Opportunity Sol 326 (Spirit Sol 347)

"Nice job!" Ray says as I walk into the SOWG meeting. It looks like our drive went just about perfectly, though some of the post-drive imaging missed its target. (Naturally, I initially suspect that this is somehow my fault. Instead, it turns out to be simply a result of poor range data from our pre-drive position -- our targets were on the hairy edge of the NAVCAMs' capabilities, and we got unlucky.)

Supposedly, the weekend is already planned out -- we did it yesterday. But, as is so often the case, it's not that simple. I initially see something in one of the PANCAM images -- a spring that dropped off the heat shield -- that makes me nervous because I can't see it where it should be in the NAVCAMs, and I'm worried we'll drive over it or some other piece of debris we can't see. (We'd probably be okay anyway, but artificial objects don't always behave like rocks; it's possible for us to get a spring wound around our axle where a comparably sized rock would be no hazard at all.) So I ask for some more drive-supporting imaging in the plan, and waste some time trying to figure out where the hell the spring is. Then I figure out it's not even close to where I thought it was; I was thrown off by the mis-pointed PANCAM images. It's nowhere close to the rover. Once I realize that, it's a simple matter to work out that we already have all the imaging we need, and we don't need to change the plan at all.

While I'm doing that, Justin Maki and Jim Bell are having an unusually, and increasingly, acrimonious argument on the telecon. Jim really wants to spend part of the weekend taking sky images to help calibrate the PANCAM (his instrument). Justin thinks this is a bad idea; as valuable as the calibration images would be, now's not the time to take them, he says. (As Justin puts it: "We're at the heat shield right now. The sky will still be there next week.") The discussion reaches such a pitch of bitterness that Ray must step in to resolve it. (Justin wins, but Jim doesn't give up. "This is your call, Ray," he says, "but I disagree with it.")

Frank mostly built thisol's sequences yesterday, making today a light day. I have time to entertain a couple of guests Art brings through, and to show off RSVP's 3-D image browser to Jay Torres. Jay's one of the TAP/SIEs -- he works with the scientists to create the detailed plan for the sol, then does most of the hard work involved in integrating the sequences and preparing them for the spacecraft. Since he's expressed an interest, I load up some of the coolest 3-D images of Wopmay and hand him a pair of the LCD shutter goggles to view them.

He looks through the goggles, and his jaw drops. "Woah, you have a cool job," he says. "Our job sucks."

"No, your job is cool," I reassure him. "You're miscalibrated. Most people, like, sell insurance and stuff.[1] They would kill to do what you do. Your job is cool!"

He laughs. "Well, okay," he says, "but your job is cooler."

No argument. This is something I've been thinking about lately: JPL is already one of the greatest places in the world to work, and even other JPLers envy me. Is it shallow or selfish of me to absolutely love this?

So be it.

Though the day's a generally simple one, I do spot a potential problem at the CAM, the very last review of the day. The first IDD sequence ends with a tricky maneuver that places the MB on the capture magnet; the second sequence retracts the MB to start some other work. Since it expects the IDD to be in contact with the rover, the second sequence temporarily turns off the IDD flight software's normal self-collision detection, which is what keeps the IDD from whacking into the rover body. The thought that occurs to me at the CAM is, What if the first sequence doesn't make it up to the spacecraft? Then the second sequence will start off stowed, and we'll turn off collision detection and tell the arm to move .... That could be bad, very bad.

Fortunately, we have a sort of stock workaround for this type of problem, so the solution is well understood and we just have to take a few minutes to implement it. "Good catch, Scott," Frank says. "And I'm glad I was here for the last time the rover drivers derail the CAM in 2004."[2]

So we finish, and then we head downstairs to check out a happy rumor: we've heard Spirit is depotatoized! It's a rumor Chris and Ashitey are glad to confirm. Indeed, the news is even better than we'd thought: Art told us they weren't sure where the rock had gone, so it could still be in a part of the wheel we can't see. But Chris and Ashitey found that they could indeed see a sliver of it in one of the images, and it is definitely ejected.

We have a new rule to live by: when driving in this type of terrain (loose sand, steep slopes, and rocks), don't try to overcommand the drive -- that is, don't tell the rover to drive much farther than it really needs to go as a way of accounting for large amounts of slip. When you do, you make it more likely the rover will sink in and pick up a rock like this one -- that was the essence of how we got into this problem. Better to turn a one-day drive into a two-day drive, than turn it into a week-long nightmare. When climbing the rest of this hill, it's slow and steady for Spirit.

But for now, all's well. Spirit is potato-free, all six wheels once again in working order, and ready to resume its uphill charge. Opportunity is performing historic work, imaging its own heat shield on Mars. The team couldn't be happier, and neither could I.

So, from Mars to Earth, Merry Christmas. And Happy Festivus, for the rest of us.

[Next post: sol 352 (Opportunity sol 331), December 29.]


[1] No offense.

[2] The year wasn't over yet. In retrospect, that seems unusually optimistic for Frank. ;-)

No comments: