Opportunity Sol 421 (Spirit Sol 441)

To my surprise, the last time the rover was driven was my last shift. Or rather, that was the last long drive -- they had a 7m bump to get the rover up on a nearby ripple, and they've just been IDDing it since then. Now that I'm back, we're pulling up stakes and moving on.

Well, I've been on the other side of that and didn't like it. But Frank (who's been doing the IDDing, with Jeff) has a good attitude about it, unlike what I had. "Hey, when you guys are driving, I just sit in the back seat and enjoy the ride," he grins. Now why can't I be more like that?

Anyway, the drive is a relatively simple one. We're about 70m from Viking Crater, and they just want us to drive to a position next to it so we can image it on the following sol. Amazingly, we actually have an obstacle to dodge: there's a hollow, like a small crater, about 20m away. From what we can see, it's about 20cm deep, and we can't see its bottom so it's likely a bit deeper. We could probably just drive right through it, but for safety's sake, we treat it as a hazard and drive around. For safety's sake, and, hell, for the sake of variety -- driving across this parking lot has been almost too simple. It's a far cry from driving Spirit, where there are more hazards than dust grains.

The tail end of the drive should leave us in Viking's "ejecta blanket," the rocky field that surrounds a crater. Those are the larger rocks tossed out of the explosion that formed Viking Crater millions of years ago. (The larger rocks naturally aren't thrown as far; they stay close to home.) I want to take advantage of this, so I turn on suspension limits that should stop the drive if we the rover drives onto anything bigger than a brick. That way, we have some chance of ending up with something scientifically interesting right in front of us.

But this choice has another side effect: it creates some uncertainty about the ending position of the drive, which now might end anywhere in the last 10m, where the suspension limits are active. And that means that the post-drive imaging of the crater can't be done by aiming relative to the rover (which is how it was originally sequenced); instead, it will have to be done using site-frame pointing. This will help ensure that we nail the center of the crater, but if we end up with a significant tilt, the whole panorama will be tilted as well, possibly cutting off the sides of the crater. If that happens, it'll be my fault. Oy.

After we're done with this crater, we've got big plans for the weekend. Friday, we're driving from Viking to its twin, Voyager, which we'll also want to image. Then we're driving on, on autonav. Somewhere in there, we're supposed to stop, image a crater, and drive on, all without ground intervention. Which means we need to get that drive just right; otherwise, we won't get images of that mid-drive crater. Or, as Matt puts it, "We'll miss a scientific opportunity." So, no pressure. Brian has a suggestion on what to name that crater if the attempt fails: Scott's Folly. Just how I wanted to be remembered!

It might happen that Scott's Folly will be Someone Else's Folly, though. After another couple of days, I'm going downstairs to work on Spirit for a while, to cover for John Wright's absence. I have a feeling that, very soon, I'm going to miss this parking lot.

[Next post: sol 443 (Opportunity sol 423), April 2.]

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