Spirit Sol 112

Today's the first day of our Rover Driver Exchange Program, which is what I've dubbed Eric and Chris's experiment in switching rovers. Chris will drive Opportunity today, and Eric Baumgartner -- the IDD FSW lead, who's been driving Opportunity -- will drive Spirit.

Which only adds to my surprise when, the second I walk in, Art says, "You're our rover planner today."

I look at the workstation where Eric would normally be sitting. There's nobody there. "Where's Eric?" I ask Art. "Eric's gone," Art says. "You're it."

"Oh, and by the way, we're running behind," Art adds.

So I get to it. Autonav left us in front of a relatively large crater (we have a damn cool picture of the rover peering over the crater's edge, its shadow stretched out along the bottom), and before he left -- wherever the heck he went -- Eric planned out a reasonable path around it. I don't see anything obviously better, so I just start fleshing out the sequence. It doesn't take me long to turn Eric's six commands into the hundred or so commands it will actually take to do the drive.

While I'm on that, Squyres comes in to remind everyone that Opportunity will be completing 90 sols of operations today. "We have now achieved full mission success for both rovers," he says. "Complete success by anyone's criteria." Again.

Eric returns. It turns out, not surprisingly, that he had a very good reason for leaving -- he had to go talk to the NASA Office of the General Counsel. He doesn't specify why, and I don't ask. But there are only so many reasons something like this happens. My bet would be that Eric reported an ethical violation, one serious enough to get the OGC involved. Whatever happened, when they want to talk to you, you go. So he went.

Now that he's back, the Rover Driver Exchange Program starts showing its value. At the beginning of each drive sequence, we've been setting some parameters and saving them to EEP (one of the rover's on-board non-volatile storage areas). But EEP is a finite resource: save to it too many times, and it stops working. Since the parameters don't normally change from day to day, saving them when they haven't changed just wears out the EEP for no reason. So Opportunity has been avoiding saving to EEP whenever possible. It's definitely a good idea, so we make the change.

In a similar way, Spirit's been avoiding reinitializing the PMA when we don't see a need for it. Opportunity's been doing it frequently. This costs motor revs -- another finite resource. Eric doesn't seem to have been too thrilled with this practice, and when he learns that we don't do it, he looks happy. I have a feeling Opportunity won't be reinitializing the PMA so often in the future.

The rover should be able to make good time tomorrow -- once we get a little way past the crater, we've got a nice, clear path ahead of us. The one thing Eric and I don't like about the drive is that the first part takes the rover through a small hollow to the right of the crater. This shouldn't be a hazard, but we're not too comfortable about it. The slope of the hollow's rim is about 15 degrees, close to the rover's limit of 20 degrees. The rover can actually negotiate much steeper slopes -- the mechanical limit is about 45 degrees -- but we set it to 20 degrees for safety. If the rover decides it's on a steeper slope than that, it stops driving. So if our estimate of the slope is off by a few degrees, or if we've missed something, the drive will cut out early. At the activity plan approval meeting, I express it this way: "If we make it through the first ten meters, we should have a great drive."

Tomorrow the scientists plan to dig a trench. I haven't been involved in trenching before, so I'm looking forward to that. This plan leads to some argument at the activity plan approval meeting, though. Trenching, and the IDD work that precedes it, will consume a fair amount of energy, so we can't use so much energy today that we won't have enough left over for that work tomorrow. But Squyres thinks we're being too conservative in our power models -- we could drive another 20 minutes today (he thinks) and still have plenty of energy tomorrow. So he and Art debate this for a while. In the end it's Scott Doudrick's call, and Scott is in a foul mood today already. (He's normally our TDL, and today he's doing two other people's jobs as well -- for the first time. He's stressed.) "No!" says Scott, and there endeth the argument.

Our first-time activity du jour is to add drop-ins into the rover driver sequence. "Drop-ins" are what we call pre-planned science activities that can be dropped into the plan if it turns out that there's room for them; we've been using these since early in the mission to help us maximize science return. But we've never put them in the drive before. Today the concern is that the drive could error out when the rover is trying to drive through that hollow, and the rover would end up just sitting there for a couple of hours. So we work out a way to have the sequence detect this situation and respond to it by running the drop-ins.

As it turns out, we're able to find a way to improve the drive's chances of success -- which will make the drop-ins irrelevant, but by then we've already put them in, and we might as well leave them. We get another downlink pass that brings more imagery, and it turns out that if we head off even farther to the right, we can negotiate a way around the crater over almost flat ground -- no hollows there. So Eric picks out the waypoints and I sequence them. It turns out to be the longest blind drive we've ever planned on Spirit -- 54m -- and after that, autonav will fill out the sol. We won't make 100m thisol, but we might come somewhere close to 90. Which would be yet another new record.

There's a reporter here from, of all publications, AutoWeek. I talked to the guy on the phone several weeks ago -- very nice guy; his dad worked on Voyager -- but apparently he's just now getting his chance to come on Lab. I keep expecting him to drop by the sequencing room, but he never does, and I don't actually see him -- though I do overhear him talking to Justin Wick at one point, and he says something about having talked to the Opportunity drivers. So I'm OK with that outcome -- at least he got to talk to a rover driver, which is what he wanted. But I'm sorry I missed my chance to meet him.

As the CAM is winding down, Squyres says something about the hills getting closer all the time. "What will we see as we get closer to the hills?" I ask. "Well, I confidently predict we'll see more rocks," he jokes. Then he gets serious. "We'll get a chance to see bedrock -- we can see bedrock on the hills, even from here, but it's way up there, and I don't know if we can get to it."

"There was a lake here," he adds. "I know it. I just can't prove it yet."

The free ice cream will be discontinued soon -- this time, I think, for good -- so I decide to take advantage of it one last time before it's gone. While I'm up there, I run into Chris.

"How's the Opportunity driving going?" I ask.

"There's not much of it," he says. They're terribly power-constrained thisol, and as a result they've been squeezing the drive. "They've cut us down to fifteen minutes," he says.

That's a shame. But at one point it looked like they weren't going to get to drive at all, so it's better than nothing.

Not much better, I guess. But better.

Courtesy NASA/JPL-Caltech. Spirit spots her own shadow in a crater.

Courtesy NASA/JPL-Caltech. Just to put things in perspective, this is the traverse map showing the road ahead. The solid red line is everything we've done up to this point, and the dashed red line was how far we had yet to go.

1 comment:

Doug Ellison said...

That's the pan I was talking about at dinner :) And there's you thinking I'm a Meridiani kind-of-guy!