The Curiosity mission's final pre-landing press briefing wrapped up a short while ago. There wasn't much in the way of news, which is a good thing. Curiosity is healthy. Odyssey is healthy. There's not much left to do but wait.
The navigation has been so well-targeted that they've waved off the last two opportunities to adjust Curiosity's trajectory. A team member explained to me yesterday that with one of those it would have been possible to nudge Curiosity's position slightly closer to the center of the 3-by-12-kilometer box they're targeting at the top of the atmosphere. So why didn't they do that?
It's because with the amount of tracking they've done of the spacecraft on its current trajectory, they know its target position very, very precisely. If they were to fire the thrusters, they might get closer to the center of the target, but they'd significantly reduce the precision of their knowledge of its position. Because of Curiosity's guided-entry capability, they can "fly out" up to 10 kilometers of target error. They are significantly closer to the target than that (I'd guess 2 kilometers from eyeballing yesterday's chart). Thus, counterintuitively, they will be able to aim more precisely by accepting their current very slightly off-target (but still within the allowed range) trajectory.
There was an interesting discussion today about the gender of Curiosity. Some refer to the machine as "it," some as "she." I'm inconsistent. I call Spirit and Opportunity "she" but it doesn't seem natural for Curiosity yet. I think it's because we haven't seen the rover operating on the surface yet, don't know it to have a personality yet. Soon after landing, both Mars Exploration Rovers had definite personalities. Spirit was the difficult one, the one who had to struggle hard for everything she earned, the one who suffered setbacks yet kept pushing and pushing until she could push no more. Opportunity has been the lucky one, the one for whom the scientific payoff came almost instantly, the one who could drive and drive for miles and miles with her eyes closed, and never (well, almost never, we shouldn't forget Purgatory) cause any trouble.
For Curiosity, I keep coming back to something one of the engineers (whose name I wish I had written down) said to me when I asked him whether he referred to the rover as an "it" or a "she." He said the behavior was mixed, and that for him it was still an it because it was still inanimate. He looked at Curiosity and said, "It doesn't have a soul yet, but it will." When Curiosity is ensouled by a successful landing on Mars, then it will acquire personality, and rover huggers like me will switch over to referring to the thing with a gendered pronoun.
If, of course, tonight's landing is successful. I was exasperated by some of the media questions at today's briefing. They kept pushing at how we would get confirmation of a successful landing. The details are important, I know, for news reporting; but the plain truth is that we will know instantly about confirmation of a successful landing from the jubilation of the people in the "dark room," mission control. This wonderful panorama shows who they are and where they will be sitting.
I'm spending the day at home, a normal weekend day with my kids, and plan to show up at JPL at around 6:00 p.m., which is still 4.5 hours before landing. I'll probably file one more blog entry before landing, and may do a Google+ Hangout. After landing, well, it's hard to plan, not knowing what's going to happen.
As the hours tick down, I have to admit that my confidence is flagging a bit. Not for any specific or rational reason; I think I'm just terrified of the aftermath of a landing failure. I believe it can work; I'm hopeful that it will work; I'm fearful of the possibilities. It doesn't matter, though. The die is cast. It's entirely out of human control now. Que será, será.