Opportunity Sol 262 (Spirit Sol 283)

So we nailed the drive on Spirit. It cost us a lot of sweat Friday, but the post-drive front HAZCAM made it all worthwhile: there's Uchben, dead in front of us, pretty as a -- well, as a picture.

Too bad I don't care, because today's my first real shift on Opportunity! If I'd realized this before late last night, I'd have read more about what our sister mission has been up to. As it is, well, I'll just have to figure it out as I go along.

Working on Opportunity reminds me of nothing so much as visiting Australia. One of the things I was most struck by when I went to the wonderful land of Oz was that it was a lot like America ... but different. At times you were obviously in a foreign land, but at times it was almost like you were home. And a lot of the differences would be weird little things, things that wouldn't quite register consciously, like details of how people dressed. Exactly how they feel when they come here, no doubt.

One of the differences between the two missions is the habits of the RPs. On Spirit, the RP-1 comes in early and leaves early (usually leaving just after the walkthrough); the RP-2 comes in before the APAM and leaves at the end of the day, after the CAM. And there's a moderately formal handover in between. But on Opportunity, the RP-1 and RP-2 come in at about the same time and often leave at about the same time, and they kind of work on everything together, so there's very little distinction between the two roles. Luckily, I'd heard about this already, so I get my ass up early for the SOWG meeting.

And see, this is what I mean about it being almost, but not quite, like home. They're on Mars, with the same kind of vehicle, but they have a lot more solar energy available, and the rocks are all different and have weird names, and the terrain is different (crater vs. hills). Not that I mind, it's just ... weird. (And that reminds me of that one scene in Pulp Fiction ("It's the little differences"), but that's a little too much of a tangent for now.)

Fortunately, I'm here just in time to help explore one of the most interesting rocks we've seen on either mission. This is a huge rock officially dubbed "Wopmay," but unofficially everyone calls it "the dino brain." Because that's what it looks like: an enormous, crenellated brain. (Yes, I know real dinosaur brains were tiny. You look at the damn rock and tell me what comes to your mind.) They spotted it weeks ago and have slowly made their way over to it, reaching it a few sols back, after some tricky driving. Thisol will be our last sol here, and I get to help with what might be our last IDD sequence on it before we drive away for good. (We're going to drive around to the other side after the IDD sequence completes, and maybe come back and poke at it a little more if the other side looks interesting.)

Only the IDD sequence has a problem. ("Figures," Frank grumbles. "The days with tricky drives are the days when the IDD sequence gets tough.") The problem is that the target they've chosen -- Hercules -- is pretty much at the upper edge of reachability. When we try to MI spots above the target (that is, higher up on the rock face), we get errors from the simulation. Once we realize that's the problem, the fix is easy enough: I just shift the mosaic down the face.

Hey, it's my first sol upstairs, and I'm already helping! Woo-hoo!

Frank and I commiserate about the science team's habit of choosing targets on the edge of reachability. I think the problem is caused by the way the reachability information is presented to them -- using SAP, they get an image with a translucent green overlay showing approximately what area the IDD can reach. My theory is that the interesting part of a big splotch of color is the edge -- that's where your attention goes, so that's where the scientists pick targets.

"Maybe for the next mission we could define some notion of degrees of reachability," I muse. "Then we'd have multiple colors, splotches within splotches --"

"-- like a bullseye!" Frank says, picking up on the idea.

"Yeah, and that would draw their attention in, toward easier-to-reach spots, rather than out, toward harder-to-reach spots," I finish.

Note to self: pitch this idea to Jeff Norris.

So the day's other sequence is a drive. We back 2.5m away from the dino brain, turn, and head about 7m to get to a spot on the far side of the big rock, using visodom all the way. Wopmay's a big rock, big enough to clip the solar panels, so we need to be sure to avoid it. Frank shows me a trick they've been using to simulate slip, inserting extra commands to make the simulated rover periodically drive a short distance downhill. He fiddles with this until the simulated rover is driving more or less in a straight line to where he wants to go, then takes out the extra commands. This is so much better than how we've been dealing with slip on Spirit ("Um ... and then we should end up about ... I dunno ... there, ya think?") that I decide immediately to adopt the trick. Until the next version of RSVP comes out, which will model slip elegantly, but that's another matter.

Frank's sick, so he leaves a little early, but fortunately he calls in with a potential problem he thought of on his way out. We introduced a bug at the last minute: because of the conditional commands we chose to use, the rover could back off, decide not to do the turn, and then drive the second leg -- likely whacking it pretty much straight into Wopmay.

Naturally, I quickly fix this. After all, I don't want to break Opportunity on my first day.

I should at least wait until next week.


Courtesy NASA/JPL-Caltech. Uchben, positioned right where Spirit can start poking at it.

Courtesy NASA/JPL-Caltech. Opportunity makes shadow puppets using the rock dubbed "Wopmay" (a.k.a. "the dino brain") as a backdrop.


Anonymous said...

"He fiddles with this until the simulated rover is driving more or less in a straight line to where he wants to go, then takes out the extra commands."

How often did they mangle a sol because they forgot to take out at least one of the extra commands?

Scott Maxwell said...

@Anonymous Not once! It helped that we flagged the "slip commands" with a special comment that we could automatically search for.