I decided to add a new topic since we are all following it closely and something is bound to happen soon. Jim Erickson said that earliest Oppy would be making her move would be on Friday, but Steve's update might be read that it isn't happening so soon. I doubt they will be doing anything during the weekend, so Monday maybe?

Anyway the Planetary Photojournal (http://photojournal.jpl.nasa.gov/gallery/snt) has some images from sandbox testing at JPL.

A nice slope in the background from testing Spirit's cilmbing-up-the-hills ability

Note the 7 degree toe-in on the FR wheel

Doug

Even the sand is stuck on the wheels covering their outside almost completely !
This is the mother of all realistic martian simulations

They indeed found a very good match for the soil. Hope they manage to avoid it in times coming.

At this rate, when we finally have a human Mars landing in the year 2105, MGS will provide CPROTO coverage!

Great images, but it's more a sand trap like the sand-holes at Gusev than a dune
Probably it was impossible to simulate such a dune.

And Spirit has just reached the top of Husband Hill

Regarding the sandbox pictures. I think it looks like the rover is in a hole, not much room to drive out of the dune. How come?

Thanks for supplying the link to those images. I'm really curious as to what they're using as a proxy for the Martian dust. At first I thought it might be talcum powder, then I wondered if it might be lime. (What IS that white powder?).

In one of the photos you can partially see a box that probably containes some of the stuff they are laying down the word "Pure..." can be made out. Anyone able to do some more detective work?

http://photojournal.jpl.nasa.gov/jpeg/PIA07894.jpg

Almost looks like powder for making custard.

How do they compensate for the 1/3 gravity on Mars? The test rover does not look like it's much lighter than the real ones.

Strap some helium balloons to the thing

I'm reminded of two things, both sold in those types of bags: lime and drywall powder........

Lime is sold as quicklime, which is calcium oxide (CaO) and as hydrated lime, which is calcium hydroxide Ca(OH)2.

Drywall is gypsum, which is a calcium sulfate CaSO4*2(H2O)

A blow up of the TIFF version of the photo gets oh-so-close to displaying the mfgr. name on the box. Anyone recognize that logo?

Anyone from the States recognize the logo on the box ?

'

Doug

The logo on the box is for Pooltime D.E. filter powder, otherwise known as diatomaceous earth.

http://www.pooltime.com/ABspecialty.shtm

Ahaa, pool time, therefore the hole

The logo is clear the same and even by the logo is written "D.E. Filter Powder", isn't it?

Thanks Stevo!

Diatomaceous Earth:

Info from wikipedia.

Basically crushed chalk. Had to laugh when i read that considering what chalk is. Oh the irony.

From a different supplier comes the following bit of info:

Crushed to a fine powder and observed through a microscope, the particles resemble bits of broken glass.

Sounds like a suitable substitute for lunar soil too.

Very good, stevo!

I, too, love the fact that JPL has settled on this biologically-created material in order to replicate this particular section of the plains of Meridiani. That should give the conspiracy theorists a charge, and adds a whole new perspective on the "Fighting the Surf" topic.

From the MER website today:

=======
In JPL's In-situ Instrument Laboratory sandbox, engineers, scientists and even the project manager have been mixing sandy and powdery materials, digging holes and building dunes. A mixture was concocted to simulate properties of the soil underneath Opportunity, using sand, clay and diatomaceous earth (silica-rich powder composed mainly of microscopic plant shells, used in these tests for its texture, not its fossil origin). The team wants to have a full understanding of how Opportunity will respond before commanding it to back out of its current position.
=======

Heh, they're well aware of where the discussion of what they are using to simulate the dunes could lead...

JPL now has a news release about the testing. Jim Erickson says "We choose to proceed cautiously, so we don't expect to begin actually driving out of the dune before next week, possibly later". There is some waiting for us still.

One sort of worrying item in the release is how they say:
Opportunity had driven about 40 meters (131 feet) of a planned 90-meter (295-foot) drive on the rover's 446th martian day when its wheels began slipping. [...] The wheels kept rotating enough times to have covered the rest of the distance if they hadn't been slipping, but the rover eventually barely inched forward.

I wonder if they really mean that Oppy slipped for what was supposed to be 50 metre driving distance?

That press release answers some questions. We now know that the rover -did- attempt the end-of-drive turn. It never had a clue it was not moving forward after 40 meters as it should have been.

That's exactly what it sounds like. No wonder she dug in so deep.

If we get out of here, it sounds like we're going to be going a lot slower and with a lot less "blind drive" action...

-the other Doug

But this sounds a little more encouraging:

Dr. Robert Sullivan of Cornell University, Ithaca, N.Y., a rover science team member, worked with engineers in the JPL testbed to match the properties of the test sand as closely as possible with those of the sand beneath Opportunity, based on images of wheels and wheel tracks on Mars. "We found that when the wheels dig in, the material we're using does stick to the wheels and fills the gaps between the cleats, but it doesn't stick when you're just driving over it. That's good because it's the same as what we see in the images from Opportunity," Sullivan said.

Experiments indicate that in this more powdery material, the test rover positioned comparably to Opportunity can drive out after some initial wheel-spinning. More testing, analysis, planning and review will precede any actual commands for Opportunity to begin driving away from the dune.

Thanks stevo

So ....
In order to simulate the soil properties at Meridiani, JPL is using the fossilized remains of hard-shelled algae, that are usually found in proximity to either current or former bodies of water, and are generally divided into two categories based upon source: freshwater and saltwater.

RCH must be giving a party right about now

ok now i think my question has been answered. It was trying to make a turn. now the second question?

scott

Looks like we are online again

A new update from Steve
http://athena.cornell.edu/news/mubss/

Good to see he is working in the weekends also.

He warns that even if we see motion it will only be small cautious movements, but he stills seems optimistic about getting out

Yes how DO they do that?! I dont see any counterweight lines connected to the test rover....and like you said it doesnt look 2/3 lighter. hmmmm

No batteries, no minites, no insulation, no solar arrays, no heaters, and infact, it might well have an empty WEB - with all the electronics situated at the other end of those cables

There in engineering model with none of the instrumentation - it's just for mobility - and that compensates very nicely for the gravity difference I'm sure.

Doug

If the wheels did really end the whole planned drive, then they rotated circa 60 times at this dune. 60 times sounds to me rather much and so the actually depth of the wheels is astoundingly little. That makes hope they get he out without major problems.

I agree. I didn't remember them ever doing such a long blind drive, so I looked back over the mission updates. On sol 385 they started doing longer blind drives. They drove 105m on that day. I guess they figured that there wasn't much to run into, even if they couldn't see that far. My question is if they can detect that kind of slippage with inertial guidance, why wouldn't they set it to abort under those conditions? They definitely have a tilt abort. Spirit stopped on that quite a few times. I'm pretty sure they can't detect it. Does anybody have anything difinitive on inertial guidance?

The advantages of the blind drive are speed, lower power consumption, and reduced computer resources. The disadvantage is... pretty obvious. It seems to me that they should rely more heavily on the nav software. They could also start deleting the images from the nav sw as they become obsolete. As it stands now, they only have about three days of auto nav before they fill the flash memory. That's too fast.