There's a very real possibilty of not being able to drive down into Victoria Crater - just as there was with Endurance, which I think we were lucky with. If that is the case, what kind of science plan will the team come up with? Perhaps drive around the rim and producing lots of large panoramic mosaics? There doesnt seem anywhere else to go a beyond the crater.

>There doesnt seem anywhere else to go a beyond the crater.

Head Southeast, topographically lower and down-section.

--Bill

I'd be astonished if there wasn't a single way 'in' around the entire rim - on the understand that the interior of Victoria Crater would be a suitable place for the 'end of mission'.

However - if we can't / don't go in, then obviously one would do a lap of the place, work Mini-TES to the bone, I'd say three Pan positions ( 10 O'Clock, 6 O'Clock and 3 O'Clock ) - and then perhaps NE to some interesint white features and larger ammount of exposed rock in and around the area in the NE part of the Victoria Apron.

Other than that, anywhere else involved going through a lot of Purgatory like terrain...or even worse. The only interesting target would be the larger crater to the ESE, but that's more than twice as far as the rover has covered to date ( 12.7km ) ...and all the "ooo 50m/sol, 3 sols a week.." maths really just don't work as we've seen so far. You could speculate that sort of maths to make it anything between about 200 and 1000 sols. Perhaps MRO imagery would help route-finding for such a field-trip, but I imagine much of it would be like the area between Olympia and Purgatory....pretty bloody terrible driving.

Truth be told, if we got to Victoria with no Endurance-like easy way in....I would be very tempted to find the best drive-in place, even if it were 35 degrees or so....and just take it nice and gentley and go in anyway - traverse the slope to make it less agressive and see what happens. Given there is no realistic target beyond Victoria - there isn't much to loose in terms of getting stuck on the way into, or at the bottom of Vic. If we do get stuck down there, the Atmos scientists could have a Mini-TES field day, Wolff could get his Sky hemisphere (LOCO Mike, LOCO ) and heck - thing of the imaging one could do stuck in there.

In conclusion to that long winded nonsense - realistically, we've almost got to go in, even if the best access point isn't proven to be driveable, because we've got nothing left to go and do.

Doug

Do we really need to drive into the crater? I think the most interesting areas are the rim wall of the crater.

The most interesting view of the rim wall will be looking up at it.

Bill:

Yes. While the MER can roll, it should!

Bob Shaw

Hopefully - driving down one of the ramps into the crater, we'll essentially have the outcropped layers to one side as we progress further in. It will be nothing LIKE what I've attached, but that's the sort of thing I'm talking about. Yellow is the outcrop. Green the drive-route in. Blue the IDD-reachable outcrop, and brown, normal soil.

Doug

Well said! I can't wait for those views, especially when the Sun angle is low and every ledge and outcrop is thrown into stark relief... seriously, the thought of those pics gives me shivers.

( And welcome aboard the good ship UMSF Diane )

I have already zoomed in to max level the picture PIA08546.tif of 16 MBytes. The best place to go down is close to "Far Rim", close to the sides of the bright color minicrater. There has a soft slope of sand into the bottom. Sure it would be a soft slope. It has around 250 meters from the rim to the bottom the height of Victoria crater is around 30 meters between the bottom and the rim. So the slope angle would be: Tan(x) = 30/250 (I have no idea on how to get the angle) >> (tan(45) = 1). Hence its slope would be very soft, much less than the maximum allowable down slope for MER is of 35 degree.

Rodolfo

It's about 6.8deg. (Arctan 0.12). Provided it's a uniform slope then its angle is well within Oppy's capabilities. We're not going to know how uniform it is until we get there though.

Thanks Helvik, I have forgot much from the university! Sure you are right that the uniformity of slope is still unclear. Sure that at the beginning, close to the rim has steeper slope than the lower heigths.

Rodolfo

I was referring to driving all the way down. I don't see a need for that.

If I had to do it, I would do as following, knowing that the most probable near-term failure mode of Oppy is a Spirit-like wheel stuck, and that the primary objective of reaching Victoria was to see as much deposits thickness as possible:


1) approach Victoria by the fastest way

2) take some rough pictures of the closest slope, to see if it can be suitable.

3) if not, begin a turn around the crater and try 2) on another spot

4) if it seems suitable, take 3D panoramoc images and high resolution 3D orbital images to accurately assess it it is possible to go down. (Idealy the latest should be done before reaching Victoria)

5) when a suitable path is found (no harsh slope, no sand, no blocks, exposed outcrops) to descend very slowly, say 2-3 m each time, and take as much science data than possible in each stop. The entire descent may take 200 sols, but no matter.

6) even if no further target is found for Oppy, to try to get out of Victoria anyway. It will be alway better to make atmospheric observations without half of the atmosphere blocked by a crater wall!

I think the slope in Victoria cannot be so steep that in Endurance, as larger craters tend to have flatter proportions.

I remember that the max slope available for Oppy (and Spirit) is 45°. It will be unbeliveable to don't find any point where the slopes are equal or inferior to 45°. No?

I love the smell of mathematics in the morning...

Good work, boys, but I suspect that the sedimentary strata we came here for will all be found in the upper third or so of the crater walls. We may never risk going down to the 'volleyball courts'. It depends on the nature of that long dark slope. I've suggested before that we will most likely attempt entry on the south side, somewhere near Sofi Crater, because we'll want to thoroughly reconnoiter the walls from the rim first. The south wall, of course, also offers us the north-facing slope we need over the winter. We'll also want to find a nice breezy slot somewhere around the rim to get a good cleaning, though I wouldn't know offhand where the best side would be. Pity there isn't a nice big 'windsock' hanging from the beacon.

45 degrees is the point where they are stable - but to actually drive, it's something like 35 degrees - strongly dependant on surface.

Doug

I think as we get closer we may see sufficient evidence of dust trails on the lee side of various protrusions on the rim, just drive around some of those while the spring winds begin to pick up.

OK, showing my lack-of-cred as a space geek, since I don't even know how to search for this...

What's available in the way of other orbital photos of Victoria, correlated with time of day and incident sunlight angles? If we can see shadows of the rim wall inside the crater, can we even begin to estimate height and slope?

One thing that stands out about Victoria is that the rim seems to be fairly "sharp" in the MOC image, most of the way around. Are we looking at a real "edge" or a difference in albedo due to soil differences, compaction, etc?

Unfortunately, all the high res MOC images will have been from pretty much the same time of day (intentionally - MGS orbits at a particular 'local' time relative to the surface it's overflying) - roughly 2pm I think

Not too sure if there's anything else really to bring to the table - even Odyssey imagery's taken from pretty much the same time over day each time, 4pm - but is much lower res than the MOC imagery.

HRSC MEX imagery is lower res as well - different times of day for that, but not of much use really.

Doug

The best ones, the most recent ones that I found is located at:

http://photojournal.jpl.nasa.gov/targetFamily/Mars

2006-06-28 Mars Mars Global Surveyor (MGS)
Mars Exploration Rover (MER)
Mars Orbiter Camera
2500x2199x3
PIA08564:
'Beagle Crater' on Opportunity's Horizon (Orbital View)
Full Resolution: TIFF (16.51 MB) JPEG (633.1 kB)

Rodolfo

Well if we know the time of day and the date then we can get a solar angle at least to a reasonable approximation. There are a couple of points with clear shadows in PIA08564 that are between 7.5 and 9.5 pixels from the shadow source. For the sake of kicking this off just taking a purely random guess at a date of Dec 5 2005 @ 2PM. Noon solar elevation is 81.7deg azimuth is 180deg (southerly) though and at 2PM it's passed back north to approx 60deg. Back to our old trig friends and the height of the "cliff" edge is between 9.8 and 12.5 pixels. A rough check seems to put the scale of the image at around 1m/pixel. So we would have approximately a 13-16m "cliff".
However if the image was taken at midwinter then the solar elevation at 2 PM drops to approximately 30deg at 2.00PM. In that case the cliff could be between 4 and 5.5m.

Anyway if someone can put an exact date and time on the image we can refine this somewhat but it isn't totally useless for getting an idea of how deep the crater walls themselves are and how steep the entrance ramp features may be.

Sorry for the delayed reply, Diane. Had things to do.
It's not that easy to research crater dimensions, since there are a substantial number of variables: crater diameter, yes, but also target rock induration and layering, degree of slumping and backwash, age and erosion state etc. The theory is a work-in-progress.
Keith Holsapple has designed a nice calculation tool to draw up a crater of any desired size:
http://keith.aa.washington.edu/craterdata/scaling/index.htm
but the result is a nice fresh crater, not the old, worn, sagging kind like Vikky (We still love her; youth isn't everything.)

I would say that the rim edge is real. It should be about as sharp as the edges of the many evaporite outcrops and crater edges we've seen elsewhere. Of course the dark sand adjacent to the edge will enhance the look.

Welcome to UMSF.

Well - that image from the JPL beacon map isn't 'out' yet....

But..

http://www.msss.com/moc_gallery/r22_s04/im...2/R2200640.html

Solar longitude (Ls): 99.27°
Local True Solar Time: 14.49 decimal hours
Emission angle: 16.71°
Incidence angle: 45.18°
Phase angle: 58.47°
North azimuth: 92.96°
Sun azimuth: 41.85°
Spacecraft altitude: 384.57 km
Slant distance: 399.70 km
Get out your calculator.

Sheesh, I read this, and it comes out in Al Bundy's voice...

--Bill

Don't even need a calculator. The shadow is approximately 8 pixels across, the measurement error is +-2. The incidence angle is roughly 45deg, Tan(45) is 1. The vertical cliff is as high as the shadow, ie 8+-2m.

The inner crater floor could be a further 5-15m down but there are clearly relatively flat zones inside the initial rim that should be navigable without having to risk going into the dunefield.

That's the enjoyable kind of theory.

Vikky was young once. She probably knows how keep her surprises.

Thanks to all for the welcome!

(In response to your question which seems to have disappeared, no, I'm not Diane Lane. I did hang out in sci.space.history some years ago, so I do see some familiar names here.

From one USENET sci.space.* "veteran" ("survivor," actually) to another: You have my sympathies.

Welcome aboard the HMS Sanity (for the most part), just the same!

I'll get back to you on this, Bill, as soon as I figure out who Bundy is. I hope he's not that serial killer I read about some years back.

LOL not that Bundy!

Al Bundy is a fictional character from the U.S. Sit-Com television series Married... with Children, played by Ed O'Neill.

In comment to the original question of the thread...

If we can't drive into Victoria, perhaps we can drive into Beagle. Or the small dimple crater on Victoria's southeast corner, almost directly on her rim.

There are several other small craters in the area, but most appear to be pretty well filled in. I'd say Beagle or that unnamed dimple crater would be our best bets to find a north-facing slope on which to winter.

-the other Doug

Thanx, Zeke, (you're the only guy I know named Zeke!) I feel better now. A "U.S. Sit-Com" guy can't be that bad.
Happy Not-Having-Tomorrow-Off.

OMG, the parallel is uncanny.

--Bill