Opportunity Sol 265 (Spirit Sol 286)

Did we make it? That's what I'd like to know. When I come in, the downlink pass is over, all the data is on the ground, and we can't see any of it. By one of those rare but weird coincidences, there are independent problems with the network, SAP, and MIPL's downlink processing, all showing up at more or less the same time. The upshot is that we don't have the data in a useful form and therefore don't know anything.

The SOWG meeting starts anyway, on the assumption that everything's OK. This official optimism is pleasant but, given recent events, it hardly seems well-founded. But when the data starts coming in, Art's able to announce: "This is very, very, very preliminary, but it looks like the drive was successful."

And whaddaya know, it was. Sure, it was simple, but it did just what we needed, backing away from Wopmay carefully and safely, and ending up pretty much exactly where we'd wanted it.

Now we have breathing room. Our next step is to try to get uphill, so we can get past Wopmay on our way to Burns's Cliff. As usual, the drive is simple, but deciding what it should do is complex. We decide the best course of action will be to drive straight uphill, which means at a heading of 25 degrees. (To be more precise, the rover is facing 25 degrees, but we'll be driving uphill backward, so our direction of motion is 205 degrees.) We settle on this heading after analyzing slip data from yestersol, which is a bit spread out but lies in the range 16 to 34 degrees.

We want to do the longest drive we can in the time available, and as I'm thinking about how to do this I have an insight. Visual odometry limits how far you can go between position updates, so we usually keep our commanded distance to 60cm or so. But since we know we'll be slipping a lot, we can command larger steps. After all, what matters is not how far you told the rover to move, but how far it actually moves, between taking visodom pictures. To leave a little margin for error, we command 80cm steps -- this should come out to 40cm or so after slip, easily small enough for visodom to work.

With that approach helping to extend our limit, we command an uphill drive of about 20m, which should come out to about 10m after slip is accounted for. That should leave us plenty of room to get past Wopmay, and from there on we're clear.

I have one other quick-witted moment thisol. I've still got laryngitis left over from the flu, so when Art overhears me talking to Mark Maimone, he says, "You sound terrible."

"Yeah, but you look terrible," I reply, "and I'll get better."

If you're going to steal, steal from the best.


Anonymous said...

Hi Scott

Great Blog - I've been following it for a while now.

Just wondering how the second picture was taken (in the blog entry for Opportunity Sol 265 (Spirit Sol 286).

The top centre of the picture seems to show a part of the Rover but can't figure out how the picture was taken to put it in that position.


Scott Maxwell said...

Thanks for the compliment!

The second picture is a rear HAZCAM image, taken from one of the two fisheye cameras mounted on the rear of the vehicle. That structure you see at the top of the image is the underside of the rear solar panels -- the rear HAZCAMs are mounted on the main body of the rover itself.