We're driving again!
Or, for the label and topography inclined:
As some have correctly guessed (or… knew…), Opportunity has been on the move. In fact, we've been moving so quickly that I had lost a lot of the context for why we were suddenly moving. I wouldn't call it a sense of urgency, just prudence.
There are two very simple things that we, as the MER tactical team, like to see:
1) A rover that is alive
2) A rover than is doing science
#1 always takes precedence. Always.
#2, of course, isn't just a nice-to-have, it's a must-have. ("Design is based on requirements.")
How do we reconcile these two things? Very, very carefully. The current context is that the "countdown to winter" clock was unofficially started a few weeks ago, meaning we had to boogie on out of the parking spot at Chester Lake in a campaign that is primarily about finding north-facing slopes. We don't need to be there for a few months, as winter solstice is on March 31. Here, I'll prove it. With math. Well, with SPICE*. So I'm cheating. But not really.
(Rule #319: SPICE is everybody's friend!)**
Although it doesn't look like it, the southern hemisphere of Mars — Oppy's hemisphere — has its winter when it is farthest from the sun. (And, of course, its summer happens to occur when Mars is closest to the sun. The same thing occurs on Earth, incidentally. Summers in the southern hemisphere are noticeably harsher because of just that little bit that the Earth is closer to the sun during that time. Recall that season is only defined by tilt relative to the Sun, not distance to the Sun!) Here, take this plot of Sun-Mars range over time:
(Rule #320: SPICE is still everybody's friend!)
Ok, so, right, fancy plots. So what?
The point at which we need to find ourselves some nice parking spots with north-facing slopes isn't just at the tip of the plot (March 31). It's a time period a little before then through a little after then. Where, then, are our options? We could go north, and we could go south. Here — context image! Take it! You'll need it!
To the north is more Cape York, and some great candidates for both science and north-facing slopes. To the south, our long-term targets of Sutherland Point, Knobby's Head, and Solander Point. Sutherland and Knobby are reachable by the time we need to be concerned, but from the looks of it, they don't have any lily pads worth our time (or our rover). As I've pointed out previously, there's still science to be done at Cape York, where the phyllosilicates are waiting to take an atomic beating from our Mossbauer. So, the game we're playing is to find a spot — or series of spots — that first and foremost protects our rover by tilting her for solar juice and that has exposures for science collection. MB'ing is not power intensive, so conducting the campaign of "mapping" Cape York now is the best choice. Given the drive path and its cadence with the sol numbers, we can expect limited science collection with the IDD until we find a spot to catch our breath.
What we get, though, are image sets that remind us of the long trek to Endeavour: Pancams and Navcams galore. Our Pancam and Ecam PULs are pulling the trigger on new sequences every day. Although Cape York is much more bland
Stolen from fredk and Jan van Driel @ UMSF!
We're also getting some interesting drive paths, as you can see in the "V" drive at the end — we saw that small, ~15-meter diameter crater and decided to do a drive-by shot to characterize its southern bits, which face north, and then head back Northeast.
Expect a busy bit of driving and exploration, despite the move into Restricted planning starting this Friday — a drive every 3 sols or so will be the norm, unless we find aliens. In which case… meh.
*Follow that link and you'll be inundated with kernels. How do you use SPICE? Well… that will take a while. Gotta know orbital mechanics and gotta know programming. In any case, the lesson here is that you can learn an extraordinarily huge amount of stuff about the planets and all of JPL's spacecraft with SPICE, and it's all free and open to the public. Want the code? I did it in MATLAB (an old student version, too!), since I'm awesome.
**Bonus points if you can tell me why everything is tilted into the Z-plane. I did the plots in the J2000 frame, for the record…