Mars Rovers Have Incorrect Instruments Installed 294
Christopher Reimer writes "The New Scientist is reporting that the twin Mars rovers, Opportunity and Spirit, has instruments installed in the wrong rovers. From the article: 'While the bungle does not undermine the main scientific conclusions drawn from the data collected by the rovers, it is an embarrassing slip-up for a space agency that once lost a Mars spacecraft because engineers mixed up metric and imperial units.'"
Re:Confusion...Why differing configurations? (Score:5, Informative)
Of course, it becomes a problem when you use the wrong calibration curve for the sensor.
Not wrong, but swapped (Score:5, Informative)
No big deal... (Score:5, Informative)
They're the same device on each machine, with the same function. The only problem has been that the data received has been interpreted with the wrong calibration adjustments. Swap the calibration adjustments and rerun the data, and it'll be correct.
It would have been far worse if, say, one had a spectroscope and the other had a *drill*, and they were swapped, and each rover couldn't use the other's tool. And in that kind of a switch, it would be really bad, because the two devices would be visually distinct. But the swapping of two devices that are 99.99% identical, on two rovers that are identical, is no big thing.
Compared to the fact that the rovers are still running long after they were expected to die, this is a tiny, tiny thing.
Re:Confusion...Why differing configurations? (Score:5, Informative)
However, nothing is perfect, and each sensor has slight imperfections. Before they were sent up, each sensor was measured so that those imperfections could be accounted for. This calibration data is unique to each sensor. They used the calibration data for Spirit on the data from Opportunity, and vice versa. Luckily, since they still have the original(un-corrected, raw) data, it is easy to correct.
This doesn't effect results (Score:3, Informative)
Re:If... (Score:5, Informative)
when you have 100 resistors at 0.5% tolerance, you are gonna have drift, and you will have to calibrate them to the right parts, you can make 100's of those cars of the same make and model, but none will be exactly the same, especially when you have sensitive equipment. (Think odometer)
Mixed up units (Score:4, Informative)
I'm getting pretty tired of this sound (text?) bite the media throws out. It wasn't mixed up units; it was error accumulation from switching back and forth between the units.
Re:Confusion...Why differing configurations? (Score:5, Informative)
Re:Confusion...Why differing configurations? (Score:5, Informative)
This is not a major thing. Yes, all the data collected from these sensors will have to be re-analyzed, but that should be a simple thing.
Re:If... (Score:5, Informative)
It's a calibration, the whole concept is no two things are the same. Any piece of instrumentation needs to be calibrated and that calibration is set for that device. No manufacturing can produce 2 identical things, just not possible since the two items could not share the same time and space in the universe together thus both are going to be slightly different.
Anytime you get a piece of gear, you get it setup, then you take some means of calibrating it and test it with something that has deemed to be as accurate as possible. Maybe some source such as a rock. But basically anything that will provide a common test basis for the device.
So say you are measuring temperatures on something in a lab. You set up a big system for collecting data off a bunch of thermocouples. Each one has it's own channel through it's own voltage modules and thermocouples and so forth. So you take a calibrator and have it feed a signal through the system to mimic a thermocouple. you get a calibration curve for a channel, then you go to the next channel with the same device and do the same for the next channel, this will be a different calibration. and then you work through them all. I have system set up with 16 channels at work and all use the same parts, but there is about 4 closely similar calibrations across the channels, but no two channels follow the same calibration.
NASA did the same, they built the devices, then calibrated them with the same rocks, and developed a calibration curve for each system, and that was to be kept with each rover, they swapped the instruments, so now they switch the calibrations and everything is fine.
This all goes back to simple accuracy and how close you can get things, but bottom line no two things are the same. Look at computers, you can have 100 computers, exactly the same built right in a row, with the exact same software and so forth. Turn them on and let the run under exact same conditions, some will have hardware failures, some will have software get wacky on them and so forth. It's just the way it works.
Re:I want to fight for NASA but come on... (Score:5, Informative)
How can i possibly advocate for a mars mission when they can't even get this shit right?
The Mars mission is stupid but not for the reason you give.
Re:Confusion...Why differing configurations? (Score:5, Informative)
As a science teacher, I weep. For any instrument, it's important to perform calibration: to check the instrument against known samples, values, whatever, so that you can take the unique response of the instrument and convert it into a believable interpretation of the data. Every instrument has its own peculiarities, resulting from the (essentially unknowable) history of the construction of the instrument. Most of these features are entirely unimportant, if you know about them. So you run calibrations and figure out how to correct for the individual features.
NASA did its job here, in that the instruments were calibrated. Yay. Then they mixed up the instruments and installed package A into rover B, meaning the calibrations were in fact wrong. Luckily they keep all the raw data, so they can simply run it through the correct calibration filter now. Double yay.
But for all those saying "This is a small thing.": Wrong. They mixed up an entire package. Didn't it occur to anyone to actually, you know, label the two? Or to in fact make sure they weren't in the same lab at the same time? Or if that proved impossible, to keep track of which was which? Or to -- oh, I don't know -- check which package they were installing?
Excusing this as "just a minor thing" is akin to minimizng a case where you fall asleep while driving and are awakened by the rumble strips on the side of the road. Sure, you fell asleep. But you woke up and no one was hurt. No harm, no foul, right?
A minor screw up on its own, it still speaks volumes about NASA's continuing inability to cross all the t's and dot all the i's. And it's a pretty close relative to the error that cost us Mars Observer.
'Bungle' is a bit too harsh... (Score:3, Informative)
Once the mistake was realized, they could easily accomodate it through other calibration techniques. I think the parent article is trying to raise a sandstorm in an otherwise rarefied atmosphere.
Speaking of slipups... (Score:4, Informative)
Re:Mixed up units (Score:5, Informative)
The cause of the loss wasn't mixed up units, though they contributed. The loss was caused by ignoring a growing discrepancy between the precalculated navigation values and the actual navigation values. The errors were well within the correctable range, but for a variety of reasons the subtly different but incorrect values were ignored until it was too late to correct for them.
Re:Puddnhead Wilson Goes to Mars (Score:3, Informative)
From The Tragedy of Puddnhead Wilson:
He was a homely, freckled, sandy-haired young fellow, with an intelligent blue eye that had frankness and comradeship in it and a covert twinkle of a pleasant sort. But for an unfortunate remark of his, he would no doubt have entered at once upon a successful career at Dawson's Landing. But he made his fatal remark the first day he spent in the village, and it "gaged" him. He had just made the acquaintance of a group of citizens when an invisible dog began to yelp and snarl and howl and make himself very comprehensively disagreeable, whereupon young Wilson said, much as one who is thinking aloud:
"I wish I owned half of that dog."
"Why?" somebody asked.
"Because I would kill my half."
The group searched his face with curiosity, with anxiety even, but found no light there, no expression that they could read. They fell away from him as from something uncanny, and went into privacy to discuss him. One said:
"'Pears to be a fool."
"'Pears?" said another. "Is, I reckon you better say."
"Said he wished he owned half of the dog, the idiot," said a third. "What did he reckon would become of the other half if he killed his half? Do you reckon he thought it would live?"
"Why, he must have thought it, unless he IS the downrightest fool in the world; because if he hadn't thought it, he would have wanted to own the whole dog, knowing that if he killed his half and the other half died, he would be responsible for that half just the same as if he had killed that half instead of his own. Don't it look that way to you, gents?"
"Yes, it does. If he owned one half of the general dog, it would be so; if he owned one end of the dog and another person owned the other end, it would be so, just the same; particularly in the first case, because if you kill one half of a general dog, there ain't any man that can tell whose half it was; but if he owned one end of the dog, maybe he could kill his end of it and -- "
"No, he couldn't either; he couldn't and not be responsible if the other end died, which it would. In my opinion that man ain't in his right mind."
"In my opinion he hain't got any mind."
No. 3 said: "Well, he's a lummox, anyway."
That's what he is;" said No. 4. "He's a labrick -- just a Simon-pure labrick, if there was one."
"Yes, sir, he's a dam fool. That's the way I put him up," said No. 5. "Anybody can think different that wants to, but those are my sentiments."
"I'm with you, gentlemen," said No. 6. "Perfect jackass -- yes, and it ain't going too far to say he is a pudd'nhead. If he ain't a pudd'nhead, I ain't no judge, that's all."
Re:Mixed up units (Score:3, Informative)
Re:Mixed up units (Score:3, Informative)
Do you happen to have a source for that? Wikipedia says the following:
http://en.wikipedia.org/wiki/Mars_Climate_Orbiter
The Mars Climate Orbiter's reaction wheels were kept within their linear (unsaturated) range through thruster firings in a procedure called Angular Momentum Desaturation (AMD). When an AMD event occurred, relevant spacecraft data was telemetered to the ground, processed, and placed into a file called the AMD file. The JPL operations navigation team used data derived from the AMD file to model the forces on the spacecraft resulting from these specific thruster firings. Modeling of these small forces is critical for accurately determining the spacecraft's trajectory. Immediately after the thruster firing, the velocity change (DeltaV) is computed using the firing time for each of the thrusters, and an impulse bit, which models each thruster's performance. The calculation of the thruster performance is carried out both on-board the spacecraft and on ground support computers. The AMD software installed on the spacecraft used metric units, newton seconds (Ns), for the impulse and was correct. The ground software reported the impulse bit to the AMD file in English units of pounds (force) seconds (lbfs), rather than the metric units required by the project's Software Interface Specification. Subsequent processing of the impulse bit values from the AMD file by the navigation software underestimated the effect of the thruster firings on the spacecraft trajectory by a factor of 4.45 (1 pound force = 4.45 newtons).
Re:Oops. (Score:4, Informative)
I know you were joking, but keep in mind that the names "Spirit" and "Opportunity" were chosen very late into the mission, as the result of a contest. Within JPL, the probes were known as MER-A and MER-B, and the rovers were known as MER-2 and MER-1. To make things even more confusing, for various sensible reasons they ended up putting MER-2 inside MER-A, and MER-1 inside MER-B, even though that made things more confusing.
So, considering that they were otherwise identical, can't you see how easy it would have been to get otherwise identical parts mixed up...was it supposed to go in MER-B? Or MER-2? I just remember it was the second one of something...
Not informative, but wrong (Score:5, Informative)
"On September 27, 1999, the operations navigation team consulted with the spacecraft engineers to discuss navigation discrepancies regarding velocity change (V) modeling issues. On September 29, 1999, it was discovered that the small forces V's reported by the spacecraft engineers for use in orbit determination solutions was low by a factor of 4.45 (1 pound force=4.45 Newtons) because the impulse bit data contained in the AMD file was delivered in lb-sec instead of the specified and expected units of Newton-sec."