Spirit Sol 678

Opportunity experienced a disturbing failure this weekend: her IDD failed to deploy. We talked about it this weekend long enough to rule out a sequencing error, which meant we shouldn't try to bring in the normal uplink team to try to fix it and salvage the IDD work. It's possible we would have tried to get the right people together, but it was Thanksgiving, and many people were out of town, and so on. And these days we don't engage in heroics. So we let it go until Monday.

Now it's Monday, and it's not immediately clear what we should do about this, because it's not immediately clear what the failure is. We know we got a tiny amount of motion followed by a motor stall, but why? Eric Baumgartner's (well-educated) guess is that we've simply lost a small amount of knowledge as to the position of the IDD. As a result, when the IDD tried to go to the commanded position as part of its unstow routine, it actually failed to get the IDD off of the little hook it stows itself on, and then it couldn't rotate itself away from the hook. This hypothesis has some confirmation in some image analysis Paolo performed, which may show a tiny discrepancy in the arm's position after the last time we stowed it.

This would be relatively straightforward to solve -- not easy, but not dreadfully bad. We'd have to figure out where the arm actually is, then manually guide it through the unstow routine, at which point we'd be able to recalibrate the IDD by driving each of the joints against its hardstop. We might also need to repeat the "Martian Tai Chi" routine that recalibrates the camera models, so that the IDD and the cameras would be in agreement. It would be a long, slow process -- maybe a week or two, all put together -- but in the end we'd be as good as new.

But Eric's explanation isn't the only one that fits the observed facts. Ashitey fears there's something worse going on. One of the actuators in the testbed rover has started to fail, and it stalls out in pretty much the same way as we've just observed Opportunity's joint motor stall. If this is what's going on, it means the IDD has become unreliable -- every once in a while, our IDD work might randomly fail in this way. That would introduce a severe, somewhat random penalty into all IDD work.

With the testbed rover's IDD, the failures are merely annoying; repeat the failed command, and it usually works the second try. If Opportunity's IDD is indeed failing in this way, that means we have an occasional one-sol penalty to look forward to; probably nothing worse than that (though that would be unpleasant). But it could be worse still: the actuator might simply have failed permanently. And if that's what happened, a large fraction of Opportunity's scientific potential just disappeared forever.

There are other possible explanations, too, with varying degrees of benignity. Erickson wants the full-up anomaly investigation, and the right guy to do that is Ashitey. But Ashitey's RP-1 on Spirit today, which would leave him precious little time for something like that. So he and I switch places -- he heads up the investigation, and I go back to Spirit.

Which means I'm driving today -- driving to Miami. (I try to remember not to leave the left turn signal on.) This drive is reasonably simple, snaking around a few rocks before heading more or less straight toward Miami. Well, not quite Miami -- Coral Gables. See, I didn't have an exact target for Miami, just picked a spot in the neighborhood, and Coral Gables is a Miami suburb ....

Maybe you had to be there.

If all goes well, we'll cover a third to a half of the distance to Miami in this drive. (Maybe we'll stop for the night at a HoJo's. Sorry, I can't help it.)

I'd seen a birthday card in the Spirit sequencing room last week, but it hadn't registered on me until today. I pick it up and read it. I figured it was for someone on the team. Turns out I was right; it's for the most important member of our team. It's a birthday card for a one-year-old -- our one-year-old, Spirit. (Or maybe that should be a "birthsol" card, but I'm not picky.) From the nice (and clever) folks at unmannedspaceflight.com.

I love it. We should make them Spirit's godparents or something.

[Next post: sol 680, December 1.]

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