This was one of the busiest days I've had lately. RP-1 shifts are usually busier than RP-2 shifts, but this one reminds me of the super-stressful days of the nominal mission. It's not as bad as that, but it's close.
Naturally, I loved every minute of it.
Yestersol's drive was another good one. It went only 35m, including 15m of autonav, mainly because we were limited by the lack of PCAM coverage. But at the end, we turned for comm, so we got a good downlink and are rarin' to go again.
Of course, our comm direction is basically north, and we have to drive basically south. So we have to do a nearly 180-degree turn, on a vehicle where large point turns are prohibited, and in a relatively confined space (due to ripples before and behind).
Our first approach is to drive backward down the current trough a bit past the point where we plan to hop the ripples, then do a series of sharp forward arcs that change direction and put us in the next trough over. (We have to end up heading forward at some point because we can't autonav backward as well when using the NCAMs -- their view of the nearby terrain is blocked by the rover deck.)
But this involves a bit too much uncertainty, so I bag it for a different approach. Counterclockwise arcs work well even with the stuck RF steering actuator and aren't subject to any rules-of-the-road limits, so I decide to use a bunch of those. First, we arc 75cm forward with a 22.5-degree counterclockwise heading change. Then we back straight up 50cm. We repeat this maneuver until we have the desired heading, then drive on -- straight -- for the rest of the sol.
Why not make the forward and backward arcs the same length? Because that would take us back and forth over the soil in the same spot too many times, and we're a bit worried about whether that will interfere with our traversability here. We had an experience like that in Endurance, and it left its mark. Of course, maybe it will just compact the soil and make driving better, not worse -- but if we always knew stuff like that, it wouldn't be exploration. So we try the asymmetric approach, and document it copiously with HAZCAMs as we go. And somesol soon, when those images get downlinked, we'll know whether this is a good or bad technique to use next time.
Other than that, this drive is not too remarkable -- about 30m blind, then switch to autonav. All through the sol, our TUL, Rich Morris works to free up more time, and when he's done, we have a whopping two hours and 47 minutes. This is a little embarrassing for me, actually, since if the slip checks work a little faster than they have been, we might actually complete the drive. That wouldn't be such a bad thing, although it would be a shame to waste any time.
Emily Eelkema's picture of the day is an image emailed to her by Ray Arvidson, a picture of the Rio Tinto. This is a naturally highly acidic river in Spain, so acidic that it's actually red. Some shallow pools of the stuff, the color of a nice Cabernet, take on a jelly-like consistency if you stir them. "That's Meridiani Planum, four billion years ago," says Ray. How appropriate. Even Mars's water was red.
And the Red Planet -- and with it, of course, our girls Spirit and Opportunity -- are about as close as they're going to get for a while. The one-way light-time is three minutes 52 seconds. Monday it will start rising again. Mars makes its closest approach at 8:52 PM Saturday -- tomorrow. Maybe I'll take Zenobia[1] outside with me and have a look at it.
[Next post: sol 655, November 5.]
[1] My cat, then. She was ornery and bossy and I loved her to pieces.
2010-10-29
2010-10-28
Opportunity Sol 626 (Spirit Sol 647)
Our autonav drive actually went great -- a total of 45 meters, quite respectable by current standards. That means we got about 15m out of the autonav, which is good news.
The only fly in the ointment is that we failed to do our turn for comm, and for a reason we should have thought of. When we planned this drive, we planned for it to extend beyond the time-of-day limit. This is common -- indeed, something we used to do all the time when using autonav; we just have it drive until the time-of-day limit kicks in, then we have the sequence detect that we were stopped by the time-of-day limit, clear the error, and reset the limit to allow time for end-of-drive activities such as turning to comm. We did all that logic on this drive, so we thought we were in the clear.
But here's what we forgot: both the blind and autonav portions of the drive are punctuated by slip checks, helper subsequences that try to drive a short distance and preclude further driving if we didn't make a decent fraction of the commanded distance. After the time-of-day limit hit, the sequence dutifully tried a slip check, noticed that it hadn't actually gone anywhere, and precluded driving. This is something our end-of-sol error-clearing logic didn't check for (indeed, has no good way to check for). So we still had an error -- the rover thought it was stuck in another dune -- and we didn't turn for comm.
Oops. We're still happy, but oops.
Well, our downlink was still pretty good. We didn't get the PCAMs, so that limits our blind driving thisol.
Hey, no problem. Jeng and I plan a sequence that drives blind as far as possible, then uses autonav until stopped by the time-of-day limit.
And this time, we do it correctly.
The only fly in the ointment is that we failed to do our turn for comm, and for a reason we should have thought of. When we planned this drive, we planned for it to extend beyond the time-of-day limit. This is common -- indeed, something we used to do all the time when using autonav; we just have it drive until the time-of-day limit kicks in, then we have the sequence detect that we were stopped by the time-of-day limit, clear the error, and reset the limit to allow time for end-of-drive activities such as turning to comm. We did all that logic on this drive, so we thought we were in the clear.
But here's what we forgot: both the blind and autonav portions of the drive are punctuated by slip checks, helper subsequences that try to drive a short distance and preclude further driving if we didn't make a decent fraction of the commanded distance. After the time-of-day limit hit, the sequence dutifully tried a slip check, noticed that it hadn't actually gone anywhere, and precluded driving. This is something our end-of-sol error-clearing logic didn't check for (indeed, has no good way to check for). So we still had an error -- the rover thought it was stuck in another dune -- and we didn't turn for comm.
Oops. We're still happy, but oops.
Well, our downlink was still pretty good. We didn't get the PCAMs, so that limits our blind driving thisol.
Hey, no problem. Jeng and I plan a sequence that drives blind as far as possible, then uses autonav until stopped by the time-of-day limit.
And this time, we do it correctly.
2010-10-27
Opportunity Sol 625 (Spirit Sol 646)
I've switched rovers once more. Back in the Land of Opportunity, they've backed away from the northern part of Erebus Crater -- pretty far away, as in 100m or so -- and now we're planning a drive to the west side of Erebus Crater. They had to back off so far because of the enormous ripples they encountered in the crater's immediate vicinity, and we're going to keep our distance as we head west.
Or that's what Frank and I think. The scientists would like to complicate things by adding a stop to the tour: in the orbital images, we can see a large expanse of outcrop at the northwest part of the crater. Can we stop by on the way?
Frank puts it to them bluntly: we can drive south to that outcrop, but if the ripples there are like they are elsewhere near the crater, we won't be able to go directly from there to the point where they're thinking of entering Erebus. Instead, we'll have to drive north from the outcrop before we can drive west to the point where we can drive south to get to the west entrance. Just thinking about it is enough to make your head spin, and it'll definitely make our wheels spin for an extra week or more.
This leads to the usual lengthy back-and-forth, and eventually to a compromise solution: we'll drive a little south of west, at an azimuth of 240 or so, hoping it will help us reconnoiter without driving all the way to the outcrop. If what we see tells us that the outcrop would be an expensive journey, we'll skip it; else we'll go there.
No matter how we do it, this will be a lot of driving. So I suggest to Frank that Opportunity revive an old trick, one Spirit uses often but Opportunity hasn't used for quite a while: autonav. We're in such a benign zone right now -- no ripples over 15cm, and nearly all under 10cm or so -- that we ought to take advantage of it to get as much extra distance per sol as we can.
Frank readily agrees. In fact, as it turns out, he and Jeng tried to do just this a few weeks ago, but that drive stopped for other reasons before it got to the autonav section. Nevertheless, it's a straightforward matter to add an autonav section to thisol's drive sequence.
When we actually do the math ... even with about two and a half hours to drive, the visodom-based slip checks are just so time-consuming that autonav is going to end up giving us only 5 or 10 meters. That's discouraging, but, well, it's something. Five meters here, 10 meters there, pretty soon you're talking about ... well ... it's something.
Or that's what Frank and I think. The scientists would like to complicate things by adding a stop to the tour: in the orbital images, we can see a large expanse of outcrop at the northwest part of the crater. Can we stop by on the way?
Frank puts it to them bluntly: we can drive south to that outcrop, but if the ripples there are like they are elsewhere near the crater, we won't be able to go directly from there to the point where they're thinking of entering Erebus. Instead, we'll have to drive north from the outcrop before we can drive west to the point where we can drive south to get to the west entrance. Just thinking about it is enough to make your head spin, and it'll definitely make our wheels spin for an extra week or more.
This leads to the usual lengthy back-and-forth, and eventually to a compromise solution: we'll drive a little south of west, at an azimuth of 240 or so, hoping it will help us reconnoiter without driving all the way to the outcrop. If what we see tells us that the outcrop would be an expensive journey, we'll skip it; else we'll go there.
No matter how we do it, this will be a lot of driving. So I suggest to Frank that Opportunity revive an old trick, one Spirit uses often but Opportunity hasn't used for quite a while: autonav. We're in such a benign zone right now -- no ripples over 15cm, and nearly all under 10cm or so -- that we ought to take advantage of it to get as much extra distance per sol as we can.
Frank readily agrees. In fact, as it turns out, he and Jeng tried to do just this a few weeks ago, but that drive stopped for other reasons before it got to the autonav section. Nevertheless, it's a straightforward matter to add an autonav section to thisol's drive sequence.
When we actually do the math ... even with about two and a half hours to drive, the visodom-based slip checks are just so time-consuming that autonav is going to end up giving us only 5 or 10 meters. That's discouraging, but, well, it's something. Five meters here, 10 meters there, pretty soon you're talking about ... well ... it's something.
2010-10-26
Spirit Sol 645
I'm Spirit's RP-1 today, but Spirit doesn't really need an RP. That's because they planned two sols yesterday, leaving nothing for an RP to do today.
Well, not quite nothing: I do have to weigh in on whether we should take PCAMs to support a possible southward, as opposed to the originally planned eastward, drive. My reaction: meh. We still ought to drive (eastward) to the lip and see if the slope there is as bad as we suspect before we give up on that path and head southward, so a south-looking PCAM from this position isn't likely to help much. But they're looking to spend the bits and taking it does keep our options open, so they take it anyway.
See? I'm not completely useless today.
Well, not quite nothing: I do have to weigh in on whether we should take PCAMs to support a possible southward, as opposed to the originally planned eastward, drive. My reaction: meh. We still ought to drive (eastward) to the lip and see if the slope there is as bad as we suspect before we give up on that path and head southward, so a south-looking PCAM from this position isn't likely to help much. But they're looking to spend the bits and taking it does keep our options open, so they take it anyway.
See? I'm not completely useless today.
2010-10-23
Spirit Sol 642
Spirit saw no safe path, so she gave up after only about 14m. Happily, this is mainly due to the conservative autonav settings; the new images reveal a perfectly safe path straight to the lip, now about 20m away.
But between us and the lip is an enormous patch of outcrop, and it might just be too shiny for the science team to ignore. They're going into restricted sols next week, so if we stop to IDD this outcrop, we're going to end up spending the whole week at it. That's a big time investment, considering that the sun's gradual southward motion means we now have a deadline to get to south-facing slopes.
"RPs, whaddaya think?" Steve asks.
"It's a science mission," I answer. "You know the constraints as well as anyone. If this is important for science, then let's delay going to the lip."
And that's what we do. So the drive itself turns out to be pretty easy, just a gentle 6.7m descent to a big outcrop patch. I have a bad feeling about it, just the same. Something about it reminds me of the hell that was Mazatzal: a big time investment in a highly important science target, a low rock just 7m away, and I think it's easy ... and I came in after that drive to find out we didn't really hit our target, and I felt miserable for a week. (And I still feel that way about it, in case you can't tell.) So I check and recheck, and if I made a mistake thisol, it won't be because I didn't try to learn the lesson.
The rock itself is named "Kansas." This is continuing the practice of naming stuff in this area in honor of Larry Haskin, who apparently was a well-liked friend and well-respected colleague to many on the science team (and who is, sadly, now deceased). Apparently, he had a farm in Kansas, and targets on the rock will be named after towns near his farm.
Me, I'm just excited because when we drive away, we'll get to say that we don't think we're in Kansas any more.
[Next post: sol 645, October 26.]
But between us and the lip is an enormous patch of outcrop, and it might just be too shiny for the science team to ignore. They're going into restricted sols next week, so if we stop to IDD this outcrop, we're going to end up spending the whole week at it. That's a big time investment, considering that the sun's gradual southward motion means we now have a deadline to get to south-facing slopes.
"RPs, whaddaya think?" Steve asks.
"It's a science mission," I answer. "You know the constraints as well as anyone. If this is important for science, then let's delay going to the lip."
And that's what we do. So the drive itself turns out to be pretty easy, just a gentle 6.7m descent to a big outcrop patch. I have a bad feeling about it, just the same. Something about it reminds me of the hell that was Mazatzal: a big time investment in a highly important science target, a low rock just 7m away, and I think it's easy ... and I came in after that drive to find out we didn't really hit our target, and I felt miserable for a week. (And I still feel that way about it, in case you can't tell.) So I check and recheck, and if I made a mistake thisol, it won't be because I didn't try to learn the lesson.
The rock itself is named "Kansas." This is continuing the practice of naming stuff in this area in honor of Larry Haskin, who apparently was a well-liked friend and well-respected colleague to many on the science team (and who is, sadly, now deceased). Apparently, he had a farm in Kansas, and targets on the rock will be named after towns near his farm.
Me, I'm just excited because when we drive away, we'll get to say that we don't think we're in Kansas any more.
[Next post: sol 645, October 26.]
2010-10-20
Spirit Sol 639
Ahh, it's one of those sols where we don't have to start until noon. Oh, my, this feels wonderful.
"I got to sleep until ten today," I say blissfully to Saina.
"I can't sleep until ten," she says. "I get bored."
Which makes no sense to me. But there's not much time to dwell on it; we've got a rover to drive.
About 25-30m away from us, the terrain slopes down more sharply. We can't see over this lip, so we don't know if there's a safe path to Haskin Ridge from here. So our plan is, naturally, to drive to the lip and peek over. If we like what we see, we keep going; if not, we'll have to head most of the way back up to the summit and find a different path down.
Between us and the lip, there's another problem. About 15m from here, there's a series of obstacles that cuts across our path. To the left is a ridge; to the right is a knoll -- which is, perversely, both too tall and too narrow for us to climb.
And straight ahead is a rock. The rock isn't that tall, only about 10cm on the face we can see. But because of the shape of the terrain around it, we can't tell what the terrain looks like on the far side, meaning we can't tell what slopes or dropoffs the rover will experience as it climbs over. The first point we can see beyond the rock is 30cm below the rock's top, meaning the rover could potentially experience a dropoff of that size, and that's too big for this vehicle.
The solution: let the rover handle it. Our plan is to drive Spirit about 11m straight toward the danger area, then turn on autonav and let her find her own path through. (Starting autonav a few meters back from the hazardous area means she can see more of it, giving her a better chance to find a passage.) If she finds a way, great. If she doesn't, then at least tomorrow will bring us better images, which we can maybe use to blind-drive past this troublesome area.
[Next post: sol 642, October 23.]
"I got to sleep until ten today," I say blissfully to Saina.
"I can't sleep until ten," she says. "I get bored."
Which makes no sense to me. But there's not much time to dwell on it; we've got a rover to drive.
About 25-30m away from us, the terrain slopes down more sharply. We can't see over this lip, so we don't know if there's a safe path to Haskin Ridge from here. So our plan is, naturally, to drive to the lip and peek over. If we like what we see, we keep going; if not, we'll have to head most of the way back up to the summit and find a different path down.
Between us and the lip, there's another problem. About 15m from here, there's a series of obstacles that cuts across our path. To the left is a ridge; to the right is a knoll -- which is, perversely, both too tall and too narrow for us to climb.
And straight ahead is a rock. The rock isn't that tall, only about 10cm on the face we can see. But because of the shape of the terrain around it, we can't tell what the terrain looks like on the far side, meaning we can't tell what slopes or dropoffs the rover will experience as it climbs over. The first point we can see beyond the rock is 30cm below the rock's top, meaning the rover could potentially experience a dropoff of that size, and that's too big for this vehicle.
The solution: let the rover handle it. Our plan is to drive Spirit about 11m straight toward the danger area, then turn on autonav and let her find her own path through. (Starting autonav a few meters back from the hazardous area means she can see more of it, giving her a better chance to find a passage.) If she finds a way, great. If she doesn't, then at least tomorrow will bring us better images, which we can maybe use to blind-drive past this troublesome area.
[Next post: sol 642, October 23.]
2010-10-18
Opportunity Sol 616 (Spirit Sol 637)
It's 06:30 at the start of a tight sol, and Beth Dewell is as bleary-eyed as I am.
"I think the rovers were missing you guys," she yawns, reciting the litany of things that went wrong while most of us rover drivers were away at the conference. Opportunity underwent another mystery reset during the AM science block, then missed a crucial part of the uplink, so that she ended up doing nothing but runout science for a couple of days. And we had ground system problems, with a crashing file server among other things. ("I think you can say that Friday was legally a nightmare," as Brenda Franklin puts it.) There's more, but I'm too tired to remember it.
It's not a terribly difficult day, just a Sunday -- er, Monday -- drive, hunting decent ripple-crossing spots as we trend west around Erebus Crater. The only hard bit is that we're on such a tight schedule: we need to be done by about 13:00.
And, what the hell, we make it. Man, I need a nap.
[Next post: sol 639, October 20.]
"I think the rovers were missing you guys," she yawns, reciting the litany of things that went wrong while most of us rover drivers were away at the conference. Opportunity underwent another mystery reset during the AM science block, then missed a crucial part of the uplink, so that she ended up doing nothing but runout science for a couple of days. And we had ground system problems, with a crashing file server among other things. ("I think you can say that Friday was legally a nightmare," as Brenda Franklin puts it.) There's more, but I'm too tired to remember it.
It's not a terribly difficult day, just a Sunday -- er, Monday -- drive, hunting decent ripple-crossing spots as we trend west around Erebus Crater. The only hard bit is that we're on such a tight schedule: we need to be done by about 13:00.
And, what the hell, we make it. Man, I need a nap.
[Next post: sol 639, October 20.]
2010-10-08
Spirit Sol 627
"We can't say we're stable," Ashitey says, "and we can't say we're unstable." What we know is, we wiggled the wheels, and we slipped. But we slipped more the first and second time, losing about two degrees of overall tilt in the process; the change on the third wiggle was definitely less. But then, at the end, when we cocked the wheels against the direction of slip, we slipped more during that motion.
My take on this is that everything is in fact just fine. We're on a slope; we're tilted; we're going to move when we wiggle the wheels. But we shouldn't be freaking out about that, because it's not what we care about. What we care about is whether we're going to move (or tilt) when we deploy the IDD, which is a different question. And when you look at how little we slip when we wiggle the wheels, I think you'd have a hard time saying we're going to slip when we deploy the IDD.
We're freaking out more because we took the wiggle-cam images -- hazcams before and after wiggling the wheels -- when we first got here, and we saw a change in those images. But the thing is, we've never taken such images before, so we don't really know whether that change is in family with what's happened previously.
At the SOWG meeting, I advocate a staged approach. Take it slowly. On the first sol, just deploy the IDD -- nothing more. Take images before and after this deployment. If we see any vehicle motion, or an unacceptable change in tilt, don't uplink the next IDD sequence. On the second sol, we do just one more thing -- place the MB. Again, accompany this with lots of imaging, and pull the plug on the process if we see any unexpected changes. We'll go on in this way for each of the days until the RPs are back in town (nearly everyone's going out of town for a convention).
This is generally accepted, in principle, although Emily is still reluctant to deploy at all. ("I reserve the right to change my mind," she is careful to say.)
So Ashitey and I move ahead on working out these sequences. They're not hard, but it turns out that this is one of those days with a high debate-to-command ratio. We're only about halfway done when Justin Maki puts together a movie showing each image of the rover sliding as we had it wiggle its wheels several times over the last few days, and then the concerns blow up again.
That isn't the only thing that blows up. Ashitey and Justin get into an argument about whether it's safe to deploy, and Ashitey just loses his cool. Ashitey's trying to make the point that our decision should be based on analysis, not on anyone's gut feeling, but Justin keeps cutting him off. Suddenly, Ashitey's had enough. "Stop interrupting!" he snaps. Next thing I know, Justin's grabbed his coffee and stalked out the door.
This is not a normal sol.
By this time I've already realized two things. One is that I need to stop advocating a position and go back to basics: regardless of any questions about winning or losing, what is objectively the best thing to do?[1] And second, we need to know whether what we're seeing is normal behavior in similar conditions.
We haven't taken wiggle-cams before, which is part of the problem. But we do have very good data on the tilt changes. We always collect this data at 8Hz -- the maximum rate the rover's capable of -- during wheel wiggles. So I've been trolling through past sols, looking for times when our tilt's been high. I find a couple of these, plot the tilt data, and -- yep, looks to me like what we saw is normal. I still have to convince the doubters, but it's good evidence.
But first I have another concern. Justin's a smart guy who's done a lot of good on this mission, and we ought to make sure we've heard him out on this topic. So I track him down -- he's upstairs, in the Opportunity room -- and talk it out with him. In the end, it's just gut feeling on his part (he says so himself), and while I don't want to dismiss gut feelings, evidence counts for more. (While we're having this conversation, Ashitey comes to find me. And apologizes to Justin. So that's back on track.)
Also in the Opportunity sequencing room is Jeff Biesiadecki. He knows the rover's mobility system better than almost anybody, and we don't call him "Paranoid Jeff" for nothing, so we drag him downstairs to have a look through it. Somewhat to our surprise, not that we're complaining, Paranoid Jeff gives our careful, phased plan a thumbs-up. So far, so good.
But Khaled gets wind of this, and objects. Strongly. "I wouldn't deploy in this situation," he says firmly, "no way." He doesn't directly take issue with the historical data showing that what we're seeing seems to be normal, but he raises the Shuttle Fallacy: just because we've gotten away with something dangerous in the past, that doesn't mean we're safe to do it again in the future.
"The problem with that," I point out, "is that in situations like this you don't know whether what you're doing is dangerous, and you're getting away with it; or it's safe, and you're worrying for nothing. You can't tell the difference between the two cases without data, and the data we have shows that the rover doesn't tilt excessively when we deploy the IDD in circumstances as close to this as we've gotten."
The debate rages. Some people are trying to figure out exactly where the left front wheel is, and in particular whether it's solidly planted. Jim Erickson and John Callas get involved. They're arguing with Steve Squyres, who pushes the scientific importance of this particular observation. (Squyres nearly scores an own-goal: when discussing what damage could occur to the IDD in the pose where the MB is deployed, he says, "You know, the steel noseplate on the MB is one of the most robust parts of the arm." You don't say it'll survive the scraping to people who want to hear that it's not going to scrape against anything at all.)
This goes on for, I'm not kidding you, three hours. Emily is stressed. She doesn't want to (seem to) be the one to destroy the IDD, with its irreplaceable science value, but I think that in the end she recognizes she doesn't have a fact-based argument. So she makes the right decision: "We're going to proceed with the deployment," she says at last.
But with careful, objective limits on the tilt changes we'll use to decide whether to pull the plug. (We already have decided that no change in position would be acceptable: even a shift of a millimeter would put a stop to this little excursion. But tilt's another matter: we always see a small change in tilt when we deploy the IDD.) Ashitey and Terry Huntsberger do some additional data mining, to come up with numeric bounds. The final number: 0.3 degrees.
We see more tilt than that, and we switch to an IDD-less, image-heavy backup plan. Less tilt, and we proceed.
Surprisingly, even Khaled eventually agrees to this. And with Paranoid Jeff and Even-More-Paranoid Khaled on board, we must be doing something right.
[Next post: sol 637 (Opportunity sol 616), October 18.]
Courtesy NASA/JPL-Caltech. Slipping slowly down the face of Hillary.
Footnotes:
[1] Always, always, always the right approach. Whenever I've strayed from it, I've regretted it, and whenever I've gone back to that path, I've been glad of it. Always.
My take on this is that everything is in fact just fine. We're on a slope; we're tilted; we're going to move when we wiggle the wheels. But we shouldn't be freaking out about that, because it's not what we care about. What we care about is whether we're going to move (or tilt) when we deploy the IDD, which is a different question. And when you look at how little we slip when we wiggle the wheels, I think you'd have a hard time saying we're going to slip when we deploy the IDD.
We're freaking out more because we took the wiggle-cam images -- hazcams before and after wiggling the wheels -- when we first got here, and we saw a change in those images. But the thing is, we've never taken such images before, so we don't really know whether that change is in family with what's happened previously.
At the SOWG meeting, I advocate a staged approach. Take it slowly. On the first sol, just deploy the IDD -- nothing more. Take images before and after this deployment. If we see any vehicle motion, or an unacceptable change in tilt, don't uplink the next IDD sequence. On the second sol, we do just one more thing -- place the MB. Again, accompany this with lots of imaging, and pull the plug on the process if we see any unexpected changes. We'll go on in this way for each of the days until the RPs are back in town (nearly everyone's going out of town for a convention).
This is generally accepted, in principle, although Emily is still reluctant to deploy at all. ("I reserve the right to change my mind," she is careful to say.)
So Ashitey and I move ahead on working out these sequences. They're not hard, but it turns out that this is one of those days with a high debate-to-command ratio. We're only about halfway done when Justin Maki puts together a movie showing each image of the rover sliding as we had it wiggle its wheels several times over the last few days, and then the concerns blow up again.
That isn't the only thing that blows up. Ashitey and Justin get into an argument about whether it's safe to deploy, and Ashitey just loses his cool. Ashitey's trying to make the point that our decision should be based on analysis, not on anyone's gut feeling, but Justin keeps cutting him off. Suddenly, Ashitey's had enough. "Stop interrupting!" he snaps. Next thing I know, Justin's grabbed his coffee and stalked out the door.
This is not a normal sol.
By this time I've already realized two things. One is that I need to stop advocating a position and go back to basics: regardless of any questions about winning or losing, what is objectively the best thing to do?[1] And second, we need to know whether what we're seeing is normal behavior in similar conditions.
We haven't taken wiggle-cams before, which is part of the problem. But we do have very good data on the tilt changes. We always collect this data at 8Hz -- the maximum rate the rover's capable of -- during wheel wiggles. So I've been trolling through past sols, looking for times when our tilt's been high. I find a couple of these, plot the tilt data, and -- yep, looks to me like what we saw is normal. I still have to convince the doubters, but it's good evidence.
But first I have another concern. Justin's a smart guy who's done a lot of good on this mission, and we ought to make sure we've heard him out on this topic. So I track him down -- he's upstairs, in the Opportunity room -- and talk it out with him. In the end, it's just gut feeling on his part (he says so himself), and while I don't want to dismiss gut feelings, evidence counts for more. (While we're having this conversation, Ashitey comes to find me. And apologizes to Justin. So that's back on track.)
Also in the Opportunity sequencing room is Jeff Biesiadecki. He knows the rover's mobility system better than almost anybody, and we don't call him "Paranoid Jeff" for nothing, so we drag him downstairs to have a look through it. Somewhat to our surprise, not that we're complaining, Paranoid Jeff gives our careful, phased plan a thumbs-up. So far, so good.
But Khaled gets wind of this, and objects. Strongly. "I wouldn't deploy in this situation," he says firmly, "no way." He doesn't directly take issue with the historical data showing that what we're seeing seems to be normal, but he raises the Shuttle Fallacy: just because we've gotten away with something dangerous in the past, that doesn't mean we're safe to do it again in the future.
"The problem with that," I point out, "is that in situations like this you don't know whether what you're doing is dangerous, and you're getting away with it; or it's safe, and you're worrying for nothing. You can't tell the difference between the two cases without data, and the data we have shows that the rover doesn't tilt excessively when we deploy the IDD in circumstances as close to this as we've gotten."
The debate rages. Some people are trying to figure out exactly where the left front wheel is, and in particular whether it's solidly planted. Jim Erickson and John Callas get involved. They're arguing with Steve Squyres, who pushes the scientific importance of this particular observation. (Squyres nearly scores an own-goal: when discussing what damage could occur to the IDD in the pose where the MB is deployed, he says, "You know, the steel noseplate on the MB is one of the most robust parts of the arm." You don't say it'll survive the scraping to people who want to hear that it's not going to scrape against anything at all.)
This goes on for, I'm not kidding you, three hours. Emily is stressed. She doesn't want to (seem to) be the one to destroy the IDD, with its irreplaceable science value, but I think that in the end she recognizes she doesn't have a fact-based argument. So she makes the right decision: "We're going to proceed with the deployment," she says at last.
But with careful, objective limits on the tilt changes we'll use to decide whether to pull the plug. (We already have decided that no change in position would be acceptable: even a shift of a millimeter would put a stop to this little excursion. But tilt's another matter: we always see a small change in tilt when we deploy the IDD.) Ashitey and Terry Huntsberger do some additional data mining, to come up with numeric bounds. The final number: 0.3 degrees.
We see more tilt than that, and we switch to an IDD-less, image-heavy backup plan. Less tilt, and we proceed.
Surprisingly, even Khaled eventually agrees to this. And with Paranoid Jeff and Even-More-Paranoid Khaled on board, we must be doing something right.
[Next post: sol 637 (Opportunity sol 616), October 18.]
Courtesy NASA/JPL-Caltech. Slipping slowly down the face of Hillary.
Footnotes:
[1] Always, always, always the right approach. Whenever I've strayed from it, I've regretted it, and whenever I've gone back to that path, I've been glad of it. Always.
2010-10-07
Spirit Sol 626
This morning brings good news and bad news. The good news is, we made it. This is truly spectacular and receives its due of praise from all concerned: it was one of the most difficult approaches we've ever done, and we nailed it.
The bad news is, it's not safe to IDD. At the end of the drive, we carefully wiggled the wheels, and the data and images show that the vehicle moved during the wiggle. This implies that it might well be unsafe to deploy the IDD. So we won't be able to start IDDing thisol; we're going to have to spend the sol figuring out how to either settle the rover a bit better or bumping to a new position. (We also displaced a rock we drove over on the way in, tilting it up such that there was probably only 2-3cm clearance between it and the bottom of the WEB. Oops.)
The basic decision is: wiggle only, or drive and then wiggle? Ashitey wants to drive first, but I eventually talk him out of it. In this area, treacherous as it is, driving is merely a way of trading the devil we know for the devil we don't. We don't have any good way to raise the odds that we'll be stable at the end of the next little bump, so we might as well try to make Spirit more stable right here.
This argument would probably have been a loser, given that thisol is absolutely our last margin sol -- we can't just try for stability thisol, then drive and try again nextersol if this doesn't work, because we're going to be on travel then. (Or, to put it another way, we could drive nextersol, but there's not much point because nobody will be around to develop the IDD sequences that are the real point of this endeavor.)
But Squyres declares that Hillary is such a high-priority science target that they're willing to wait. If we simply can't get the IDD into position before leaving town, they'll wait until RPs start returning to town Wednesday. That means we have sols to spare, so we can try one thing thisol and something else nextersol if it doesn't work. That's the least risky approach, so we go with that.
The settling tactic itself is a fairly straightforward one. We wiggle each wheel, one at a time, taking plenty of documentation images and visodom updates as we do. Then we cock each wheel to the left, so that the paddles are transverse to the direction of slip. If all goes well, we'll come in tomorrow and see a tiny amount of slip on the first wiggle and no slip after that, and we'll be stable and ready to deploy the IDD. If not, well ... the scientists will have a lander for a few days.
"Alternatively," Steve says, "if this doesn't work, we could give up and drive to another rock. There are other rocks around here -- much less interesting from a science perspective, but they'd probably tell us what we need to know. It's the RPs' call."
"I'm not going to want to give up, Steve," I tell him. "I'm still pissed off about Burns Cliff."
And I am, too.
Courtesy NASA/JPL-Caltech. Some days I rock. Other days I rock hard. This was one of the second kind.
The bad news is, it's not safe to IDD. At the end of the drive, we carefully wiggled the wheels, and the data and images show that the vehicle moved during the wiggle. This implies that it might well be unsafe to deploy the IDD. So we won't be able to start IDDing thisol; we're going to have to spend the sol figuring out how to either settle the rover a bit better or bumping to a new position. (We also displaced a rock we drove over on the way in, tilting it up such that there was probably only 2-3cm clearance between it and the bottom of the WEB. Oops.)
The basic decision is: wiggle only, or drive and then wiggle? Ashitey wants to drive first, but I eventually talk him out of it. In this area, treacherous as it is, driving is merely a way of trading the devil we know for the devil we don't. We don't have any good way to raise the odds that we'll be stable at the end of the next little bump, so we might as well try to make Spirit more stable right here.
This argument would probably have been a loser, given that thisol is absolutely our last margin sol -- we can't just try for stability thisol, then drive and try again nextersol if this doesn't work, because we're going to be on travel then. (Or, to put it another way, we could drive nextersol, but there's not much point because nobody will be around to develop the IDD sequences that are the real point of this endeavor.)
But Squyres declares that Hillary is such a high-priority science target that they're willing to wait. If we simply can't get the IDD into position before leaving town, they'll wait until RPs start returning to town Wednesday. That means we have sols to spare, so we can try one thing thisol and something else nextersol if it doesn't work. That's the least risky approach, so we go with that.
The settling tactic itself is a fairly straightforward one. We wiggle each wheel, one at a time, taking plenty of documentation images and visodom updates as we do. Then we cock each wheel to the left, so that the paddles are transverse to the direction of slip. If all goes well, we'll come in tomorrow and see a tiny amount of slip on the first wiggle and no slip after that, and we'll be stable and ready to deploy the IDD. If not, well ... the scientists will have a lander for a few days.
"Alternatively," Steve says, "if this doesn't work, we could give up and drive to another rock. There are other rocks around here -- much less interesting from a science perspective, but they'd probably tell us what we need to know. It's the RPs' call."
"I'm not going to want to give up, Steve," I tell him. "I'm still pissed off about Burns Cliff."
And I am, too.
Courtesy NASA/JPL-Caltech. Some days I rock. Other days I rock hard. This was one of the second kind.
2010-10-06
Spirit Sol 625
I must be bad luck or something. This is the third consecutive sol I've worked where we were missing important drive imagery.
Thisol we're missing most of the NCAMs that were to support our final approach to Hillary, a juicy rock target here at the true summit of Husband Hill. Fortunately, the one NCAM we do have covers the straightforward approach to Hillary. Unfortunately, the straightforward approach is a no-go for comm reasons. So instead of tackling it head-on in a northward drive, we have to skirt around so that we're heading at it more northeasterly. And this means taking on much higher tilt -- nearly 30 degrees, above our comfort level.
(Hillary is, of course, named in honor of Everest conqueror Sir Edmund Hillary. To my surprise, the man is still alive, in his late eighties. Squyres is planning to email him some images of the rock we've named for him. I find this somehow bizarre, as if we were going to send a fax to Erik the Red.)
We're trying to get Spirit into position to IDD, including some very long-term MB and APXS integrations, for the few days that there's no RP coverage because everyone's in Hawaii. We could possibly recover if we need to use tomorrow (Thursday) for a final bump, but that will make Friday hellacious. And if we don't make it on Thursday either, well, somebody's not going to Hawaii, I guess.
The high tilt on this drive is making everyone nervous. After much discussion, Ashitey and I come up with a set of safeguards that should keep Spirit safe while still giving us a good chance of making it to the goal. An even lengthier discussion sells it to the rest of the uplink team. "Just give me time to update my résumé," deadpans Saina.
Courtesy NASA/JPL-Caltech. Our NCAM of Hillary.
Thisol we're missing most of the NCAMs that were to support our final approach to Hillary, a juicy rock target here at the true summit of Husband Hill. Fortunately, the one NCAM we do have covers the straightforward approach to Hillary. Unfortunately, the straightforward approach is a no-go for comm reasons. So instead of tackling it head-on in a northward drive, we have to skirt around so that we're heading at it more northeasterly. And this means taking on much higher tilt -- nearly 30 degrees, above our comfort level.
(Hillary is, of course, named in honor of Everest conqueror Sir Edmund Hillary. To my surprise, the man is still alive, in his late eighties. Squyres is planning to email him some images of the rock we've named for him. I find this somehow bizarre, as if we were going to send a fax to Erik the Red.)
We're trying to get Spirit into position to IDD, including some very long-term MB and APXS integrations, for the few days that there's no RP coverage because everyone's in Hawaii. We could possibly recover if we need to use tomorrow (Thursday) for a final bump, but that will make Friday hellacious. And if we don't make it on Thursday either, well, somebody's not going to Hawaii, I guess.
The high tilt on this drive is making everyone nervous. After much discussion, Ashitey and I come up with a set of safeguards that should keep Spirit safe while still giving us a good chance of making it to the goal. An even lengthier discussion sells it to the rest of the uplink team. "Just give me time to update my résumé," deadpans Saina.
Courtesy NASA/JPL-Caltech. Our NCAM of Hillary.
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