Where did you find that?

Brian

Ustrax emailed him. He replied.

Doug

Jeez, nice going Ustrax. Nice to hear it from Steve too.

Yea good to hear that!

I guess they'll start soon (directly) the "common" backward maneuver.

It's good to hear that they are not really concerned about this hiccup.
But I still think we should not expect any move tosol (835) but *maybe* on sol 836. Images from sol 835 should arrive tomorrow morning (GMT); images from sol 836 on Thursday.

PS: For the time being there is no planned imaging sequence recorded on the pancam tracking web database for sol 835.

Thanks Ustrax, nice to hear from Steve himself.

Nico

It is twice good! 1) to share us the Steve's words and 2) Oppy is not in the danger as I have pointed out in a yesterday's post.

Rodolfo

Thanks for passing that along, Ustrax!

There are a few words through official channels already here.

Plan for Sol 835:



Imaging of the tracks using all cameras (hazcam, navcam, colour pancam)

Thanks for mentioning the official update, fredk. It was interesting to learn that such locations are officially known as "wheel embedding hazards (WEH). They may have used this term previously and I forgot, but as I have a penchant for looking up word definitions and acronyms, I chuckled when I found this.

I also smiled when I read that they are now targeting "energy-rich "lily pads."" I guess they can always wink and say they meant to do this, but on the first attempt they didn't get the angle quite right due to an unexpected WEH.

It's nice to feel free to find humor in this event, now that the initial surprise now looks to be a delay of only a few sols.

To that Oy Vey, I can only add "ribbet"...

--Bill

You're welcome...But it's Mr. Squyres you should give thanks to for giving a bit of his precious time to answer.
On the update an attempt is referred, I would like to believe it to be before the weekend, tomorrow maybe, to get this baby rolling towards CC. Or else we'll have a week stuck in the same location...

What do you think about this new picture ?

http://marsrovers.jpl.nasa.gov/gallery/all...GBP1918L0M1.JPG

To me it looks like Opportunity didn't go very far before deciding to stop kicking up dust.
It should be able to get out of there simply by backing up.

I am curious. A few weeks back we looked at the surface of a dune, and it was covere with blueberries. I don't see any blueberries here. What is the difference between the two places to cause this change?

Initially Oppy was going toward the right hand of the picture. Then it backed, seems, due to the change of the direction. After moving back, Oppy went toward the down of the picture. It seems that Oppy was not able to climb a ripple of sand, hence, its wheels were slipping on the surface.

The surface has few Blue Berries and it looks very powdry. The hint is the carat are still well cohesive and it does not break or fall off.

According to the MER' JPL press:
As Opportunity eases its way into the Martian winter season, rover planners have started to target energy-rich "lily pads" (regions with a northerly tilt) at the end of each drive. This way, planners can maximize the amount of sun on Opportunity's solar arrays.

This means, in spite of the fact the Oppy will always try to climb to hang up close to a crest of a ripple at the end of each drive, that Oppy's wheels will be become embeded in sand. Hence, the calculated distance is a paramount importance so that Oppy won't overcome the crest and remain on top of it. It is the most difficult position to get rid off.

However, according to the MOC pictures, the crest of ripples run about NorthWest to SouthEast and there will be very few places with sand surface tilting close to North side. Maybe, the next good tilting place would be on the north side of next Crater Corner.

Rodolfo

Rodolfo

I don't think Opportunity backed up at any point Rodolfo, you're just seeing the tracks of the forward wheels.

So: she went onto the ripple, made a turn and started churning dust. She's done quite a lot of churning I'd say but because of the favourable slope I tend to agree with the optimistic view that she will soon be off this drift.

Incidentally new navcam pictures are up (or down?) now.

Yes or no.

• The pictures there are two tracks, aren't?
• The Oppy was going with its IDD on back, wasn't it?
• The oldest track is ones which runs from right to left since the other track, toward below, superimpose to the oldest, doesn't it?
• The recent track, the ones with stir sand is the ones which Oppy was trying to climb onto a ripple, wasn't it?
• Then Oppy has remained on slope of a ripple before reaching a crest, does it?

Hence, Oppy will be able to pull back without any much problems due to many factors. Close to the bottom of ripple (firm surface), favour gravity slope (dropping), and short track (short time) and very luckly Oppy is not sitting on the crest of ripple (the hardest place to get rid off).

Rodolfo

Not wasting any time

Plenty of lessons learnt at purgatory - they know the routine

Doug

How's this for some wild speculation: the bedrock below the sand in the trough Oppy's in is lower where we got stuck (eg, there's an old crater burried under there). So as Oppy drove over what seemed to be a thin layer of sand in the trough, the sand actually got substantially deeper, hence the stuck.

Really, I hope the problem was something flukey like this. If instead we're moving into territory with ultra-sticky trough sand, then that would seriously affect our mobility.

• Yes
• Yes - all my references to "front" and "back" wheels are relative to the (single) direction of travel, towards the bottom of frame. This picture is looking "behind" Oppy for the purposes of this day's travel.
• No. The older track is from the first set of wheels to go that way.
• Yes - but you can only see the stirred sand from the back wheels in those photos. The front wheels are doing the same elsewhere.
• Yes, I hope that Oppy is still on the "front face" of the drift, which should be make the recovery straightforward.

Opportunity's turns are sudden affairs in which each wheel can go in a different direction, not like a car where all wheels tend to track after each other even around corners.

I was more impressed by this one:

http://qt.exploratorium.edu/mars/opportuni...GBP1918L0M1.JPG

From that perspective, the texture and flatness of the surface makes it look not unlike a carpet--which some great clod of a rover has now gone and ruined.

======
Stephen

Incidently, speaking of that last entry of mine the shape of that curving movement of the rover's trail looks not unlike those visible here in this front hazcam shot from Sol 830:

http://marsrovers.nasa.gov/gallery/all/1/f...DLP1275L0M1.JPG


Clearly one set of wheels was slipping on the surface even then.

======
Stephen

Some colour shots of this mess.

Click to view attachment Click to view attachment

And in false colour.

Click to view attachment Click to view attachment

Good comparision observation.
There is much difference of sand consistency between Sol 830 and 833. The older ones has less amount of sand (close above of outcrop) and the ones of Sol 833, the sand surface i is deeper and softer. Hence, Oppy got more trouble on that ripple of sand.


Fantastic color. The squaredf shapes of sand originated by the clods looks alike to small stones. Need a good eye to differentiate them.

Rodolfo

I guess those are only clods of earth (mars?) in that left-hand image, but darn if they don't look like little pieces of broken-up rock.

======
Stephen

The two Navcam frames stitched.

EDIT: Replaced with a better projection.

Click to view attachment

Yes, same strange slippage was highlighted also here.
If the issue is related to sand consistency/depth, I'm worried by the uniform, rockless desert surrounding Victoria... Oppy should travel at least 400m in this dangerous new territory!

New images available; the backwards manouver has started but the rover is still on the sandtrap.

After: http://nasa.exploratorium.edu/mars/opportu...GBP1230R0M1.JPG
Before: http://nasa.exploratorium.edu/mars/opportu...GGP1214R0M1.JPG

One or two moves like this and we should be "on the road again".

Yay! Oppy moves!

http://qt.exploratorium.edu/mars/opportuni...GBP1217L0M1.JPG
http://qt.exploratorium.edu/mars/opportuni...GGP1151L0M1.JPG

An animated gif.

Click to view attachment

I think the problem is associated to sand consistency, but related to the dunes orientation and not to a "new territory". In this whole area, the ripples/dunes are mainly north/south oriented but sometimes we find smaller drifts on different headings. Have a look for instance to the east/west oriented drifts in this navcam image from sol 830. The rover got trapped when trying to cross the first of those, seen just below the right wing (from the camera point of view).

For reasons we do not completely understand now, some areas of sand are "fluffy and uncompacted", rather like newfallen snow, as opposed to more compacted and consolidated sands which make a good driving surface. My intuition tells me that this may be related to the age and deposition of the sand.

At any rate, as long as Oppy monitors her wheel slipppage and does not get mired too deeply this is a minor problem.

I'd intuit that the ejecta blanket around Victoria is more rocky or gravelly than loose sand and will noit present a driving hazard. If it were sandy, we'd see more ripples om the surface.

--Bill

Well, maybe...

Judging from the rear hazcam:

http://qt.exploratorium.edu/mars/opportuni...GGP1314R0M1.JPG

they've only backed out maybe an inch or two. Let's hope they do better on the next attempt.

======
Stephen

More important than absolute movement is the slippage ratio; until we have good info (hello insiders?) about the commanded wheel turns, we can only guess about being a good or bad manouver.

BUT, thinking of Purgatory I, remember that the initial moves were really really small and once the rover started to move inches it was out really fast.

(I must recover my notes of Purgatory I from DVD this evening...)

Edited: Found this "mosaic" I did a looooong time ago, a sort of "route map" at a tiny scale.

Yes, Oppy has already moved backward at least between 5 to 10 cms.


Yest it is certain. The reason is that the crest of ripples is not always in a straight line from north/south orientation and neither are parallel between them. it is like the following text graph:

CODE

|     |
|     |
|  X  |
   |
   |
   |
|     |
|     |

The problem that Oppy (X) has meet was that it stucked on the change of crest of ripples.

Rodolfo

A few details here from New Scientist on Oppy's sticky situation.

Opportunity looking at the wheeltracks.

Mosaic taken with the L0 navcam on Sol 835 and Sol 836.

jvandriel

Sol 837 is planned as driving sol; same/similar sequences pattern as for sol 836.



Will this be the day we'll sing "On the road again..."?

I hope someone has remembered to disable or even invert the slip check routines... we want to drive as long as we're slipping, and only drive one more rover length once we're not slipping!

turning but not moving... (why are they headed off the left??)

On this same article:

I was thinking that JPL could implement a sort of "auto-extraction" functionality for Opportunity. Once they figure they are stuck, just use the slip detection functionality in "reverse". I.e. keep moving backwards from the trouble until Oppy detects that it is NOT slipping anymore (or until power levels or other restrictions are reached).

This could even be done automatically if Oppy detects that it is slipping.

There could be some problems in this. If Oppy for some reason changes direction during the extraction, she could end up just digging herself into worse trouble. Other problem might be that Oppy runs into another deep dune after extracing herself from the initial trouble - and continues the extraction process, digging herself again.

But JPL being who they are, they are just taking it slowly (though considerably faster than during the Purgatory event).

<< Commands for the escape were due to be transmitted to the trapped rover at about 0130 GMT on Thursday [Sol 836]. Ray Arvidson, the mission's deputy principal investigator and a planetary scientist at Washington University at St Louis, US, is confident: "I think we'll pop out relatively quickly." >>

To be honest Akuo - it would take just as long to extract via sol by sol 'dumb' routines than it would to write the more intelligent routine

Doug

At least it would be ready for the next time Oppy gets stuck then :-P

That's the best we can expect of course If Oppy can reach Victoria mobility-wise another investigation after 'PI' might well be worth the time to avoid a third incident -by really being able to correctly identify these risk spots up front?

Nico

Oh great another investigation,how long this time ? a month like last time after getting extracted from the puratory dune ? Purgatory took 2 weeks just to access the situation,2 weeks give or take for extraction and a month of investigating.

We aren't going over huge,deep,wide dunes,quite the opposite. I think with a little common sense that 7 episodes of getting stuck and getting free again using knowledge already gained with some expediency would add up time wise to 2 time wasting purgatory ordeals.
I swear sometimes it almost seems like some people here are just are not happy unless the rover is just sitting still for long periods of time or investigating every grain of sand.

I think the turn was what caused the trouble. You can the spot where the middle wheel was when Oppy pivoted around it. It looks like Oppy didn't sink in until the right front (trailing) wheel hit that spot.

Many Geology Field camps are taught by professors who do exactly that.