Thursday, August 25, 2011

A Week In the Life, bSols 2694-2696: Like A Big Camera Saw

If the Microscopic Imager (MI) was a saw, we'd have two Tisdale-2's.

If the amount of action in MER town were anything to go by, it seemed like it was a few weeks since my last tactical shift as TAP/SIE. It was more like 10 days — long enough to get me itching for some more. Lucky for me, I just came off a slew of 4 planning shifts in a row: Friday, Monday, Tuesday, Wednesday. They say you get a much better perspective as a tactical engineer when you do consecutive plans, and boy are they right.

My last shift was for sols 2683 and 2864, when we were planning a drive to get the first good shots of the inside of Odyssey crater. Since then, we've parked in the ejecta field from this small crater:

We imaged around a bit (notice Tim Parker's overlays of the rover images!), taking our foot off the pedal, and selected a few beautiful targets. The one of most importance? Tisdale 2:

With its flattened and gold-dipped top — suspiciously looking like an aircraft carrier deck — and its layered "breccia" appearance (ask a geologist, I'm just here for the lulz), the SOWG picked it as the target as the next victim of the IDD. The failed — errrrr, slightly off nominal — drives left us in the situation where the RPs needed to really do their homework. Indeed, Paolo and Kevin pulled off one hell of a drive on sol 2692. It was complete with a nice turn in place and a careful approach to get the center of the rover within about 1.2 meters of the edge of Tisdale 2:

(courtesy mhoward on UMSF!)

They nailed it. 

We walked in on Monday to plan Sol 2694 with a fresh sequence crew and a ready science team. Looking ahead, I saw two weeks of Nominal and one week of transitioning to Restricted planning via Slide planning sols. That means heads down, power through it, we've got some IDD'ing to do. The IDD work volume appeared right on our screens, constrained by the busted shoulder joint to be a straight plane. We'd be pushing the boundaries this week.

The idea of this week's IDD campaign on Tisdale-2 was to effectively make a run of MI, MB, and APXS measurements up and down that work plane, from top to bottom of the edge of the rock. Looking at multi-spectral and contrast-stretched images, we could see all sorts of interesting features. The SOWG teamed up with the RPs to plan a series of 4 targets, appropriately named "A/B/C/D," for the usual suite of IDD work:

1) Touch the target with the MB to get an accurate idea of where the surface is
2) Take some MIs
3) Rinse and repeat

On the last target, we drop the APXS and let it blast (lightly!) the surface with its radioactive Curium-244. Our Navcam PUL filled out a missing part of the surface and sky to the rover's left, filling out a nice mosaic for targeting in future sols:

On Tuesday, our downlink was a little thin — we could barely tell what had happened, only that we had successfully placed the APXS (meaning the whole MB/MI/APXS sequence executed nominally). Very few images had come down. Diagnosing, we found out we were just victims of bad luck with poor weather at the DSN station; looking into the future, we see more scant downlinks and few opportunities to make up the lag.

(Every sol, the LTP report contains a recommendation and a qualifier — "thisol's collection limit is 150 megabits, but it's a soft requirement" — that accounts for both the desire to collect new data, the downlink capability for that sol, and the long term picture of what our downlink schedule looks like. Every sol from 2964 through 2996, the LTP recommended the usual number — call it X — and we tended to more than double it. We understood the consequences. I always liken the collection of data and amount of stuff left over after each sol's downlink to eating and weight gain: Just as you'll see a few days' lag from over-eating and weight gain, you'll see a few days' [sols'] lag from data collection to flash volume left over.)

Sol 2695 was more of the same: Pick a few new spots, and do the MB-MI-APXS suite of measurements on each. These were a little more challenging: Ashley, verified RP ("IDD pilot") pointed out that one of the spots was extremely close to one of the other spots from sol 2694; there was concern about having too much soil on the lower spot of the rock to make the APXS useful; could we reach the top of Tisdale-2?; etc. In the end, we did another top-to-bottom approach to moving between targets. The slew of targets on the screen looked like a dartboard, especially when you layered in the targets from sol 2694:

Don't be fooled by the perspective: There's a little bit of yaw that you can't "feel" in this image, and remember that the wrist of the IDD has another degree of freedom, meaning that we can actually reach out of that constrained work plane by a limited amount. With this set of targets, you get the feeling that we're cutting this puppy in two, trying to figure it out, trying to tell a story. 

Already, the scientists are buzzing about the composition of Tisdale-2. What's unique about this is the tactical role of science on MER: with rovers, many of your decision points are determined by the science you collect. Say the APXS comes down — boom bam, quick analysis, yeah it looks good, we can move on — suddenly you've got a wealth of power at your hands. You can stop and breathe if you need to. With orbiters, you've usually got only one shot to get the geometry right, and you won't be coming back any time soon. Moreover, the science you collect certainly doesn't feed into decisions made tomorrow. Or even next week. Takes a little bit longer. With rovers, you get a closed loop feedback cycle from your science team. Like this:

Reader, Tisdale-2. Tisdale-2, reader.

Then came sol 2696 ("Where did the week go?" asked Mission Manager Scott) — more of the same. A few new targets, a few more MIs. Same deal. Only… these were complicated. In the pilot seat for the RPs were the illustrious Scott, Vandi, and Julie. The targets that the SOWG wanted were very difficult to maneuver to. There were a few "wrist flips," IDD joint moves, and off-plane target goals. When queried for a time when they'd be ready for APAM, the RPs paused: "… 1pm."

Ok, cool, perhaps we're in it for the long haul. Our uplink was a little earlier that night than we wanted, but it was manageable. But I looked at my schedule from Monday and Tuesday (planning sols 2694 2965, respectively) and noticed a slip every day in the APAM time: almost an hour later every day. Historically, APAM tends to be a good measure of the length of the planning day, if we ignore those pesky anomalies when we're there until 8pm. When I peek back at my schedule over the last year, a 1pm APAM tends to mean a long day. 

Then again, there was a distinguishing quality of those longer planning days: They were caused by curveballs in the planning process. A script breaks here, an integration goes awry there, someone spills coffee on the keyboard. On this occasion, sol 2696, the lateness of APAM was mandated, controlled, intended. This bodes well because it is an act of foresight, and intuitive measure of how crappy things might get. We reap all sorts of benefits from this (though not always), the biggest two of which, I think, are:

1) Extra intended time means extra preparedness for the next walkthrough.
1) Everybody has the mindset that we're up to our neck in this sequence, and we better bring our A-game.

When a delay is unintended, we are off the balls of our feet, off axis, expecting the worse, freaking out a little. Attitudes towards computers grow increasing hostile. But when we mean for something to be late, we're on the ball.

I wrote that thought down around 10:30am that morning, not thinking I'd be so clairvoyant: Indeed, APAM was a quick 15 minutes; the next walkthrough was a mere 20 minutes; and we had the sequence ready for delivery before yesterday's plan. Being prepared actually bought time back. Everybody was on the same page at every meeting. Snip snap done. Like that.


Oh! Right! This week's albums of the day:

Sol 2695: Surfin' USA — The Beach Boys**

*Actually, this is from a different album. Meh.
**This was Brenda's request. I only abided because she's nice to me and she was shadowing me on TAP/SIE duty on Tuesday. I hate the Beach Boys. No video for you.

1 comment:

JoeRanch said...

Keep 'em coming. You owe us a Juno Mission tutorial also. Thanks.