Part 4: "… and then we have a RAT hole" — Chester Lake Gets It
Hey! I'm back! Spent a few weeks back in Colorado for the holidays and am now back in the groove. Time to continue where I left off: Chester Lake. At the time of writing, we're almost 100 sols beyond this part of the story — and 150 since we hit Cape York.
Must… finish… this… story…
2709 to 2735
We pounced on a flat outcrop and hung out — for a while. We even Mossbauer'd!
Highlights from Matt's Notebook
> Today's Secret Woids: Fran / animosity / Bobbie. I fear for their relationship because of the animosity between them. (*rimshot*)
> Squyres: "We've been preserving the RAT for this. It would be foolish to leave."
> How many RPs does it take to change a light bulb?
Details ("the deets")
I didn't have a lot of tactical shifts between leaving Tisdale-2 and our next target. For about a week, I had this notion that the rover was faced one direction and the Chester Lake was at some spot on Cape York, only to find out that I was about 90 degrees and 20 meters, respectively, off. I blamed my busted ankle, which, in retrospect, seems a pretty fair judgement (as far as unfair judgements go).
After giving Tisdale-2 a taste, we started hunting down something smooth and representative of Cape York. We were here to get a taste of Cape York so that we could learn a little about Endeavour. We found just such a target: Chester Lake.
In particular, we focused on a nice smooth spot that we called Salisbury-1 (Salisbury-2 wasn't as appetizing, apparently), circled in pink here.
Now, context: a perspective shot on Cape York, vertically exaggerated by 5 times, looking northwest-ish (thank my Google-image-search-"RayArvidson"-until-my-fingers-bleed talents).
I have layered in my own annotations here, most notably the direction that the front of the rover faced for the Chester Lake campaign, to give an idea of where how Oppy was oriented. To the northwest: a feature called Shoemaker Ridge, which forms the spine of Cape York running roughly north-south. To the northeast, the inboard side of Cape York and the effective edge of Endeavour Crater. Lots of interesting things all around us.
And just to convince everyone that we were there, the MRO spacecraft used it HiRise camera to find Oppy perched right where we thought we were — we call it the "ultimate locator"!
While we started thinking about taking a poke at Salisbury, we queued up a high-resolution Pancam mosaic of Endeavour — hey, whaddya know, our first Endeavour Pan!
Note the pretty. (Click for full-res.)
Suddenly, we were right on top of Chester Lake and wanted to get going. Thus began an intense IDD campaign that lasted longer than we expected. We started with a basic MI+AXPS attack on both Salisbury-1 and −2, settling on a targeted campaign of Salisbury-1:
After the APXS results came in, there was an itch to leave and head towards Shoemaker Ridge or more due north. As my notebook indicates, Squyres (and, well, everyone else), agreed that we should dig deeper — literally. We queued up the RAT and got her grinding. After a seekscan (where it finds the surface), a brush, an MI+APXS set, another brush, and another MI+APXS sequence, we had a nice clean RAT hole:
The Mossbauer spectrometer on Oppy's arm is nothing but a dim light bulb — it's radioactive source has a half life that was selected based on a 90-sol mission, wouldn't you know — but we gave it a try for a few sols, setting it down in the RAT hole.
Pretty pictures and the slew of MI's aside, the Chester Lake campaign was a pivotal point for the MER team. Chester Lake had long-term effects on our rover and our strategic planning that we never planned on, causing some unpleasant hiccups in operations. First, there were the anomalies beyond our control. As with most things for MER, the concepts are simple but they tend to interact in a complex way. Remember that our tactical timeline is on the order of days; what we do today affects tomorrow, directly and drastically. Then, remember that we rely on an entire system of elements and pieces to maintain this tactical timeline. When one element fails, the tactical timeline is altered beyond our control and we have to adjust very quickly. It's not a metaphorical house of cards or a game of Jenga, because that would mean that we literally couldn't operate Opportunity if an element failed. Obviously, this is not the case. It's just a very fragile system. When it works, oh boy does it ever work. When it doesn't, there's a bout of sweating and legwork to get back to normal.
While at Chester Lake, one of the orbiters circling Mars couldn't relay the data that Opportunity had collected because of its own problems. We the MIs, RAT data collection, and MB integrations going on, we needed the data back each and every planning day in order to make good time and get out of there. When this couldn't come, and when we started losing uplinks and downlinks with the Deep Space Network itself due to the orbiter anomaly, things slowed to a halt: we adjusted and added hours on the MB; we used runout plans; we turned single-sol planning days into multi-sol planning days; we uplinked early and often. Sols 2720-2730 were a blur to me: lots of shifts, each of which was unique and different because of the new anomalies presented to me as a TAP/SIE. All told, we "lost" about a week's worth of sols because of the delays in data acquisition and downlink. I use the term "lost" loosely, because it didn't prevent us from collecting more science or stop us in our tracks.
The second hiccup hit us very suddenly: Winter was approaching. Solar insolation — and its proxy, the wattage generated by Oppy's solar arrays — wasn't looking terrible, but it certainly wasn't looking good. She's a dusty rover and she hadn't had a cleaning in a few months. The engineering team threw together a detailed analysis and projection of the rover's power state for the winter that had an obvious takeaway: find any slopes that faced north and get there. Quickly.
So we boogied to find the Promised Land of Northerly Slopes. Which brings us to Part 5...