Opportunity Sol 421 (Spirit Sol 441)

To my surprise, the last time the rover was driven was my last shift. Or rather, that was the last long drive -- they had a 7m bump to get the rover up on a nearby ripple, and they've just been IDDing it since then. Now that I'm back, we're pulling up stakes and moving on.

Well, I've been on the other side of that and didn't like it. But Frank (who's been doing the IDDing, with Jeff) has a good attitude about it, unlike what I had. "Hey, when you guys are driving, I just sit in the back seat and enjoy the ride," he grins. Now why can't I be more like that?

Anyway, the drive is a relatively simple one. We're about 70m from Viking Crater, and they just want us to drive to a position next to it so we can image it on the following sol. Amazingly, we actually have an obstacle to dodge: there's a hollow, like a small crater, about 20m away. From what we can see, it's about 20cm deep, and we can't see its bottom so it's likely a bit deeper. We could probably just drive right through it, but for safety's sake, we treat it as a hazard and drive around. For safety's sake, and, hell, for the sake of variety -- driving across this parking lot has been almost too simple. It's a far cry from driving Spirit, where there are more hazards than dust grains.

The tail end of the drive should leave us in Viking's "ejecta blanket," the rocky field that surrounds a crater. Those are the larger rocks tossed out of the explosion that formed Viking Crater millions of years ago. (The larger rocks naturally aren't thrown as far; they stay close to home.) I want to take advantage of this, so I turn on suspension limits that should stop the drive if we the rover drives onto anything bigger than a brick. That way, we have some chance of ending up with something scientifically interesting right in front of us.

But this choice has another side effect: it creates some uncertainty about the ending position of the drive, which now might end anywhere in the last 10m, where the suspension limits are active. And that means that the post-drive imaging of the crater can't be done by aiming relative to the rover (which is how it was originally sequenced); instead, it will have to be done using site-frame pointing. This will help ensure that we nail the center of the crater, but if we end up with a significant tilt, the whole panorama will be tilted as well, possibly cutting off the sides of the crater. If that happens, it'll be my fault. Oy.

After we're done with this crater, we've got big plans for the weekend. Friday, we're driving from Viking to its twin, Voyager, which we'll also want to image. Then we're driving on, on autonav. Somewhere in there, we're supposed to stop, image a crater, and drive on, all without ground intervention. Which means we need to get that drive just right; otherwise, we won't get images of that mid-drive crater. Or, as Matt puts it, "We'll miss a scientific opportunity." So, no pressure. Brian has a suggestion on what to name that crater if the attempt fails: Scott's Folly. Just how I wanted to be remembered!

It might happen that Scott's Folly will be Someone Else's Folly, though. After another couple of days, I'm going downstairs to work on Spirit for a while, to cover for John Wright's absence. I have a feeling that, very soon, I'm going to miss this parking lot.

[Next post: sol 443 (Opportunity sol 423), April 2.]


Opportunity Sol 413 (Spirit Sol 434)

Well, we were hoping for another 200+m drive, but we didn't quite make it. Autonav found some obstacles to avoid -- probably just larger ripples -- and that slowed it down enough that we made only 182m.

"Remember when that used to seem really far?" I ask Jeff rhetorically. "Now it's like, 182 meters -- I'm almost ashamed to show my face."

For a change of pace, thisol we're driving. South. 200m or so. It might be our last chance at a record-length drive before we reach the etched terrain, which the orbital images suggest is coming up fast.

So I get a little worried when our TUL relays the Mechanical team's request to do an engineering checkout drive. She's willing to take time out of the drive to do it, but I want one more shot at the record, as unlikely as it is that we'll make it. So I point out that the engineering checkout sequence hasn't been tested on Earth yet, and that seems to pretty much put the kibosh on it. Instead, the engineering checkout will be delayed until someone else's shift. I'm officially evil now.

As it turns out, we don't end up with enough drive time to set a new record anyhow. With our final allocation, we'll likely be able to cover only 180m or so. Oh, the shame. I'll never be able to show my face around here again.

[Next post: sol 441 (Opportunity sol 421), March 30.]


Opportunity Sol 412 (Spirit Sol 433)

Ah, that's the stuff.

Two hundred nineteen point seven meters.

It's not merely a new record -- we broke the 200m limit, and then some. Steve Squyres calls in to the SOWG meeting to congratulate us. "Two hundred meters, that has to be close to the theoretical maximum for these vehicles," he says. "Pessimist!" I reply.

And not only that, we drove a total of 843m last week, according to Charles. Heck, I'll have to take his word for it -- I lost track. But this is just absolutely amazing stuff, so far beyond what we thought these machines were capable of that it almost seems unreal. We're now only about 650m from the next big target, a pair of craters called "Viking" and "Voyager." At the rate we're going, we'll be there by the weekend. Jeff Favretto brought congratulatory doughnuts again, prompting groans from Saina, who's trying to diet but can't resist the sweets.

Plenty of people are congratulating me, but I almost feel I don't deserve it. Our success is mostly a mix of luck -- nastier terrain would cut these drives short in a hurry -- resources allocated to us by the planning team, and the terrific work done by the rovers' designers and builders. I just happened to be at the wheel, or rather keyboard.

Or maybe I just have a problem with accepting compliments.

In other good news, we got the NCAMs down from the previous drive, and they show James Caird Crater right where it was supposed to be. So we know where we are, or rather where we were 200m ago.

219.7m ago.

Downstairs, DS-1 and MRO continue to invade our space (so to speak), and this time, it's personal. MRO put up a huge sign just across from the 5th-floor elevators. The sign masks the words "Mars Exploration Rover," which have been painted on the wall for over a year. And still are, I suppose, though you can't see them. I know this must have been worked out with MER management already, but I'm still offended by it at first. I take my petty revenge by being exaggeratedly condescending in my mind: "Yes, their little project is important, too. Oh, what's that you've got there, a little orbiter? Yeah, that's creative, never been done before. I'm sure you'll be very proud of it." By the time I reach the sequencing room, I'm laughing to myself about the whole thing.

For the past week or longer, we've been seeing these dark smudges on the horizon. Justin Maki has a theory about what they are: he thinks they're Viking and Voyager craters, with the much larger Erebus beyond. Funny, we didn't expect to see them at all, much less for them to show up the way they are. But heck if he doesn't seem to be on to something. He and Tim Parker go off and start drawing some lines on maps, and it turns out the smudges are at just the right azimuths to be those features. That's not proof, yet, but it shows where the smart money would bet. Justin is smart.

Still more good news: we have an even longer drive time thisol. The range data for planning the drive isn't as good as on previous sols, so we have to cut the blind drive a little shorter, but the total time is more than ever before, so the additional autonav time will roughly balance. My guess is that this drive will compare with the record-busting weekend drive. I mention to Saina that we might possibly set a new record, which means more doughnuts. "Please, no!" she begs.

Yet there's some bad news to mix with the good. Spirit's RAT has started acting funny, bouncing dangerously as it grinds. This can break the IDD, so they've precluded any further use of the instrument until they can figure out what's going on. The leading candidate theory is simply that the RAT's drill bit has worn entirely away, which would mean no more drilling for that rover. (They could still use it to brush off surface dust, but no more seeing beneath a rock's surface.) If that's confirmed, Spirit's RAT would be the first instrument to fail permanently on that rover. (Perhaps joining Opportunity's MTES, though the final chapter in that story is not yet written.) It's sad to see these capabilities disappear, a depressing preview of what must someday happen to the vehicles themselves.

All good things must come to an end, I know. But not yet, damn it! Not yet!


Opportunity Sol 409 (Spirit Sol 430)

You want the good news first, or the bad news?

The good news is, we set another record: 190m.

The bad news is ... huh, there is no bad news. It's all good news.

Jeff was the first to announce the results. He got up way early (or stayed up way late) and sent out a triumphant email at 5:45. I was up to see it at about 6. And neither of us is exactly a morning person.

To congratulate us, Jeff Favretto -- our mission manager that sol and this -- brings in doughnuts, with a congratulations message hand-written in black marker on the top of the pink box. Charles has the honor of announcing the record as the Spirit SOWG meeting is breaking up to make room for Opportunity, and there is much rejoicing. "So that's where the dust devils are coming from," one of the scientists jokes.

It couldn't be a more appropriate sol for the quote that illustrates our rear-looking track image in the Long-Term Planning report, which (as usual) leads off our SOWG meeting. It's a Dakota proverb: "We will be known by the tracks we leave."

The drive should have left us just next to a crater which, yesterday, Ray dubbed "James Caird Crater." (Caird, a whaler, was an important part of Shackleton's expedition. Caird was a Scotsman, which makes him all right by me.) The problem is, we can't see this crater in the images we have. The minimal downlink only gave us forward-looking images, and the crater would be to the west or southwest of us. That crater was our only landmark, meaning that, in a sense, we have no idea where we are.

Perhaps I shouldn't be so dramatic: we have some idea of where we are. Probably a pretty good idea. We'd just like to be able to prove it.

We took NCAM images after the drive; when they make it to the ground this weekend, we should be able to see James Caird Crater in them. Or so we hope. But it seems a shame to be sitting just a few meters from what looks in the orbital imagery like a pretty darn nifty crater, and not get some good images of it. Plus, solid images with good range data would help localize us really well. So, in the back row, Justin Maki and I start scheming. But to little avail: in the end, we fail to talk the science team into spending the bits on it. They might catch it in a PCAM panorama they're taking before we drive on, but the panorama is probably aimed too high (this one needs to be, for science reasons). So we might never see the crater at all.

Well, that's a shame. But the upside is, if indeed we don't see it, it will be because we drove away. Really, really far away. In order to help avoid a repeat of Spirit's squeaky-wheel problem, we're letting the rover rest Friday (today) and Sunday. But Saturday, we're driving with a vengeance. We would have driven a little farther than 190m on the previous drive, but autonav found some obstacles to avoid early on and lost a little time edging around them. Assuming that doesn't happen again this weekend, we'll break 200m this time for sure.

Once the drive sequence is in the bag, Jeff and I take a little time to brainstorm ways to drive even farther on future sols. We don't see a lot to optimize in the current approach -- all the parameters are cranked up as far as is safe, and the general structure of the drive sequences is about as good as it can get. We blind-drive as far as we safely can given the imagery we've got -- lately, this has been about 100m -- and then we switch to the much slower autonav. So the most obvious way to squeeze more time out of a drive is to extend the length of the blind segment.

But we can't, because we're driving as far as our stereo imaging allows. Unless -- "Hey," I say, "what if we did long-baseline stereo? Take an image-pair in the drive direction, drive laterally a few meters, and take another image-pair." I think this is a great idea, but it doesn't seem to set Jeff afire. Turns out they've done this before on the plains, and it didn't seem to improve the data all that much.

Oh, foo. I thought I was being all creative.

[Next post: sol 433 (Opportunity sol 412), March 22.]


Opportunity Sol 408 (Spirit Sol 429)

The regular science team has returned from their conference, so Charles is out as SOWG chair (after a damn honorable term of service) and Ray is back.

And thisol is the first sol we're going to seriously shoot for 200m. Apparently, Steve Squyres has been privately campaigning for this. Another person who likes the idea has a pithy reason: "Just to stick it in MSL's eye."

So they give us a heck of a long time to drive: an hour of blind driving followed by three and a half hours of autonav. In the best possible case, this would give us time to drive 235m or so, with 210m being a more likely outcome.

But this judgment is reduced on appeal, as it were. The PCAM team wants to do some damn imaging or something, and then other stuff comes up, and by the time it all settles out, our 3.5 hours of autonav is down to 2.5.

So we won't break 200m thisol, not even by extending the blind drive. But we might come close. And that'll still be pretty darn good.


Opportunity Sol 407 (Spirit Sol 428)

I have mixed feelings about the result of yestersol's drive. Frank and Brian were given a record-long amount of time to drive -- four hours and fifteen minutes -- and they put it to good use. The new one-sol record is 183m. Great news for the project, but as the now-eclipsed record holder, I can't help feeling a little sad.

And I won't get to regain the title today; they can't spare enough time to drive. We might get 150m or so, though, which used to seem really good but now seems hardly worth spitting on. Since we can't beat the record anyway, I generously accede when they ask for a couple of unusual procedures -- one where we'll stop in the middle of the autonav segment and do some mid-drive imaging (a first, I think, so at least I get to invent something); and another where we have a second, comm-turn-only, drive sequence. Maybe agreeing to this will make me feel like less of a bastard if I decide to refuse them on some sol where we could set the record.

Aw, who am I kidding? I'd never do that.

Charles Budney is the SOWG chair this week. Normally he's a Mini-TES guy, but he's temporarily filling in for a number of absent SOWG-chair types, who are off at some conference. He's been only too happy to let the rover drivers drive, which, as I tell him, is going to make him one popular SOWG chair.

"Just as well," he says, "since it looks like the Mini-TES is dead." This has been the subject of investigation for the last couple of weeks or so. The normally reliable instrument suddenly started returning errors instead of data. The more stuff they've tried, the more their hope has faded. I know Charles in particular has a pessimistic streak, and there's been no formal announcement yet, so I'm still holding out some hope myself (read: "I am still in denial"). The loss of this instrument would be bad, since it helps us determine chemical composition at a distance -- a very powerful tool in our toolkit. I guess we'll see.

Maybe rover death is the somber theme of the day. Downstairs in the sequencing room, Brian Cooper and Justin Maki start talking about what it will be like when one of the rovers dies. "They'll start making fault trees" -- "Pulling people back from other projects" -- "They'll keep trying for about two weeks" -- "Yeah, two weeks is about right, two weeks in denial" -- "They'll think maybe they saw a glitchy signal" -- "It's sad, but you learn a lot about radio science when something like that happens."

"Chris Salvo was saying it's gotten to be like the rovers are right in our back yards," Justin says. "And he's right, it is. But at any minute, they could be a hundred million miles away again. It could happen like that."

What a comforting thought.

In happier news, the dust devil that recently cleaned off Spirit's solar panels seems to have removed the dirt clod from the magnets as well. That's the dirt clod that's been there since the MB picked up a chunk and wiped it off on the magnets, way back during conjunction. I haven't seen the MB lately, but last I saw, a lot of the dirt that had stuck to it was gone as well.

"I need crater names that start with a 'V,'" Charles announces. "These are supposed to be ships of exploration." He doesn't get enough suggestions that start with "V," so he relaxes that requirement and suggestions start flowing faster. Jay Torres suggests "NCC-1701." Cooper suggests "The Minnow," and that one is definitely going to get used.

"We should use that name for one of the craters where we stop and IDD," I say. "Because the target names are so obvious -- Gilligan, the Skipper, ...."

"And if we don't," Charles says, "The Minnow would be lost."

That one almost physically hurt. What did I ever do to him?


Opportunity Sol 403 (Spirit Sol 423)

Yesterday we planned sols 402 and 403 (which executes today); today we plan the weekend sols, 404 and 405. Khaled could use the experience, so I have him do the bulk of the RP-1 work today.

Which is easy, since he already did most of it yesterday. I spend most of the day struggling with a tricky m4 problem. Don't get me started. But he calls me over to help out with something weird: the INCONs file ("INCONs" is short for "initial conditions" -- it specifies the rover's last known position, which is how it will start the day) shows the rover with the APXS in the wrong position. Instead of being directly on the target, the instrument is laterally offset by about 3.4cm.

On comparing the numbers from that file to the numbers we expected, we find it's offset by the right amount to be an MI poker offset. This term takes some explanation. When we're trying to get good MI images of a rock surface, often we first touch it with the MI's poker, a small, thin, steel rod affixed near the MI's lens. When it senses contact, we back off a known amount, and we can trust that the resulting images will be in good focus.

But the poker doesn't project directly out of the lens, obviously, which leads to a minor problem: when the rock surface is uneven, the poker might contact a position higher or lower than the area we're trying to image. This could lead to out-of-focus images or, in the worst case, we could smash the MI lens while the poker felt nothing.

So in these cases, we do the poker touch differently. First, we slide the instrument over by a known lateral offset, putting the poker where the lens was. Then we touch and retract. Then we slide back, putting the lens directly over the position the poker touched.

And the offset we're seeing in the APXS placement has just the right magnitude to have been introduced by this procedure -- if, for instance, we slid over but didn't slide back. Nothing else we normally do moves the IDD in this exact way, so it has to be some kind of poker-slide problem. And the scientists aren't going to like it: it would mean that some if not all of our instrument readings have been at the wrong location. Basically, we might have wasted one or more entire sols, and we'll have to do them over.

But there's still a puzzle. While the offset has exactly the right magnitude to have been caused by this error, it's not in the direction we would have used in this case. And when Khaled and I look carefully through all the sequences that have executed since the last known-good placement, we can't find the problem in any of them. So we look again, and we still can't find it.

But it has to be that. And I'm quite prepared to believe it is, since we very nearly made exactly this mistake in the last IDD sequence I built; I caught it in time (because I noticed the simulation looked wrong), but we know the problem could bite us.

So it has to be an MI poker-slide problem. But it isn't. What the hell is going on?

Grasping at straws, we reload the INCONs file -- and suddenly the IDD snaps into the right position. Turns out there was an error in the original file, and the Mobility/IDD team corrected it, probably right after we loaded the erroneous version. Everything's fine. We've just wasted half an hour chasing a ghost.

Well, I'll say this: it sure as hell could have been worse.

[Next post: sol 428 (Opportunity sol 407), March 17.]


Opportunity Sol 401 (Spirit Sol 422)

Four hundred sols, baby. That's what I'm talking about!

The drive to Vostok went damn near perfectly, which apparently means the curse is lifted. As we suspected from the previous images, Vostok is large but very shallow, kind of like Shaquille O'Neal. (Just kidding, Shaq!) Over the millennia, the crater has almost completely filled with dust and soil. Now, only a broad ring of broken stone, like a circular garden path tens of meters across, shows where a meteor struck once, untold ages ago. At least some of Mars's ancient wounds have healed.

Frank and Brian spent yesterday starting on some IDDing of outcrop that ended up right under us, just as we were hoping. We'll likely continue that work over the next several days.

That's what we're doing today, for example. We're planning two sols today and another two tomorrow, so that we won't have to work Saturday. I think this is a great approach (heck, I advocated it myself yesterday), but it so happens that the two most complex sols out of those four are the two we're planning today. Well, if the work weren't difficult, they could find someone cheaper than I to do it.

What makes the sols complex is that we're RATting on both of them. I haven't done this for a while and had almost forgotten how much there is to it. RATting is usually part of a broad campaign that involves complex placements with all of the instruments, and this time's no exception, so the sol keeps me hopping.

It does give me a chance to play with a new flight software feature that tests directly for RAT contact with the terrain. It's a vast improvement over the old way we had to do it, which required deliberately generating a fault and some tricky logic to determine the cause of the fault and conditionally clear it. So this is good.

But the large workload and short timescale (it would be a tight sol even if we were planning only one) has a predictable effect: I revert to get-the-fuck-out-of-my-way mode, in which I trade politeness for efficiency. (Ahem.) I've been trying not to do this, but old habits die hard, and I have to admit this one is damned effective. Andy's already worried that he's been scheduling me for too many shifts, so he asks later, "Are you okay? You seemed a little testy earlier." I hope my reassurance suffices, because I want him to schedule me more! More! MORE!

Uh, anyway. What with all the work, I miss my chance to appear in an IMAX movie[1] they're filming downstairs; among other things, they're attempting to re-create the landing and egress. But it's probably just as well: the world doesn't need to see my face on a screen the size of a city block. On a screen the size of a thimble, maybe that's something the world needs to see. But a screen the size of a city block, forget about it.

Tomorrow would be simpler than today no matter what, but once today's in the bag (with an hour to spare, mind you; maybe I really don't need to be such a jackass), Khaled and I get to work on tomorrow's sequences. Khaled hasn't built IDD sequences from scratch yet, and doing it with no time pressure is the right way to do it. He's come along really well, and is turning into a fine rover planner.

But he can't have any of my shifts. More. More! MORE!

Courtesy NASA/JPL-Caltech; mosaic image hosted at Wikipedia. This is the entire 360-degree NAVCAM panorama, including (centrally) the broad ring of outcrop outlining what's left of Vostok Crater.


[1] This, of course, was Roving Mars.


Opportunity Sol 399 (Spirit Sol 420)

Yestersol's drive seems to have ended more or less where we meant it, about 35m from Vostok. But we have a goal error.

While Frank deals with the SOWG, I look into why we got the error. It turns out we didn't leave quite enough time for the worst-case end-of-drive housekeeping, and the worst case occurred yestersol. We timed out at the very, very, very end of the drive, a few seconds before we finished turning for comm. Literally another couple of seconds would have made the difference.

Oh, well. We're where we meant to be, and facing the right way, with only a little bit of egg on our faces. Thisol's drive is so simple that Frank effectively has it finished before the SOWG meeting ends: turn to 150deg and drive about 35m to Vostok, and that's about it. If it goes how it's supposed to, we'll end up with Vostok right under our wheels. If it goes the way the other recent drives have gone -- hell, we'll probably end up in the Pacific Ocean.


Opportunity Sol 398 (Spirit Sol 419)

The good news is, we did a record-setting blind drive on sol 396. The bad news is, we didn't mean to.

The problem stemmed from a mistake in a waypoint command. A waypoint is actually a "waydisc" -- an imaginary circle on the terrain. The rover drives until it's inside the circle, or until it runs out of time trying. The mistake they made yesterday was that they moved the circle away but forgot to make it bigger, so the rover had to drive farther to reach it. What was intended to be a multi-stage 100m drive with increasingly paranoid suspension checks turned into a single-stage 125m drive with relatively generous suspension limits.

That could have been bad. It's not that we mind making more distance than expected, it's that the mistaken command sent the rover beyond what we could see well in the available imagery. If there had been a rover-killing obstacle out there, we could have sent the rover to its doom.

Luckily for us, the terrain the rover was driving over had no such hazards. (Admittedly, such hazards are rare in this terrain. But as Andy says, we're paid to be paranoid. And brother, we earn it.) Indeed, it stopped only because it ran out of time; if it had been given a couple more minutes to drive, it would have reached the circle anyhow, despite its greater-than-intended distance, and proceeded to the next command. That would have compounded the problem.

Frank needs no reminder that he made a potentially dangerous mistake. It's actually worse for him, because he almost caught it. He and Khaled noticed yesterday that something was screwy with the simulation, but they found a different error -- the rover's initial position was set incorrectly -- and thought that explained what they were seeing.

We've all had days like this. Yesterday it was Brian's and Frank's (and Khaled's) turn. I've had my turns, and I don't need another; they can have mine. Because one of these days, we're afraid we're going to come in and have to tell a story a lot like this one, except it will end with, "and that's how we killed the rover." Before the day is out, I have an automated check in place that will catch us if we make that mistake again. But Murphy's law is merciless: the number of potential mistakes seems infinite.

I try to cheer Frank up. "Still, you set a new blind-driving record! And it's one we're never going to break, at least not on MER!"

"Just what I needed," he groans, "my stupidity enshrined for all time in the Guinness Book."

I'm not very good at cheering people up.

Because the rover timed out while striving for the waydisc, the sol-396 drive didn't go as far as intended, and the sol-397 drive (an automatic continuation drive meant to execute Sunday) noticed the leftover error and, properly, didn't go anywhere at all. So we haven't quite made it to Vostok yet; today's just another long drive.

And believe me, we check the waypoint.


Captain's Log, Supplemental

I'm proud and humbled and thrilled and honored to say that this blog was presented with the 3rd Spirit Award from UnmannedSpaceflight.com today. As I've posted there in my thank-you to the members of that excellent forum, I'll try to continue to earn it.

I'm also going to try to figure out how it's possible to be both proud and humbled at the same time. It doesn't seem like one could be. But I am.


Opportunity Sol 394 (Spirit Sol 414)

Cindy Oda's one of the nicest people I know, and she's going through a really rough time. Her mom's teeth are in really bad shape, and they're worried about her getting a bad infection. But they can't put her under to fix it because of some medication she's taking, and they're afraid to take her off it. Meanwhile, her husband, Jeff -- one of the other RPs -- has had to fly back to Illinois to deal with his own ailing dad, who has a heart infection or something like that.

So they're unhappy. Things like this make me almost feel bad about how well things are going in my life right at the moment.

Meanwhile, uh, things are going well in my life. (Sorry.) We're doing another uber-drive thisol. Actually, it's more of a mini-uber-drive -- no autonav. If we trip the suspension limits, we'll just have to stop.

I spent some time last night working out a prototype drive, which of course Khaled and Brian and I end up hacking up somewhat. Last night I didn't have time to analyze the past drives, so I wasn't really sure what limits to specify for this one. As the day wears on, Khaled and I keep thinking of something else we should check, look at the data, and interrupt Brian to tweak something else in the sequence. Tilt, bogie/differential limits at various points -- all of it comes up for review.

What we saw during the drive to Trieste was a tilt high-water mark of 11.5 degrees -- very close to the 12-degree limit that would have stopped the drive altogether. Both the tilt and suspension limits for that drive were higher than we've seen lately, which makes sense: we've been driving south, along the ripples, but the Trieste drive took us due west, straight across the ripples. So we were climbing up and down the ripples all the way. It's a wonder Opportunity didn't get seasick.

Because this drive took us somewhat off our intended southerly course, we're driving back to Vostok at a southeasterly angle. This is the worst of both worlds, as far as expected vehicle articulation is concerned. Not only will our tilt vary just as on the Trieste drive, as we climb up hill and over dale, but also our suspension will articulate more when we drive across the dunes at an angle than when we drove directly over them. This is unfortunate, as it means we may have to choose suspension limits that are hard to distinguish from what would happen if we encountered a real obstacle.

And that's a problem, because our drive-direction imaging is none too good. Usually we have good range data out to at least 80m or so, but thisol it peters out at 65m, and that's if you're being generous. Beyond that, we can't reliably determine a hazard from here, and if we can't tell the vehicle what one looks like in a way that distinguishes it from a ripple, we're in trouble.

In the end we decide, of course, to play it safe. We use more-generous-than-usual limits for the part we can see well -- that is, the part up to 65m -- and the usual paranoid limits beyond 65m. We'll probably make between 35m and 65m of progress, and then we'll have a data point that will be useful for planning the next drive. The next drive is going to be a weekend uber-drive series that should take us all the way to Vostok, or mighty close, so this will be very useful information to have.

Before Opportunity can start her drive to Vostok, though, she has to make it out of the crater. ("Crater," hah. Next to Eagle and Endurance, Naturaliste is a dimple.) Yesterday, when Frank and I were working ahead, I initially sequenced this egress using visual odometry. The strategy was a tried-and-true one: have Opportunity use VO to keep careful and highly accurate track of her progress, and stop when she's out.

Then we came up with the idea of using new R9.1 functionality[1] that can check for tilt. This seemed to let us express more nearly what we wanted -- we could have Opportunity drive until she's flat, assume that means she's out of the crater, and then proceed toward Vostok. We liked this better than the first approach, because we were worried the rover would yaw as she backed up, and end up on flat ground but not in the target zone. But if she only checked for tilt, we'd succeed no matter where she ended up, as long as it was flat. So I rewrote the whole thing to do it that way.

But today, when Khaled and I look at the data more closely, we see some problems with that idea. The area immediately behind Opportunity is flat, but the area just behind that has a largish ripple, one it would be easy for Opportunity to end up on. Given that she might be there, what tilt value do we choose to represent a flatness threshold? Too small, and the limit might be tripped because of the ripple, even though she had in fact egressed. Too large, and she might think she was out of the crater even when she wasn't. Neither of those outcomes would bring us joy.

Well, the reason we switched from a position-based approach to a tilt-based approach was that we were worried about yaw. And when we look at what happened on the way in, we see that Opportunity didn't yaw appreciably. Since we're backing straight up, leaving the same way we came in, she probably will do the same on the way out. In other words, yaw isn't likely to be a worry after all.

So I change it all back. Sigh.

Well, one thing I know for sure: if that's the worst thing that happens to me today -- and it is -- I'm damn lucky.

I'm damn lucky.

[Next post: sol 419 (Opportunity sol 398), March 8.]


[1] That is, new functionality that had been added as part of the recent (R9.1) flight software upgrade.


Opportunity Sol 393 (Spirit Sol 413)

I show up a few minutes late for the meeting (acceptable, since I'm RP-2 today), and Frank tells me he's already done. Not because he's a genius (though I'm not saying he's not), but because all we're doing thisol is a simple tool change -- one real command, the rest auto-generated boilerplate. (Just to leave my mark on the sequence, I change the 13.5cm backoff to 13.4cm.) It's going to be a slow day.

But that's okay. I expected that, and came in raring to do tomorrow's work, since we already know what it will be. I come up with the idea of combining the crater egress with the next drive toward Vostok (we had originally planned to do these two things in two sols); Ray likes the idea, so I go ahead and sequence it. One hopes this will mean tomorrow's a slow day as well, but you never know.

We're possibly going to rename RSVP for future missions. I suggest the name "R2" -- a nested acronym for "RSVP 2"; I love that it gives us an obvious mascot. Frank and I like it, at least. We'll see if it flies. Or, rather, drives.


Opportunity Sol 392 (Spirit Sol 412)

Even though it's because I'm a dumbass (a patriotic dumbass, but a dumbass all the same), the rock we're IDDing is still named "Normandy." So when Albert Yen asks for suggestions for target names, I immediately suggest "Utah," "Omaha," and "Juno." I forget about "Gold" and "Sword," but no matter; the names stick. We'll be IDDing Omaha.

Jeff's father's very sick, so he has to leave town unexpectedly. Cooper gallantly volunteers to fill in, little realizing that he's already committed on Spirit (an unusual occurrence; no wonder he overlooked it in the schedule). So Jeng fills in for him.

It's a simple IDD day: unstow, then MI and MB Omaha; later, we change tools from MB to APXS. I could just about sequence it in my sleep. Because the generally flat rock surface is slightly uneven at the microscale, I get paranoid about the lateral MI move to take the stereo image, and sequence it in an unusual way -- the way we used to do it, by retracting the IDD farther from the surface before moving it over. In the end I decide this is simply too paranoid even for me, so I put it back to the usual way. Unsurprisingly, this prompts another discussion about the RPs and their relative paranoia. Jeng identifies himself as closer to the less-paranoid Wright/Leger end of the scale than to the Ashitey/Biesiadecki/Maimone end (which, it must be said, is where I locate myself). Since John happens to be here to ask, I ask him whether he considers himself or Chris to be the least paranoid RP.

He laughs, then thinks about it. "I am," he says. "But both of us -- well, both Chris and I feel that the rovers are more capable and robust than is generally acknowledged, let's put it that way."

Good spin. But I realize that even though I put myself on the more paranoid end of the scale, I must have some boldness when it comes to driving. After all, I'm currently the long-distance record holder for both rovers. I can't be all that much of a scaredy-cat.