Spirit Sol 750

Today was brutal. There's just no other way to put it. Brutal.

The science team has identified four rocks in the vicinity that they'd like us to drive to -- A, B, C, and D. Rocks C and D are definitely out; they'll take multiple sols to get to, and one constraint on the solution is that we strongly prefer something we can get to in one sol. Rocks A and B are about equally easy (or difficult) to get to, but A has a patch of sandy material around it, which B doesn't. So at yesterday's pre-plan meeting, I tentatively identified Rock B as the best candidate.

Last night, I took a more careful look, and started falling out of love with that idea. Another constraint on our solution is that we want to be able to RAT-brush our chosen rock, so that we can get a clean APXS measurement on it, and the RATtable face of Rock B is aimed somewhat away from the best path to it. To get to that face, we'd have to clamber up onto the rock pile beside it, which would simultaneously raise our tilt and reduce the stability of our footing. So that's bad all around.

I send out email about that, and the science team weighs the options at the SOWG meeting. What it comes down to is that Rock A is more eroded, so that there will be less layering for the MI. While Rock B offers better MI-ability, the uncertainty about being able to RAT it tilts the choice in the other direction. So Rock A it is.

Before we drive there, we've got some IDD work to finish up at our present location. And it looks like it's going to be hairy; the scientists are still dithering about exactly what they want, and that never turns out well. I turn to Paolo, RP-2 today and still in training to be a full rover driver. "Paolo, which one do you want?" I ask him. "The drive or the IDD?"

"I'm more comfortable with the drive," he says.

"Great!" I answer. "You get the IDD!"

"I knew that was going to happen," he laughs.

Today's going to be tough for him, I can see that. But at some point he's going to have to get his trial by fire, and it might as well be today.

So Paolo and Terry (who's shadowing him) work on the IDD sequence while I put the drive together. The drive to Rock A turns out to be not so terribly complex; we're basically just backing downhill past it, turning, and crawling back up a bit to put it right in the IDD work volume. As always, the devil's in the details, but all in all it goes quite well.

That is, until the TUL tells me there's another constraint on the drive. We've got to be at a heading of 120 degrees for comm. This is significantly different from the "natural" heading we'd otherwise end up at, about 80. It requires a completely different approach, and that means I've got to scrap almost all the work I've done -- I had already finished -- and start over.

A false start or two later, and I've got the new approach roughed out. We'll back somewhat farther downhill, curving until we're straight downslope from Rock A, then turn to about 120 degrees and climb back up to it. This is going to suck. It'll take longer, it means we're trying to drive up a steep slope through sandy material (with the attendant risk of getting bogged down and possibly even picking up a potato), and we've got less time to study it now.

We don't even notice until the walkthrough that the new approach leaves us with the left front wheel up on a 16cm rock. And there's just not much we can do about it, either. As Paolo points out, our choice of destination constrains us in X and Y, and our heading is dictated to us by comm. Therefore, the rover's final position and orientation are more or less completely determined by the constraints on the solution, and if there's a rock under the wheel as a result, then there's a rock under the wheel. We're able to shift the rover's position by a few cm, but will it be enough? Doubtful.

All in all, I'm quite frustrated by this outcome. We were trying so hard to find a scientifically desirable rock we could reach in one sol; our sols here are already limited, and Monday we enter restricted sols, which means we'll blow two more sols if this doesn't work. And I don't have any confidence that it will work: I think we'll come in Monday and have to reposition. This just sucks.

Worse yet, switching to Rock B (or C or D) at this point wouldn't help: C and D are more than one sol away no matter what we do, and B still has the same problem of higher tilt plus unsure footing, especially if we know we'll have to come at it with a 120-degree heading. So we wouldn't have options to fall back on even if the team weren't too tired and stressed out to attack them.

With all this going on, it's no wonder we discover -- after delivering -- an error in Paolo's IDD sequence. One part of the sequence is a column of MI stacks marching up the rock face. The rock face curves away from us slightly, and Paolo's sequence doesn't account for that. As a result, we're not quite touching the rock at the top end of the mosaic, and the resulting MI images might be out of focus (though the lower images in the stack will probably be just fine). Maybe I shouldn't bother with this, but I have to do my job. I smile sweetly at our TUL.

"Hey, Colette," I say as casually as I can. "What would you say if I told you there was a problem in the IDD sequences?"

Fatigue's written all over her. "Is it a spacecraft safety issue?" she asks.

No, it's not. And our SOWG chair doesn't feel like bitching about it, either. We don't fix it.

So today just was not a good day. It doesn't help when, during our end-of-day post-mortem, our other TUL, Matt Keuneke, says that they discovered that a heading of 80 degrees actually would have been okay after all. We didn't need to switch to the 120-degree heading, with all the problems that introduced. "I didn't feel like we should tell you, though," he says. "I figured you'd kill me."

I'm too tired to care about it. I think that's a real bad sign.

[Next post: sol 753, February 14.]

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