Saturday, March 31, 2012

I'm gonna go with… Mars Quake. Because I can.

(Alternate title: "I have eighteen theories regarding the Opportunity phantom movement anomaly, and unfortunately none of them include aliens...")

Sometime between sols 2894 and 2899, the rover moved. Which is cool and all, since that's what a rover is supposed to do. Except when it's not supposed to.

Subtle; notice that it was only the left wheel:

Courtesy user elakdawalla from UMSF -- thanks!

This is significant mostly because it's a mystery why it happened at all. It is not significant from a rover health perspective. Put a two dozen engineers in a room and tell them that only some nearly indeterminably small thing happened, and you'll suddenly have two dozen engineers picking each other's brains for hours. The thing happened, the thing wasn't dangerous… but my god, that thing has an explanation somewhere. It bugs us when we can't explain something.

Of course, when you're not expecting anomalies with the rover, you're not taking a whole lot of pictures and you're not collecting a whole lot of data. We certainly didn't expect any kind of movement and therefore the number of pictures at our disposal to catalog the sequence of events is rather low. 

We know a few things: 

> It occurred sometime over a range of a few sols
> It occurred around IDD activity close to the surface
> It is possible that the right rear wheel moved as well
> It is possible that there was additional movement on sol 2900 or 2901

We don't know some other things:

> Our exact attitude (orientation) before the movement — more on this in a bit
> When in the possible sequence of events the movement happened
> Why the movement happened

Now, not only do we not expect the movement of the rover at all, we don't want it. Although the change in orientation is on the order of a few hundredths of a degree, and although it doesn't affects the amount of sunlight hitting the arrays because the change in orientation is below our level to detect the corresponding change in solar power reaching the rover, and although we can easily adjust for such a small movement for high-precision IDD work, there is one thing for which this matters:

Radiooooo Ssssscience

(Say each word with a pause, imagining that you're both a) Neil deGrasse Tyson and b) in a big room. Say it out loud, too, no matter where you are.)

Alas! Radio Science! 

The collection of the radio science data is pretty much invisible to the amateur MER followers. It doesn't produce pictures, it doesn't move the rover, and it doesn't have that wow factor… Well, at least at first glance. To the MER team, radio science has been this thorn in our side because Opportunity simply didn't have the power levels to execute as many as we wanted. We wanted all those radio science tracks to get in, but it's just so damned hard. Sometimes you win, sometimes Mars wins.

A few weeks back, the guy in charge of the radio science campaign gave a presentation to the MER tactical team regarding the data he had collected so far. Simply stunning. The science all boils down to measuring the doppler shift*, subtracting out the components of this shift that are due to known sources, and seeing what's left. What's left is the signature of the planet's wobble. Right, so, why does such a small movement of the rover — on the order of millimeters, as are as we can tell — matter?

The signature of the Mars' wobble, like that of Earth, is very small. Very, very small. The changes it induces in the shift of the radio signal are on the order of… well, something really small. When that is mapped into a velocity, it's under a millimeter per second. The exact position of the rover doesn't matter for the collection of the radio science data, as long as it doesn't move; if it does move, the movements need to be known down to below the centimeter level of precision. (We can measure that, by the way, using the rover's VisOdom software; we just chose not to move due to power levels this winter. Two birds, one stone.) If the rover moves, and we don't know exactly how or where, this has a magnified effect on the quality of the radio science data.

Right. So. We shouldn't move.

I think I can speak for the MER team when I say that our current best theory for the movement is that this wheel is perched on some crumbly rocks. All the math and mechanics and discussion we throw at it boil down to that: just crumbly rocks. It's a decent theory and it explains most of what we've seen. (Ahem… most.) 

In the coming sols, we'll be taking lots of orientation data and lots of new pictures to get a high-fidelity feel for our current state, so if it happens again, we have something against which we can take a difference. We've got roughly a month left until we will start moving again — we have to wait for the sun to get higher in the sky** and we want to collect another months' worth of radio science to get those error bars down.



*Yes, I'm still working on that promised Radio Science post. It will include all activity up to now, a brief overview of the basics of the science, and how we chose to squeeze it into Oppy's daily activities. Big deal!
**Happy Solstice! 03/31/12, winter solstice hit the southern hemisphere of Mars. Recall that minimum solar insolation was a few weeks before that.

Sunday, March 11, 2012

A Squyres Sighting

It was one of those days: Eight different people wanting nineteen different things at four different times on three different floors. (Hey, at least they were all in the same building.) I was running all over the place and making phone calls and sending emails in the elevator.

I'm not in my office very much; my boss, two doors down from my cube, is always surprised to see me. On this one day in particular, before the madness started, I had spent 3 consecutive hours in my office — a veritable record for the last two and a half months, no doubt. Two days before I was on as TAP/SIE for Opportunity, and she had just had that little dust cleaning. Gave us a few watt-hours:

Courtesy user "dilo" at UMSF

It was late-morning by now, meaning it was time for the APAM (Activity Plan Approval Meeting) where the power analysis is shown for the sol(s) that the team is planning that day. I had to drop by a co-worker's office on the same floor for another task so I hurried up to the MER sequencing room to get that tag-up out of the way to make it to the MER meeting. I opted for the stairs; my building's elevators are notoriously and commonly out of order, so I didn't want to take my chances. As I made it up to the fifth floor, I could hear someone coming down from the floor above. This guy opened the door from the stairwell to the halls of the fifth floor and held it open for me. He was shorter than me and walked with a lot more intent; cowboy boots, to boot. As soon as he stepped into the hallway, he stopped dead in his tracks, apparently lost. Being in the hurry I was, I had no patience to wait for him to make a move. I walked right around him and headed straight for my destination. The best shortcut happened to be through the MER area of the fifth floor, and as I took off around this guy in that direction, I noticed that he was following me. I held the door open for him and noticed something very familiar about him — did I know him? 

Meh, I was too busy to turn around.

After my quick tagup around the corner, I came storming into the MER sequencing room to see if I had missed today's power analysis report. Mike the Mission Manager was on duty, and he told me: "There's been a Squyres sighting! He's here for the MSL Surface ORT [Operational Readiness Test] and decided he'd stop by to, 'Drive a real rover on the surface of Mars'."

My eyes shot to the top of my head as they do when I'm thinking back in time: Hey, that son-of-a-gun that looked lost was Dr. Squyres! If only I had turned around to see where he wanted to go, I could have had some good face time* with the man who so boldly leads us into the vast unknown of Mars. Dr. Squyres knows that there is a person named Matt Lenda, and that this Matt Lenda does TUL and TAP/SIE work for the MER project. Dr. Squyres does not know if Matt Lenda has a face at all, much less a face that he would recognize. So even if I had turned around, he would have thought I was some nice stranger.

Damn. Well, there will always be more opportunities to run into Dr. Squyres by happenstance in the building 264 stairwell.*

Right, so, why the heck was Squyres at JPL? As my bracketed insert above tells us, the MSL project had a surface operations test that week. In these tests, the team simulates real-time data going to and coming from a rover clone down the street at JPL; it exercises our processes, our tools, and our teamwork. (I also participated, but several days later.) Squyres was there as a co-investigator. He couldn't ignore his loyal MER team and decided to walk down a flight of stairs to say hello. He brought with him an announcement: He had prepared a presentation especially for the MER team, to be given the next morning.

After hearing this news, I looked at my calendar: I was triple-booked at the time Squyres had proposed. I quickly emailed three people: "Cancel my 10am with you. I've got cooler things to do."

The next day, I got to the room twenty minutes before the presentation was going to start. (The only person to beat me to the room was Scott Maxwell.) Fifteen minutes later, the room — small given the expected crowd — was filled to the brim. People had brought chairs form offices and placed them in the hallway; standing room only in the main room. We were all excited to hear Steve just… talk.

We all welcomed him and Project Manager John Callas gave the room to Steve — to uproarious applause. We needed this invigoration after three months of frustrating winter ops, and we let Steve know it. He was all ear-to-ear smiles, excited, jumpy, ready to unleash all sorts of awesome upon the willing**.

[insert Steve's talk here]

Well, I can't spill the beans and scoop the science team. A lot of the stuff in Steve's talk was not news to us or the rest of the world; what was new was the story that Steve and the rest of the science team had put together. We had all these pieces to the puzzle of Cape York and now we have a full story to tell about this place. It's some of the most fascinating science you can imagine when you start hearing Steve describe, well, rocks. Just rocks. That's all. The team has submitted a paper about the science so far at Cape York to the journal Science. And when we see that paper drop, we can celebrate. But only briefly, because there's work to do. We're over the winter hump and we're ready to boogey.

Steve ended his talk clocking in at about an hour and a half (including questions from the team), and then he was off again.*** Despite the stay being so short, the team felt juiced, pumped, rocking and rearing to go.

Now that's a leader — a guy who walks into the room, grabs its attention without a moment's hesitation, and says, "Here's what up…"


*This is blatantly untrue.

** = us. In case that wasn't obvious. Which it was.

***There was one last bit to Steve's talk I didn't mention: "What's next?" Simple: Although we see evidence of the phyllosilicate clays at Cape York, we don't expect to get that lucky. We'll stick around CY for a bit then head south to Cape Tribulation as soon as we can — giving us the chance to climb a mountain.

Monday, March 5, 2012

Over the hump!

It's been over a month since my last post. Upwards of a dozen people have asked me, "When are you posting again?"

Well, right now.

But the point of their question was, really, "Where have you been?" A few things combined chaotically into a fully-functioning ecosystem of busy:

1) MSL is a hard bird to fly. Long days, long nights, lots of time away from MER.

2) Oppy's been quiet. Filling out the Greeley Pan (part 45 to be taken tonight) has been the biggest consumer of bits, maybe second only to the MI stacks of Amboy. The MI mosaic is something like 17Lx2Wx5D and we've got maybe one-third of it captured. The Mossbauer has been accumulating hours of integration time, trying to sharpen up the resolution of the composition curves the scientists derive from its data. We're somewhere north of 50 hours by now, with 100 being the target. We're playing the power game sol-to-sol balancing the activities. Nothing new has really happened for about… 2 months?

3) I've been working on a Radio Science post. Being roughly halfway through the Radio Science season (ahem, winter), we've collected a huge amount of data to get those error bars down. This post is still in the works and is a bit difficult to put to together; it's driven by some cool geometric simulations that are easy to understand but hard to create. A friend works for the NAIF[link=] folks across the street from my office building at JPL and she's been debugging the issues with me. On a scale of 1 to way-cool-awesome, it's about a 12. Stand by for that bad boy.

4) Got a new sound system for my vinyl records. Wasted a lot of time listening to it — sounds gorgeous. Much like the Mossbauer, I'm accumulating hours on it: it's tube-driven and the tubes take, incidentally, about 50 hours to be broken in. I find this all sorts of meaningful. It's like my own Mossbauer. In my room. Making loud noises.

So there you have it.

The big piece of news this week was that there was a small cleaning event[link=]. It bought us a handful of watt-hours that made all the difference. This comes at a time when we're approaching minimum solar insolation (power from the sun) — to hit sometime this week — after which it's pretty much only going to get better. We're over the hump! It's the Wednesday of the winter season.

In other major news, there was a Steve Squyres spotting this week. That'll get its own post because the experience served as a reconstitution of the MER spirit (pun not intended) for the whole project .