Going To Mogollon..., ...and points South Options

[Tesheiner]

Anyone know what the strategy is for Opportunity regarding winter, and how that translates into travel plans?

Bob Shaw

Good question (Doug, take note of that for the next interview).

On this flat terrain the option of a "hill's north slope" is ... not an option, and I guess the winter will hit Oppy on the middle of the travel to Victoria.
How this translates on travel plans: maybe shorter drives due to less available energy, and imo more important, very careful driving when traversing by the dunes/ripples. Just think of what could happen after an aborted drive with a bad tilt?

[Burmese]

http://www.newscientistspace.com/article.ns?id=dn8730

"Jacob Matijevic, the rover mission team's chief of engineering, also at JPL, said if possible, the team would like Opportunity to winter in Victoria Crater, a large impact crater 2500 to 3000 metres away. "That would have the same benefit as we saw in our investigations of Endurance Crater," Matijevic says.

The journey to Victoria Crater is likely to take at least three months, he adds."

[helvick]

Good question (Doug, take note of that for the next interview).

On this flat terrain the option of a "hill's north slope" is ... not an option, and I guess the winter will hit Oppy on the middle of the travel to Victoria.
How this translates on travel plans: maybe shorter drives due to less available energy, and imo more important, very careful driving when traversing by the dunes/ripples. Just think of what could happen after an aborted drive with a bad tilt?

Oppy has a slight benefit in terms of location at mid SH winter since it is so close to the equator (1.95deg S) vs Spirit at 14.57deg S. In practical terms this gives Oppy approximately 15% more insolation at mid winter. It also means that Oppy will have a slightly easier time finding optimal slopes from an insolation perspective, and finally the penalty for ending up in an unfavourable position is less than it will be for Spirit.

The precise amount of dust on the panels could still cause a major problem for either rover but all other things being equal Oppy has an easier environmental situation in SH winter time.

[Bill Harris]

Also since this site a only a couple of degrees South of the equator there is not much difference between the mid-summer and mid-winter altitude of the Sun (62 and 68 degrees, respectively) so it might seem that a north-facing slope isn't critical. But given that these angles represent a loss of 47% and 37% based on ther cosine function, it might require some north-facing slopes to increase the solar incidence on the solar panels.

The big problem is the orbital eccentricity. Mars is some 19% farther from the Sun in the Martian Southern Winter (which we are approaching) so the sunlight will be less intense by xx% so some time on a north-facing slope may be needed to top up the batteries.

--Bill

[djellison]

Power 19% further out will be 41% lower, I think

Doug

[Phil Stooke]

Burmese quoted a story from New Scientist,

"the team would like Opportunity to winter in Victoria Crater"

Oh come on! There's no way. I'd like to see it, certainly, but it can't possibly get there until spring.

Phil

[Tesheiner]

Not only that, but the rover would have to make the whole way around the crater to it's southern size (northern looking wall) AND find a path into the crater.

[Toma B]

Not only that, but the rover would have to make the whole way around the crater to it's southern size (northern looking wall) AND find a path into the crater.

Oh, but we aren't going to Victoria just yet as Jim Bell says...
There are some more places around that they want to see, and maybe then they will decide that there are some more places nearby, after that there will be some more IDD to be done here, after that there will be some things that we have never seen before...
Opportunity will never reach Victoria Crater at this pace...PLEASE make up your mind and start DRIVING!!!

[helvick]

Power 19% further out will be 41% lower, I think

The local microclimate and dust deposition\cleaning patterns are causing major differences at the moment it seems.New Scientist MER update.

Jones says in order to be productive during a sol, the rovers need at least 400 watt-hours. That amount of power allows an hour-long drive, a couple hours of robotic arm work or remote sensing and a daily data uplink to the Mars Odyssey spacecraft. To simply stay alive, they need about 280 watt-hours.

Spirit is currently operating with about 450 watt-hours per sol, but the available power has dropped by about 100 watt-hours over the past 50 sols, Jones says.
.....
The coming winter is less pressing for Opportunity, which is closer to the equator and is still operating with about 600 watt-hours of power each sol.

Time for me to go off and properly calculate some power curves for the onset of winter but my quick calculations tell me that Oppy will stay above about 330 whr throughout winter and has at least three months ahead when she should be able to manage an hour or more driving per sol. Spirit is losing between 10 and 15 whr per week at the moment so she really has to get to McCool hill within about 40 Sols or she risks getting stranded in a less than ideal spot unable to move.

[Nirgal]

Time for me to go off and properly calculate some power curves for the onset of winter

Thanks helvick !
I've been already anxiously waiting for your detailed update ... major concern was for Oppy not reaching the slopes of Victoria in time (whereas Spirit will have no problems to reach it's winter parking position)
... I thought it must come close to the 300 Watts "deadline" even for Oppy .... so the cited 330 W minimum for Oppy is encouraging ...
And, unfortunately, as for further cleaning events, as nice as they are, they are not something we can count on ...

[Marcel]

B)-->

Opportunity will never reach Victoria Crater at this pace...PLEASE make up your mind and start DRIVING!!!

[/quote]

I can understand the frustration. I'd love to see the place as well: the possibility to reach it is there, and this will diminish every day that long drives south are postponed and mechanics and electronics are aging.

But (and it's said before often): This mission is not about pretty pictures, it's about science. About understanding what we see. Try to reconstruct what happened on this part of the surface. Relate morphology with rock/soil composition (while the cobalt source still radiates within workable levels, before it's out of operation), look for geologic context. And: do it as thoroughly as possible. This, combined with the knowledge that the quality of the scientific results is highly dependent on the quantity (that is: statistically reliable) AND te quality of the data (that is: complete, without forgetting to record just about everything that's within the capability of the instruments). And this costs time. A lot of it. And this is why we're not in Victoria (yet). It's a balance between continuing the trek across the line southward and feeding hunger for new terrain, and relating it to the knowledge that returning to a spot to fill a gap in the data is probably not going to be an option.

In other words: it's choosing between knowing some things for sure (like the prime target: pinning down water related processes), than a lot of things superficially.

[Nirgal]

But (and it's said before often): This mission is not about pretty pictures, it's about science.

My feeling is that Victoria will offer both: "pretty pictures" *and* the most valuable science at the same time
just as it has been the case with the other long distance treks to Endurance, Columbia Hill Summit
and now Home Plate. Imagine we could be still turning every pebble at "Adirondack" but so far, each time we did take the "risk" of driving longer distances to new horizons, the reward has been a whole new chapter of discoveries there
Apart from accuracy and thouroughness It has always been also the Couriosity and the explorative spirit of trying new things and taking risks that have been the drving force behind science

[helvick]

Victoria is apparently somewhere between 2500 and 3000m away depending on the route taken.

To see how realistic a target it is I'm making some assumptions:
1. Driving consumes approximately 100watts between the drive motors and navigation processing\imaging.
2. 0.5 cm/sec is a realistic speed for driving aggresively but with some care (so as to avoid another Purgatory).
3. Dust accumulation will cause additional power loss at a rate of 0.18% per Sol (this should be a worst case situation).
4. Oppy doesn't get stuck.
5. We start driving soon.

Opportunity should have enough power available over the next 94 sols (when power will drop just below 400 whr) to drive about 3300m.

To achieve that she would have to start soon and initially average around 50-60m per Sol. By the time she reaches Victoria she would be driving for about 18m per Sol.

I haven't factored in things like restricted Sols but there is a 10-30% margin in the above numbers depending on route and my calculations target reaching Victoria when power is still approx 400whr per Sol so she still has enough juice to do some real work\find a nice sunny ledge to park on for winter.

[Marcel]

Imagine we could be still turning every pebble at "Adirondack"

Which would make no sense, because there was nothing but volcanic rock there. Oppy however, is in a treamendous complex and interesting spot at the moment. This combined with the problems with her arm, and all the microscopic work makes that it's been a while around here. I must admit however, that continuing to another spot is about time.

[djellison]

Not only that, but the rover would have to make the whole way around the crater to it's southern size (northern looking wall) AND find a path into the crater.

OR - outside the crater on the northern slope that approaches the rim ?

Remember the southern slope they had driving around the southern edge of endurance making Oppy very power-low (in SS's book)

Doug