Opportunity Sol 517 (Spirit Sol 538)

I've got my clock/radio tuned to the news station, so I'm literally awakened by the news that my favorite city in the world, London, was viciously attacked by barbarous cowards today. Bombs on the subway, and on one of those iconic red double-decker buses. Dozens of people are known dead, hundreds more probably dead. Maybe a thousand injured. Nobody really knows just how bad it is yet, but it's bad.

Not for the first time, I think to myself that I'm making a mistake. As much as I love it, I should leave Mars and go work in counter-terrorism in some capacity. I have a moral responsibility to act. I can't solve it all myself, but I should do my tiny little part rather than fuck around with an interplanetary Erector Set.

I usually tell myself that my job actually is important, that people need something to live for and we're part of providing that. But on a day like today, that justification -- I should call it a rationalization -- sounds awfully damn hollow.

I don't know what to do. I love you, London. I go to work.

Our drive onto the on-ramp, sol before yestersol, went fine. Yesterday Cooper and Jeff took us to the other end of the on-ramp; today we drive onto the freeway -- or East Path, or the Blue Line, as I've started calling it (from the blue lines in Rob Sullivan's images, designating the path we eventually chose).

Today's plan is to make about 15m total distance, about 10m of which will actually be along the Blue Line. Over the weekend, we might do some IDD work on the magnets or the solar panels -- or we might just do one drive followed by light remote sensing, to let us clear flash a bit.

Flash is a big worry, because our downlinks haven't been that great. Thisol we're looking at a meager 46 Mbits, for example. And since the drive and associated post-drive imaging consume about 35 Mbits of that -- maybe more -- there's not a lot for the science team to squabble over. The plan that comes out of the SOWG is heavy on the drive, light on science. And that's even after we help out by cutting back the motor/IMU data-collection rate from 8 Hz to to 4 Hz, nice fellas that we are.

While Khaled works on the drive, I scramble around, looking into a number of issues we need to resolve for thisol's plan. First priority is to meet with the Spirit rover planners to understand why they considered the limit-cycle check (which stops drives if the vehicle detects excessive slip) a hair-trigger check on their drives. I had formed the impression that the limit-cycle check wasn't very reliable, but it turns out I was wrong; it's reliable, they just didn't want to use it to detect slip much under 100%. This is good news; it means we can use it on Opportunity to detect slip in the neighborhood of 30%, which is all we're allowed.[1]

Next thing is to look into the suspension and tilt limits. I graph the data for the last several drives to try to understand how we're articulating when driving in this terrain. The idea is to set limits that are a bit higher than we expect, and it turns out that we're already setting them pretty close to the right numbers.

Finally, I have to scare up a Mobility/IDD person to do some longer-term analysis. I've generally been wanting them to do more of this. We ought to know more about how the vehicle has been performing -- how close IDD placements have been to predictions, how well visual odometry has been performing, and so on. During the nominal mission, those guys spent a lot of time at such tasks as these, but not any more. So I figure I should set them tasks as they occur to me; there's plenty they could be doing, but they don't always know what we want. But it turns out that the Mobility/IDD guy on shift today is Marcel -- who's from London, and has family there. I let it go.

Khaled and I spend some time working on the drive together, and then he works out the tricky visodom pointing with Mark while I take care of a visitor -- another friend of Susan Kurtik's, someone's foster child or something.[2] Like most kids, she gets into playing around with the rover, zooming the camera around and dragging it all over the terrain.

It's been a hectic day, and it doesn't stop at the CAM. Turns out they messed up an ODY comm window request or something, and instead of the meager 46 Mbits we thought we were getting, we're going to have only 27 Mbits. Oops. That's not even enough for the critical drive data. People start scrambling, and luckily there's an ODY ACE on console who's able to command the spacecraft to accept more data. So we're back up to 46. Lucky us.

A hundred million miles away, a long way from all this pain and death and worry, a plucky little robot trundles slowly toward its next destination. And so it goes.

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Footnotes:

[1] Briefly put, the limit-cycle check periodically looks to see how far the rover has actually progressed versus the distance commanded. When you're driving with visodom, this is an easy-to-sequence slip check -- though expensive because visodom driving itself is expensive. Later, as our paranoia levels subsided slightly, we switched to a much less expensive slip-check technique.

[2] Susan Kurtik, as you'll recall, is the woman who hired me at JPL in the first place, recruiting me from the University of Illinois at Urbana-Champaign. Whatever Susan asks me for, Susan gets.