Oppy went right back up the same route today, just slightly off-center from the tracks that had started to dig in.

http://qt.exploratorium.edu/mars/opportuni...FYP1254L0M1.JPG

One would like to know how much of this is part of a plan versus flip-flopping decisions each day. Are they packing down the dirt to facilitate crossing the dune? Did they simply decide that the rover was in no real danger and loosen up her drive parameters and send her back the same way?

Perhaps they were simply testing the traction the first time, decided it was okay, and proceeded accross?

I am sure that the rover can come back on the same trail to cross the ripple knowing that she must be keeping driving fast and without stopping until she has past the highest point. Then, when she has past that point, everything would be easy with the down slope.

Rodolfo

Get your blue/red glasses ready

Is this really another attempt at the dune or a backing out photo?

That aphrodisiac color of airman's eyeglasses, I can see the trails more crispy. Since that picture is of one time, I cannot know what way she is driving: in or out of ripple. However, those trail are already paved and so she can go up to the end of the trail. When the back wheel is on the end of trail, the rest front wheels would already be on the down slope. So she will be slipping down to the next outcrop.

Rodolfo

Here's a closeup from the pancam

What is the problem? Can you express what is your worry?

In spite of the fact that there is a little level difference of sand between the paved trail and original. Perhaps, it would be around 3 cms. The friction force to 2 front wheels can be overcame to go down slope by the push of the traction of 6x6 wheels. The other important factor is that slope is very smooth on both sides of the ripple.

Rodolfo

I have no probs or worries and agree with you that they could have just kept going

Maybe they could have commanded Oppy to go forward and drive upon the dune.

But remind that the rovers are not driven in real-time. There is no actual driver but just algorithms with some sort of "safety nets" just in case there are driving parameters (e.g. slippage) out of the expected values.

Once the driving is aborted they have to take a decision about going backwards or forward, and there is nobody in Mars to "touch the dune" and decide if it's soft or not. Based on previous experience (read Purgatory Dune) the best manouver in this situation is drive backwards, and that's what they have done.

I think that was the correct decision in the current situation.

Perhaps in anticipation of some inevtiable dune crossings they are experimenting. It could be that this one was reminiscent of Purgatory. They are checking it out, a toe in the water, so to speak.

I wouldn't be surprised if we didn't see a few more approach-and-retreat attempts in the coming weeks with various size and shapes of dunes at various approach angles.

If I were in charge I would do that. Actually I would have done it a while ago. My view is that Purgatory was an anomaly. If further study can establish the parameters that caused the rover to bog down, then perhaps we can once again put her in top gear and get going at a speedier clip on the way to Victoria [EDIT].

I don't think anyone wants to go back to Purgatory

There were a lot of sub-frame Hazcam images taken during the driveout, just eyeballing them as JPL site thumbnails I don't see obvious "churning" as the wheels turn. This ripple material impresses me as fluffy and compressible, but not slippery. This is my first close look, I may be wrong.

We need to do a GIF animation of this sequence.

--Bill

Sorry I mant to say VICTORIA

I think this demonstrates that the slip-detection feature they implemented after the episode at Purgatory works pretty well. In this case Oppy detected a slip larger than what was allowed and stopped the drive (somewhere around 40-ish percentage range)... After that it was decided to drive back out to the outcrop.

A "Freudian slip" ? (german: "Freud'scher Versprecher";)



Hopefully not a bad omen


In earnest: I'm actually quite confident in the current (post-purgatory )
more sophisticated driving technique ...
I'm all the more optimistic, because once we will have circumvented Erebus, the
direction will be mainly south, i.e. not that much ripple crossings necessary then ...

It is very good with the newely implemented software alogaritm to compute the percentage of slippage as a new feature of slip-detection.

However, I think that the rover must not pull out and try to another way. Hence, the reason is that after the first intent, the trail is already paved (not always but it happens often and after a visual inspection will decide if or not for the second intent) and so the rover can go up on the same trail with fewer slip or nothing. Thus, the software alogarithm of slip-detection must be reset before the second intent. Hope this new technique is very common for the off road. The first ones in front has greater effort to open a new sand trail and the followers on the same trail goes much easier.

Rodolfo

Here's a question: how fast can the rovers go? I don't mean per Sol, but per hour (as in MPH, KPH, etc). A s-l-o-w grind into a dune would be quite different from a fast burst into a, you know, wossisname, ripple...

Bob Shaw

Good point RNeuhaus, however, just to clarify -- the backing-out manuever was commanded by the engineers, not by the rover itself. Once it detects the excessive slippage it just stops the drive and sits there waiting commands from the masters.

Bob, the rovers go very slow, with a top speed of a whopping 5 centimeters (2 inches) per second (link).

Yes you are entirely correct Pando, its a crawling pace with a negligible forward momentum. So if the rover loose traction it will start to dig in.

S-L-O-W is all they can do. Top speed is like a quarter mile per hour.

To say slow is an understatement. 2inches/sec is 10 feet/minute (5cm/sec=3m/minute). I've tried driving a riding lawnmower at that velocity and it's glacial. I guess we all have this mental image of tour intrepid explorers bounding across the Martian landscape when in reality we know that they are creeping.

The average speed make the total odometry an impressive feat.

--Bill

Bill,

here is your GIF animation of the left front wheel of Opportunity.

Sol 605 L0 front Hazcam.

jvandriel

and here is the anomation of the Right front wheel.

Sol 605.

jvandriel

Here is a single animation ( not a loop ) from the Right front wheel.

The animation starts at the top of the Dune and ends at the bottom of that Dune on the

bedrock.

jvandriel

Pando:

Thank you for pointing out the WEB page about the Rover technical information capabilities. The rover's speed is 180 meters / hour. The offroad capabilities become even tougher. For a slow ones, It is better to pull out and try to attack in another angle with lower height and softer slope. The solution to that problem is to increase contact area surface of wheels to compensate of its very slow speed.

Rodolfo

What I've taken from the discussion regarding MER speed (or, more properly 'slow'!) is that our learned responses on Earth are not especially useful on Mars - and that the MERs may not even tell us all that much about locomotion for future rovers... ...speaking of which, anyone know what sort of driving speeds are expected from future vehicles?

Bob Shaw

I think the speed is mostly determined by the rovers ability to see and analyse their surroundings, and their overall progress rate is clearly primarily dependant on the fact that they still need to be "driven", that introduces days of latency as the drivers and planners need to analyse each new location and decide what to do next. The imaging and processing constraints will probably improve by a factor of 100 for MSL but even so I don't think it will actually be able to progress much faster than Oppy did when it was ripping south at 100m/Sol.

The DARPA Grand Challenge seems to have achieved it's aim of vastly improving the quality of autonomous vehicle capability. So far at least four vehicles have crossed the line completing the 132 mile traverse in under 10 hours.

That's about 13mph. 100x MER speed is about 18kph so it would seem that at least on earth 100x MER speed for a "rover" is now realistic.

Today is drive day.

Sol Seq.Ver ETH ESF EDN EFF ERP Tot Description
--- -------- --- --- --- --- --- ---- -----------
608 p0755.03 0 0 0 0 0 0 navcam_5x1_az_270_3_bpp
608 p1201.03 0 0 0 0 0 0 front_haz_penultimate_1_bpp_crit16
608 p1214.05 0 0 0 0 0 0 front_haz_ultimate_4bpp_pri15
608 p1235.04 0 0 0 0 0 0 front_hazcam_stumble_0.5_bpp_pri_56
608 p1235.04 0 0 0 0 0 0 front_hazcam_stumble_0.5_bpp_pri_56
608 p1235.04 0 0 0 0 0 0 front_hazcam_stumble_0.5_bpp_pri_56
608 p1235.04 0 0 0 0 0 0 front_hazcam_stumble_0.5_bpp_pri_56
608 p1235.04 0 0 0 0 0 0 front_hazcam_stumble_0.5_bpp_pri_56
608 p1311.06 0 0 0 0 0 0 rear_haz_ultimate_1_bpp_crit18
608 p1335.03 0 0 0 0 0 0 rear_hazcam_stumble_0.5_bpp_pri_56
608 p1335.03 0 0 0 0 0 0 rear_hazcam_stumble_0.5_bpp_pri_56
608 p1335.03 0 0 0 0 0 0 rear_hazcam_stumble_0.5_bpp_pri_56
608 p1335.03 0 0 0 0 0 0 rear_hazcam_stumble_0.5_bpp_pri_56
608 p1335.03 0 0 0 0 0 0 rear_hazcam_stumble_0.5_bpp_pri_56
608 p1655.01 0 0 0 0 0 0 navcam_5x1_az_90_1_bpp
608 p2393.06 0 0 0 0 0 0 pancam_drv_dir_7x1_L2R2
608 p2600.07 0 0 0 0 0 0 pancam_tau
608 p2600.07 0 0 0 0 0 0 pancam_tau
608 p2627.01 0 0 0 0 0 0 pancam_sky_radiance_thumbs_L457R247
608 Total 0 0 0 0 0 0

I still reckon there was no slip. I think that this is the front right wheel track at the point of backing out, which shows that the wheel was not slipping.

But - it COULD have slipped like mad going forward, but had good traction driving back again - we would never know :0

Doug

Not slipping tracks

Slipping tracks

The second image was taken while on the dune. Clearly it was slipping!

I disagree. The "slip" image is not conclusive evidence of slippage, only of some material pick-up in the tread. The image I referred to shows a series of tread marks, the most advanced of which connects to the surface in a way that would be unlikely in the extreme in the case of slippage.

The anti-slip protection could well include some check on the suspension configuration to protect against slip-inducing cases of wheel loading, but even if it triggered in a precautionary fashion this does not demonstrate silppage.

I also think it's slippage. Check images of tracks made on level ground. They are usually very neatly compacted. These tracks aren't. But it doesn't look like it was very bad. At least the safety kicked in.

I agree, if only that the drive would not have terminated unlees the threshold of slippage programmed for, had not been exceeded

Me too.
My first impression when looking to that slipping tracks was they were quite similar to those seen while stucked at Purgatory Dune.

I presume they made it over the dune?

http://qt.exploratorium.edu/mars/opportuni...JLP1311R0M1.JPG

I think you can see the original track on the crest of the dune in the background.

Something that might add to the "slip" argument is that if you'll notice in the animated sequence of Oppy backing out of the dune, there was a significant amount of dust accumulated in the right front wheel's treads. That condition has accompanied "slips" in the past. The dust falls out when the rover is on more solid ground, but its presence in the treads has been very strongly correlated with "tough going" scenarios in the past (think Wopmay and Purgatory).

Sunspot,

I would say so, but the hazcam pic's resolution is quite poor to be sure about the dark spot on the dune.

We should wait until the whole navcam pano is downloaded -- there are still 180º missing, the part looking back -- to be 100% sure. But frankly speaking, I've already updated my personal "route map" assuming a drive across the dune.

I think they did, looking at this Hazcam image and also the Navcam/Pancam forward images. The rearward shots from the Navcam/Pancam haven't made it to Exploratorium yet.

There may have been forward slippage at that ripple, but I didn't see any slippage backing out. Thanks for thre animates GIFs, jvandriel.

I hate to sound negative, but we may be having occasional incidents like this; the Ochre Brick Road has gobblins...

--Bill

http://qt.exploratorium.edu/mars/opportuni...JLP2393R2M1.JPG

At least Mars is close to Earth, transmission rates are bumped up for more/faster data downloads, and they are not in the drive-every-other-day situation at the moment. Allows for quick analysis and recovery from hiccups. The rover stopped (almost certainly due to a detected slip condition), they ordered it to back up, looked at the situation, then went right back at the drift - all in 4 Sols, it appears.

Nice dunes, isn't it?

And I would like to recall an early post I made when Oppy was nearing the first outcrops on the way to Erebus...

But a UHF pass is a UHF pass. Proximity to earth doesnt really make a difference for Rover Comms. It means Odyssey can downlink a UHF pass quicker to Earth, but for the rovers, that doesnt matter.

Doug

Judging from the latest pics, Oppy got past that drift just fine and has a fairly clear path circumventing the deep dunefield. We'll see if the situations changes as she turns to the south rounding the west side of the crater in (hopefully) another week.

It appears the rover could scoot right up to the edge of the crater from this vantage point, looking downt he aisle between some dunes.

http://qt.exploratorium.edu/mars/opportuni...JLP0755L0M1.JPG

Today (sol 610) is planned as driving day.
Available info suggests a move WSW followed by NW driving on next sols.

And here is a final Navcam looking back at the drive around the "problem" ripple...

--Bill

Yup - Purgatory 2 is right on the left there, then a rather brave drive between bits of dune to head out onto more outcrop...

The rover drivers are getting very clever

Looking at the increasingly valuable pancam tracking those navcam frames are from...
608 p1655.01 10 0 0 10 0 20 navcam_5x1_az_90_1_bpp

609 was restricted, and 610 was further driving. These reports of 30 - 40+ metre drives are very promising, even with restricted sols, that's a weekly drive distance of 150m or so, not too shoddy.

Doug

Some great looking dunes, are we getting too used to the awesomeness of it all??

Some great looking dunes, are we getting too used to the awesomeness of it all??