Again, the weekend is not terribly complex for the RPs. Sunday, we do a little IDD work, mainly a short MI series intended to establish whether we can speed up the MI imaging sequences. Since the start of the mission, we've had to wait 15 seconds before taking an MI image, since that's how long the IDD is permitted to take to dampen its vibration after moving. This doesn't sound like much, but it adds up on sols with multiple MI series. Opportunity has experimented with waits as short as five seconds, with good results, so we'll try that ourselves on Sunday. After that we stow and go, attempting to retry the drive to Uchben that was interrupted by the latest appearance of the dynamic brake anomaly.
Speaking of which ... I manage to make it to part of the daily meeting on the anomaly investigation. Things are looking better and worse. Some problems that would definitely be unfixable from the ground, such as loose wires and failing solder joints, have been ruled out as the cause. It's good to know those aren't the problem, but we still don't know what the problem is. The leading candidates that come out at the meeting:
- The relay contact is sticking when closed.
- The relay contact is "dirty open" (that is, mostly open but with enough physical contact to appear electrically closed).
- The relay is jammed. (It's not clear to me how this differs from the preceding cases -- I think they mean physically jammed, which would differ from merely slow or dirty.)
- The electronics that sense the relay's state are faulty in some way.
Some of these could be worked around from the ground, for instance by telling the flight software to give the relay a little more time to open. Some can't. Guess what I'm hoping for.
Leo's been heading the anomaly investigation, and I think he's getting tired of it. He wants to decide by this time next week whether to just blow the fuse and live without the dynamic brakes for the rest of the mission.
I hope it doesn't come to that, as it'll likely be annoying to try to deal with wobbly, unreliable steering on top of the other challenges. But if it comes to that, we'll deal with it.
At one point during the day I overhear Andy discussing the changing character of the mission. "The first 90 sols were a sprint," he says. "Now it's turning into a marathon. And you can't do those two kinds of missions the same way."
As usual, it looks to me like he's right. I think there are a lot of people on the team who could use a break. Leo's one of them. Emily Eelkema is another. The TUL position is one of the most stressful, and thanks to a TUL shortage, she's been the TUL every day for the last couple of weeks. Plus, she's on call this weekend and is working part of next week.
I don't know how they'd have made it through the day if I hadn't brought donuts.
[Next post: sol 283 (Opportunity sol 262), October 19.]