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Saving Huygens
TazMainiac writes "This months IEEE Spectrum is running an article on how a Swedish scientist discovered that the Titan probe Cassini had a communications flaw that would cause it to lose all data sent back from the Huygens lander as it plunges into Titan's atmosphere. The problem - Doppler effect. The fix: go read the article."
THIS kind of stuff is what NASA needs to be held accountable for. Had it not been for this engineer, the Huygens mission would have failed due to complacency and bureauocracy, having been rejected and deemed "unnecessary".
What is wrong with NASA? Here's a great example.
occultae nullus est respectus musicae - originally a Greek proverb
The article says he is a 26-year EASA veteran, it does not say that he is 26 years old. Though, I thought the same thing on my first pass and had to re-read it.
http://www.busyweather.com/
This is not a simple subcontractor arrangement. It is cooperation between government agencies in different governments, each of which has private contractors working for them.
Besides the obvious contractual nightmare this represents, there is also the issue of Export control between governments, which cannot be countermanded with a simple non-disclosure.
IMNAL, but I work on a similar project and you need to learn some of this stuff, sadly, to get your work done. I'm hopeful this incident will help to clear up these sort of cooperation issues in the future.
Good work in resolving this all involved! Remember Slashdotters, we explore to learn...
They were supposed to run a simulation, as one of three safety nets to catch such problems, but decided not to because of the cost.
Which doesn't make sense: did nobody at NASA have the brainpower to conceive of sending an emulated signal just like the one they actually ended up using? How much could it have cost to run a few hours' testing of Cassini's commlink prior to assembly of the craft? It's *always* a good thing to check system components in a full emulation environment.
I think there were many problems, and one of them was that the system (or system test) engineers didn't stop to think of the Q&D way to get some proper failsafe testing done.
https://app.box.com/WitthoftResume Code: https://github.com/cellocgw
A shining example of the promblems with proprietary design. No one can see what's wrong with it without expending a huge amount of effort. I'm just glad someone did decide to spend the effort.
Ever been done for speeding by radar gun?
To run the test they would have had to dismantle part of the craft and then go through an expensive recertification process to put it back together. Apparently the cost for all of this was very, very high. Probably not as high as the fix for this problem, though.
http://www.busyweather.com/
Sure, everyone knows that a)something Doppler related went wrong with Huygens and b) they fixed it with "fancy flying", but that's like saying don't bother to read a history of World War II because everyone knows a) Hitler started it and b) the Allies won.
The point of the story was to explain the problem with a level of accuracy and detail that was simply missing from most report and to tell the story of some stone-cold great work by an engineer, something of interest to most engineers, and I would hazard, to most slashdotters.
As far as I am aware, no-one else has told the story of how Boris Smeds pushed through the comms test that showed something was wrong, despite intial rejection and then later, modified it on the fly to reveal the problem was Doppler related, saving months of delay. Learning about his example of how to be a great engineers is the article's real utility, not teaching Spectrum readers how to fix Titan landers.
Disclaimer -- I edited this story for IEEE Spectrum
"Just once, I'd like to meet an alien menace that wasn't immune to bullets." -- The Brigadier, Dr. Who
You mean "What is wrong with proprietary?" right? After all, the entirety of this problem was because NASA bought a black box proprietary technology, and without access to its specs could only pray that it performed as advertised.
In this case, the black box didn't meet the required standards, but there was no way NASA could have known that this company built the black box out of off-the-shelf terrestrial design principles unfit for cosmic use.
If I have been able to see further than others, it is because I bought a pair of binoculars.
Now you know how they fixed it, so no need to read the article.
Thank you for the summary! I tried to RTFA, but I got tired of the tedious dumbed-down human interest after the first thousand words of breathless "Could the mission be saved, or was it too late?" tosh that these journalists always seem to feel they have to pad their word counts with.
I guess I should be glad they hadn't quite managed to turn it into One Man's Struggle Against the Establishment. And if the guy had got divorced or lost a child while he was working on Huygens, they'd probably have forgotten to put any science in the article at all...
I'm uptight because its annoying when you work on an article and people comment without bothering to read it -- yes, I know that's endemic to /., but it's still a pain in the ass.
/. decided to post the story.
The point is that we dug up an aspect of the story you're not going to see any where else, let alone a general overview program, but a really cool story of a guy who deserves a lot of credit, Boris Smeds. I would hate for anyone to not bother to find out about him because a related program on the telly happened to be braodcast the night before
"Just once, I'd like to meet an alien menace that wasn't immune to bullets." -- The Brigadier, Dr. Who
Keep in mind that Cassini was launched in 1997. That means that initial system design was begun probably somewhere around 1990 or so. What was the state of SDR in 1990?
However, having read the article, the complexity of the mission is such that I am possibly more amazed that more didn't go wrong.
The Huygens probe has yet to be deployed to Titan. Thus, it is too early tell if there are not other significant problems.
Table-ized A.I.
The problem was uncovered because the communications equipment had something like 14 sceduled tests en-route to Saturn using simulated data from Huygens to Cassini. Obviously, the first scheduled test showed up the problem so from there...
This conflicts with my reading of the article. The techie who suspected a problem had to fight tooth and nail to schedule a decent test run. The standard set of tests would not have detected dopler issues.
Table-ized A.I.
Ever heard of a guy named Marconi?
This is why spacecraft design should be "open sourced" and put up for download so that engineers everywhere can review it and point out problems.
Contractors should be heavily punished if their designs fail -- make them pay to redesign and refly, for instance. "You can cram your agreement up your ass because we paid to buy this from you and because it's on a publicly funded spacecraft. We're posting this on the web now so stop whining."
And why do we keep buying from Lockheed when they've fucked up so many missions in the recent past? JPL knows how to build stuff that actually works. Lockheed apparently doesn't. How about Boeing and the other companies out there that can do it?
And I agree... these idiots couldn't be bothered to even explain their mistake.
i am a soviet space shuttle
This is Slashdot. We don't point out inconsistencies and conflicts with the content of articles; we only point out conflicts with our preconceptions and prejudices. Please rephrase your post.
taken! (by Davidleeroth) Thanks Bingo Foo!
In many European countries there is a month long period where everyone goes on vacation. As I understand it, pretty much the entire country except for basic service industries shuts down for a month. I don't understand the specifics, as I've never been to Europe during a vaction, but I did work on a project once with SwedenPost (the Swedish Post Office) that ended up being pushed back quite a bit because the original project schedule had us going into client QA right as the entire company took a month and a half off for vacation. And this was the Post Office!
So I doubt that the fact that all of the company's officials were on summer vaction at the same time reflects on their abilities to design complicated hardware. It's just business as usual over there.
And as the article points out, NASA probably could have gotten the specs if they had signed an NDA but they didn't believe they were necessary. Given that statement, it's quite possible that no one would have looked at the specs close enough to notice the problem, even if they had them.
If I don't put anything here, will anyone recognize me anymore?
So instead they're altering the flightpaths so that Cassini is now far enough away from Huygens that the broadcast vector is mostly perpendicular, with minimal Doppler shift -- think about standing very far away from the racetrack instead of right in front of the car.
Today on slashdot I learned that angle of incidence is a function of distance. Thanks for the "informative" post.
mefus
In Open Society, GPL Software frees YOU!
But I'm trying to figure out how "on the ground" testing would have discovered this problem. The actual probe and the actual spacecraft could not have been moving so fast relative to each other on a test bench to duplucate the Doppler effect it would encounter in Titan.
It would have to have been simulated on the test bench, right? But the reading of the article suggests that simulating this, even if both craft were on the test bench talking to each other, would not have been performed because no one but this guy thought to do it years after the fact.
In fact, it seems to me that if testing actual inter-craft communications HAD been done, NO ONE would have still been thinking about it years later, and the REAL PROBLEM might not have ever been considered, tested, and taken care of.
In othe words, it sure was a good thing that no one tested the communications systems on the test bench between both craft!
I'm sure I'm misunderstanding something though, so if someone knows, I'd love to hear it.