Opportunity Sol 707 (Spirit Sol 728)

Ah, that's a relief! Our second try at stowing the IDD in the "thinker" pose worked! The images look just as predicted, and the telemetry shows that the IDD's final position is spot on.

Now we just have to drive it. We've already put in a couple of days' work on the drive sequence, which is a good thing, because this one's going to the testbed for sure, later today.

Even with that testing, Ashitey expects me to be pretty worried about this -- "You won't sleep well tonight!" he laughs.

Won't I? I'm not so sure. "I'm not really that worried about it," I say, realizing it's true even as I say it. "I already told everyone it might take us more than one sol to do this, so it's okay if the target's not reached at the end of this drive. I mean, at this point, we just want to demonstrate that we can do a successful drive without tearing the IDD off." Maybe I shouldn't have phrased it that way, but it's essentially accurate.

Then again, Opportunity's been sitting still for almost 60 sols. Purgatory Ripple was only 40. As long as we get the damn rover in motion, I think some people wouldn't mind if we did tear the IDD off.

But that would disappoint Ashitey and Frank, who are hoping to use it tomorrow to start the 7x7x5+stereo MI mosaic of Upper and Lower Overgaard. (Well, maybe it would disappoint some of the scientists, too.) If we end up doing the whole thing, it'll be the largest-ever MI mosaic of a single object on Mars (obliterating one of my records -- the 6x4x5+stereo on Keystone). "I'm happy I'll be doing the first drive with the arm in this weird pose, but I was hoping to be in on that mosaic," I tell Ashitey.

He commiserates. "If you want it, you won't get it. That's how it works." He feels my pain, since he's been missing out on the cool Spirit drives we've done while he's been struggling with this IDD problem. "They promised me the last half-meter to Home Plate, though," he jokes.

Eventually, our testbed time rolls around, and Ashitey heads down there with Jeng to test our sequence. I stick around the sequencing room for a bit to handle the walkthrough, but then I can't stand it any more -- I have to go down there, too. Before I leave, Rich, the TUL, asks when I think they'll be done in the (notoriously time-eating) testbed. Who the hell knows? I shrug, look at the clock. It's a little after 3. "Uh, 4:27," I tell him.

By the time I get to the testbed, they're just starting to run the sequence. Amazingly, the thing runs all the way to completion without a hitch -- even the tight suspension limits work, at least in the testbed. As we're finishing up and preparing to head back up to the sequencing room, I check the time. 4:25.

I wait two minutes before calling them to tell them we're done.

Despite our success in the testbed, I'm actually somewhat pessimistic about the drive. Larry Soderblom asks me what I think are the odds it will succeed, with Upper Overgaard in the IDD work volume. "Fifty-fifty," I tell him. Then I can't resist completing the old joke: "Either it'll happen or it won't."

"I bet you a beer it'll work," he says.

I have a policy: never bet against the rovers. Besides that, I don't drink. So I'd have nothing to look forward to: either I "win," and get a beer I can't drink, or I lose, and have to buy him a beer. Nevertheless, in the spirit of camaraderie -- what the heck, just this once, I accept the bet.

[Next post: sol 732 (Opportunity sol 712), January 23.]

---

Courtesy NASA/JPL-Caltech. The IDD in the "thinker-stow" position.

Opportunity Sol 706 (Spirit Sol 727)

Opportunity's start time is sliding later, thanks to the Earth-Mars day-length difference, but it's not late enough yet that I can actually come in to work any earlier -- between 9:30 and 11:30, there's no parking to be had.

As a result, I'm in a couple of hours before we actually start, and this gives me time to check out Ashitey's meeting with Erickson, Callas, Eric Baumgartner, Joe Melko, and so on, about the current state of the IDD investigation. The first question is whether we should finish the mini-Martian-tai-chi (our cute name for the recalibration activity we were doing) before stowing. Nobody wants to bother; they just want to get the damn arm stowed so we can drive. So much for that.

Next question: is it OK to increase the rotor resistance for the duration of the stow? This resistance value is the thing that lets us work around the broken motor winding, and which had been preventing stalls until this weekend. Eric's take on this, which mirrors email he wrote over the weekend, is that this will be fine. They'd worked out the present value partly empirically, and everyone's willing to believe that we simply needed a little more margin in that number.

What else do we need to do to get ready to drive? We won't be driving today -- we're just going to stow the IDD in its new stow configuration -- but it's what everyone's gearing up for. First, we have to make sure we're not driving over anything too big. Ashitey negotiates a slight relaxation of the definition of "too big," but we're still left with this rule: the front and middle wheels can't go over anything bigger than 3cm; the rear wheels, 4cm. This is about what I'd already planned for, so no problem there.

Next, we have to set up the new stow parameters. The FSW's Fault Protection code has a feature where you can tell it what joint angles represent a stowed IDD and have it check constantly whether we're in or out of bounds; if we're out of bounds, it will stop the drive. We never used this on Mars, because when the IDD is stowed the normal way, it hangs securely onto a hook. But we'll be setting it up today.

Finally, Ashitey suggests reducing the wheels' max speed by 66%, on the theory that that should make us come off of an abrupt drop (if we screw up and have one of those) a little more gently. To my surprise, this is rejected: the rovers already move so slowly that there's little to be gained by this.

Oh, and we have to clear the errors left over from the most recent stall fault. And Jim Erickson asks me to add a rule to our flight rule checker that warns if you send the "stow IDD" command on Opportunity, since what that command does is no longer what we want to do.

That's all for the meeting. As was the case Friday, the sequencing itself is simple. Today it's even simpler, since we're basically just repeating Friday's sequence (after clearing the errors and increasing the rotor resistance). But, once again, it's worrying about the upcoming drive that consumes the greater part of the day.

First, Ashitey relays a concern from the science side about closing the APXS doors. You close the APXS doors by rotating the turret to one of the extremes, and in the new stow configuration, we're commanding it pretty close to that value. In addition, the wrist and turret have more "play" than the other joints -- they'll jiggle around while we're driving -- and we might therefore end up crossing over the line we're starting so close to. This is worrisome because the doors are so hard to get open once they're closed. That wasn't always the case, but we started having trouble with it on the surface, so we decided just to leave the doors open permanently. What happens if we inadvertently close the doors and can't get them open again? We effectively lose that instrument, and with it the ability to sense the chemical composition of rocks and soil.

But we're dealing with a failing mechanism here, and we need to make some hard choices. And that's the risk we decide to take.

We also spend a considerable time working out the suspension limits. We frequently set these limits, especially on Opportunity (come to think of it, I don't know if we've ever set them on Spirit), to help us decide whether we're crawling over something bigger than expected. So in theory, we should be able to just work out how much a 3cm or 4cm rock would articulate the suspension, poke in those limits, and proceed with a bit of extra insurance.

The problem is that, as with so many things we do, this is beyond the limits of what the hardware is rated for. The potentiometers that sense the suspension aren't accurate to more than 2 degrees or so -- they're not intended for this level of precision -- and a 3cm rock changes the rocker differential by a little less than that. Ashitey wants to be fairly generous with the limits, but I don't. "We've already sold everyone on the concept that this might take us a couple of sols here," I point out. "We might as well be conservative." We add a little margin, but it's still possible we'll stop for no good reason. So be it. I'm getting paranoid.

By the end of the day, we've got a pretty decent drive sequence. It's not terribly complex; it's another one of those sequences with a high discussion-to-command ratio. But that's okay. We're doing something new and weird, and we can screw things up that we could never fix again. So the more talk, the better.

But first let's just hope we can stow the damn arm, so that we can find out whether this even works.

Opportunity Sol 702 (Spirit Sol 723)

Because Monday is MLK Day, we're doing a 3-sol plan this weekend. We expect it to be fairly simple, if a little scary: we're putting Opportunity's IDD in its new stowed configuration today. This is the "Rodin's Thinker" pose: the IDD will be swung up over the solar panels, elbow-out, with the turret resting about 5cm over the left front solar array hinge. Ashitey's worked everything out in the testbed, where they've even tried driving in this configuration. But it's scary all the same.

Actually, just putting the IDD in that pose won't be scary -- driving like that will be.

Anyway, our day will be relatively simple. Unlike Spirit's. Spirit has turned around to IDD the chewed-up Paso-Robles-like stuff she turned up while climbing Husband Hill. This stuff appears to be salts, and since salts are mobilized by water -- you know, the stuff we're here to find evidence for -- most of the science team is hopping-up-and-down excited about it. (Though not Larry Soderblom, who dismissed it in email as "bright dirt." He thinks we should spend this time zooming toward Home Plate, as we're increasingly behind schedule. I can't say I think he's wrong, but I'm no scientist.) And they're doing one hell of an IDD campaign, some twelve targets or so over the 3-day weekend.

John Wright's the RP-1, so I have no doubt it'll get done, and get done well, too. But people keep asking me, "Aren't you glad you're not on Spirit?" And I have to tell them no. Truth is, I wish I were John. The harder the task, the greater the glory.

I guess I'll have to let him have a little glory.

Since we have a lot of time, I go ahead and get to work on next week's drive. I expect a lot of scrutiny, so the earlier I get a handle on this, the better. Happily, Ken Herkenhoff is out here, so I discuss the bump target with him and Wendy Calvin. They want us to get to a pair of rocks -- "Upper Overgaard" and "Lower Overgaard" -- that are slightly ahead of us and to the right. Before going there, we need to back up 1m and image the outcrop we've been parked in front of since the IDD anomaly.

Normally, this would be trivial: turn on visodom, back up, take our pictures, turn, and bump forward to the new target. But, oh, the restrictions we labor under now! In addition to the limitations we already have when driving Opportunity -- the requirements for periodic slip checks and the problems induced by the failed RF steering actuator -- we have new restrictions caused by the IDD's new stow configuration. In particular, we've decided we can't tolerate a drop of more than 3cm, as this might cause the arm to jounce too much and whack the turret against the solar panel. So we can't drive over anything bigger than two or three centimeters -- in common units, about an inch.

You think there will be anything bigger than that between us and Victoria Crater, still some kilometers away across Meridiani Planum? Naaahh ....

And, of course, since we're also restricting the IDD's azimuth -- to ensure that we can still drive even if it fails altogether -- we have to really nail the drive.

And there are a couple of obstacles of just the right size, right where we need to go. Of course. (And there is no position that gets both Upper Overgaard and Lower Overgaard into the new, sharply narrowed work volume, without doing something like driving way around and approaching from a different direction. Which we won't.)

So I have to plan the drive very, very carefully, and one crazy thing I come up with is not to use visodom. This is something of a gamble, but I think it's a sound one. Our slip is likely to be low, and it will carry us mostly away from the many 3cm-or-larger "obstacles" scattered all around us. It might mean we need an additional sol for fine positioning, but I can sell that. Everyone's so happy to be moving at all, they'll buy it. The alternative is to risk a bad visodom position update that would cause the rover to drive farther than it's supposed to, climbing the obstacles and possibly forever damaging the arm.

Did I say I wanted this to be hard, to increase the consequent glory? I take it back. Less glory, please.

Just as we're wrapping up for the sol, about 7 PM, we get the downlink from yestersol. I take one look and sigh. "Bad news, everyone!" I announce. "The last sequence faulted out near the end, during the return to the ready position." I hope this is another joint-1 stall, as opposed to a completely different problem, but that data hasn't come down yet. "So the stow sequence we built today won't execute over the weekend. Worse, the MB is aimed directly into one of the HAZCAMs." This is a condition we're supposed to avoid; the instrument's radiation source can damage the cameras.

So should we try to recover? Luckily for us, Jake Matijevic is still here. Jake gives us a pass on the MB situation, pointing out that the MB's radiation source has degraded significantly since we got to Mars, and at its current distance from the cameras, it should no longer be a threat to leave it like this for a few days. Emily decides not to reassemble the team at this point to try to fix the problem, especially because, due to missing data in the pass, we don't even know exactly what the problem is yet.

So we go home. I can't help thinking that one consequence of this fault is that it'll be at least one more sol before we can stow, so at the earliest we'll drive Wednesday instead of Tuesday (the day after the holiday). Depending on the analysis, we might have to push the drive later than that. And since I'm on Opportunity only Tuesday and Wednesday of next week, that means I might not get to do the first Mars drive in the new stowed configuration.

Hey, I want a little glory. I'm only human.

[Next post: sol 727 (Opportunity sol 706), January 18.]

Opportunity Sol 701 (Spirit Sol 722)

This was not a big sol. We were planning to do some RAT bit imaging, but that got scrapped at the SOWG meeting.

"Just so you know, we need to do the RAT bit imaging before the next time Opportunity uses her RAT," Emily Eelkema pointed out.

But, somebody replied, Steve's position was that "the next time the RAT comes out will be at Victoria Crater."

"I guess we've got some time to do the imaging, then."

And that was about that for that.

Still, we at least had something to do -- namely, we did more tai chi. The latest results showed about a 7mm discrepancy between the predicted position and the position computed from the images -- within our error budget, sure, but there's room for improvement all the same. So thisol's big IDD activity will be to move to the image-computed positions, take images there, and run them through the stereo correlation again to help with the (potential) recalibration.

It's not much to do, and delays elsewhere in the process make it a fairly slow day. This is a good thing, as it gives Matt Heverly, who's shadowing Ashitey thisol, a chance to really dig into the sequence. Indeed, Ashitey has Matt pretty much build the sequence from scratch, then disappears. Matt and I take the time to go over everything in the sequence in great detail, a good learning experience for him (I hope).

Life in the Land of Opportunity will stay slow until we start driving again, which could be this weekend but likely won't be until next week. Our next drive target is Overgaard, part of the same outcrop we're studying now -- the drive will of course be a very short one. But it's still important and interesting because PCAM imaging revealed "festoons," little smile-shaped ledges that are strong indicators of past liquid water. So compelling is this evidence that Emily refers to Overgaard as "the Holy Grail of Meridiani Planum."

"I thought that was Victoria Crater?" says Wendy Calvin.

"That's too far away," Emily says simply. "Let's focus on the present."

Victoria Crater is indeed far away. But so were the Columbia Hills when we started driving to them. Behold the triumph of persistence.

Opportunity Sol 698 (Spirit Sol 719)

Ashitey's already seen the IMAX movie -- he saw it this weekend. "It was okay," is his review, though he's more enthusiastic later when discussing it with Squyres. They both got to see it because they helped -- Steve, by being in it; Ashitey, by running the testbed's RAT and PMA actuators so that the movie could use realistic sounds.

Opportunity (I'm back to the other side of the planet) doesn't have much to do today. We're not driving yet; that gets pushed back about two weeks every two weeks. No real science-related IDD work, either, though we're doing a miniature version of the "Martian tai-chi" IDD recalibration. Not because we really think we're out of calibration, but because people keep asking Ashitey about it at the IDD anomaly meetings, and he wants to have something to tell them.

So it's a pretty easy day on Mars.

Before leaving, I get into a discussion with Chris Leger about the Spirit driving plan. We've been trying out these two-sol drives with an autonav-only drive on the second sol, but they haven't been working out too well, and he's worried that the time we spend on them gains us little and costs us a lot of attention that would be better spent on the first sol's drive. I don't quite disagree with this, but I think he's a little too pessimistic. All of our techniques start off with large investments and little initial return, but we rarely regret developing them. I see this as being another instance of the same deal. He doesn't quite disagree with that, but we both have the "I don't disagree, but let's both agree that I'm right" disease, so the conversation limps along a lot longer than it should.

Fortunately, it's interrupted by a phone call from my parents, telling me excitedly that they just saw me on the CBS Evening News. (It still hasn't aired out here, so they also want to let me know so that I can catch it.) I filmed an interview with a news crew last week, and I was just going to record it on the TiVo and send DVDs to the family as an FYI. But it turns out they caught it when it aired. Funny thing: when I'm on the phone with Dad and Trish, Roxanne[1] calls to tell me the same thing. Who knew that many people watched the CBS Evening News? Apparently, it's some kind of big deal or something.

When I get a chance to see the interview myself, I'm relieved. I didn't really feel that it went all that well, but the piece came out great, and I even look like I know what I'm talking about. Good editing, I assure you. I expected the two-and-a-half minute piece to be two minutes and fifteen seconds of Squyres, then ten seconds of Nicole (whom they interviewed about naming science targets) and one shot of me saying "It's great!" It turns out to have less of Squyres, more of me, and -- erk -- no Nicole. Well, that sucks, but it's America's loss.

[Next post: sol 722 (Opportunity sol 701), January 13.]

---

Footnotes:

[1] My then-mother-in-law.

Spirit Sol 714

"Our objectives today," Steve announces, "are to drive like the wind and then get the uplink team home in time to watch Texas beat USC." It's Rose Bowl Day, and Steve, in case you hadn't guessed, is a Texas fan.

Spirit made a respectable showing for her second Earth-birthday: 65m, most of it in the direction of Home Plate. It's not as terrific as I was hoping for, but it's sure not bad. Slowly but surely, the drive-metric graph is starting to look less scary.

She made it a good chunk of the way through the dune field that yesterday lay between us and Lorre Ridge, but a slip check measured 70% slip -- apparently real, not a visodom artifact -- and stopped the drive a little earlier than it would have otherwise.

Looking at our tracks, we can see that we really are slipping a lot. Rather than leaving nice, widely spaced cleat marks, the wheel tracks are all bunched up. However, we're not digging in, so Chris and I agree that it's safe to drive away.

Which will be fun. The path out of the dune field is relatively obvious, and firmer terra (marsa?) is only about 12m away, but on the way is a 30cm rock pile we definitely don't want to climb. With that, and the fact that we're slipping so much, there's only one way out: visodom. It'll be slow, but we've got a whopping four hours to drive, so we've got plenty of time for it. And after that we have a short blind segment followed by autonav until the time-of-day limit. (I'd rather spend the four hours on an 80m blind drive followed by a three-hour autonav segment, but we aren't in that kind of terrain. Mars wins.)

And there's something we need to do before we even get on the road. For the last few sols, we've been getting intermittent stall warnings from the left front wheel. We got another batch yesterday, and Matt Heverly and Terry Huntsberger work out that it happens whenever autonav decides to take a sharp left, meaning that that wheel is steered almost to the extreme counterclockwise position.

This probably isn't a failing actuator, but it could be. More likely, it's either a miscalibrated actuator or some junk physically jammed into the wheel. Hoping for the former, we start the drive with some commands to recalibrate the wheel, steer it to the troublesome position (to see if we get more stalls), then straighten the wheels and install new soft-stops that will prevent Spirit from steering that wheel back to the position where we get the warnings (for the rest of the day, giving us a chance to look at the data before she tries to go there again). If we see no warnings tomorrow, then the recalibration likely fixed it. If we do see warnings, well, we'll make the new soft-stops permanent. The new limit is only about one degree away from the old limit, so that won't compromise Spirit's driving appreciably anyway.

All the same, I'm hoping it'll go away and stay gone. One rover with a bad steering actuator is plenty.

[Next post: sol 719 (Opportunity sol 698), January 10.]

---

Courtesy NASA/JPL-Caltech. Spirit's tracks look a little closely spaced -- this is different terrain, probably with somewhat looser soil, than we normally drive her in. Still and all, though a little worrisome, it's traversable.

Spirit Sol 713

I couldn't resist checking in on the drive from home last night, and I was somewhat disappointed. Shortly after starting the autonav segment of her drive, Spirit found herself in a cul-de-sac. Her existing path planner isn't smart enough to find its way back out when this happens, so she just struggles with it for a while and gives up in frustration. Total progress: 50m or so -- respectable, but much less than we hoped for.

"What are the chances we'll get outta the cul-de-sac and make progress on sol 712?" Steve asks me just before the SOWG meeting starts. That's the final sol of the weekend plan, whose data should start flowing in in half an hour or so.

"Slim," I answer. "Less than ten percent."

"Well, that's Mars. The plan for today and tomorrow is gonna be drive, drive, drive."

"Well, if you insist," I shrug as he laughs.

When the data arrives at last, it confirms my prediction. I'd have been happier to be wrong, but so be it. I don't have much time to worry about it, not only because we've got a sol to plan, but also because today's Spirit's "Earth-birthday," as Brenda calls it -- the second Earth-year anniversary of her landing on Mars. I still have trouble believing it -- not just believing that they've lasted so long, but also that I've been on mission operations for this long.

So we interrupt sequencing long enough for a small celebration in the SOWG room. Jim Erickson and Charles Elachi and Pete Theisinger and Steve Squyres all say nice things, and thank and congratulate the rest of the team, and then we're back to work.

An occasion like this one is a time for personal reflection, too. It's so corny to say it, but I've grown and changed a lot in those two years. I can see it in looking over some of my earliest notes on ops. I never thought of myself as lacking self-confidence, but back then I was ... well ... I'm different now. These rovers have changed me, and they've changed me for the better. They're old friends to me now. We've been through a lot together.

What better way to celebrate than by dodging some rocks, putting the pedal to the metal, and lighting out for Home Plate? So I do that -- or, rather, I ask Spirit to do it. As far as I'm concerned, there's really no difference any more, if there ever was.[1]

---

[1] Happy birthday, Spirit, my love.

Spirit Sol 710

Today we're planning three sols. For a long time now, when we've had three sols to plan, we've usually done it so that the rover drivers have only one sol to plan -- at most, two. Today we have stuff to do for all three sols. The first sol, we're continuing IDD work on the El Dorado scuff; on the second, we stow and drive; on the third, we do an autonav-only continuation drive.

Which is kind of insane. But, as Larry Crumpler points out at the SOWG meeting, we're 300-400m behind our drive metric. You know, half of our original mission-success drive metric, more or less. Nothing major. So we need to squeeze in as much driving as possible.

I hate to admit it, but I don't handle it very well. Not in terms of my attitude, which is fine, but in terms of delegating. I somehow get the idea in my head that I should first knock out the IDD stuff and then work with Chris on the drive. But I take longer to finish the IDD work than intended, leaving Chris with little to do. And the drives are both pretty complex. What I ought to have done is push the IDD work onto his plate immediately and take care of the drives -- or vice versa. Another lesson learned, or so I hope.

Not to mention that I keep getting interrupted. The biggest interruption is a tour group behind shepherded around by Charles Elachi and Pete Theisinger. So I figure that's important enough to interrupt my work for a little while. (Turns out they're all related to some high muckety-muck whose name I don't recognize but who's always on our review boards or something. Good call.) I've done a million of these; I give them the usual spiel about why we can't joystick the rovers, what we're up to now, here's a bit about our software, and so forth. They love it, and I love doing it, so what the hell.

Nevertheless, all this delays getting the drive done. Even for a relatively simple drive, this takes longer than it used to, or it feels that way. What makes the game so hard (and so much fun) is that there are a million little things to worry about, many of them interact, and you have to get them all just right. "I almost long for the old days, when we didn't know what could go wrong with a drive," Chris says, and I know what he means. Ignorance wasn't quite bliss, but it can seem that way in hindsight.

[Next post: sol 713, January 4.]

Spirit Sol 706

The good news is, Ashitey was right: we did make contact on the first retry with the tweaked surface normal -- none of the fancy new stuff was even needed. The bad news is, the resulting RAT brush was fairly poor, so they had to redo it last week. The good news is, the second one worked, and they drove away already.

And a nice job they did of it, too: 71m on the first sol, 47m on the second (autonav-only) sol. (Incidentally, this was Spirit's first such back-to-back drive.) The bad news is, the drive was sort of perpendicular to Home Plate, so our radial distance to our long-term goal remains more or less unchanged, even as time wasteth. Not that I'm worrying about it.

Anyway, as a result, we're only about 40m from El Dorado, and John and I are looking to get the rest of the drive today. Happily, it's just about as simple as it could be -- there are practically no obstacles here, just a nice flat zone. Just before El Dorado begins, there's a slight rise, so we'll have to be on autonav for the last part, but it shouldn't be any problem at all.

The big question is whether we should enter El Dorado or not. Our goal here is to find out what this thing is made of, which we intend to do by digging a trench. If we enter it thisol, then tomorrow we'll know a lot more about what it's made of and what we can expect from the trench. The problem is, maybe we'll know too much -- maybe we'll be bogged down in it, just as Opportunity was at Purgatory. And with winter coming on, and us already behind the curve ....

On the other hand, if we're going to trench the thing, we've got to enter it sometime, at least with the front wheels. Ideally, we'd stop with just the front wheels in it, but it's 40m away (or so -- our range data is poor, compounding the problem) and if we want to plant the front wheels only, we'd have an error budget of only 50cm or thereabouts. We just can't drive these vehicles that precisely. (They were designed for two-meter approaches. We do a lot better than that, but 40m really is out of the question.)

Fortunately, of course, we've got world-class experts to help us answer these questions. I ask both Brenda Franklin and Rob Sullivan about what we can expect from El Dorado. They agree that the material is coarse-grained (you can tell because it's dark -- dust is light). Brenda thinks the stuff is likely relatively compact, though maybe not; Rob's not even that sure. At least it's not likely to be quicksand -- so-called "foo-foo dust," which we'd just sink right into.

John and I decide we're going to proceed with caution. We'll just zoom right over the stuff we can see, but when we're about 10m from El Dorado, we turn on autonav and start doing slip checks every 2-3m (as opposed to the usual 10-15m between checks on this vehicle). That way, we can't get more than about a vehicle length into a trouble zone. And we make the slip checks pretty paranoid; if they fail to converge, we bail on the whole drive -- a common practice on Opportunity, but not something we usually bother with on Spirit. By the time we're done messing with it, we've got a drive that's likely to give up early for one reason or another. But better that, than be lost forever in El Dorado.

Mark Adler keeps discovering more about how things have changed since he was here last. "You're not doing anything during the 11 minutes of drive heating?" he asks incredulously. We used to pack the sol as full as possible; we'd have found something to do during those 11 minutes.

"It's not like it used to be," I shrug. "It grated on me for a while, but I got used to it. We have to make compromises to get out of here in shorter amounts of time, and to keep people from burning out." Sad, but true. I'd been thinking about just this when walking in this morning. When we changed the mission from a sprint to a marathon, we adjusted our pace accordingly. It was the right choice, and yet I regret being unable to use the vehicles to their fullest capacity -- it seems such a waste of a priceless scientific resource that the limiting factor in their operation would be us humans. I suppose that's a lesson to take forward to MSL: engineer them (and the ground tools, and whatever) so that they can be used to their fullest capacity in an eight-hour planning cycle.

But Mark remains stubbornly old-school in another way. "I'm gonna play a wakeup song," he announces. "It's 'El Dorado,' by ELO." He plays it for us. I'm sorry to say it's a pretty lousy song. But it's nice to have the old days back, even in such a small way, all the same.

[Next post: sol 710, January 1.]

Spirit Sol 699

Yestersol's IDD sequence had mixed results. The RAT failed to establish solid contact with the bumpy surface of this rock, so we didn't do the brush. Instead, the sequence simply proceeded to take MIs of the unbrushed surface and place the MB there.

This isn't the worst thing that could have happened. The MB is pretty good at seeing through the dust anyway, so we'll still get good science results from it even though the brushing never took place. However, the APXS can't see through the dust, so we really need to brush the darn thing thisol. We're falling farther and farther behind our drive metric all the time, and with Christmas coming this weekend, a failure to brush now could end up blowing most of a week. And that really wouldn't be good.

What happened yesterday was complex: almost exactly at the nominal contact position, the RAT's contact switches tripped briefly, but then rapidly gained and lost contact several times in less than a second. The initial firing of the contact switches stopped any further motion toward the rock face, but the sequence's subsequent check for contact failed because the switches had changed state by the time that check happened.

Clearly, we need some approach that checks whether we've made contact and autonomously tries again if it hasn't. The solution Frank and Matt Heverly and I come up with is something we've never tried before; we call it the "phased approach." First we'll try to place the RAT the same as we did yesterday, only without attempting any overdrive. (This will probably work, since we contacted 2mm early yestersol.) Then we'll have the sequence check for contact, and if it doesn't see contact, it'll push forward 5mm and check again. If still not in contact, it'll push forward 5mm and try again, then yet again, for a total of three tries (and 1.5cm total overdrive, about the most we dare command). And if we're still not in contact after all that, we'll try the whole routine again on an alternate target -- the same position, but with a slight tweak to the surface normal, so that we'll come in at a different angle.

If we're still not in contact, well ... then we give up. But at least we will have tried, and tried hard.

Though this approach sounds pretty complex, it's reasonably simple to sequence. I'm a good chunk of the way through it when Ashitey arrives to object. At first he's not comfortable brushing at all, since this switch-bouncing behavior isn't something we've seen before. He ultimately relents there, but still has problems with what we're up to.

"I think what you're doing is too complicated," he says. "You're doing things we've never done before." He doesn't say so outright, but this is clearly a sort of threat -- if we want to do what we're doing, he's going to make enough of a stink that we'll have to run it by Project management. "You should keep it simple -- just try again one time, with the tweaked surface normal."

"Besides," he continues, "you know it'll make contact if you just try again with the tweaked target."

But I don't know that. And I don't really think what we're doing is unreasonably complex, especially considering the downside: we have to stay here until we get this done, and since Home Plate is slipping farther and farther away every day, we should make every effort we can to get this to work (consistent with the safety of the vehicle, as always). And while it's true that we're doing something we've never done before, all of the parts of it are things that we have done before. "We invent techniques all the time without taking them to the Project level," I point out. "You think we should involve Jim Erickson every time we add something to a slip check?"

Ashitey backs off on the "first-time activity" line, but still pushes to make the thing simpler. We argue about it for a while, and perversely, our eventual compromise is even more complex than what we had when he came in. Now, we're first going to try the usual-style (non-phased) approach on the tweaked target. If that fails to make contact, we go to the original plan: try a phased approach on the original target, and if that fails to work, we try a phased approach on the tweaked target -- and only then, only if all that fails, we give up.

I'm not sure how that happened, but that's where we wind up.

All of this arguing pushes us pretty late -- by the time we're done, it's approaching 08:00, rover time, only an hour or so before we uplink. Someone remarks on this, but it fails to impress Mark Adler. "Ah, that's nothing," he says. "We used to CAM during the uplink window."

Well, I know they did that once. But it's not something anyone wants to repeat, you may be sure.

[Next post: sol 706, December 28.]

Spirit Sol 698

I love this rover. I really, really do.

I'm up at 05:45, and the first thing I do is log in and check the data from home. No images. That's just a touch worrisome. Maybe it's another OSS crash? But I see no evidence of that.

Hmmm ... I keep poking, and find that we did get some data -- so Spirit's alive -- but I find nothing to show that we've moved at all. It's as if the drive sequence never executed.

I shake it off, take a shower, and get to work as fast as I can. By the time I get there, the processing glitch -- if that's what it was -- has been resolved. We've got at least some drive data, and, most crucially, the post-drive images.

They show Comanche Spur dead in the middle of the IDD work volume. It's beautiful. We couldn't have gotten it more perfect. Or let me say, she couldn't have gotten it more perfect. All credit to our awesome rover.[1]

Visodom failed to converge at the end, and as a result, we didn't do our normal wheel wiggle, which we normally strive to do in order to settle the rover before deploying the IDD. When we look carefully at the images, though, we're able to convince ourselves that all wheels are in a stable configuration. This, coupled with past data and recent testbed work that has helped demonstrate that this rover design is highly stable when deploying the IDD even on apparently unstable surfaces, makes us willing to proceed.

What we proceed with is our pretty much standard IDD campaign -- MI, RAT-brush, MI, MB. Depending on the MB results we see tomorrow, we might stay here an extra sol, or cut things short and light out for our next destination, a large dark blob nicknamed "El Dorado."

Chris is RP-1 thisol, back on the rover after a FSW-induced absence of a couple of weeks, and he hasn't lost his touch. He cranks out the IDD sequence, I patch up a couple of minor errors, and the day's over before you can say "Jack Robinson."

Well, maybe not that fast. But pretty fast.

---

Courtesy NASA/JPL-Caltech. Comanche Spur, dead in our final front HAZCAM. I am more proud of this image than of almost any other in our nearly seven years on the surface.

---

Footnotes:

[1] I am unable to express just how proud I am of this drive to this very day. It was an amazing piece of work under extraordinary circumstances; if not my very best ever, it has to be damn close. Also, trying it was plain crazy, and hot damn, did it ever go perfectly. Big. Fat. Win.

Spirit Sol 697

Amazingly, the drive went absolutely perfectly. During sequencing, I'd realized that if we changed the direction we turned when scuffing, we should be able to get a perfect view of Comanche in the FHAZ -- and there it is, large as life. The NCAM images are spectacular, showing just what we expected -- the larger, main part of Comanche on the left, a smaller spur on the right, and a kind of saddle in between.

The scuff, too, is right where it's supposed to be, although the soil here was hard enough that the scuff (Squyres derides it as a "smudge") isn't scientifically interesting. As a result, they decide after some discussion to bag IDDing the scuff and just do a couple of sols of remote sensing followed by an approach to Comanche.

So that's all good. But the OSS -- our shared filesystem -- crashed over the weekend, which means that all the automated processing of downlinked data is screwed up and backlogged, which in turn delays our start. And, of course, we're still in tight sols, and we're trying to do a three-sol plan today. All in all, it's a perfect day for a critical piece of infrastructure to have hiccups.

Fortunately, our drive is going to be perfectly simple. The most obvious approach, a Hillary-style drive partway up onto Comanche, won't work; the exposed rock face is too far up, and we'd have to cross too much loose sand to get there. But when we cast around, we find another solution, a couple of low, flat rocks lying on the ground on the northeast part of Comanche. They're only about 10m away, and we've got a nice, smooth path straight to 'em. Admittedly, they're dusty-looking, except for one small, possibly more-or-less vertical face, but them's the breaks. So that's nice and easy.

Only one fly in that ointment: when we show Steve where we're thinking of heading, he sums up his reaction in these words: "I hate it."

Oooo ... kaaaaayyyyy ....

Well, there is one other option we'd previously dismissed. We could just climb up into the saddle between the two chunks of rock; plenty of good stuff up there. This is more difficult, and somewhat more dangerous. Not to mention that thisol's RP-2 is Frank -- normally an Opportunist, not a Spirit -- which makes the whole thing a shade more risky.

We do it anyway. If all goes well, Spirit will climb more than a meter up a rocky 14-degree slope, hang a right, and drive across a relatively narrow channel to the spur. To her right will be a sharp sandy slope, which we might or might not get stuck on; to the left, a wide sandy patch, which we could bog down in. Monday, we'll be about 8m from here, with Comanche Spur dead in the center of our IDD work volume.

That, or we'll never hear from Spirit again, and have to live with ourselves forever.

Oddly enough, even though part of me says this is insane, I have so much history with this rover, and so much trust in her, that I'm not as worried about it as I'd expect. Am I right to think so? Monday morning, I'll know for sure.

---

Courtesy NASA/JPL-Caltech. Our final front HAZCAM, showing Comanche right in front of us.


Courtesy NASA/JPL-Caltech. A NAVCAM view of the same scene, aimed at the "saddle."

Spirit Sol 694

In summary: a good drive, but not great. We made 30m of progress, carrying us all the way to the ridge. But Murphy's Law is interplanetary, and visodom failed to converge during Spirit's top-of-ridge slip check. Which, thanks to our increased paranoia, meant she stopped driving.

As it happens, she probably would have stopped driving shortly after that anyway, since there is a rough semicircle of autonav-unfriendly tilts just a couple of meters below us. However, it's something we feel comfortable blind-driving through.

In fact, as we look down the ridge and across the terrain separating us from Comanche, it looks like we could blind-drive across the whole thing. It's a total of about 40m to the base of Comanche, and there are hardly any obstacles at all. They've allocated over three hours for driving again thisol, and I end up giving most of it back.

(The scientists have no problem figuring out what to do with the time, though. Turns out we're parked on the largest expanse of outcrop they've yet seen at Gusev, so they pack in plenty of PCAM and MTES imaging of it before we leave it behind forever. We'll also be taking a couple of pictures and relaying them through MEX as a friendly bit of international cooperation. Since our European friends plan to show them off, as one person notes, "Let's make 'em pretty." We settle on a nice color PCAM of Comanche and an NCAM of the intervening terrain. Should look pretty darn cool.)

The nice straight path makes the sequencing simple as well, which leaves me time to get lunch. As I'm walking over there with our prodigal son, Mark Adler, I ask him what impression he has of how MER's changed since he left.

"There's a lot of automation," he says immediately. "It all runs really smoothly. 'Course, if something goes wrong, well, that's a runout sol."

He's right about the increased automation, but as to the rest, I don't remember the last time an automation failure led to dropping the plan and executing the runout. I don't know if it's ever happened. We don't have the kind of team that likes to let it happen.

Another kind of automation failure gets us worried, though -- at one point, the file server freezes for a few minutes. We can't do anything without it, so this brings the process to a grinding halt. Fortunately, it comes back after a short delay, and the ball resumes rolling.

While all this is going on in the Spirit World, Opportunity's been making progress of her own. Slowly but surely, they're performing a limited IDD campaign on the juicy bit of outcrop we parked in front of, lo, these many sols ago. In the process, they're learning about the fault, and one of the things they learned yesterday is that the amount of resistance caused by the broken wire isn't a constant. Instead, it seems to vary as the arm articulates.

But the way they found out was by having another joint stall, so they're in the middle of a tool change -- with the MI pointing straight up and its dust cover open, to make matters worse. It was supposed to be a skip sol, but they need someone to help them recover and get things back on track. And who just became available, but little old me?

So I go upstairs and help Ashitey sequence the recovery tool change. It's not quite the first time a rover driver has worked on both rovers in one sol -- if nothing else, Cooper did it when the rest of us were in Hawaii -- but it's the first time I've done it. ("A personal best," as Emily Eelkema puts it.)

Two Mars rovers in one day, baby. It's every geek's dream.

[Next post: sol 697, December 19.]

Spirit Sol 693

We made a respectable 25m of progress -- good, but not great. The visodom and blind segments went fine, but autonav failed shortly afterward, after finding no safe path. Oddly, we're not sure why autonav didn't want to proceed; what we can see in the images looks good.

Anyway, we're slowly but surely gaining on Comanche. We've still got about 35m to the ridge, and we've got a good chance of getting there and beyond because they've scared up over three hours of drive time today.

The path from here will be an odd one. After a bit of maneuvering to get onto the mesh, we've got to make our way through a trio of rocks arranged as the vertices of a roughly equilateral triangle, whose closest side lies transverse to our path about 10m from here. Our plan is to drive between the rocks to the center of the triangle, then jog left to dodge the rock at its apex before getting back on course and heading to the ridge.

About 10m after that -- still before we get to the ridge -- there's enough undulation in the terrain that our mesh starts to drop out. So we'll switch on autonav for the remaining 12m to the ridge, then turn and head to Comanche.

We're still worried about that ridge, though. I think there's a better-than-even chance that the far side will be too steep or too rocky for autonav to make any progress, in which case I'll feel guilty tomorrow about blowing a lot of drive time. But there's not too much I can do about that and still keep the rover safe.

One other modification we make to our usual Spirit-driving practices is to make the slip check more paranoid. Before starting autonav, and periodically during autonav drives, we've been having Spirit perform slip checks, looking to see whether she's slipping too much and stopping the drive early if so. Normally, if visodom fails to converge -- that is, if the slip-check calculations don't work, so we don't know what our slip is -- we let her drive on anyway. After all, that's a fairly unusual case, and even if that slip check fails, there will be another one shortly.

But in this case, we're just nervous about that. Once she gets over that ridge, she could be in really bad territory, and if she can't prove she's safe to go on, we want her to stop. So we tell her to do that. Will it cut our day short? We'll find out tomorrow ... same Mars time, same Mars channel.

---

Courtesy NASA/JPL-Caltech. Comanche, dead ahead.


Courtesy NASA/JPL-Caltech. In the other direction, a look back at our tracks. My girl's such a trouper.

Spirit Sol 692

The drive went well. Spirit hit a limit cycle check -- she wasn't making progress fast enough, so she stopped driving after the first autonav waypoint -- but she still made a respectable 30m of progress. We're far enough around Miami (which looks even more impressive from here, as we've descended about 3m) to see Comanche from the other side.

And the news from here is not so bad. Rather than a shallow ramp all the way to the valley floor, it looks like we've still got a ridge to cross, but we've got a decent path to it, at least. And no time pressure -- today's Spirit's skip day, so Frank and Jeng and Ashley and I are planning the drive a day ahead. Frank and Jeng are as experienced at rover driving as they come, but they spend all their time on Opportunity, so we're avoiding making them plan a drive on an unfamiliar rover on a tight schedule, which is what would happen if they waited until tomorrow.

It's a good opportunity for me to revisit what's different between the vehicles. Frank actually has to ask what's the height of obstacles we're worried about -- after all, they never see anything that big on the other side of the world. "When we see a rock over there, they want us to drive onto it," he points out. And he's quite right: for months, the only rocks Opportunity's seen have been either tiny cobbles or, more commonly, flat outcrop patches that make for good driving.

Well, they showed up for an interesting drive. We've got several actual obstacles to avoid, so we'll have a visodom segment at the beginning to help navigate around them, then a short blind drive through a friendly patch, then autonav from there. I don't think we'll quite make it, but if we get really lucky, we'll make it to the ridge and have a spectacular view of the valley beyond. (And an equally good view of whatever we're going to have to cross to get down there.) If that doesn't happen this drive, it'll happen on the next one. And since I'm working on Spirit for the rest of the year, while they continue to investigate Opportunity's IDD problem, I'll be sure to see it.

I can't wait!

Spirit Sol 690

We didn't get all the data we were supposed to get -- it's stuck someplace on Earth, but hasn't made it to the flight ops LAN yet.

The question is whether we can still do the drive with what we've got. (Or rather, with what we had yesterday: we came in then and planned most of the drive already, since there was no time pressure that way.)

We could do a better drive if we had all the data, but it looks like we've got enough -- at least we have NAVCAM coverage of the areas to the right and left of Miami, which towers over us, like, uh, a tower or something. What we can see of the direct path to Comanche is unpromising; most paths are blocked or worrisomely bumpy, and from what we can see, the one path we find that leads straight to the ridge looks like we'd more or less fall right over it. Visions of Wile E. Coyote dance in my head. Of course, we'd have the rover on autonav, so she'd keep herself safe, but our best estimate, backed up by what we can see of this area from images taken higher on the hill, is that the path down from there is steep and bumpy.

This contrasts with the longer path that leads to the left (east) around Miami -- which I take to calling the Miami Bypass. There the route is relatively smooth along the area we can see, and the earlier images suggest a smooth and gentle path. A longer one, but an easier one; all things considered, the long way might be faster. So we go that way.

It's starting to feel like Old Timer's Day around here. Mark Adler's been here recently, though not today. But Julie Townsend is back, as is Matt Keuneke, and Rob Manning stops by for a visit. As does Steve Squyres, which is always a pleasant surprise. He's on a layover between flights or something, and couldn't stay away.

He also bugs us about the drive we're planning -- why are we going to the left of Miami, not to the right? He's only seen the 2-D versions of the images, as it turns out. I bring up the true-stereo 3-D images in RSVP, and Steve slaps on the goggles. It just takes one glance. "I'm convinced!"

[Next post: sol 692, December 13.]

Spirit Sol 687

Second time was the charm. "As usual, a perfect drive!" exclaims the SOWG chair. "As usual," John mutters sardonically, "not as always."

Well, be that as it may. They have indeed revised the drive metric, making us a whopping 100m behind schedule. So we're driving.

Ha, ha! Only kidding. Of course we're not driving! Instead, we're spending the next couple of sols IDDing the patch of outcrop this drive took us to. And, of course, imaging nearby rocks and such. The outcrop is named Algonquin, and the target names have been selected from a list of tongue-twisting Indian names. After listening to the team stumbling over the names in the SOWG room, I thumb the mike and say, "I just wanted to remind everybody that the reason we name features is to make them easier to refer to." This wins laughter and applause. The SOWG chair proposes that our next target namespace be limited to three-letter names.

The IDD sequencing is our usual abbreviated campaign: on the first sol, an MI mosaic followed by an APXS placement; on the second, a RAT brush followed by a repeat of the MI mosaic and APXS placement. John has this well in hand -- true to form, he mostly copies and pastes from a previous campaign -- which leaves me time to look ahead to Friday's drive.

Which doesn't look pretty. About 15m away is a ridge, beyond which we can see terrain, but we have no range data on it -- that is, we have no idea how far away it is. PCAMs usually can give us range data out to 100m or so, so the fact that we're getting nothing suggests that what we see is at least that much farther away. So our strategy must be to drive to the ridge, then switch on autonav and hope for the best beyond that.

If we can even get to the ridge. The terrain here is just rugged enough to make that really, really difficult -- every apparent solution is thwarted by some rock or other.

Moreover, the target beyond, a big red mound called Comanche, is part of the stuff we have no range data for. So we don't know how far away it is, and thus we don't know how long it'll take us to drive there.

Because Monday's such a tight sol, we don't want to plan a drive that sol. Instead, we'll take the unusual step of planning two drives Friday. The first will take us to the ridge, then autonav past it. The second will be an all-autonav drive. Since we're fairly sure Comanche is more than 100m away, and the two drives combined aren't likely to make that much distance, we can just pick a point ~ 100m away and have both drives aim for it.

We've never done this on Spirit, but it's similar to what we did on Opportunity over President's Day weekend, so we're confident it'll work. We end up scrapping the idea, though, less for technical than for staffing reasons. Next week, John will be absent because of his fiancee Helen's surgery, Ashitey is still tied up with debugging Opportunity's IDD, and Chris Leger is focused on the FSW release. This leaves me as the only usual Spirit RP, and I have an unavoidable doctor's appointment Tuesday, a follow-up with my surgeon.

As a result, Sharon's had to schedule two Opportunity RPs, Frank and Jeng, for Tuesday. And we really don't want to make them drive. They're both good RPs, and everything would probably go fine, but the combination of a tight uplink, two RPs somewhat unfamiliar with Spirit, and unknown and likely hazardous terrain makes us nervous enough to call it off.

Instead, Friday we'll plan just one drive, and Monday we'll look at the data from that drive and plan the next one. We won't send that sequence Monday, though -- Monday's schedule is just too tight for that -- we'll hang onto it and have Frank and Jeng send it Tuesday.

This means I get to work on the rovers Monday, instead of spending Monday pushing on the RSVP software release for Phoenix. I can't say I'm disappointed.

[Next post: sol 690, December 11.]

Spirit Sol 685

The weekend drive faulted out right at the start, before even going anywhere. Painfully, it was really a rookie mistake. They fired off a helper sequence, and, as we usually do, put in a check to see if the helper was present, precluding further driving if not. The problem was, they accidentally reversed the sense of the test, precluding driving if the helper was present. Which of course it was, so the drive kicked off the helper sequence and then refused to go anywhere.

I'm just glad it wasn't me.[1]

Partly as a result of this mistake, we're now well below our drive metric. Also contributing to the problem is that they're going to raise the bar. Recognizing that our power has dropped and will continue to drop, we're revising our estimate of when we need to make it to Home Plate. The result will be more driving -- and more pressure on us to get it right.

Not that they seem to be in a terrible hurry. This drive will be all of 15m or so, to a nearby rock target called Algonquin. Where we'll stop to IDD. "But let's have the discipline," SOWG chair Albert Yen cautions, "to spend only one drive sol there." Since we're in restricted sols, that really means spending two drive sols there -- we'll drive only once more this week.

This mistake is the third time in about a week that we've blown all or part of a drive. The first case was when we hit the tilt limit right at the start of an autonav drive, which cut that sol from something like 40m to something like 20m. The second was when we screwed up the time-of-day limit logic, blowing our turn for comm. (At least that one made all of its planned distance, but the mistake is still troubling.) And now this is the third one.

I talk about these mistakes with John and Ashley, to see if we can come up with fundamental underlying reasons. "Complacency" is John's answer, which might be as true as anything. Still, we come up with a couple of new flight rules, which I write automated checks for. Maybe they'll help.

Later, I talk to Frank about how Opportunity is doing. There's good news and bad news, he tells me. The bad news is that we're still not seeing any motion from Opportunity's IDD. The good news is that Joe Melko has identified a failure mode in which a wire cracks, doubling the resistance. And there seems to be some support for this theory in the data. If this were true, we'd be able to resume normal work by just doubling the current through that joint.

If it's true. I can't help getting my hopes up, but I have to remind myself that we still don't know what's wrong, and the IDD could still be lost forever.

I'm hoping not.

[Next post: sol 687, December 8.]

---

Footnotes:

[1] Technically, I'm glad it wasn't I.

Opportunity Sol 660 (Spirit Sol 682)

I'm not needed to cover Ashitey's shift thisol, so I'm back on Opportunity, where things are not looking up. The day starts with a meeting in which the usual suspects are gathered around the table (or on the phone line) for a review of the spacecraft's state, and to try to figure out where we go from here.

In short: no joy. The IDD is showing small or no motion. To make matters worse, since it's in the stowed configuration, where there's very little room for it to move, we can't command large enough motions to get a lot of data. So there are few new facts to argue about, which is good or bad depending on how you look at it. Mostly bad.

Thisol will be more of the same: a couple of short motions designed to rotate the arm slightly -- just a couple of degrees -- forward, the usual next step in the unstow process. We're going to be a little more liberal in what we allow, permitting the startup current to be high for a little longer, in the hope that this will get it over whatever hump it needs to get over in order to move. And we're taking a bunch of pictures. And keeping our fingers crossed.

[Next post: sol 685, December 6.]

Spirit Sol 680

Our drive failed. Well, that might be too strong a word. We got through the blind portion, the initial 25m or so, but when we switched to autonav, we lowered the tilt limit (as usual), almost immediately drove over a relatively sharp little ramp, and tilt-faulted.

What makes this more annoying is that, unbeknownst to me, we had terrain meshes covering that entire area -- from an earlier sol, sol 667, when they'd driven up to that point and looked out over it. (I was on Opportunity then and missed that part of the story. When I came in, they'd driven back to examine some outcrop they'd passed by previously.) So we could easily have done a blind drive right through this area -- with a higher tilt limit, so we wouldn't have faulted.

Foo.

Just to make things more awkward, there was a problem at the DSN station, and they somehow lost a bunch of data from our downlink. (The data somehow made it all the way from Mars to Spain, but couldn't quite make it the last few thousand km to California. This is like swimming the Atlantic and drowning a meter from shore.) As a result, we have very little imagery from our current position -- HAZCAMs are all we had last night, though the PCAMs showed up in the morning pass. We're still missing the creamy middle -- I mean, crucial middle -- that's ordinarily supplied by the NCAMs.

We'll be able to do a drive, but it will be mostly autonav and therefore rather short -- but, hey. We still have that imagery from sol 667! John loads up the terrain mesh, and though it shows we've accumulated significant position error, we've still got good enough data to extend the blind drive to 12m or so. That gets us to the start of the PCAM coverage, which would ordinarily mean we'd be able to extend the blind drive even further, but there's some scary-looking stuff at the start of the PCAM coverage that we don't want to blind-drive through. Oh, well.

Anyway, there's a growing sentiment for bypassing Miami in favor of Comanche, a slightly more distant target that's redder (as opposed to Miami's black, which might suggest it's just regular old basalt) and has a more unusual morphology. So we aim this drive for a spot to the right of Miami -- somewhat splitting the difference between it and Comanche. And off we go.

Just after I deliver, I check the data -- and sure enough, the NCAMs have just come down. And they show what we suspected even without them: we'd have been perfectly fine sequencing this entire drive as a blind drive, which would have more than doubled our distance. Too late to change it now. Double-foo.

While I've been covering Ashitey's shifts on this side of the planet, he's been on the other side of the planet, investigating Opportunity's IDD anomaly. And the news isn't good, or at least, that's what Frank tells me. They haven't done anything with Opportunity's IDD since the fault, but they've been busy in the testbed, and their testing there has tended to disconfirm the hypothesis that the IDD is simply temporarily having trouble getting off its hook. Rather, it's looking more and more like a real actuator problem, a hardware problem we won't be able to solve and may not be able to work around.

I'll be back on Opportunity tomorrow morning, starting with an early meeting to explore the results of the tiny move they'll send up tonight. And then we'll know more.

[Next post: sol 682 (Opportunity sol 660), December 3.]