Friday, December 16, 2011

100 Sols on Cape York — An Absurdly Brief (Read: Long) Summary (Part 3/8)

Part 3: The Odyssey Crater Ejecta Field — Zinc at Tisdale-2

~2690 to 2703
"tl;dr" Description
We found this thing that looked like a gold-plated aircraft carrier. So we looked at it… really, really closely.
Highlights from Matt's Notebook
Sols 2692-2693: 
> Some… ahem… involved… discussion at sequence walkthrough, but all is well. VisOdom for the win.
Sol 2694: 
> Today's Secret Woid — "bogy" — and I just checked behind me to see if the computer was about to murder me.
Sol 2695:
> Ecam PUL: "Is that what you said? I thought I heard something else…" // RP1: "You did, but we don't hear those voices."
Sols 2703-2705:
> Planning an escape from the clutches of Tisdale-2 tosol! We'll be back.

Details ("the deets")
I didn't have another shift for some 2 weeks after the first arrival at Endeavour and Cape York. I was in the loop only because I like to walk up three flights of stairs from my office to catch the SOWG meetings. 

Suddenly we had driven to straight into the Odyssey ejecta field and I didn't know left from right. Good thing I'm not an RP. There was all this hoopla about these "Tisdales" and this "Ridout" and, for that matter, why there hadn't been a TAP/SIE Album of the Day in so long.* Tisdale-2 was right in front of us and it was to be our first Endeavour victim.

The challenge presented by Tisdale-2 was twofold:

1) From a few meters back, pick out targets on a very rough rock with interesting features from Pancam imagery, interesting features that were not unambiguously smooth for all the touchy-feely that we'd be doing to it. (With the IDD! With the IDD! Come on!).
2) Actually IDD the damned thing.

One could say that we could have pulled right up to it and taken the close-up Pancams to get ourselves some nicer ideas of good targets, then "bumped" or simply turned to our selected target. Two sols, snip snap done. Right? Nope. One would also be pulling a classic "jumping the proverbial gun" in this case, because that plan would, well, take two sols. We like to take a little bit longer looking at our options in the morning when the downlink rolls in and then nail that drive in one sol. We are a success-oriented team, in more ways than one. Only rarely do we try to get part of the way there and correct thereafter; only rarely do we try to get part of an image or part of an APXS. We only do that when we have to, like when we're restricted by available time in the Martian day**.

The lesson: trust that rover. (Also, the RPs. But, you know, they smell like robots***, so…)

While we planned the approach and ramifications thereabout, the scientists planned their targets. The strategy of an approach drive is, by the way, relatively independent of the final target, since that final target just becomes a parameter somewhere that we change with the click of a mouse. We can get a detailed engineering backbone prepped for when the science team finally comes along and says, "Here, please." For this approach, a VisOdom hiccup (well — feature) gave them an extra day to look and decide. Tack on some tough love for good measure and they decided on two targets for more thorough discussion:

Fake color, by the way. Rookies. I got you good, didn't I?

Clearly, neither was smooth enough to be brushed. Not even the top of the entire rock, with a coating of a composition that we still don't know because we never sniffed at it before moving on, was even close to acceptable. The Rock Abrasion Tool (RAT) is a consumable resource — brushes and grinders and stuff wear out. No point in wasting it here. No worries, because we still had the Microscopic Imager (MI) and APXS (… scatterometer-science-gathering-thingy-mabob) to go at it.

Of course, there's a critical show-stopper for Oppy's arm: A bad shoulder joint has it canted to the left at a few degrees. Also, we don't allow IDD and drive activities to occur without ground in the loop in between them (except for things like the "stow and go"). Combine these two pieces of information and you get the result that if we've approached a target for an IDD campaign, and if we want to choose a new target that's at a different rover-relative azimuth (rotation clockwise or counter-clockwise looking down), it takes two sols — a "bump" or small turn and then the actual IDD work — rather than the single sol to just move the shoulder joint if it actually worked.

Keeping this in mind, the science team chose Target A for surgery. We got an initial taste with the MI and APXS by working in the so-called "workplane" of the IDD, a literal 2-dimensional plane created by the stuck shoulder joint. We took that initial taste, turned it on its head, said it wasn't enough, and did it several more times. Since Tisdale-2 was so rough and rocky on its side, things stuck out. We could reach a few target points with the gunsights of the MI and APXS with a slight roll out of the workplane (roll, pitch, and yaw are independent, children!). All told, we captured a nice chunk of data, a veritable dart board for the ages:

(with MI's overlaid on the second image):

Significant tasty herein.

After less than two Mars weeks, the results from the AXPS were in. At least, in and prepared for a news conference, since we knew everything the day after the data was collected (plus or minus a good downlink with Odyssey and MRO — space only plays nice sometimes!):

Real, actual science.

This tells us that there is an unusually high zinc content in Tisdale-2 compared to the other rocks examined by both Opportunity and Spirit. Not only unusually high, but drastically high — that's a logarithmic y-axis. The one-sentence explanation of this big adult word is that if the change is big on a logarithmic axis, it's huge on a linear axis. Which means stuff. And, remember, stuff means science.

Without much of a fuss, the RPs took the keys and candy-cane'd us out of there:

Next up: Sniffing down a RAT-able target — and finding one that smelled kinda funny.


*Actually, nobody cared, which, you know — expected. One of them was a doozy: Wish You Were Here by Pink Floyd. By the way, Newton's 4th Law: You can't turn "Wish You Were Here" down. Universal implosion, black holes of death-inducing doom, trolls who steal your coffee. The usual.

**Example: Last week we couldn't put together a full 2x2x5 MI stack of Boesmanskop at Winter Haven because of lack of time in the day; we got bottlenecked by a few standard engineering things. So, instead, we planned two 2x1x5 stacks.

***Like solder, incidentally. But the good kind, like whatever the kind is that talks, eats, drinks, drives rovers, and makes me smile. I guess this means that I would accept Cylons into our world.

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