Slashdot Mirror
NASA Finds Cause of Voyager 2 Glitch
astroengine writes "Earlier this month, engineers suspended Voyager 2's science measurements because of an unexpected problem in its communications stream. A glitch in the flight data system, which formats information for radioing to Earth, was believed to be the problem. Now NASA has found the cause of the issue: it was a single memory bit that had erroneously flipped from a 0 to a 1. The cause of the error is yet to be understood, but NASA plans to reset Voyager's memory tomorrow, clearing the error."
Nobody knows you've done anything at all.
-|BlackErtai|-
Let me guess: cosmic ray. Is it really that hard? What else causes a single bit-flip error in space?
http://pinopsida.com
the voyager probes use a radioisotope thermoelectric generator so that wouldn't work anyway
http://pinopsida.com
Why don't they just always try that first?
What else would it be?
According to some German, aliens.
W
PS is "Cosmci Ra" related to Mumm-Ra? Or She-Ra for that matter?
-------------------
This is my SIG. There are many like it, but this one is mine.
"Blow in the DTR!" "No, no! Jiggle the CCS!" "Did you try uninstalling the MGA?"
This is why you DO WANT nuclear energy in space! OK, Voyager 1 and 2 have RTGs, but even those are considered politically incorrect these days, especially such massive ones as in the Voyagers.
More nuclear power in spacecraft, I say. To provide propulsion (ion drive, or even better, explosive drive) and energy when far from the Sun. Fuck PC.
"The agriculture ministry is not in charge of Gundam" - Japanese ministry official.
NASA is my hero. They do cool shit all the time. Even when their stuff breaks, it's cool. Then they fix it and it's even more cool.
No sig for you. YOU GET NO SIG!
First I was going to suggest that this satellite would careen forward out of control like a Toyota, but then realized that wouldn't be quite accurate.
The cosmic rays we get one Earth are actually short-lived particles such as muons (a fat electron, probably most well known aside from the standard protons-neutrons-electrons) that result from cosmic naked hydrogens hitting our atmosphere. Out in space though, it'd be interesting to see if those protons would have the same effect as a terrestrial "cosmic ray".
All that and no "Try SCE to aux"?
Voyager is anything but brand new. Voyager is probably older than most Slashdotters, having been launched in 1977. Think about it: 1977 - when advanced microchips were not as powerful as the chip driving the shatty calculator you buy today at the dollar store. 1977 was a different time, when information technology usually didn't even involve transistors, yet, and vacuum tube testers (for your TV) were still found at the local drug store.
And yet, some 33 years later, Voyager 2 is still chugging on, after visiting ALL of the outer planets, still going waaayayyyyyyy past its original design limits, still providing meaningful information on its way out roughly towards the star Sirius. It's now twice as far away from the Sun as Pluto is.
Like the Mars rovers, this is truly good engineering at work.
I have no problem with your religion until you decide it's reason to deprive others of the truth.
You telling me NASA doesnt even use parity memory? Seriously?
=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Friends don't let friends enable ecmascript.
The Voyagers are my favorite probes!
I wonder how many bits they'll have to send to change the one wrong one, and how long that will take.
Leave it to the stoner astrophysicists Carl Sagan to oversee one of the more amazing feats of space trave!!
Radioisotope thermoelectric generators are awesome!
Anyone know how much fuel is remaining? They've been heating up for knowledge for a long period of time.
Personally, I want about 6 of the units in Voyager 2, screw solar!
Nah, thats just like rebooting a Windows 2003 server. 14 days and it's still "Applying Computer Settings"
Calling someone a "hater" only means you can not rationally rebut their argument.
One of the upgrades the Voyagers had over the Viking computers was CMOS memory (instead of plated wires). Read all about it at http://history.nasa.gov/computers/contents.html Apparently, there was some debate at the time over whether these new-fangled memories would be reliable.
The spacecraft is in an incredibly hostile environment. Who's to say that there *wasn't* ECC and it's just that it's Hamming code wasn't enough to compensate for the error - it would make sense: as the hardware ages, the device leaves the solar system, the errors start getting closer and closer to the limits of error correction until one day - bam, even with error correction it slips through the net and ends up as a bad bit in memory.
Technically, this is possible (but incredibly rare) on even the greatest error correction in the world. Error correction is a statistical function, that says that the *chances* of an error occuring are 2^8, or 2^16 or whatever.
And, from my coding theory class, Voyager's signal was originally something ludicrous like a (24,12,8) code even when it was nearby. (This presentation, especially the final slide, appears to confirm that: http://www-math.cudenver.edu/~wcherowi/courses/m6409/mariner9talk.pdf).
ECC is a probability function - the probability of a bit error going undetected is significantly reduced compared to, say, just sending the data and hoping for the best. But reduced does not mean eliminated. Not all errors can be detected and only a small portion of those can be corrected. But that still leaves room for an error that goes uncorrected, undetected and ends up in RAM without anyone noticing until they do a full bit-by-bit check - the same as your 25+ years newer technology harddrive, Ethernet connection, computer bus, etc. There's no such thing as guaranteed data delivery - but we make the chances of an error slipping through so infinitesimally small that it doesn't affect normal, everyday operation. For instance, a corrupt download with an SHA-1 checksum would be seen as valid approximately one in every 2^160 transactions. Small, but not impossible by a long stretch considering how many downloads occur each day.
Voyager didn't have the luxury of Megabytes of RAM to hold extraneous checksum data, Megahertz of CPU to check everything that came in at line speed, or a broadcast technology that could keep a Gbit data rate going all the time. They made compromises and, later, changed the ECC algorithms as more and more errors could theoretically creep in. We just had a run of bad luck that meant a single bit was out, that's all. And that's even assuming it's not a hardware failure anyway. I think Voyager did pretty damn well, running for decades after it's supposed operational time. And a one-bit error on a random chance is pretty damn minor - let's just hope it wasn't inside anything too critical, like the communications routines.
While not naming specifically cosmic rays as the cause in this case, what examples of actual cosmic ray-induced debacles are there in software eng. history?
Well, okay, as long as they don't get the "Press any key to continue" message...
Free PC version of ChipWits at http://www.breueronline.de/klaus/chipwits/
Analogue amplification gives even harmonics whereas digital amplification gives odd harmonics. And even harmonics are more pleasing to the ear. You can obviate the problem of odd harmonics by producing more harmonics to nudge the signal back to more pleasing shapes, but that means that an op-amp running at 192kHz can produce a pseudo-analogue amplified signal equating to an analogue amplifier with a ceiling of 30kHz.
It's one reason why early CDs were, frankly, crap: the sound engineers used the same techniques making the sound track for the CD that they did for the analogue LP. But the CD has different strengths and weaknesses and some processes that utilised the strength of LP and avoided the weakness of them were unsuited to the CD characteristics.
AFAIR, the re-release of the White Album was the first one where they went back to the original tapes and worked the signal to accord with the CD and digital amplification strengths.
Now they're ditching the high dynamic range of CD in the loudness war.
Way to go, guys.
All I hear is: "Blah blah blah tube blah blah loud blah blah" *ringing in my ears*
You probably haven't had much experience with these older computer systems. They did what they need to do and that is it. The hardware was wired to do what it needs to do. Every bit had a purpose If that bit failed you knew that something was wrong. Making it fairly easy to find the bit that was bad.
1K can be represented in a 32x32 square. these systems had only a few k of memory to view. And millions of dollars for funding Finding a missing bit is actually very easy. Especially if you go threw the design specs and see what bit does what.
General Purpose Computing, was a tradeoff that I think for the most part has better benefitted us. If every computer needed to be made bit level specialized to do one/few thing(s) and do them well, we will have a lot of very secure and extremely reliable computers... However only a few large organizations would be able to afford them as they will need a full custom design of their processes. And in terms of power they will be a lot less then they are today.
The General Purpose computers while are very complex and can cause a lot of problems.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.