Thursday, November 17, 2011

A Day In the Life, bSols 2778-2779: Oh how we loves the tilty goodness

In the shadow of MSL's launch, Opportunity has been trekking north as fast as the gods of solar power allow.

Well, you know, except for the week-long detour for one hell of a science target.

To put the last two weeks' worth of activities into context, it's necessary to recall an abbreviated version of the trek northward since departing Chester Lake:

1) "This way to Shoemaker Ridge A and Shoemaker Ridge B" 
The trek northward began after the intense IDD MI+APXS+MB campaign at Chester Lake in the Odyssey crater ejecta field, along the south end of Cape York. During the Chester Lake campaign, the engineering team began formulating plans for the winter; local solstice for Opportunity is on 03/31/12 Earth time. The science team agreed to begin driving northward as often as we could in order to effectively image-map the purported north-facing slopes on the north end of Cape York.

The primary reason for the trek north was, of course, to find those slopes that give us good sun angles for good power. All estimates point to Opportunity surviving the winter with plenty of margin. However, margin can easily be eaten away by the unknown unknowns. With that in mind, we tried to reason how quickly we'd need to find a parking spot. January seemed a good last-minute date to aim for, if push came to shove. With that date in mind, we considered one other major factor: The launch of the Mars Science Laboratory on November 25.

The view periods of the MSL spacecraft after launch happen to interfere with all other Mars missions. Immediate post-launch priority for DSN coverage of a spacecraft is very high; Opportunity, being much older and of a much lower status for requesting DSN time, gets the short end of the stick along with everyone else. This means that we may very well lose the time we've already scheduled with the DSN. Some more strategic analysis showed that if we did not finish mapping Cape York's northerly slopes by the time MSL launched, December and January would not provide us enough time to do that mapping because the incoming solar power would be too low.

We had made it clear: Thanksgiving or bust.

2) "Notional" hunt for veins begins

So-called "veins" are cross-cutting, exposed rocks resembling blood veins in shape. While we trekked north, the strategic path was revised to take Opportunity along the western "apron" exposed outcrop that defines Cape York while going north. The science team deemed it unlikely that we'd hit anything geologically interesting along the way, but the whole team agreed that it was worth a shot to look for veins while we're going north anyways. We began "banking meters" very quickly — meaning, we had gotten into that "haul butt across the Meridiani" mindset from the pre-Endeavour (pre-Cape York) days  and this bought us margin. We're good at making Opportunity drive. Very good.

3) First close approach to Cape York "apron" reveals "Homestake"

Once we hit the apron, we found a goodie: a rich, exposed vein, about 1cm in diameter width**:

When the science team starting thinking of names for this goodie, Squyres popped his head in: "Make it a good one, guys." They chose well — "Homestake."

Immediately, the science team got very excited. Immediately, the acronyms "MI" and "APXS" found their way into the SOWG meetings every morning. Of course, the question was not whether or not we could take a detour, but for how long we could hang out. The MSL launch date was looming. The engineering team accepted the risk after several long, fruitful, and constructive conversations.*

Then, another caveat: We needed APXS data on some surrounding material in order to know the context of Homestake. So add another three sols, boys and girls: Here's deadwood.

The problem was that we weren't satisfied with the "bump" drive from Homestake to Deadwood — a drive on the sub-meter scale, by the way. Accounting for the re-bump and IDD activities, we had eaten away all the margin we built along the way to Homestake. Things got tight.

4/5) Onward to winter haven image mapping

We did a quick dog-leg around a funny-looking dune, with some quick imaging of purported northerly slopes at the #5 label.

6/7) Some candidates for good slopes

On sols 2778 and 2779 (executing now), we drove towards label #7. Our imaging on the ground correlated well with the orbital observations of MRO's HiRISE camera. We see northerly slopes in excess of 15 degrees, and we see them in several spots. We have imaged "Turkey Haven" and "Winter Haven" and plan on doing a little more exploring. For now, here's our latest Navcam 6x1 aimed right at our feet looking south: 

What's next? More image mapping, more strategic planning. We still have some trekking to do to find all the best slopes, and to see what slopes also have good science targets. We've got plans. Oh, do we have plans. If we find a good slope with a good target, you can bet your bottom dollar that we'll place that MB on it and get a nice, fat, multi-week integration. I expect activity to dwindle down throughout December, with January-April being "hunker down" months with occasional science activities.

Might give me time to breathe.


*This is something, by the way, that is unique to rovers. The time scale over which these conversations were had is astounding: literal days. The Homestake  finding was a surprise to most everyone and it had just about the worst timing imaginable. Everyone wanted to know what Homestake is and not have to come back to it next Martin spring — late next summer for us on Earth. (Ahem, those in the northern hemisphere.) We made several well-informed, hard-fought, sweeping tactical decisions without even blinking. It's like we've done this before or something. Even though science leaned towards staying at Homestake longer and engineering leaned towards getting the hell out of there, the push-pull between the two teams worked to our advantage. The result: good science in good time.

**Ahem. :p


Anonymous said...

Another excellent entry. You're living the dream, Matt, and thanks for sharing it with us.

Judge said...

Good stuff. I bookmarked it to come back to later.

Keep up the good work.

Wretch Fossil said...

Rock guys, here are real blood vessel veins: