Mars and Me: Spirit Sol 693

We made a respectable 25m of progress -- good, but not great. The visodom and blind segments went fine, but autonav failed shortly afterward, after finding no safe path. Oddly, we're not sure why autonav didn't want to proceed; what we can see in the images looks good.

Anyway, we're slowly but surely gaining on Comanche. We've still got about 35m to the ridge, and we've got a good chance of getting there and beyond because they've scared up over three hours of drive time today.

The path from here will be an odd one. After a bit of maneuvering to get onto the mesh, we've got to make our way through a trio of rocks arranged as the vertices of a roughly equilateral triangle, whose closest side lies transverse to our path about 10m from here. Our plan is to drive between the rocks to the center of the triangle, then jog left to dodge the rock at its apex before getting back on course and heading to the ridge.

About 10m after that -- still before we get to the ridge -- there's enough undulation in the terrain that our mesh starts to drop out. So we'll switch on autonav for the remaining 12m to the ridge, then turn and head to Comanche.

We're still worried about that ridge, though. I think there's a better-than-even chance that the far side will be too steep or too rocky for autonav to make any progress, in which case I'll feel guilty tomorrow about blowing a lot of drive time. But there's not too much I can do about that and still keep the rover safe.

One other modification we make to our usual Spirit-driving practices is to make the slip check more paranoid. Before starting autonav, and periodically during autonav drives, we've been having Spirit perform slip checks, looking to see whether she's slipping too much and stopping the drive early if so. Normally, if visodom fails to converge -- that is, if the slip-check calculations don't work, so we don't know what our slip is -- we let her drive on anyway. After all, that's a fairly unusual case, and even if that slip check fails, there will be another one shortly.

But in this case, we're just nervous about that. Once she gets over that ridge, she could be in really bad territory, and if she can't prove she's safe to go on, we want her to stop. So we tell her to do that. Will it cut our day short? We'll find out tomorrow ... same Mars time, same Mars channel.