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.

Wednesday, December 14, 2011

100 Sols on Cape York — An Absurdly Brief (Read: Long) Summary (Part 2/8)

Part 2: Landfall at Endeavour Crater — Cape York and Odyssey

~2680 to ~2690
"tl;dr" Description 
We made it! We made it! We made it! Ohhhh look at the pretty!
Highlights from Matt's Notebook
Sols 2683-2684: 
> "This plan is skinny by design." - Ray — interesting, since we're at Odyssey. LIKE, COME ON.
Holy crap we're here!
> "This is somewhere." — Posted a picture next to my cubicle. Nobody noticed except for my boss, who is, you know, supposed to care.

Details ("the deets")
Suddenly… arrival, Monday August 8, planning sol 2681 (-ish, depending on what one considers "there" to be). We hit the southern tip of Cape York and parked next to Odyssey crater, which was a landmark close to the non-specific "Spirit Point" locale that identified our arrival:

"But, Matt, Spirit Point isn't a point." Don't care.

"Hey, isn't that your blog's background?" Perhaps, but the demon in me says it's Photoshopped.

Of course, that second image confused everyone in the wide world outside of the MER enthusiast: With headlines like "Opportunity Arrives At Giant Endeavour Crater," you might expect the panorama that actually showed as much of Endeavour as possible, but instead most folks passed around that image of Odyssey, which is in the 10-15 meter diameter range, and said, "That's not that big. I'm already bored."

We had to throw on the brakes, hard. Suddenly, drives were precisely targeted and the entire mission changed. At least, it did from my perspective — the only Oppy I ever knew was the one that silently trekked hundreds of meters across the Meridiani at a time. A little poke at a rock here, a little imaging of a shallow crater there, nothing much. Then it was wham, we're back in this science collection gear that I'd never seen before. We weren't driving just to drive, or IDD'ing just to IDD, but we were doing those things to do other things

(And, honestly, it made the science team's role that much more apparent to me. It's an obvious thing — you know, we're there to do science in the first place, Matt — but I don't get obvious things very well. In the Meridiani, I looked at them as if they were the last remains of the mission that used to be; now, they were front and center. They owned the mission.)

The Odyssey Crater was the first thing that captured our attention:

What, you don't have your red-blue glasses? What is this, amateur hour?

And, to the east, towards the inboard side of Cape York and Endeavour itself, a nice ejecta field from Odyssey's creation:

Stu's black-framed images make me look classy, don't they?

The goodies — those smectites and phyllosilicates — were located somewhere in the middle of Cape York, or north of our "entry" point on to Endeavour. At least, according to orbital imagery and remote sensing. We shirked the direct path to these targets mainly for several reasons:

1) Cape York dips down into Endeavour on the inboard side and instead of poking our head over the proverbial edge didn't seem to be a very prudent way of attacking Cape York as a whole.
2) The true traversability of Cape York, especially on its inboard side towards the center of Endeavour, was unknown until we had some imagery from the rover itself. Our RPs took a look at Cape York and identified two paths: one that would have approached from just north and west of Odyssey, and the one that we took, from the south side and working northward to capture as much of Cape York as possible.

I've illustrated these paths on this perspective Google Mars shot of Cape York that I stole from Stu near sol 2680:

Conveniently, "A" stands for "actual" and "B" stands for "backup". I will pretend I knew this before I made the annotations to the image, and you will faithfully affirm this delusion for me.

Remember, these were notional only, meaning this was a strategic plan. As we'll find later, Path A actual curved back north much sooner than indicated here. In any case, the immediate advantages to path "A" were that nice ejecta field from Odyssey for analyzing and poking and sniffing. Odyssey not only had its own story, it also exposed the internal bits of Cape York itself. Another Google Mars shot from Stu's blog gives us an idea of where we stood:

Right in our gunsights was Tisdale-2. On approach just a few meters to the southwest of Odyssey (and its large, perched rock, Ridout), here was our view this aircraft-carrier-looking beauty:

If you still don't have your red-and-blues, don't come back until you do.

But, wait, Tisdale-2 was a whole new treat, a whole new taste, the start of this new mission. So, just as this "phase" of the Endeavour Campaign was short — roughly 10 sols by my arbitrary estimate — so will this part of the story be! 

Monday, December 12, 2011

100 Sols on Cape York — An Absurdly Brief (Read: Long) Summary (Part 1/8)

Just as you might expect for a young-gun Generation-Y'er, I'm wired. I use my iCal, Mail, and everything else in my Macbook to manage my world. ("Manage the crazy. Bring out the talent.") I need things to be organized, so rightly placed and micromanaged that it would make a normal person wonder how (or why) I'm not on Ritalin. However, I have one holdover from the olden days. That holdover?

The notebook.*

Don't get me wrong: I am a fan of TextEdit and other flat-text, note-writing programs. Who needs all that markup, right? But there are so many places to put files that you forget not only what you named the file, but what's in it. With a notebook, it's all right there, ready for consumption, with perhaps a little page flipping.

I have several notebooks for work. First, one for all my multi-mission work — you know, the Juno's and MRO's of my world. It's got scribbles and notes and it's a total brain scatter. I love it. Organized, but not. Second, one for logging my days. Like a work journal, but abbreviated and totally half-hearted. I tend only to log the more important days, because those days are usually filled with actual work and I have less to write ("7am: MER shift. 7pm: Sequence model development for MSL.") Third, one exclusively for MER. I never kept a MER notebook until I felt it was important enough. That time, that crossing the threshold of "important enough," was when we hit Endeavour Crater. Rightly so, the notebook is named "The Endeavour Campaign." 

This notebook serves the purpose of reminding me of what I did on each of my shifts — new tricks, bug fixes, engineering tidbits, that sort of thing. I never thought it would turn into the monster that it did. A few weeks ago, someone asked me a question to which I had the answer in my notebook; I couldn't remember where it was, so I started flipping the pages. "Geez, it's right here, gimme a sec… Hang on, I know I'm close… Man, I've written a lot…" 

As it turns out, "a lot" is about 100 pages in 100 sols.

Holy crap, we've been here 100 sols!

To drive it home further, a former-colleague-and-classmate-now-new-colleague-and-MER-TDL-in-training-and-drummer-in-my-Sunday-jam-sessions friend asked me today, "So I've seen all the news stories about the Gypsum find, but nothing yet from your blog. What gives?"

Well, trees give. They give very easily, in fact. He understands my pain, though: we both experienced 50 hours without power at our respective houses. Even so, this blog has been empty for most of December. What else has been going on? 

This post, is what!

I've been prepping this post for a few weeks. I have this uncanny ability to steal pictures from the various Cape York UMSF threads and Stu's blog. By steal, I do mean borrow with credit (Stu said I could! I swear!). I also have this uncanny ability to be incredibly wordy. So, onward!

(Courtesy Dr. Awesome XVII)

My intent is, as always, to provide context and insight into what happened these last three months. You can expect a little chaos here: 8 parts, each with the intent of informing people who aren't so in the loop as some of us are. The purpose is to be a summary, so if you know what happened, don't spoil it you crazy goons.

(Remember: For full-size images, click them!)


Part 1: The Approach to Endeavour Crater

[forever ago] to ~2680
"tl;dr" Description
We drove for, like, ever.
Highlights from Matt's Notebook
[No notebook! Boooo!]

Details ("the deets")
About 1000 sols ago, the Opportunity rover was commanded to drive away from the Victoria Crater. Having expired her manufacturer's warranty nearly 20 times over already, the team said, "There's this large-ish hole in the ground, way over there, so let's go. Who knows?" 

When describing this new mission for Opportunity, Project Manager John Callas could make no promises for when we'd arrive at Endeavour. It was 19 kilometers away (not quite as the bird flies) — more than Opportunity had already driven in its 1700 sols on Mars. And there was all this stuff in the way, like the Purgatory dune field and small craters and rocks everywhere. His — the team's — best guess was, "When MSL lands in 2012. Maybe." Our target was this little guy on the west side of Endeavour, named Cape York:

(Ignore the red circle on the second image.)

For an idea of the size of Cape York, check out Stu's post. That third image is a perspective view looking roughly north, giving you an idea of how it bends in towards the center of Endeavour. Spirit Point was the destination, the small Odyssey crater being a nice landmark for us to shoot at.

Somewhere in that journey, near sol 2310, I joined the MER team fresh out of school in Colorado. From the start, I noticed this curious little countdown meter in the LTP (Long Term Planner — someone who represents the SOWG) reports when the most recent traverse was shown in aerial imagery from the MRO spacecraft. This countdown meter counted down the distance from Victoria Crater to Endeavour Crater. The number was in the mid-40%'s when I joined, and that last 55% was a seemingly insurmountable task. We chipped away, little by little, and suddenly that number was 80%… 85%… 90%… All we would see in the LTP reports were images like this:

Very tantalizing. "What's it really going to be like when we get there?" we found ourselves asking.
Then we did this whole thing: 

And we did it a year ahead of schedule. Neat.

To capture the journey, I spent a few hours going back through every LTP report since sol 2310 and picked out a traverse roughly every 10 sols to build a "distance traveled" plot. (The maps posted at the MER website don't have the detailed Ohio State maps with the countdown meter as often as I need them. The information could also be found in the Google Mars maps that Stu and company make, arriving at the same answer.) This plot? Oh yeah, it's right here!

Several things here: 
> I layered in text annotations of targets and key events to give us some context.
> The left-hand side (blue line) is the percentage from Victoria to Endeavour ("V2E") according to the Ohio State traverse maps. 
> The right-hand side (green line) is the distanced remaining, derived from the V2E line.
> Not all meters are created equal. More on this in a minute!

Cool, right? ("Right!") 

The obvious trend in here is rough, linear progress. The other obvious trend is the long stop at Santa Maria for an extended science campaign and Solar Conjunction, or when the Sun gets directly between the Earth and Mars, from December 2010 through February 2011. Also, note the other key events. My favorite is what I'm calling the "Squyres Week," when Steve Squyres came in on a Monday and said, "I'm SOWG Chair all week and I want half a kilometer by the end of the week." Sure enough, that week's Mission Manager report proudly toted nearly 600 meters of drive distance in 5 planning days. 

Now, some explaining is in order. The distances reported in the were based on the so-called "Pink Path," which changed as we approached Endeavour. Therefore, I say the phrase "not all meters are created equal." Meaning, a given meter of progress towards Endeavour is not the same as another meter of progress at some other point in the journey if the Pink Path changed. Which it did — a lot! The arrival point was always Cape York but the twists and turns between Victoria and Cape York changed quite a bit.

We get a notion of "speed" (literal meters per sol) of the rover by looking at the slope of the "percentage progress" line (or the negative of the slope of the "kilometers left" line). We see that before and after the long hiatus at Santa Maria the slopes of the line is generally linear and about equal. We were just a little bit more of the "PEDAL TO THE METAL, BABY!" persuasion after Santa Maria, so why does it seem we did the same meters per sol as before Santa Maria? Because the Pink Path got longer! A given meter of progress after Santa Maria was not the same as before Santa Maria, because the SOWG got together and picked all sorts of cool little targets along the way.

(A way around all of this is to use actual drive telemetry — actual distance traveled every sol — to get a better notion of speed. But that's proprietary and painful. No thanks! Plus, the "V2E" count up is a little more fun to look at.)

Right. So. Speed. (I almost typed "velocity", but, you know… it's not that.) Why don't we just take a look at that directly? Ok!

Indeed! The speed shows up a little more obviously larger in this figure. There are two trends: first, an increase in speed — an increase in us wanting to get to Endeavour; and a cyclical "up down" pattern along this linear increase in Endeavour-wanting. That increase in speed was enough to overcome the effect of the Pink Path increasing in length! That's fast.

But, why is there a second trend? Why does it wobble? Shouldn't it be prettier?

No! Of course not! That pattern is, nearly precisely, the cycle between Nominal and Restricted planning! Remember: in Nominal, we can plan a drive every sol because the timing of uplink and downlink sets us up to know what happened before planning tomorrow; in Restricted, we can't plan a drive every sol — more like every other or every third sol — because we don't have "ground in the loop". I found this fascinating, if not completely ultra cool.

(Also, ignore that noisy large bit at the end. That's an effect of the Pink Path changing more wildly and our indicator of "progress" breaks down. The rest of the values before that noisy bit square nicely with approximations reported daily at our tactical meetings -- "assuming 65 meters per sol" was a common phrase towards the end!)

Along the same vein of "progress" indicators, here's a series of four high-resolution Pancam images of Endeavour from sols 2410 to 2681 (skewed towards the end of the timeframe because I'm lazy):

Then we have the famous Navcam Movie, another indicator of progress for the entire journey. And, as noted in the progress plot above, there was the appearance in the LTP reports of the vertically-exaggerated "Endeavour 'Fall Away'" GIF that I found on UMSF:

Hey, you know, that picture was an event in itself to me because suddenly Endeavour had opened up, like HEY EVERYBODY, EVERYBODY HEY. Simply stunning.

So what, right? We went a long way and we have all these great things telling us about the journey. Then? Then what, Matt? Is there something to the end of this story?

How about this: You all quiet down and stay tuned for…

Part 2: Landfall at Endeavour Crater: Cape York and Odyssey

(Tomorrow, maybe!)


*Not the movie. Oh god, please not the movie. Anything but the movie. I kept this phrasing because it feels so, I don't know, poignant. Or something.

Friday, December 2, 2011

No electrons

Currently blogging from a Starbucks because of this (at my house):

And this (at JPL):

There's currently a major lack of electrons (read: electricity [read: internet]) in my part of Pasadena, and I probably won't get power back until Monday.

Until I get my damaged house in order and find the trash cans that blew down the street somewhere, I won't be able to get back on the blogging horse. 

But, hey, I've got a goodie for you. In the post queue:

100 Sols on Cape York

It'll be a good one. I promised Stu that I'd have the post done a week ago, but then I forgot that we had to launch MSL and, well, you know how those things go.

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

Saturday, November 12, 2011

On Mornings

Hi, my name is Matt Lenda, and I… this is very difficult for me to admit… and I am a morning person.

Hi, Matt.


Scott Maxwell's Twitter feed can be instructive:

"Turns out that if you start at oh-dark-frakking-thirty[*], you can finish waving the rover's arm around by jesus-please-tell-me-it's-naptime."

This is in reference to a rare early start to the day: the SOWG meeting's at 8am, not 9am. (Gives the Cornell folks a chance to tag up before lunch!) We had to pull this during our Nominal planning cycles this past week to squeeze in extra planning days. 

When I was in high school, I worked the open shift at a Starbucks. The day started at 4:30am; lights on by 5:30am. I didn't have real weekends during the school year for some two years. I averaged five hours of sleep a night — hockey practice, by the way, started at 10pm four nights a week — for nine months. I was able to add regimented naps in the summertime, but the schedule was pretty much the same: early in, early out. This turned me into a morning person, against my will as it were, and now I'm stuck in that groove. My body won't let me wake up later than 9am on the weekends unless I am up until 5am working on something; then it gets me up at 9:15am instead. 

When I was a kid I slept in until 10 or 11 on my off days just like anyone else. After working those early shifts a few years later, things had changed. I remember the first weekend I had had off in a few months: I got excited because I was going to get to sleep in for once, but my body wouldn't let me. It hasn't ever been the same since.

I am, characteristically, the first person into the room when I'm on shift. If I'm TAP/SIE, I clean my area. If I'm TUL (shadow, for now!), I clean the whole room. It's easier to admit that I have OCOS — Obsessive Compulsive Oooohhh Shiny! — than it is to admit that I'm a morning person. Somehow it seems to be the dirty word around the office. During my first week at JPL a year ago, I met another guy who had then himself only been at JPL for a year. He asked me when I planned on going into work. I answered, "7:30am, usually." He said, cynically, "Yeah, that'll change."

He didn't know the extent of my morning person-ness. They never did change, my arrival habits. In fact, getting there at 7am or earlier has been my recent thing. There are things to get done. There are spacebirds to fly. There are Mars cars to command. 12 hours later I wonder where the day went, thinking only, "Thank god I got here early."

Scott told me later that they used to allow 6:30am start times for the day. His, ermmm, distaste for such an early start aside, we have on our hands an interesting thought experiment. How do you balance the needs and desires of a tactical team? We have morning people and evening people. We have east coasters and west coasters. We have people who like light and people who like night. What's the best way to do this kind of thing?

The solution for a 3-month mission is easy: Shove everybody in the same location and live on Mars time. If Mars days were significantly longer or shorter than Earth days, that would very drastically change the design of the entire mission. Just as it is easy to forget that your most precious resource is time with the DSN, it is easy to forget that Opportunity literally lives and breathes by day. To say that such a thing as local time systems would entirely change a mission design is to say a very profound thing. The optimal solution is to move everybody to a single location and then adjust our finely-tuned body clocks to start cranking out sequences on Mars Time. To hell with Earth time — who says I can't have dinner at 4:33 am? MY BODY SAID IT WAS OK.

This is, by the by, our first solution: Live On Mars Time (read: "The Golden Days")

We can also call this "inconvenience everyone equally" paradigm. But, of course, Opportunity and Spirit lasted wayyyy longer than 3 months. The operational (and personal) costs of having the entire science and engineering team at one location are astronomical — but, of course, with huge payoffs if the duration of their stay is short — so the MER project had to find a new way of doing things. This is our second option:

Option 2: Modified Earth Time (read: "What we do right now you daft fool")
What do we mean by "modified"? We mean that we schedule tactical planning shifts within some convenient day time range; we can place constraints on what's allowed and what's not allowed. For instance, we can institute a rule that states, "No planning day should start before 8am," or equally, "No planning day can exceed 10 hours in length." Stuff like that.
The problem with this is that Mars and Earth rotate at speeds just different enough to be a total pain. There are many ways to show how, but the simplest is to plot local solar time in seconds for Mars and Earth — using Opportunity's longitude and the longitude of Pasadena, CA:

See how long it takes for the full cycle to go by? Total pain. We look at this drift of time well ahead of time, and when we see that the previous sol's downlink isn't going to get down to the ground in time before a reasonable start to the day, we "back off" a few days and plan multi-sol sets of commands for the rover. There are many rules and guidelines and formulae that go into determining this strategic schedule, but you get the drift. (*rimshot*)

The idiosyncrasies of this so-called "Modified Earth time" happened to hit us this week. We've been boogeying north to get to the where the north-facing slopes on Cape York happen to be. We had to get this terrain-mapping done before MSL launches because they will likely be "stealing" our uplink and downlink times with the DSN, meaning we can't command Opportunity as often as we'd like. MSL is, after all, a much higher priority spacecraft. By the time MSL stops taking our windows from us it might be too late to do a good reconnaissance of the surrounding areas. Power is dropping as we approach winter solstice; we can only support drives on the order of an hour in duration at the moment, and we can only do drives on two or three consecutive sols before we have to take a breather and let those batteries charge up.

What happened is that we banked ourselves some meters: the RPs got into "trek toward Endeavour" mode and just took off.** We had about a week of magian to get the terrain mapping done. Then: Homestake. And then: Deadwood. (More on these targets in later posts!) And then: all of our margin was gone. So the science folks gave us back the keys, saying, "Get 'er done." To do that, we had to institute a planning day today, Saturday. A weekend planning shift hasn't been necessary since, purportedly, previous Spirit winters. In that case, it was to literally save the spacecraft from certain doom. In this case, today, it was to put some more meters in the bank. Because we need ground in the loop between drive and IDD activities, a full 3-sol plan on Friday (the usual planning schedule) would have only given us one drive when we could have two or three. Damn Modified Earth Time! So, to counteract this, we came in again today to get some more driving time.

(Totally killer day. I felt like I was in the glory days, part of the prime mission, part of a team that was ecstatic to be driving cars on Mars on a Saturday morning.)

Really, everyone seems to miss the Glory Days of Mars Time. But I think everyone would be sick of being at JPL again, as nice as this place is. Which brings me to our third option for tactical operations:
Option 3: Floating. Tactical. Cruise ship. (read: "Mars Time for Winners")

Scott told me about this. The idea: Screw being spread across a continent, and screw being on land in a single stuffy building. Put everyone on a cruise ship. Travel west to make your day about 40 minutes longer than the usual Earth day.

40 minutes drift per day = 0.67 hours drift per day = 0.0278 days drift per day
0.0278 days drift per day * 360 degrees longitude per day = 10 degrees of longitude per day ~= 600 miles west every days at the equator

That's, like, a Colorado and a half every day. Totally feasible.***

Not only would this mean that we're on the Mars clock — ahem, Opportunity's clock — but we would also have the "normal" daylight hours where the sun rises in our mornings and sets in our evenings. Walking outside wouldn't totally mess with our fragile brains.


*"oh-dark-frakking thirty" is, by the by, an actual time, though one that's not institutionally accepted. We have to translate between this colloquial clock and UTC pretty regularly. I find it unfortunate that the rover's command language does not accept colloquial times as parameters: "Start APXS integration at cold-as-crap thirty-seven, wait for god-knows-how-long, shut your face, and salute me. Dang it."

**Days Is Almost Gone" by the Derek Trucks Band is currently blasting on my record player. It has grabbed my attention at this moment for two reasons: first, it seems apt for the pre-Endeavour attitude that was all about putting back the miles and having to shirk it this mindset when we hit Cape York; and second, it reminds me that my record player's needle isn't of very high quality and is making all of my 180-gram records hiss on the high ends, like vocals and drum cymbals. This is unnerving — having music of such high audio quality that it actually sounds worse. 

***I'm leaving the logistics of such an operations architecture as an exercise for the reader. Suckers. Also, I didn't check my math. Also, I have to go flip the record… Also, nobody is allowed to point it out if I screwed the math up. 

Sunday, November 6, 2011

I know geeks

Quickly! A sidebar!

I graduated with her at CU, working with her on both our senior design and graduate degree programs. She decided to take what's known as the "icky ew nasty" route of aerospace engineering, that of aerodynamics and fluid mechanics. I mean, fluids are cool and all, but if they're not loaded with caffeine and being injected into my bloodstream by the unfortunately roundabout way of having to drink them (god forbid) first, then you've lost me.

Anyways, go read! She listens to vinyl! She uses phrases like "create an incubator for portable, cheap, and effective educational programs"! She is a supporter of the Oxford Comma! She digs science! Her boyfriend is a math major! Her dog can do backflips and triple integrals*!


*Not yet tested in clinical trials.

Thursday, November 3, 2011

This is why we can't have nice things

Well, official title: "A Lesson In DSN View Periods")

(Secondary Title: "Where Has All My Time Gone Because I Have Like Seven Posts In the Queue and I Haven't Posted A Single One Yet")

My mother told me that I could always have nice things. In fact, she still gives me nice things, like giant jars of homemade salsa straight from Colorado. It keeps up the illusion that reality isn't cruel and that it will give you salsa if you call her every once in a while.

And, it turns out, we actually can have nice things. Take Opportunity, for example. She's a nice thing*. She is the proverbial cake. But we can't always eat the cake. This is for several reasons. First, because I'm always one to remind people that the sugar in the cake — proverbial or otherwise — is bad for your blood sugar and makes your insulin response weaker over time. This warning usually disappears into the conversational ether, because, hey, I'd ignore me, too. The second reason is that operating a spacecraft is hard. Very hard.**

It's all about resources, resources, resources. I like to ask people, "What do you think the most precious commodity is for a spacecraft?" The answers are the usual: "Power" (not incidentally, from the power engineer); "Heaters" (also not incidentally, from the thermal engineer); "attitude control thrusters" (also not incidentally, from the guidance and navigation engineer). I've even asked lay people the same questions. The responses are roughly the same.

I disagree with these "average" answers, and many of the folks on both the uplink and downlink sides of operations at JPL would, too. Nay, the most precious resource, we would say, is this:

Time with the Deep Space Network
As we'll come to see, the DSN is an over-subscribed resource, constantly untangling the web of requests of several dozen spacecraft, each with different requirement and desires and idiosyncrasies. I'm going to show some neat-o fun things about the DSN being able to "see" each piece of floating metal (and more) out there.

Learning hats, engaged.


Reader, DSN. DSN, reader.

Notice the nice placement of these complexes: They are each separated by about 120 degrees of longitude, giving us petty humans the ability to continuously watch one part of the sky. Just as an object is approaching the horizon of, say, an antenna at Goldstone, it's coming into view at Canberra. These so-called "view periods" overlap by a considerable amount of time. Each complex consists of several individual and independent antennas. Because each antenna at each complex is located in a different spot, these overlap periods are slightly different at every location. However, for our concerns, it's all the same for a given complex.

Right. So. Remember SPICE? Open-source geometric awesomeness? Well, SPICE is still our friend. I've got a slew of knowledge about the DSN that I can't share, but all the SPICE stuff? Yeah, fair game! It's great. So let's use it. You know, get the nasty icky mathy stuff out of the way. We'll stick to basic view parameters, since that's all that matters to first order. 

Now, who remembers the right-hand rule?

This provides a "coordinate frame" for the antenna. Once you've established a coordinate frame and where its center is in space (literally, in space!), you can use a number of different ways to express the position of other stuff. One way is a three-dimensional vector: "Stuff is this much along the A axis, that much along the B axis, and a little along the C axis". Another way, most common for an antenna fixed on the ground, is the azimuth-elevation-range parameter set. Say you're standing straight up and you see a star somewhere in the sky. You can know everything about its position relative to you if you know its azimuth, elevation, and range in your coordinate frame. 

Usually, azimuth is measured from the North; it's also known as the "right ascension". Elevation is how high the out of the "plane" made by the horizon the stuff is. Range is simply distance to the stuff. Easy. We'll be using these terms quite a bit here.

The reader can imagine that if there are a lots of things in the same place in the sky, things can get complicated for the DSN even though there are multiple antennas at each complex. So, just how crowded is it? Let's use azimuth and elevation to find out. 

Let's stick with just azimuth. We can get a rough idea of how the view angles of some certain objects vary over the course of the year. Remember that the DSN antennas are attached to the Earth, which is tilted relative to the plane created by the orbits of the planets. Also remember that this plane is only notional and ill-defined because the planets are all slightly out of this plane. Pluto's orbit (well, I guess I'll include small bodies!), not necessarily the tilt of the body itself, has a very significant tilt with respect to the orbits of the other planets. Mercury's is also very pronounced. However, those of the 8 primary planets are roughly the same, so it goes to say that if a particular antenna sees the same azimuth for several different bodies, the antenna sees close to the same elevation for these bodies, as well.

Note: I'm going to stick with planets and not be spacecraft specific. I do this mostly because we can get a good sense of the complexity by only knowing where planets are. That's where most of the spacecraft are anyways — and, really, if you want to know where any Mars rover or orbiter is, all you need to know is where Mars is. Anything else is in the details and you don't need that precision anyways. Cassini is basically at Saturn, MESSENGER is basically Mercury, etc. Planets are proxies for many of our spacecraft. Lastly, I'm keeping the list of objects to to watch for short because there are just too many deep space spacecraft to make sense of them all in one plot. Not enough colors or plot symbols.

Let's get an initial sense of things with a plot of azimuth from each DSN complex of all the inner planets through Saturn, but ignoring Jupiter and instead looking for the Juno spacecraft. Let's grab a point in time every hour, and only plot the azimuth if the elevation is greater than 0 — i.e., the object is visible in the first place.

Ew. Busy plot. Let's dissect it. By virtue of the Goldstone and Madrid stations being in the Northern Hemisphere, we would expect that their azimuthal plots of each major body to be roughly the same, offset only by the some "phasing" or spacing in time of a given body. For Canberra, we would expect something different. indeed, most of the bodies cross the 0-azimuth (or 360, same thing) point because they are in the northern sky for Canberra antennas. The azimuth of a body, if it's visible, "flips" over when it crosses 360/0, and that's the behavior we see there.

The major thing to glean is this: Things are going on, and they're going on all the time. When one thing falls out of visibility, another one jumps in. The antenna has to constantly jump back and forth between objects, depending on who wants what and when they want it and for how long they want it.

Well, really, that didn't tell us much. I can think of two instructive ways to tell the story a little better. We'll start with a time-lapse video of the position of the planets with respect to Earth. A while back, I made just a time-lapse: I plotted the positions of all the planets relative to Earth, but not fixed to a particular point on the earth (we call this an inertial frame), every few days for a few years. Our predictions of planetary orbits are quite good, so the positions are reliable to an extraordinary degree. (*rimshot*)

I'm only capturing direction here, and making the size of the arrows the same for convenience. See how the outer planets move much slower? Look at Mercury and Venus: they move so fast that they actually have a significant "going the other way" deal as they hit the other side of their orbit and move in the other direction relative to Earth. What we are looking for here are overlaps: When Mars and Saturn overlap, the DSN has to deal with talking to rovers and orbits of all different kinds at imperceptibly different parts of the sky for several hours. Sometimes, the overlap isn't so bad. Sometimes it is. Sometimes it's in between. The DSN has to deal with this constantly — and for other things in the sky not close to the planets, as well. 

From this video, the major idea to glean is this: The planets' relationship to each other is cyclic, sometimes working to your advantage and sometimes not. Mostly not. Especially mostly almost always not. Long-term planning folks like to use representations like this just to get a good idea of what their DSN "coverage" is going to look like when they, say, want to land a spacecraft on another planet. Because if you can't talk to your spacecraft (when it's most critical to do so) because of conflicts with 17 other missions, why try to? You plan around major conflicts like this. Everything can be just perfect about a mission, and a lack of DSN coverage can totally hose you.

The second instructive way to represent this is with a combined azimuth-elevation polar plot. If you've got one of those old-school GPS units, or even a new one that isn't meant for giving you driving instructions, you might notice a similar kind of plot: Azimuth going around in a circle with elevation represented as concentric circles, increase in value as you approach a view straight overhead. An object directly above you in your local-level coordinate frame will be in the middle of this kind of plot. Take this example: it's the azimuth-elevation plot for the aforementioned bodies from the view of DSS-63, a 70-meter dish at the Madrid complex. (Combined azimuth-elevation plots for antennas at Goldstone and Canberra tell us the same story.)

The red "+" is the first point at which the object is visible over the timeframe specified in the plot title. I have also appended the time of day (UTC, of course) at which this occurs, as this plot has no way of effectively conveying the direction or start of time.

What do we see? Mercury, Venus, and Saturn are all very close in the sky on this particular day (and they will continue to be so for quite some time…). Although their so-called "rise times" (when they first appear on the horizon) are separated by a few minutes, they are close enough to be a pain. 

When accounting for handovers between stations or complexes, having multi-antenna assignments for a single spacecraft, or any other number of a dozen things I can think of, we can easily see how crowded it gets. (And remember: I'm only counting planets as proxies for spacecraft, not even mentioning the ones not close to planets.) And, just because something is visible, doesn't mean it was assigned (or "allocated," as we say) the time with that antenna. 

Let that sink in. Let that soak into your brain. Think about all the things you don't know, all the things that make that DSN engine run. 


And that, folks, is why we can't have nice things. At least, not all the time. The DSN is a monumental achievement of humanity, providing not only communication but also precision navigation services to several dozen spacecraft whose voices are but faint whispers in a background of nothingness. To place Opportunity in this picture is easy, really: She's just another player, just another bidder in a vast landscape of missions with equally crucial requirements to check in on their birds, asking them a simple question:

Hey, are you ok? Let's chat.


*A billion-dollar nice thing, but I fail to see how that makes a difference.

**Once upon a time, my roommates and I decided to play a board game. I didn't know the game, so I asked if it was hard. One of them said, "You fly spaceships, and you're asking if the board game is hard?!"