Mars Exploration Rovers Update - October 21, 2005

http://marsrovers.jpl.nasa.gov/mission/status.html
SPIRIT UPDATE: Spirit Begins Downhill Drive - sol 634-640, Oct 21, 2005:
Spirit is healthy and has begun driving downhill from the top of "Husband Hill" toward the south basin. Elevation maps produced from the panoramic camera imagery taken at and near the summit of Husband Hill showed a safe traverse (with vehicle tilts under about 20 degrees) across ridge lines east of the summit. These ridge lines (informally called "Haskin upper ridge" and "Haskin east ridge") are the planned traverse paths for coming weeks. When possible, Spirit will drive each day.
Sol-by-sol summaries:
Sol 634 (Oct. 15, 2005): Spirit finished investigating a rock outcrop called "Hillary" near the summit of Husband Hill. Spirit used the alpha particle X-ray spectrometer and the microscopic imager to study Hillary, then Spirit stowed the robotic arm. Spirit bumped back about 2 meters (7 feet) from the outcrop to complete remote imaging. Spirit used the miniature thermal emission spectrometer and panoramic camera to study targets on Hillary.
Sol 635: Spirit drove 47 meters (154 feet) east from the summit.
Sol 636: Spirit took images with the navigation camera and performed atmospheric observations.
Sol 637: Spirit drove 20 meters (66 feet) during the first of a series of drives toward Haskin upper ridge. There is an apparent drop-off near this ridge; therefore, each drive begins with a short 10-meter (33-foot) "blind" drive, followed by drives using hazard-avoidance cameras and decreased limits on how far the rover can tilt in any direction. The intent is to stop a drive short of any significant change in local elevation.
Sol 638: Spirit drove 29 meters (95 feet) during the second drive to the Haskin upper ridge. Spirit also observed the moons Phobos and Deimos at night.
Sol 639: Spirit covered 17 meters (56 feet) during the third drive of the approach to Haskin upper ridge. This left Spirit about 15 meters (49 feet) from the drop-off and near an area with rock outcrops.
Sol 640: Spirit's planned activities for sol 640 were devoted to remote sensing of the east basin, expected to be within view after the third leg of the sol 639 drive.
As of the end of sol 639, (Oct. 20, 2005), Spirit has driven 5,107 meters (3.17 miles).
------------------------------------------------------------------------
OPPORTUNITY UPDATE: Maneuvering Around Ripples - sol 613-618, Oct 21, 2005:
Opportunity is healthy and has been making excellent progress around "Erebus Crater." At the beginning of the week, the rover was in automode as it was still recovering from a partial uplink, but on sol 614 the team sent a real-time activate command and the rover performed remote sensing. The team is no longer operating under restricted sols, and Opportunity traveled 101.65 meters (333 feet) in four sols. The rover is generally heading westward around the crater, but traveled northward on sol 618 to avoid some larger ripples to the west.
Sol-by-sol summaries:
Sol 613 (Oct. 14, 2005): The team planned untargeted remote sensing. However, the master sequence did not run because Opportunity was in automode.
Sol 614: The team sent a real-time command to activate the sol 614 master sequence. The plan included remote sensing.
Sol 615: Opportunity completed an 18.5-meter (61-foot) drive heading westward around Erebus Crater.
Sol 616: Opportunity drove 24 meters (79 feet), with an average slip of 2.3 percent.
Sol 617: The rover completed a 43.65-meter (143-foot) drive, zigzagging around low points in the ripples.
Sol 618: Opportunity completed a 15.5-meter (51-foot) drive on outcrop, heading northward to find some lower ripples to cross.
As of sol 618 (Oct. 19, 2005) Opportunity has driven 6,138.07 meters (3.81 miles).
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Good to hear. :)
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Does anyone know why they miscalculated the life of the rovers so badly? Its one thing to have a platform survive twice as long as mean failure time, but this must be far longer than that? Did they actually do new Mean Time between failure calculations for all the sub-asymblies or were they using 20 year estimates based on assemblies with similar functions that were actually made up of components of completely unrelated nature. For example you can't get useful estimation of the life of a CCD Camera from data taken from a camera based on a Vidicon (sp) tube despite the similar function. In all likelyhood the two cameras wouldn't share a single component, not even resistors. The highest failure item in the tube based camera would almost certainly be the tube, and it would likely drive the failure rate for the whole camera. For a CCD camera with focus, the moving parts will be more likely to fail than anything in the video change, but the total is unlikely to approach that of a tube based camera.
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Muddy wrote:

Muddy:
I think it is largely just NASA gaming the system. By saying that the mission is a 100% success if the rovers last 90 days, they are much more assured that they can say the mission is a success. NASA regularly plans on extended missions. Remember, NASA ultimately has to get congress to approve these sorts of missions. The more successes there are, the more follow missions.
With regards to the Rovers, NASA was very concerned about whether they would be able to survive the Mars winter season due to extremely cold weather and short days (not enough light to recharge the batteries.) The Mars rovers have little pellets of Pu scattered around to keep critical pieces of them warm (source: an article in Aviation Week and Space Technology.) It seems like there was enough light to keep the batteries charged up enough to survive through the Martian winter. Frankly, it is a combination of good engineering and a little bit of plain ol' good luck.
Lastly, I suspect that various parts of the rover are failing. As long as the radio, drive train, and some portion of the vision system works, they can keep motoring around.
-Wayne
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Would you rather they had miscalculated and gotten three or four days out of them only? Ideally, something that you design and build will perform indefinately. Clearly they got the right people and contractors to do the job.

It sounds like you are unhappy about the results. Suppose they were only able to get the original 90 days out of the hardware and then it died on the spot. We have all had a toaster, car, or computer that did that. Would it have made you happier? Suppose they had only lasted half as long, and you were the contractor that had built the hardware. Now, would you feel like coughing up some sort of differential pay for that, or for funding a whole new mission? Mayeb you can talk them into adding "warranty timers" so that when the calendar runs out, it will fire a bunch of little squibs that blow the pieces off of the things. Of course, you would have to be a lunatic to try this.

And your point would be...? Look, the cost of making something that lasts under those environmental conditions is identical to the cost of making something that will last 10 times longer, in most circumstances. One would think that getting more for your money was a good thing, particularly if you were one of the taxpayers who footed the bill. Do you have a real, valid complaint about the mission?
Cheers!
Sir Charles W. Shults III Xenotech Research 321-206-1840
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Muddy wrote:

Shhhh. Something built under government contract actually outperforms expectations, and you are complaining?
Nope. It's the Martians who dust off the solar panels every night.
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Jo Schaper wrote:

Several years ago in ANALOG there was a short story where Nasa had its first successful Mars rover mission. The 'autonomous repair unit' was a terminally ill space fan; carefully undocumented.
Jim Lillie
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The expected lifetime and mission objectives were based on the worst-case estimate of dust buildup on the solar panels. Sufficient dust will deprive the rovers of power to the point where they can no longer maintain their internal temperature, leading to failure of temperature sensitive components. The dust wasn't as bad as expected and occasional gusts of wind have cleared the solar panels sufficiently for the rovers to continue operations.
The other components of the system are built to take launch, months in space, entry and landing. Stuff built to take that doesn't just fall apart rolling over sand dunes at a few inches an hour.
Tim
--
Shares are your votes in a pigologocracy.

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They planned a three-month primary mission, based mostly on how long it would take for dust settling onto the solar arrays to reduce power to the point of causing trouble. Mind you, they weren't expecting immediate problems after three months -- that was just the length of time for which they were fairly confident there *wouldn't* be problems. They were expecting more than three months of useful life, but they weren't sure just how much.
And indeed, three months were no problem, but by the six-month mark, available power for both rovers was down to about half the original level, and it was starting to limit operations. Clearly the end wasn't that far away. But then the decline stopped. And then Opportunity's available power went *up* substantially in several small steps over a period of a few weeks. And then Spirit's available power nearly doubled from one day to the next.
We still don't fully understand just *what* has been clearing the dust off the solar arrays, although it's presumably wind effects, possibly of several kinds. (After Spirit's sudden power jump, images of its solar arrays showed them almost clean *except* for streaks of dust in the wake of bits of equipment sticking up above the surface.) Spirit in particular may have had a dust devil pass right over it. In any case, nobody expected any of this.

They wouldn't have bothered. Such calculations are *averages*; they mean almost nothing when it comes to predicting the working life of specific, individual components. None of the components or subassemblies inherently had short lives(*), so there was no reason to expect hardware failures to limit the rovers' working life.
(* Batteries in particular *can* have limited lives by design. Mars Pathfinder wasn't meant to last long on the surface, so its designers saved battery weight by using types whose working life is fairly short. The death of its battery is almost certainly what killed MP, well after the end of its brief primary mission. )
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. | snipped-for-privacy@spsystems.net
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Overall Martian probes have about a 40% success rate. And that was much worse a couple years ago before recent successes. Mosty of thes failures were in entering orbit or landing. So thats probably why they "over engineer" these half billion dollar probes.
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snipped-for-privacy@earthlink.net wrote:

NASA makes it happen for all of us... Lot's of inventions you see everyday in your home and car use..
Happing roboting...
--

Dan Mathias
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On a sunny day (Mon, 21 Nov 2005 14:07:19 -0800) it happened Dan

Example plz?
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