Opportunity Sol 356 (Spirit Sol 376)

It's Leo's last sol on MER; after today, he moves on to MSL. He picked a heck of a sol for his last: we're in on a Saturday, for one thing; for another, we're planning three sols today.

So we've got a lot of work to do, but we can't get started on it. The auto-generated terrain meshes are useless; they used the horizon mask, which clips off any features above a certain height. Normally, this is a sensible thing to do, which is why it's the default for the automated process -- the stereo correlation will occasionally be confused by some distant feature and try to place it in the mesh near the rover and a meter or so off the ground, and usually we just clip that junk out.

But in this case, the heat shield shoulder piece projects above the limit. Naturally, the horizon mask clips it off just below the area we're interested in. I came in last night to pick a few spots in the imagery that are possible candidates for our MI survey, but we can't do the real work until the meshes come along.

So right off the bat, we're delayed by an hour. If I believed in omens, I'd call this a bad one.

Not only is it Leo's last sol, it's also Ray Arvidson's birthday. And Jim Erickson's.

At least we've got some free time to celebrate ....

But when the meshes show up, I'm able to get to work. We had an aggressive plan for MIing a long strip, but the three-dimensional view shows that this will be impossible: we want to avoid touching the material, and we're constrained by a fluffy piece on the left and a jagged finger on the right. The entire reachable range is maybe 5cm, much less than we'd planned for. What's more, the surface we're trying to MI is barely visible from our current position: the HAZCAMs almost can't see it, since it lies mostly along their line of sight, and in the NAVCAM we took to compensate for that (since we knew it might happen), the strip they want to image is obscured by the upthrust fluffy piece.

One way to respond to this situation is to take more images, closer together. This helps compensate for the uncertainty we're facing, and the total number of images (and corresponding downlink volume) will still be less than we'd planned for when we thought we could get a large range.

To add to the pressure, everyone really wants these MIs to turn out well. Once we get them, we're done at the heat shield and can move on to the etched terrain. We've been at the heat shield about a month, and except for our SpongeBob observations, it's been a purely engineering-oriented endeavor -- no real science at all. So the scientists are champing at the bit to move on, and the management team wants to cut loose as well.

Luckily for us, we have an ace up our sleeve. An ace named Eric Baumgartner -- Andy asked him to come in today (on a Saturday!) and help out as needed. Eric suggests a different direction for the stacks, one that might track the surface of the strip better, but ends up mostly doing analysis. Which is just as good as far as I'm concerned: if Eric says the sequence is okay, you can bet your house on it. And he says it's okay.

When I'm done, I spend some time looking over the sequence. It's about a hundred commands or so, only moderately complex by IDD-sequence standards. I find myself thinking that for all the trouble I had building the damn thing, it ought to be longer.

Meanwhile, Cooper's been working on the drive. We're going to wait until we see the MI results, and if they look good, we'll uplink the drive sequence and be gone as of sol 358. Otherwise, Cooper's just wasting his time -- yet another reason I really want to get my part right.[1]

Despite a mishap that requires Cooper to rewrite the entire drive sequence, and despite all the time I take, we're not the ones holding up the process thisol. For some reason, it's just one of those days on Mars -- both Spirit and Opportunity have a series of random ground software problems that delay the process, seemingly endlessly, and they're still holding things up when I have to leave for an radio interview.

Lucky me; since Cooper's staying, I can leave. Leo's not so lucky -- he's got nobody to backstop him, and he'd promised his wife he'd leave by 6:30 so she could take him out to dinner.

"How much do divorces cost these days?" he sighs.[2]

[Next post: sol 378 (Opportunity sol 358), January 25.]

[1] This overstates the case a little: Cooper's drive sequence could have simply been used on a later sol. It still would have meant he was spending his Saturday doing work that could have been done on a normal weekday, but it wouldn't have been altogether wasted.

[2] Comfortably into six figures. Don't ask me how I know.


Anonymous said...

I've been following the progress of Spirit's extrication and was wondering if the simulations using the test-bed rover produced wheelies (middle wheels lifting when traveling forward for example) to the same degree as Spirit has been on Mars.

Scott Maxwell said...

@Anonymous Going by memory (unwise in my case), I don't recall popping wheelies in the testbed. That's not terribly surprising: we knew there were differences between the soil simulant and the real stuff, both because of the limited time we had to create the simulant and because of our limited knowledge about the real stuff (particularly at the early stage when we were designing the simulant).

What was unusual was that, in the testbed, we could reliably pop a wheelie on the right front wheel -- something we have never observed on Mars, or (again, to my recollection) in the testbed. That was kinda weird.