Opportunity Sol 272 (Spirit Sol 293)

Because of all the time we've been devoting to driving, several of the instruments have gotten no new data in the last several sols. Flash has been full for a related reason -- in order to gain as much ground as possible, we haven't been turning to optimize downlink, so most of our downlink passes have been unusually poor.

Not that there's much for the instrument teams to do anyway. We've been in essentially the same spot for a couple of weeks now; they've taken pictures of everything there is to take pictures of and already IDDd the hell out of Wopmay, which was the only interesting thing in reach.

Two weeks -- that's how long we've been struggling to get away from Wopmay and on our way to Burns Cliff. Happily, yestersol's successful experiment made us hopeful that we're on our way at last.

We won't know for a while, though; we're in that phase where the downlink is coming in later and later, so our sequencing starts later and later. As we've been doing, we plan the sol in the blind, assuming a successful drive. We're going to do the same thing thisol whether the drive worked or not: we're going to spend a long time driving (or trying to), and fill up the rest of the time with bits and pieces of random science.

For the past few sols, I've been hearing more and more about the possibility of a return to working weekends, at least on Opportunity. Jim Erickson, at least, is getting worried about Opportunity's apparent lack of progress. He seems to be concerned that when they went to Congress and asked for an extended-extended mission, they had this long list of things Opportunity might do, and so far they've barely done any of it. This is likely why Jim's anxious to flee the crater and get on with other things. (Squyres's rejoinder to this is that the list was explicitly a list of things we might do, and not having checked off many items isn't necessarily a problem when we go back for more funding early next year. I don't think Jim's convinced.) Working one weekend day each week would allow for the possibility of an extra drive sol each week.

Both Andy and Jim sound me out about the possibility of working weekends. I'm cool with it -- actually, I even kind of miss it. ("You're all too eager to work weekends," Andy tells me later, his reproachfulness only semi-joking. Apparently, he even gets lots of volunteers to work Thanksgiving. It's fantastic to work with a team that has such high morale.) Jim's blown away when Mark Maimone and I both tell him we miss Mars time.

"I've never slept so much as when we were on Mars time," Mark shrugs as I nod agreement. "And I don't have kids, so ...."

"Don't you have a wife?" Jim asks Mark.

"A girlfriend."

Jim pauses. "And you want to keep her?"

Not long after, we get the downlink, and -- well -- it's not all that we'd hoped for. Not only didn't we make any progress, we actually lost a little bit of ground, ending up maybe 30cm downslope of where we started, and only about 70cm cross-slope. Looks like we don't have a reliable strategy for making uphill progress after all. Or, as Art puts it: "So our euphoria from the previous day's drive has evaporated."

Looks like I was wrong about whether we should continue trying to drive. And that's the general feeling (I mean, not that I was wrong, but that we've about reached the point where we should give up). Since we've already made a plan for tomorrow that includes a drive, we decide we'll give it one last chance. But we're going to meet again tomorrow, after the drive results are in, and decide what to do. And it's hard to see how it's going to go any other way than abandon the cliff and head back out of the crater.

Cooper has to go to the doctor, so we sketch out the first version of a drive together and he heads out. The rover is dug in very deep, worse than I've ever seen, with the left front wheel buried in a hole (of its own making) deeper than it is tall. We can't turn clockwise to escape the hole, since there's a rock on top of the pile of dirt the rover kicked up on that side -- likely, this will be too much for us to get over. We can't turn counterclockwise because we can't see off to that side, though of course it stands to reason that there's a big pile of dirt there as well. And we can't get out by going uphill, because that's how we dug ourselves in.

So the only way out is straight ahead -- downhill. The only sure way to get completely clear of the hole is to drive the rover about 2m forward, losing more altitude than we gained on the experimental drive. This is all very, very discouraging.

After that, we revert to the plan that appeared to work well for us on the experimental drive: a switchback, so that if the rover gets stuck, at least she'll change direction and perhaps make some progress. Three switchback legs of about 4m each, and thanks to the 2m downhill bump at the start, about the best we can hope for is that we'll break even -- that we'll be more or less back where we started before this latest drive. No closer to Burns Cliff -- and, considering what another failure will mean, in a sense we'll be much farther away.

At least we've got one more chance. Just to make it dramatic, Cooper's appointment means I get to do it all by myself. So, great: we're going to fail to get to Burns Cliff, and I'll get to feel like it's all my personal fault.

Well, what can I do to improve the odds? When I look at the drive Cooper and I sketched out, I spot a problem: switchback driving tends to carry you, on average, straight uphill. But the hole we've just dug is straight uphill from where we start the switchback. We might avoid it, but with all the slip we've been encountering, there's no certainty. So I change the drive: instead of three legs of 4m each, I use one leg of 8m and another of 4m. If this gains us enough uphill distance to get us onto the rockier terrain (the so-called "paving stones") we can see there, we won't care that we're a few meters farther from the cliff. (Just a few meters is all it would take, damn it! You could walk it in seconds.) And if it doesn't, then we'll be that much closer to the exit.

Assuming we don't just dig an even deeper hole, that is.

I name the drive "Hail Mary."

As it happens, I don't have to plan it completely solo. As I'm nearing completion, Spirit finishes its planning for the sol, so Jeff Biesiadecki comes upstairs to see how I'm doing, and Art presses him to backstop me on the sequence. Then John Wright joins him, and Art ropes him in as well.

So we decide to thoroughly review the thing among the three of us. This will delay uplink even longer, but considering the science we're trying to preserve, who cares?

Though it's a reasonably short sequence, reviewing the drive takes maybe 45 minutes or an hour. To paraphrase an old joke, if you put three rover drivers in a room, you get four opinions. Jeff and John do excellent work, poking at pretty much every decision I made, and coming up with some points I hadn't thought of. In the end, little changes -- the drive stays mostly intact, except that we convert the switchback turn from a turn-in-place into a K-turn. (The rover backs uphill through the long leg, then arcs halfway into the turn, reverses course, and arcs ahead to swing into the shorter second leg, driving forward.) I don't expect this to make a lot of difference, but it might save us some slippage, and it definitely looks cooler.

The only question is, will it work?

Courtesy NASA/JPL-Caltech. Well, crap. Looks like it was smart to keep that whole "NEENER NEENER NEENER" thing to myself.

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