Captain's Log, Supplemental

And so it was just about this time, five years ago, that Spirit took the Husband Hill panorama -- a beautiful color panorama taken from the very summit of Husband Hill. (It's also called the "Everest panorama," and sharp-eyed readers might notice it's the image at the very top of this blog page.)

The rovers have returned more than a quarter of a million images, but this one would be on my list of the top five or so. There's so much in this image. First, and maybe most importantly, are Spirit's own tracks leading to the summit, a record of the struggle and hardship we faced on the way up -- and the relentless determination we showed in its face. In the distance, there's a dust devil on the plains, caught in the act of moving between frames. (So it looks like two dust devils, but it's really one, moving as Spirit took her images using a series of three different-colored filters.)

And, of course, there's Home Plate, to whose immediate west Spirit sits today, trying -- I hope, I fervently hope -- to phone home.


The Husband Hill panorama. (The link takes you to the full -- very large -- image.)

Spirit Sol 619

Coincidentally, my last drive was performed without the assistance of the ultimate FHAZ, and so must this one be. Spirit's just a few meters away from the true summit of Husband Hill -- a slightly higher point than the spot we last thought was the summit -- and we're going to drive up onto it.

That's a given. The big discussion at the SOWG meeting is what we're going to do next -- I mean, over the weekend. Should we pick a juicy rock and IDD it, and so use that rock as thisol's drive target? Or should we just get into a good position to do imaging, and do self-IDDing (such as by putting the MB on the CCT) over the weekend if we IDD at all?

Hap's take: "We're too experienced to be wasting our time exploring dusty rocks. We should wait and do clean rocks somewhere else."

Squyres agrees: "We may have to trade this strike-and-dip imaging against the IDD position." But they can't get the pictures of rocks they want anywhere else, while the rocks they have pictures of are not particularly interesting IDD targets, so that's a bad trade. "So let's do structural imaging on some face of Hillary" -- named for Sir Edmund Hillary, of course; another rock up here is named for his Sherpa guide, Tenzing Norgay -- "and a panorama."

Alian suggests that we could get into position for imaging and IDD whatever's there, but Squyres says no. "I'm reluctant to use the IDD for low-value targets. Maybe we could get into a good position for imaging and recapture the MB-on-the-CCT measurement we recently lost." And that's pretty much it.

John handles most of the drive, with me looking over his shoulder and offering feedback as he goes. This is a practice we sometimes call "backseat rover driving," and it's a really effective one. I never feel like I'm contributing as much when we plan drives that way, but I'm actually being more useful than if I make the RP-1 do everything himself and then get involved only later.

As we review the drive at the walkthrough, Steve chimes in to remind us of what a big deal this is. "This is the final drive to the summit of a mountain we've been climbing for more than a year," he observes. "And it's our last real uphill drive for a while."

This should feel like a more momentous occasion than it does. I think we're all just kind of fatigued. Morale isn't what it once was. And that's a shame, because we put a lot of hard work into getting here, and we ought to feel damn proud of that. I'm sure we do, really. It's in there somewhere, behind all the exhaustion.

[Next post: sol 625, October 6.]

Opportunity Sol 592 (Spirit Sol 613)

I've been out for a while because of my shoulder surgery, and now, for the next six weeks, I'll have to drive the rover with my arm in a sling. My right arm is barely usable at all -- can't really type with it. Fortunately for me, we've got a relatively easy sol. Opportunity's parked on some outcrop called "South Shetland," and a couple of meters away is a chunk of dark rock called "Deception." We've just got to bump to it, to set ourselves up for a weekend of IDDing.

And, of course, it's not that simple. For some reason, the downlink was unexpectedly meager, and we missed most of the ultimate FHAZ. Fortunately, Cooper's able to work it out using previous sols' imagery and the penultimate imagery from this drive, so we'll make it. With a small dash of luck, anyway.

I'd cross my fingers for luck, but my right hand's not up to it.

[Next post: sol 619, September 29.]

Spirit Sol 607

The scientists are happier than I am. In and of itself, that's an okay state of affairs; I'd rather have it that way than the reverse.

The scientists are happy because they have a nice scuff to play with. I'm unhappy because the scuff isn't where it was supposed to be. It's on the wrong side of the dune -- the far side, not the near side. This is an error of maybe half a meter; we should have been a lot more precise than that.

Chris works out what happened. In the main drive sequence (the "backbone," as we call it), we had several clauses that were intended to help us execute the drive more precisely. They checked if we were close to our defined target, and if not, they commanded a short step in its direction.

The problem arose because of our obstacle-check helper. For that part of the drive, we were running the helper explicitly as needed (as opposed to just letting it execute in the background) because the same "variable" that it uses to check whether we're too close to each obstacle is also used to check whether we're close enough to a goal. We wanted to be sure that the helper and the backbone didn't stomp on each other's use of this shared resource. The problem that escaped both Chris's and my notice was this: the backbone didn't reset the variable's value after calling the helper. So the helper stomped on the value, then we neglected to reset it to what we wanted.

The outcome we got -- a perfectly scientifically useful scuff half a meter away from the intended position -- was just about the least bad thing that could have happened. This mistake will be the subject of an automated check very shortly.

But not as soon as I'd like, I'm afraid. I'm going in for shoulder surgery Monday and will be unable to work for at least a couple of days. Chris is already covering my Monday shift, and John agrees to take my Tuesday shift. I already had Wednesday off, so I plan to just take those days off altogether and come in Thursday to help Jeng drive Opportunity -- one-handed, for my part.

It looks like I'll be leaving the rover in some increasingly capable hands. Since I had to meet with the surgeon and have some labwork done this morning, Paolo filled in for me until I was able to get here. I was a little worried about it since we're planning IDD work thisol, and Paolo has told me he's a lot less comfortable with the IDD than he is with driving. But I ask him to walk me through the sequence, and he knows it just about perfectly. He's even able to sketch out the process of doing it; he'd probably have been able to build the sequence himself, or come close, if John hadn't been here to do it.

Impressive.

[Next post: sol 613, September 23.]

---

Courtesy NASA/JPL-Caltech. The scuff, right in front of us.

Spirit Sol 605

The Erebus Highway drive worked splendidly, putting us right where it was supposed to. Now, back on the other side of the world, I get to help pull off another miracle: an 11m drive followed by a scuff. This is just like we did on Serpent way back on sol 72 or thenabouts, only starting from much farther away. This should be a good test of our abilities: have we learned enough since then to make something like this work? Chris is more confident than I am, but I sure hope he's right.

We break down the responsibilities more or less like this. Chris is going to worry about getting us there, and Ashley and I will work out the obstacle-checker helper sequence and the scuff sequence itself. The obstacle checker is going to have an important responsibility thisol: keeping us from driving over a cliff. Really. The dune (ripple?) we want to scuff is right on the edge of a cliff, and if we go a meter or so past it, it's bye-bye, Spirit.

The way the obstacle checkers work is this. We work out a list of known obstacles, and for each one, we define a circular hazard region around it. Essentially, the obstacle is the center of a circle we want the rover to stay away from. Then we plan a path that avoids all the circles, but just in case, the obstacle checker runs in parallel with the drive, periodically checking off its list and making sure the rover is outside of each circle. If the rover strays inside a circle, the checker issues a command that stops the rover from driving any farther.

While there are several other obstacles, the most interesting, and the one I attack first, is the cliff itself. When I rotate the terrain mesh so that we're looking down on it, I notice that the cliff face is a rough semicircle. Hmmm. Working by eye, I estimate the center of that circle, pick a radius -- eight meters -- and ask RSVP to show the circle I've just defined. It matches up with the cliff face almost perfectly on the first try.

"Not gonna get much better than that," I say nonchalantly and go on.

For the scuff, we have a couple of choices. We've done two basic kinds of these. The first was the one we did on Serpent, where we started by planting a wheel where we wanted the scuff to begin. We then turned the rover about five degrees to the left, then ten to the right, then five to the left, leaving it where it started. Next, we backed up 10cm and repeated the wiggle maneuver. The result was a beautiful, broad and deep scoop in the ripple face.

The other kind of scuff we've done didn't involve a ripple; we were just scraping off a top layer of soil. That worked differently. We spun both front wheels forward, holding the other wheels steady, to scuff away any material directly under them. Then we drove the rover a few cm backward with the front wheels locked in place -- using the middle and rear wheels to drag the front two. Then we repeated the whole maneuver, spinning the front wheels to kick away any material that accumulated under them while we dragged them and then dragging them back again, and so on. The result was just what we wanted: a shallow, clean scuff that exposed the immediate subsurface layer.

In this case, we're after the deep scoop, so I pick the first one. This is quite a blast from the past: I vividly recall building this scuff sequence the first time, and though we have to modify it slightly for this new situation, I have a lot of fun revisiting it.

So the sequence is built, and we cross our fingers that this very aggressive go-and-scuff will work. As it happens, today comes with a reminder that Murphy's Law is very much in force. They missed yesterday's downlink on both vehicles due to some kind of DSN station problem, and today we find out the details. It turns out that rodents chewed through some cables at one of the antennae -- the one our downlink was coming in on -- at the DSN complex in Goldstone.

Chris has the perfect pun for the occasion. "Rats!" he exclaims.

[Next post: sol 607, September 17.]

Opportunity Sol 582 (Spirit Sol 600)

Today is Erebus Highway Day. I have a feeling about this. The last few drives have all been going great; we're really on a roll. And we can see the highway itself in the distance.

Wait -- "the distance"? Heck, that thing's only 25m away from here.

The problem is, we have only two hours to drive, and with our visodom-heavy drive structures, that's not a lot of time. But I look carefully at the images, and there's a straight path along mostly low ripples -- the highest point I can find is about 13cm, and that's nothing -- leading all the way to the highway. It's the on-ramp.

Well, Mars doesn't give us these gifts every sol, so when we get 'em, we might as well take 'em. I plant a waypoint on the highway and plan a drive that takes us straight there, with periodic slip checks. This is nothing -- should take only an hour and a half or so, even with some extra imaging we're taking along the way.

If all goes as planned, we'll be on the Erebus Highway by Monday!

[Next post: sol 605, September 15.]

Opportunity Sol 580 (Spirit Sol 599)

Thisol's drive shapes up to be rather dull. We didn't get drive-direction PCAMs for some reason, so we're limited to the NCAM mesh, and this limits our drive to 15m or less.

But, of course, it's never quite that simple. Thisol there are two complications. First is the comm heading. We end this drive by heading south along a trench to a point where we hope we'll be able to cross a ripple on the next sol. Because of this southerly trajectory, the most natural heading after this drive would be about 200deg. But this is a terrible direction for comm. Good would be about 310deg.

On Spirit -- no problem. Turn in place. But on Opportunity, turns-in-place are limited. Paolo checks out an alternative drive, where we do a sort of K-turn before heading backward down the trench, but this doesn't cut down the turn's magnitude enough to be worth the extra effort and uncertainty -- not to mention that it converts the turn to a counterclockwise one, which is even less desirable.

After wrestling with this problem for a while, I realize we've overlooked something. The turning rules are relaxed when we're on outcrop -- and at the end of this drive, we'll indeed be on outcrop. So we should be able to do the large comm turn after all.

If we're sure we're going to be on outcrop, that is. We can solve that problem by using visodom -- but we don't have time to use it the whole way. In the end we use visodom for the first half of the drive, then do a blind segment with a visodom-based slip check, and then go the final segment blind. There's a little bit of finger-crossing involved in this, but not too much. If the slip check passes, we're making real progress, almost certainly enough to make it where we think we're going. And if we get it wrong, well, the turn in place is clockwise, so at worst, we should just be piling up dirt on the outside of the turn -- not scooping it into the wheel, which is what happens if we turn the other direction. And if we're really bogged down, one of the timeouts on the turn segments should trigger and keep the problem from getting too bad.

I think I'll cross my fingers anyway.

Opportunity Sol 577 (Spirit Sol 597)

No rover driving today. Nobody thought to tell me or Cooper -- though, really, we could have figured it out if we'd looked at a (Mars) calendar. We won't even get the data for the drive they planned last Friday until 22:00ish today.

This is the latest (and I hope last) vestige of our anomaly-inspired paranoia. They wanted to make sure that all the other stuff they'd planned, which included some MTES activities, went as expected before we drove. And they wanted to avoid calling the team in over the Labor Day weekend. Plus, this week's only a four-day post-holiday week, and since we're in restricted sols, we can drive only twice this week anyhow. So they held the drive until the last sol of the weekend plan, and we'll hit the road tomorrow.

[Next post: sol 599 (Opportunity sol 580), September 9.]

Spirit Sol 592

Just in front of Spirit are a couple of tasty-looking rocks -- concave, with some kind of striations, almost as if they were wheel prints. At the SOWG there's a lengthy discussion about them. At issue is whether we should stay and IDD them -- MI at least, possibly with APXS -- or drive on and possibly return for this later.

Driving away and coming back later is not something we do often. But apparently there's already one target they've pushed onto the return stack, some rock called "Irvine," and this could become another.

The reason they're eager to leave is simply one of timing. We've already performed the first half of a long-baseline-stereo observation, taking a bunch of pictures of the valley beyond Husband Hill. The other half of that experiment is where we drive about 10m away and take pictures of the same terrain from the other vantage point. It's like having two eyes set ten meters apart, which provides fantastic stereo coverage. And all this will be important for our future exploration.

But if we don't go ahead and do the drive, we'll be sitting in this spot for the weekend -- the extended, Labor Day weekend. The obvious compromise, doing a touch-and-go, is ruled out because of time and flash volume constraints. And while these rocks are intriguing, they're not worth spending five sols on.

That's particularly true in light of the continuing southward motion of the sun. In the next hundred sols or so, the energy curve will start to strongly favor south-facing slopes, which means we want to be climbing down the far side -- the south side -- of this hill before too much longer. And we have a lot of science and reconnaissance to do between now and then.

This all adds up to what should be an obvious decision: do the more important stereo imaging now, and come back to these nifty rocks later if there's time. But Ed Guinness, the SOWG chair thisol, is trying to get this across to the particularly wishy-washy scientists who are advocating staying, and he doesn't just take charge and push forward, as some other chairs would do in his place. So this discussion takes maybe twenty minutes, half an hour.

Eventually there's a compromise. All we have now is HAZCAM imagery, which isn't good enough to help us decide whether to return. So they'll PCAM the rocks before leaving, giving us much better data for that decision. Even this, however, turns into an extended discussion. How many filters? We don't have time for that many. We can't see it from the PCAM's right eye, so we'll have to back off before we use those filters and take the image mid-drive. Oh, now you don't want the right-eye filters? And so on.

When at last the time comes to name this target, one wag suggests "Indecision." But they don't call it that, of course.

What with the extended-mix vacillation, we almost miss the press conference. This is Steve Squyres and Chris Leger and Ray Arvidson and Jake Matijevic arranged around some guy I don't know, who turns out to be the NASA guy in charge of Mars exploration.

John turns to me. "Is Chris the only rover planner who's been in a press conference?"

"Yeah," I say. "I think it's because he's the only one who owns a tie."

Steve is up first. "Today is day 591 of our 90-day mission," he begins. He goes on to sum up the progress of both vehicles, emphasizing Spirit's arrival at the summit of Husband Hill. He shows off the first three-fourths of the 360-degree PCAM panorama from the top. And he and Ray announce that as Spirit ascended Husband Hill, she found definite proof of water in Gusev Crater. He reveals that we've returned ten gigabytes of data per rover so far. But the thing I think I'll always remember from this press conference is a picture Steve Photoshopped to show the scale of Husband Hill. He took the original color PCAM image of the Columbia Hills, cast around for some familiar object that was about the same height as Husband Hill, and put that object in the image in front of the hill. That object is the Statue of Liberty.

One of the last questions they take is for the NASA HQ guy: will the rovers continue to receive funding? Well, what can the guy say? "Yes, now that you've seen this spectacular image and we've learned there's irrefutable evidence of water, we're pulling the plug"? Of course not. Instead, he notes that we already have funding allocated through September of next year, with six-month reviews. "And as long as they keep doing good science, we'll keep funding them," is the substance of it.

John Callas, watching this with us in the SOWG room, pipes up, "Everybody write that down!"

[Next post: sol 597 (Opportunity sol 577), September 7.]

---

Courtesy NASA/JPL-Caltech. The front HAZCAM view showing the rocks we were thinking about exploring. I don't think we ever had time for them, though.

---

Courtesy NASA/JPL-Caltech. That hill was this high.

Opportunity Sol 573 (Spirit Sol 591)

We're not finished being paranoid yet, so thisol's drive is still circumscribed. Callas had a 5m drive in mind, but a 5m drive would just take the rover a short way along a patch of outcrop -- it's hardly worth doing. We might as well cross the next ripple, and that's more like 10m. Somehow I manage to talk him into this, and over the ripple and through the woods, to Grandmother's house we go.

Er, or something like that.

I thought thisol would be a doddle, but it turns out to be a little more challenging than I'd expected. Not greatly so, but at least there's some original thinking required thisol. We're still copying from the sol 563/567 drive, and the next segment of that drive -- the one that takes us over the next ripple -- would leave us at a heading of 10 degrees. But that's relatively poor for comm; we need a heading of more like 65 degrees.

This change is not as simple as you might think. Back in the day, we'd just turn in place at the end of the drive. But on Opportunity, with her stuck right front steering actuator, the rules limit the size of point turns, this prohibiting this simple solution. Instead, we work out a way to modify Opportunity's heading before she crosses the ripple, which enables us to get her heading to 45 degrees. After she hops the ripple, she turns in place the remainder of the way.

This maneuver comes with problems of its own, though. Instead of leaving Opportunity heading more or less along the ripple, she's parked transverse to it. This is an uncomfortable position for a rover that can't do large point turns and can do sharp arcs only in one direction. But we keep plugging away, and manage to convince ourselves that a combination of sharp arcs and small point turns can get her back on track again. So we leave her there, with copious notes in this sequence about how the next one had probably better look.

The other thing that happens thisol -- well, first I have to tell you about my superstition. The two-weeks-to-Erebus thing doesn't count -- that's not a superstition, that's a law of nature. No, my superstition is that if you write the uplink report before the CAM, something will happen at the CAM that requires us to rebundle. Basically, it jinxes the CAM.

I've told Paolo (RP-2 thisol, shadowing Jeng) about this superstition, but he goes ahead and does it anyway. He has a good excuse -- he has to go help Mark Maimone get the SSTB rover back online -- but it availeth him not. Sure enough, during the CAM I notice an error in the RP sequence, which would cause us to record less drive data than we'd want -- part of our paranoia is that we want lots of this data, particularly when hopping ripples -- and we have to fix it and rebundle.

This superstition is well on its way to becoming a law of nature, too.

Opportunity Sol 569 (Spirit Sol 589)

First day of school. There's a line a mile long -- backed up all the way to the freeway -- along the road we share with a couple of local high schools. I cleverly go down to the next exit, which turns out to be not so clever because there's a huge line there. There's another school on that hill. The clever rover driver forgot.

What with one thing and another, I'm about five minutes late. Which I think is no big deal, since there's no way we're driving.

Except, of course, that it turns out we are driving.

Great!

Not very far, though. I notice Dan's skeleton plan allocates only one hour for driving. "What can you do with one hour -- blind driving only?" he asks me. As part of the "baby steps" plan for getting back to normal, we're under an IMHO ridiculous temporary prohibition against using the PMA while driving.

"Not much," I tell him. "Especially since we can't go more than about five meters without slip checks, and we need the PMA for those."

"That's okay," Emily Eelkema interjects. "Five meters is fine. We just want to use all the motor control boards and actuate the steering and drive motors."

Well, fine by me. Actuating the steering and drive motors is what I'm here for. I plan a drive the easy way -- take the one we were prevented from doing on sols 563 and 567, and chop away all but the first 5m or so. Looks like we will do this drive, after all. One piece at a time.

[Next post: sol 591 (Opportunity sol 573), September 1.]

Opportunity Sol 567 (Spirit Sol 586)

Opportunity's recent reset -- her little fainting spell -- is still a mystery. As with the previous, similar anomalies, we suspect that it's MTES-related, so there's no MTES this weekend. (However, we don't know that; it's just an educated guess. As John Callas later puts it, "The MTES just happened to be in Ford's Theater when Lincoln was shot. Twice.") But we're driving.

Or not. My plan is to resurrect the sol-563 drive, which never took place because Opportunity fainted before she could drive and therefore wisely decided to stay put instead. But John Callas swings by and sees it on my screen. He's nervous. "You think this is too ambitious?" he asks.

I don't. But he's getting flak from NASA HQ, which (the phase of the moon being what it is) is accusing us of proceeding too aggressively in the wake of a fault we can't explain. He goes away to worry about this, in a big meeting on the topic, while I smooth out some of the drive's rough edges.

We won't have quite as much drive time allocated for thisol as we did for 563, but Paolo works out a clever way to shave enough time off of the drive without compromising anything. We have it all ready to go when the anomaly meeting concludes.

The word: this reboot is, for some reason, worse than the last time something like this happened. (For some reason, we have no data products showing what happened immediately before the reboot -- a very unusual circumstance.) So we're doing nothing of interest this weekend. In particular -- you guessed it -- no driving.

This seems overcautious to me, but Justin Maki, who was in the meeting, provides the inside scoop. "Somebody brought up the point, 'What if you drove on without any further investigation and you never heard from Opportunity again? Could you tell the review board you did the right thing?' From there, it degenerated into a worry-fest." He grimaces. "I'm going to go get some lunch."

Worry-fest aside, the basic question is the right one to ask. Nobody thinks the investigation will turn up anything, since Opportunity was only executing a standard MTES sequence it had executed many times before. But the questions we'd face if we didn't do it ....

Okay, fine. This drive will go up someday, just not today. Meanwhile, I think Justin was onto something with that whole lunch idea.

[Next post: sol 589 (Opportunity sol 569), August 30.]

Opportunity Sol 563 (Spirit Sol 584)

Yestersol's ambitious drive accomplished little. But it's not our fault: as part of our post-Purgatory paranoia, Opportunity has been driving with lower-than-usual current limits set on her drive motors. This is meant to detect when she's bogged down in a ripple (since the motors have to push harder than usual in that case), but in this case, they tripped during an otherwise perfectly nominal turn-in-place on a patch of outcrop.

This is the first time this has happened to me, but not, as it turns out, the first time it's happened. It's the fourth, and Jeff Biesiadecki's had enough. Thisol we're raising the current limits, and picking up the drive where we left off.

"It's spooky how close we are to the predicted position, though," Jeff muses as he looks at the situation in RSVP. We drove about 5m or so, and the rover really is right where RSVP said she would be at the turn-in-place point. Which is always nice, and something we've seen from our software over and over again. We really are quite good at this.

After lunch, I'm in the elevator with several other members of the uplink team. I push the button for the fifth floor and then realize I don't have time to stop off there. "You ought to be able to unpush the button," Jeff says. "Maybe it should toggle on and off."

"Yeah, but then people like me who push the button multiple times would have to be careful. We'd have to be sure to hit it an odd number of times."

"If you were in a hurry, you could toggle off other people's buttons and get to your floor faster," Jeff points out.

This is how I know I'm at JPL. I'm in an elevator, and we're redesigning the thing's user interface.

The sol goes well, though it takes longer than it should given that we're supposedly just picking up yestersol's drive sequence. (We can't resist the urge to tinker. That's the Elevator Lesson.) "I'm hungry," Beth Dewell says at 7PM or so. "I think I hate these late sols as much as Scott hates the early ones."

Feel my pain, baby!

[Next post: sol 586 (Opportunity sol 567), August 26.]

Opportunity Sol 562 (Spirit Sol 583)

Ladies and gentlemen, Spirit has arrived.

More or less.

The science team certainly seems to think so, and sent out congratulatory email to that effect. And Chris Leger has an argument that we're there: "Spirit's NAVCAMs can see horizon in every direction. If you were standing there, you'd say you were on the summit."

But the rear HAZCAM tells a different story. There's still a slight rise behind us, which peaks just a little way out -- less than ten meters, to my eye, probably more like five.

So we're there. Or we're not, depending on how you look at it. And maybe this isn't such a bad outcome, in its way: it gives us something to argue about, and more people who can plausibly claim to have been involved. I know I'm happy.

But I'm not on that rover; I'm back upstairs in the Land of Opportunity. I've been gone only a couple of weeks, but it feels a lot longer. Opportunity has spent almost the entire time IDDing outcrop, mixing in a couple of short bumps to sample additional tasty regions. But thisol it's time for us to move on, and we're striking out boldly. The whole drive doesn't cover that much distance, only 25m or so, but it's a long, winding one, a very rough "S" that wanders south and then north and then flattens out, hopping three ripples in the process. The point of all this meandering is to take us east toward Erebus Highway, which the scientists have decided, based on the outcrop we've just seen, that they definitely want a look at. (Cooper points out that this eastward jog will more or less maintain our radial distance from Erebus Crater, thus preserving the property that Erebus is always two weeks away. My theory holds!)

I can't refrain from asking the scientists what's so interesting about
the outcrop here. "Are you just starved, or does it taste good?" I ask Larry Soderblom, who at the moment is just a voice on the telecon. "I mean, are you guys just excited to see rock again, or is there actually something scientifically interesting about this rock?"

"Some of each," he laughs. "This outcrop is different from all the previous outcrop we've seen -- all of that stuff was exposed by impact events and maybe affected by them, so now we get to see the differences between that and non-impact-affected outcrop. Also we can check out the lateral variations in chemistry." Meaning, we get to see whether the water in this area was doing the same stuff as the water where we were before.

"Are you seeing any differences?"

I can hear the shrug. "We haven't seen enough of this stuff to tell. That's one of the reasons we want to get to the Erebus Highway."

"We're also gaining elevation as we head south," I muse. "Are we ever going to reach the shore of this sea? Maybe find areas that weren't affected by water after all?"

"Don't know," he admits. "There's a debate about whether we're going up or down in the stratigraphic sequence." I guess that should have occurred to me: just because this area is higher now, doesn't mean it was higher when the water was here. That sort of thing can happen to planets. Oh, well; that's why Larry's a geologist and I'm just a lowly Mars rover driver.

A lowly Mars rover driver who took Spirit to the summit of Husband Hill.

Spirit Sol 581

We made OK progress, about what we expected or a little less. The bad news is, the summit's about 45m away. That's more than Spirit's been covering in a sol, so we probably won't make it thisol.

Not that that's going to keep us from trying. We have the advantage of being more or less atop the hill already, so the going is flatter and less sandy. We can do the first 20m of the drive blind, which is wicked fast (well, relatively speaking) and something Spirit probably hasn't been able to safely do since she started climbing. And that will help a lot.

"We might make it with three hours of drive time," Chris muses. "Hey, how much drive time do we have?"

"Two hours and forty-five minutes," Colette replies. Chris and I glance at each other -- and then turn back to Colette, wearing our most winning smiles. "I'll look into it," she says.

The planning meeting continues. As the scientists are winding down, Chris notices something in one of the NAVCAMs. He has Brenda project his screen on the front wall, where everyone can see it.

There in the distance is Home Plate.

Home Plate is one of the reasons we climbed Husband Hill in the first place. It's what's on the other side. From orbit it looks like a -- well, like home plate on a baseball diamond. It's a white, roughly pentagonal feature that might be an ancient Martian playa, an old lake where repeated evaporation events left an enduring salt crust. That, of course, would make it part of the "water story" of Gusev, so it's long been viewed as a high-priority science target.

It's exciting, of course, just to see our upcoming destination. What's even more exciting than that is the realization that WE CAN NOW SEE OVER THE HILL.

It's overwhelming, really. I don't know how to describe it. This isn't the summit, but it's the next best thing. When we started this project, Mars was so impossibly far away. Then we made it to Mars -- and the Columbia Hills (including Husband Hill) were so impossibly far away. Then we made it to the base of Husband Hill -- and the summit was so impossibly far away. And now we're within striking distance of the summit, proving it by looking over that hill.

Right now, Home Plate is just a whitish smear in the image. To me, it's one of the most beautiful things I've ever seen.

And I'm not the only one who thinks so. Alicia Fallacaro keys her mike. "Uh, Ray, Diana Blaney is requesting another PANCAM image ...." No need to say of what. We all crack up.

Having seen this sight, I'm even more okay with not making it to the summit. Paradoxically, I'm also even more inspired to make it. But whether we make it is going to be up to Colette and the rest of the team -- thermal, power, and so on -- as much as to the rover drivers. Can they give us the drive time we're going to need?

They try, I'll give them that. The answer changes through the day -- they find a way to give us thirty minutes, then have to take it back, that sort of thing -- but in the end it's the same sort of story as last time. They've already squeezed out as much time as they safely can. And as eager as we are to make it to the top, the golden rule with these rovers is: safety first.

So we probably won't make it this time. Maybe we'll have to wait until next week. Well, we've waited this long.

Our imminent arrival at the summit is starting to become a reality for everyone. Jim Erickson stops by to ask Chris and me about whether -- rather, when -- he should call a press conference to announce it. "I don't want to call it prematurely," he says, "but on the other hand, if we wait too long, we're going to get scooped by the bloggers." Yet another reason I'd rather have my job than his.

Chris and I work out the drive sequence. It's the first drive sequence we've built which, if it completes (please, oh, please!), will take us to the summit. In a flash of inspiration, Chris tells the rover to drive forward for the last few meters. We mainly drive backward -- the rover climbs a little better that way -- but traction isn't as big an issue now as it has been, and, as Chris points out, we're supposed to switch drive directions periodically anyway (to distribute wear and tear on the system).

But of course, that's not the real reason to drive forward at the end. The real reason is, in a word, style. Backing up onto the summit -- well, somehow it just isn't dignified. Would you drag yourself ass-first onto the peak of Everest? If we get really lucky, we'll end up with one of the front wheels poised on a rock, lifted slightly in a sort of planting-the-flag gesture.

Or not. As it turns out, the direction we'd be facing in if we drove forward will be bad for comm. So we have to change it back.

Undignified, maybe. But ready or not, summit, here we come.

[Next post: sol 583 (Opportunity sol 562), August 23.]

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Courtesy NASA/JPL-Caltech. There it is: Home Plate, dead center, just visible in the valley beyond Husband Hill, with Von Braun Hill visible just beyond that.


Courtesy NASA/JPL-Caltech. We were so excited that we could see Home Plate, I'm not sure we even noticed this huge dust devil at the time. We must have, surely, but hell if I remember it today.


Courtesy NASA/JPL-Caltech. Just a little farther, girl. It's right there. You can do it.

Spirit Sol 578

Our previous drive went well. From here we can see what we think is the summit -- no more need to rely on uncertain orbital data for that, we hope -- and it's about 70m away.

I have this sol and, because we're in restricted sols now, just one more before I go back to Opportunity. And 70m is probably a little too far for us to make it in those two drives. Unless we can drive longer today ....

So I start campaigning for more drive time. I even try turning on the charm, which in my case is admittedly like turning on a rusty faucet in a long-abandoned house. And it's about as productive: no more drive time. We have to nap to keep the rover from overheating, and there's no science in the plan but the drive-support imaging, which obviously we can't cut.

We plan a drive that will probably make something like 30m progress (we command 50m but expect it to be cut short due to time), which will cut the remaining distance to the summit more or less in half, and leave it there. I'll just have to cross my fingers and hope Spirit has an unusually good day.

And if she doesn't, then, oh, well. So maybe someone else will have the actual experience of driving Spirit the last few meters up onto that rounded peak. It's just as well if the honor goes to one of the more regular Spirit drivers, who have done more than I have to actually climb her up this hill. I've got plenty of feathers in my cap already; it's getting a little crowded up there.

But it would be awfully cool to add this one.

[Next post: sol 581, August 21.]

Spirit Sol 576

Ray Arvidson says, "We'll be at the summit, if we're lucky, next week. Summit Two (this hill has two peaks, and that's the nearer and taller one) was about 120m from our last target, and we did about 30 over the weekend."

But someone else reports that Larry Crumpler's localization puts us only 45m away, half that distance. I ask Ashitey for the scoop, and he grins and rolls his eyes. "Nobody knows," he says.

"Did I just hear them say there's about 50m of uncertainty?"

"That," Ashitey agrees, "plus or minus 100."

It's rather like what happened as we approached the base of this hill. We were obsessed with reaching the base, and when we got there it was just a gradual slope -- a transition, but not an abrupt one, from plains to hillside. There was never a dividing line that said "You Have Now Reached Husband Hill." And now that we're reaching the top, it's the same thing: we're looking for a flag, forgetting that we came to plant it.

LTP finally comes on the line (they were knocked out by lightning, which destroyed the badge readers at their University of Arizona building) and speaks to the point, though they don't offer much clarity: according to them, the summit is either 50m or 70m away, at an azimuth of either 104 or 140, depending on whose localization you believe (Larry Crumpler's or Ron Li's). Ashitey says he wants the summit to be about 300m away, since he's going out of the country for a week and doesn't want to miss the goal he worked so hard for. But while there's uncertainty in the numbers, there's not that much uncertainty. Sorry, Ashitey.

Well, we'll drive at 120 today; that'll be close enough for now. And we're only going 20m, because that'll take us to a ridge we need to see over in order to continue.

Ashitey does most of the work as Ashley Stroupe -- another Mob/IDD team member training for the RP job -- looks on. Then Ashley watches and works with me as I do my RP-2 thang.

She's pretty sharp and seems to be coming up to speed well. Which is what I tell Frank when he asks me. "She seems kinda nervous, but I think she's gonna be fine," I tell him.

"Nervous is good," he says. "I worry more about the ones who aren't nervous. Like, I think, 'I remember how nervous I was when I was first doing this. How can you not be nervous?'"

Which is funny and true. If you're not nervous about taking this job on, you're not taking it seriously enough.

Later, I have Ashley walk through the sequence for me, as a way of ensuring she understands everything in it. Then -- what the hell -- she understands everything anyway. "So you do the CAM walkthrough," I tell her.

She's reluctant, but she does it. And she does great.[1]

[Next post: sol 578, August 18.]

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[1] One of the pleasures for me in reviewing these notes, five years after the fact, is to see the first appearance of people who would later become rover drivers -- good ones. It happened with Jeng, and with Ashitey, and with Paolo, and now it's happened again with Ashley. Ashley, as you might know, is the lead RP for Spirit -- and I hope Spirit gives her some work again soon, when Spirit wakes from her winter hibernation.

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Courtesy NASA/JPL-Caltech. The way ahead. So close to the top that we can taste it -- and yet we're going to have to restrain ourselves to slogging ahead, one little bite of that distance at a time.

Spirit Sol 573

I'm back on Spirit. But what with the MRO launch usurping some of our comm passes, and the fact that we're in restricted sols anyway, we're planning so far ahead that we've already planned thisol. But it hasn't executed yet, so there's no data to plan a drive for the weekend. So they don't need me.

What they need is a way to fill up the downlink. This is not a problem I've been used to, over in the Land of Opportunity, but here in the Spirit World they're downlink-rich right now. They're getting something like 270 Mbits downlinked in the next plan alone.

One of the things they come up with to fill up the bits: more dust devil movies. What the heck, they're cool -- that's even how they get sold. "I just like that the scientific rationale is 'it's really cool,'" chimes in one of the scientists on the line. He's not quite objecting, but of course we do always want to use these rovers to best advantage. But quick-witted Diana Blaney retorts, "OK, I'll give you a scientific rationale. We're clearly entering a period of increased dust devil activity, and this will give us better data for statistical analyses." There's applause: Diana just solidly saved an observation we all wanted to do anyway.

And as another scientist points out: we're one and a half years into this mission, and we have a sol that's neither power- nor data-limited. These rovers are supposed to be dead. But obviously, nobody told them.

[Next post: sol 576, August 16.]

Opportunity Sol 543 (Spirit Sol 564)

"Wow, Scott, you're batting a thousand this week." Jeff Favretto is right: I'm on a roll and I know it. Once again, Opportunity is right where she's supposed to be, peeking over (and actually perched on) a small ripple, with a patch of outcrop just on the other side, lying dead center in the next trough.

The science team, having been long denied any rock targets to sink the rover's teeth into, wants us to put 'em right on top of it. So that's our plan. We could head straight for it, but if we did that we'd be crossing the ripple somewhat obliquely, and the right side would pass through a patch of relatively soft-looking stuff, which can hurt our precision. So we settle on a different approach, turning left and scooting directly across the ripple where we are, then turning right and heading down the trough onto the outcrop.

And now we have naming of parts. Larry asks for a name for the target we're trying to get into our IDD workspace in this drive. I point out that from overhead the outcrop looks like an ice-cream cone -- we're going to be driving along the cone and parking with the scoop in the IDD work volume. What I didn't realize was that Larry was asking one of the scientists to suggest a name. He suggests "Mound" -- the target being slightly raised, like a pitcher's mound.

"Yeah, that's original," I say off-mike, to the amusement of listeners in the room. "Let's go with that." (Later, Larry agrees with me, and they end up naming the IDD targets with an ice-cream theme.)

Well, they can't stop me from calling stuff what I want to call it. My uplink report speaks of crossing Fudge Ripple and driving along Rocky Road.

Mmmm, ice cream ....

Just before the walkthrough, Jeng and I get concerned about the precision of the drive. It's only Wednesday, so they can bump on Thursday if we don't get this right, and still be able to IDD over the weekend. But I want to get it right -- for the sake of my pride, and because this is my last Opportunity shift for a while, and, oh yeah, because sols cost a million dollars a day and my job is to make them go as well as possible.

Our concern is the first part of the drive, where we're crossing Fudge Ripple. If we're going to slip appreciably, we're going to do it here, and the rest of our drive depends on that part going correctly. After some discussion, we end up turning on visodom for that segment of the drive. Because of the leftward turn, we can't look back at our tracks, but there's a whole bunch of juicy outcrop in this area, so we point visodom at that instead. If it doesn't converge, we're no worse off than if we weren't using visodom at all, and if it does converge, it will help the drive go a lot better. So we'll probably win, and can't lose. Unless one of the dozen or so last-minute changes completely screwed something up.

I guess we'll see.

After I return to the Spirit World, Opportunity will spend a few days, possibly a week, IDDing this outcrop. Then she'll stow and continue toward Erebus.

She'll probably make it to Erebus in about two weeks. Or not. I've been joking that Erebus is a sort of anti-Wopmay and will always be two weeks away. I'm not actually sure that I'm joking, come to think of it. Last week or so, we thought Erebus was a little less than two weeks away, only to find that our position in the orbital mesh was wrong. The corrected position put us 75m farther from the crater -- adding another two or three days of driving, and putting us back to a full two weeks. See? If necessary, the whole planetary surface will move in order to keep Erebus two weeks away. And of course, as long as we sit here at the outcrop, Erebus will remain two weeks away.

I elucidate this theory for Jeff Favretto, who agrees sagely. "So you're saying it's some sort of Martian Groundhog Day. Every day you come in and plan pretty much the same drive, and when you come back the next day, you're still as far away as when you started."

Exactly!

[Next post: sol 573, August 13.]

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Courtesy NASA/JPL-Caltech. Our start-of-drive position -- right where we were supposed to be.

Opportunity Sol 542 (Spirit Sol 563)

At the SOWG meeting, Larry Soderblom asks if one of the RPs would give an assessment of yestersol's drive and give them a preview of what we're planning to do thisol. "Yestersol went perfectly," I reply, "and we're gonna do it again."

"All right, short and sweet," chuckles Larry.

Yestersol's drive did go perfectly -- textbook. As I expected, we can see that the jumbly bits at the far end of the drive are benign ripples, now that we're right on top of them.

So thisol we're going to drive over them, proceeding another 25m or so along this trough. At the end of that distance is another discontinuity -- probably just a small rise, but large enough that we can't see over it. Beyond that is a sweet-looking patch of outcrop. Off we go.

As I'm sequencing, I overhear Kurt telling Jeff Favretto something. Jake Matijevic has worked out that the drive motors on both vehicles have about 10 million revolutions. They were designed for 2.5 million but qualified for 4 times that, so we're right about at their limits.

Well, I always said we were going to drive these things until the wheels fell off. I guess we'll see how soon that's going to happen.[1]

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Footnotes:

[1] Five years later -- and many kilometers, and many millions of revs on the motors -- we're still going.