Spirit Sol 698

I love this rover. I really, really do.

I'm up at 05:45, and the first thing I do is log in and check the data from home. No images. That's just a touch worrisome. Maybe it's another OSS crash? But I see no evidence of that.

Hmmm ... I keep poking, and find that we did get some data -- so Spirit's alive -- but I find nothing to show that we've moved at all. It's as if the drive sequence never executed.

I shake it off, take a shower, and get to work as fast as I can. By the time I get there, the processing glitch -- if that's what it was -- has been resolved. We've got at least some drive data, and, most crucially, the post-drive images.

They show Comanche Spur dead in the middle of the IDD work volume. It's beautiful. We couldn't have gotten it more perfect. Or let me say, she couldn't have gotten it more perfect. All credit to our awesome rover.[1]

Visodom failed to converge at the end, and as a result, we didn't do our normal wheel wiggle, which we normally strive to do in order to settle the rover before deploying the IDD. When we look carefully at the images, though, we're able to convince ourselves that all wheels are in a stable configuration. This, coupled with past data and recent testbed work that has helped demonstrate that this rover design is highly stable when deploying the IDD even on apparently unstable surfaces, makes us willing to proceed.

What we proceed with is our pretty much standard IDD campaign -- MI, RAT-brush, MI, MB. Depending on the MB results we see tomorrow, we might stay here an extra sol, or cut things short and light out for our next destination, a large dark blob nicknamed "El Dorado."

Chris is RP-1 thisol, back on the rover after a FSW-induced absence of a couple of weeks, and he hasn't lost his touch. He cranks out the IDD sequence, I patch up a couple of minor errors, and the day's over before you can say "Jack Robinson."

Well, maybe not that fast. But pretty fast.

Courtesy NASA/JPL-Caltech. Comanche Spur, dead in our final front HAZCAM. I am more proud of this image than of almost any other in our nearly seven years on the surface.


[1] I am unable to express just how proud I am of this drive to this very day. It was an amazing piece of work under extraordinary circumstances; if not my very best ever, it has to be damn close. Also, trying it was plain crazy, and hot damn, did it ever go perfectly. Big. Fat. Win.


Anonymous said...

Was there any reason that the wheel-wiggle was not commanded to execute unconditionally?

Scott Maxwell said...

Because visodom failed to converge, the drive ended with an error flag set. That error flag generally keeps other mobility commands from executing. For example, if we do nothing special, it will keep the command that straightens the wheels from executing.

At the end of the sequence, there's a set of commands that says -- or means to say -- "temporarily ignore that error flag just long enough to straighten the wheels." Those commands almost always worked. But in a couple of unusual cases -- one of them being too many visodom failures -- a peculiarity of the flight software means that we effectively won't ignore the error flag after all, even if we say to.

There's a way to work around that peculiarity in the flight software, and these days we do, but back then we weren't really aware of it, and we didn't.