop and shake my TV around - the dust on the screen wont move

Doug

And, although the rovers have been jostled on occasion, there has not been a
cleaning event associated with any of the accidental bumps, so there is little
chance of a purposeful bump causing a cleaning event.

Driving activity during sol 1394 succeeded, with Spirit moving right to "Site 7".
Here's the latest navcam mosaic.
Click to view attachment

Site 7 are those rocks spread near the rover's right wing on the leftmost frame and site 8 is that "big" rock on the background behind site 7.

Abalone raises a good point - when you're parked on a slope, the point on the ground below the centre of mass is downslope of the centre wheels, so the farthest upslope wheels take the least weight. So you really should have the lame wheel at the top (plus that's the way they normally drive, lame wheel trailing, for stability).

In fact, if the slope is steep enough the topmost wheels would have so little weight on them that they wouldn't contribute much to driving, so I wonder if they might actually be able to drive back up the slope in the spring. I'm sure an engineer could plug in some numbers and see if this holds up.

I created the rover image using this Interactive 3D Rover model by eyeballing the orientation I wanted, did a print screen, pasted the image to Paint, saved and then loaded it into imagej, converted to B&W, did a polygonal select, copied, positioned and pasted the selected image to the base image.

It would be nice if the interface had a numerical input option to select lens, distance and orientation. Then a "real" 3D SFX image could be created.

And, yes, the best way to maneuver Spirit is sideways, but what would be the best orientation for maximum sunlight? My guess shows the mast shadow fall mostly on the front of the vehicle.

I would back down, as then the PCMA shadow would be mainly over the front of the vehicle, not the arrays.

Doug

Actually with a dud wheel there is no way Spirit is going back up a 30 degree slope. Whatever happens it will have to leave downslope. So you had better not park above a sand trap.

Click to view attachment

Astro0

Astro,
Once, I watched the rover drivers on a TV chanel and I saw that they use "lines references" on their computer's screen. What is strange here is that the "line references" is on the Earth image !
Nice idea anyway

If the rover is sideways on a 30 deg slope then they can choose the angle of attack to get up the incline, it could be as little as a few deg. Thats how they got out of Endurance crater right at the beginning of the mission. If they go straight over then if they dont get it right the first time there will not be much chance for adjustment

A look back at "Tartarus":

Wow, that really demonstrates the old adage that hindsight is always 20/20. Tartarus from this perspective looks like a place to not be.

Brian

I am still trying to understand the interest in sites 7 and 8. Is Spirit's miniTES still working?

I am not convinced they will approach WH3 from the top.

I thought I read that sites 7 and 8 were to be used for imaging the surroundings, since they are a bit higher than most of HP.

Why do you think they may not approach from the top? There's only 2 weeks left, and after the scare of Tartarus, I'd think they'd want to play it safe.

[quote name='mhoward' date='Dec 6 2007, 02:01 AM' post='105130']
A look back at "Tartarus":

The incident makes sense to me now. The drive was meant to bypass Tartarus (though a bit closer for comfort regardless) and you can see the point where a rock snagged the dead wheel and caused a course change to the left. No anomalous input from other wheels that would have resulted in an abort.

Convinced or not, there's no way in hell they're getting 25 degrees from the bottom in the next two weeks - so from the top is the route.

Doug

Ahh. I think I see what you mean. The snag happened just above Tartarus - you can see where the rover veered to the left in this sol 1384 navcam frame. As you say, they were a little close for comfort.

They've been pretty close to the edge of HP at times - could a course diversion like this have sent them over the edge? Are checks on rover orientation being made during drives?

Over the edge would get picked up by tilt limits. The dive into Tartarus must have been under the limits

Doug

It looks like your memory was pretty good, Rocker!
http://marsrovers.jpl.nasa.gov/mission/tm-...it-sol1391.html
That new map also names the two big rocks at site 8 "pair of plums"

Interesting to note that by even staying under the limits, the rover can be traped anyway.
Now, imagine that the whole rover drive above a "big" rock until the RFW get to this rock. If it's a loose rock and if it follows exactely the direction of the drive, nobody would realise for a while that the rock is where it is. This should not happen since we know where we go but, in a Tartarus like situation, who knows? So, my question is : we know we can drag the dead RFW, we know we can pivot around it but can we push it to get free from the above situation?
A bit Tartarus torturus idea I must admit

I wouldn't like to second guess the drivers from the comfort of an armchair, but I think that the Tartarus incident gives us some clear operating constraints. If they go in from the top then as the vehicle attacks the slope we will end up with four wheels on the slope and the trailing pair, including the broken wheel, in midair. If the rover stopped in this position and did not go slip sliding away then when comes the time to leave there would seem no impediment to climbing out forward as the dead wheel will not impede progress while the vehicle is climbing, and maximum weight and thus friction would be on the lower wheels. Driving out downward trailing the broken wheel would also present few problems.

Going in from the bottom means tackling what appears to be a 'fluffy' depositional surface in the WH3 lower approaches although if this presents no problems then climbing the slope should present no problems until the dead wheel reached the slope. But climbing out would be out of the question since we would, as at Tartarus, end up with two driving wheels in midair and the vehicle stuck. Pushing a dead wheel down into the surface trying to drive out downwards would be an interesting experience. On balance I plumb for backing down the slope at WH3 and leaving the trailing wheels suspended. since we would have to go down the slope somewhere in order to go up at WH3, doing this evolution once only at WH3 makes good applied common sense.

Thanks, fredk. I hadn't read about plans to image from those higher vantage points. That makes sense to me.

I didn't expect my statement doubting a top-down approach to be so controversial. I can imagine various advantages and difficulties with both the top-down and bottom-up approaches. I favor the bottom up approach because:

• I am not certain that the site having the best science targets will be approachable from the top,
• There are two WH3 sites currently under consideration, and I suspect additional, local reconnaissance may be in order,
• While Spirit is probably not capable of climbing over Husband Hill again, I am pretty confident that the rover handlers can handily drive Spirit up a 25 degree incline in many places around the periphery of HP.
• Although 2 weeks is the recently stated goal, Spirit has a bit more time than that to slide into her next winter haven.

They've said that they can manage 8 degrees with the FRW stuck. If they drive off, and can't get up from the bottom (which is almost certainly true) - then they've got to drive all the way around to the east side to get back on top. Driving off the top to try and drive up a 25 degree slope from the bottom would be virtual suicide.

Doug

Given the veer off to the East in the last couple of drives, assuming this isn't just circumventing an area that they thought might be troublesome between 1394 and WH3, my best guess is that they are planning to circle back and approach WH3 at an angle instead of straight over the edge. Similar to what Oppy did to exit Eagle when the straight out approach didn't work. This would also make for a much easier egress, but of course not knowing the topography, this is all speculation.

Brian

I'm puzzled by this move to the east too. I don't think it's about angle of attack to the slope at WH3, since the surface of HP is pretty flat up to the edge, so they could've driven directly to the edge of HP from 1394 and then turned to take the slope at an angle if they wanted. Anyway, I'd think they'd want to do some imaging of the edge to find the best WH3 site before going over the edge, so I was expecting a drive along the north edge first, much closer to the edge than they are now.

Perhaps they didn't like the look of the surface between the 1394 site and the edge, as you said. Maybe it's Fuzzy Smith, as someone said in the route map thread. But there's really not much time to do science now, and if they were keen on Fuzzy why didn't they study it when they first reentered HP three months ago? I think we'll have a better idea with the next drive.

We're driving no more than 15 meters from the edge of NP so, we're at 1-2 sols of the closest North facing slope. That's a pretty safe situation to continue "wandering around" for another week and take time to select the best spot or get to the closest if needed.

I agree, climber. I think if we watch for one or two more sols, we should better understand the plan.

I'm may be pushing the limits here, but here's a plan for this winter.
Last winter we basicaly did a MEGA pancam picture so, let's shoot for a MEGA microscopic picture this winter. The North facing slope of HP will be ideal for this since it is realy a North facing (and quite regular) slope for several meters. We're heading now to the East of the area so we could start there and go to the West during the 8 months of wintering and cover a large and wide surface (1 x 20 m).
Ok, I know the objection : we'll be in a survival mode instead of a science mode. Nevertheless, I'll be currious to know if this plan is totaly unreasonable of if we could have a chance to run it regarding the available energy. Basicaly we need to operate the arm, take pictures and transmit them. Then, once in a while, to rove to next position. Any figures (other than NO, Nope, No way...) ?

Well - you're asking to traverse across a 25 deg slope - with 5 wheel drive. I don't think that's particularly wise. The chance for slippage OFF the slope would be significant. Even dropping from 25 to 15 degrees might be that slight extra challenge on the shortest days that Spirit might not survive.

I've got not problems at all with a significant and extensive MI survey within the IDD work volume (it'd be fantatsic) - if they can park up in an appropriate place at the start of winter where the slope is at its very best - and that site includes the sort of interesting rock that we saw on the north rim of home plate back in the mid 700's.

We've got a very thin piece of winter haven here - and to tread along it any more than is needed would be an unnecessary risk.


Doug

Actually I think it would be feasible to do an intensive arm study of a work-volume-width strip down the slope. As you drive over the edge, your tilt will increase from zero to the max (30 degrees?) and then back towards zero as you reach the bottom. We won't need the maximum tilt immediately (we're surviving now with zero tilt, after all), so you could start by driving just a bit over the edge, studying the heck out of the work volume, then as power drops you drive 30 cm (or whatever) further down to get a better tilt, study the new work volume, etc. You'd have the strongest tilt when the solar illumination is lowest, and probably do no moving or science for a long period. Then as spring approaches you move down again and examine the lowest parts of the slope.

I can't see that occasional 30cm drives downslope would require much power. Then again, they may prefer to play it safe and drive to the maximum tilt immediately.

It's taking too much of a chance to assume you will be able
to maneuver to get the slope you want when you want it.
Surely IMO what they will do, is to get into the best position
ASAP after going over the edge, and stay put!

SAFE!!

(Overheard in machine language over DSN: Spirit: Hey Ma! Look at ME! Hee Hee!
Mrs Jay Peeyell: Get away from that edge, you silly fool! You'll break your IDD!

The view in the drive direction on Sol 1395.

Taken with the R0 Navcam.

jvandriel

Click to view attachment

Yep, here we are:



The drifts below look non-threatening to me, at least from this perspective.

The trick is to not go down as far as the drifts, but I assume we are somewhat east of our haven. Tesh?
Can anyone see our tracks from last year?

"Well, duh." I was looking ahead to when Spirit gets to finally drive away, many months from now.

Interesting spot...

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Ok, I guess I am a believer in the top-down theory, now.

Shaka: I think Spirit is just a bit east of WH3. That black basalt boulder in the images just to the right of Spirit (see mhoward's pano above) is likely to be the black spot on Tesh's route map, right between WH3 and Effa Manley. I've spent a good deal of time trying to identify tracks. There should be plenty of tracks right off from here, but I can't say I saw anything that was very convincing.