Spirit Sol 792

ODY's back, and to try to make up for lost time, we're in here sequencing on Saturday for the first time since -- well -- it's been a while. We're even planning two sols. With Spirit's precarious energy situation, we're driving on alternate sols, and using the intermediate sols simply to recharge. I was like that when I was recovering from cancer: I'd walk a little, and then have to stop to breathe a while. I didn't like it, and I'm sure she doesn't, either. Poor thing; she was so healthy, so recently.

The good news is, we have data from Spirit at last! And a lot of it, too -- a whopping 110 Mbits!

The bad news is, she's not telling us what we want to hear. Our last drive was supposed to turn about 85deg and then head off toward a waypoint 10m away. It turned about 8deg and then failed. Worse, we can't deduce why it failed, because despite the size of the pass, we're missing some crucial data.

In addition, while the other wheels are doing just fine, the RF wheel is now about halfway dug into the fluffy soil we're perched on. Clearly, we need a change of technique, and we need to get a move on.

Why did the last drive fail? While we're missing some of the details, the picture starts to emerge. Our only good technique for turning Spirit now involves making use of the fact that the failed RF wheel acts like an anchor: if you simply drive forward, she pirouettes clockwise around that wheel. So they were trying to use that, alternately pushing forward to change our heading and then backing up to try to get away from the hole this technique makes. It seems that we were unable to perform the backups -- the wheel was acting as an anchor then, too. So we'd spin clockwise just fine, but when we tried to back up, we just twisted back the other way.

If only we still had a rover wakeup song -- we could play "The Twist." Or maybe that would be bad luck.

Anyway, Ashitey thinks he knows how to fix this; we're going to use a variant of the same technique, but change how we do the backups. I also come up with a way to build a slip check into the backup, so that we'll be able to tell if we're actually getting ourselves out of the hole or not; if we're stuck, we'll at least stop making the situation worse.

Naturally, all the analysis and tricky sequencing takes some time, so newly promoted project manager John Callas goes out to buy us all Subway. "But we have to see the drive animation before the rover drivers can eat," he warns.

Ashitey's a bit grumpy today, so I try teasing him to lighten the mood. "I can't believe you're letting them get away with 1-bit-per-pixel ultimate imaging, Ashitey." He's notorious for pushing for higher-quality imaging than that.

"I just don't have the energy any more," he chuckles.

"You and Spirit both! You need to get to a north-facing slope, man."

[Next post: sol 794 (Opportunity sol 773), March 28.]

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