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The James Webb Telescope, the largest science project in US government history

arstechnica.com

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Re: The James Webb Telescope, the largest science project in US government history

#21

Post by drzaiusapelord »

tfm wrote: post #3

"Putting an astronomical telescope in space was a natural solution, and it followed directly—and, according to some, very directly—from the spy satellite program." Can anyone expand upon this? I know the NRO has recently donated some of its old gear to NASA, but is there much cross-pollination between the space-operating agencies?

I also have trouble with this claim. Its been documented several times that problems NASA stuggles with have sometimes been solved by the DoD, but due to classification cannot be shared with NASA. No, this isn't some evil conspiracy, but NASA is open-ish and the contractors that do their work don't do so under classification, so anything given to NASA would quickly fall into the hands of America's enemies.

That said, I think this is true in a very general sense for more commodity space tech. Lets say, lens grinding on this level has been done for DoD projects, but because that's probably not classified (at least past a certain level), its easy for NASA's contractors to just re-use that lens grinding method than re-engineering a new one. Because the spy satellite programs are classified, we really can't know how much of it goes back into NASA programs, but I imagine something might.

Re: The James Webb Telescope, the largest science project in US government history

#22

Post by basch »

leephillips wrote: post #18
basch wrote: post #17

Earlier quoted context omitted.

I'd argue Manhattan Project and Apollo are tied. They both could be measured in % of GDP, at .4% each.

I think it might have been better if the "largest" claim had not wound up part of the title, because it's led to a great deal of distracted quibbling. NASA claims that the Webb is its largest-ever science project, and others have judged it to be the largest in US history. If it's important, we can note that the Manhattan project was military, not science, although of course plenty of science was done there. Apollo mi…

Manhattan wasnt one project any more than Apollo was and most of the money went to Uranium enrichment.

http://blog.nuclearsecrecy.com/2013/05/17/the-price-of-the-m...

Re: The James Webb Telescope, the largest science project in US government history

#23

Post by jgalt212 »

kjs3 wrote: post #11
melling wrote: post #4

Earlier quoted context omitted.

I'm not sure what you are trying to reason. X was cancelled but Y was almost cancelled. That makes no sense. According to Wikipedia, $2.2 billion was spent on the SSC before it was cancelled in 1993. https://en.m.wikipedia.org/wiki/Superconducting_Super_Collid... It's unfortunate that it was never completed, it was going to be bigger than the LHC. Everything we are learning now could have been learned a generation ag…

Claiming we'd have learned everything the LHC taught us a generation ago also doesn't make much sense, considering the vast improvements in sensor technology and data handling that happened between the last generation and this. It's just as likely we'd have seen little or nothing because our "eyes" weren't sensitive enough or we couldn't find the needle in the data haystack.

Perhaps, but in high energy physics, size matters. Or at least size matters more than most other dimensions.

Re: The James Webb Telescope, the largest science project in US government history

#24

Post by TheOtherHobbes »

jgalt212 wrote: post #23
kjs3 wrote: post #11

Earlier quoted context omitted.

Claiming we'd have learned everything the LHC taught us a generation ago also doesn't make much sense, considering the vast improvements in sensor technology and data handling that happened between the last generation and this. It's just as likely we'd have seen little or nothing because our "eyes" weren't sensitive enough or we couldn't find the needle in the data haystack.

Perhaps, but in high energy physics, size matters. Or at least size matters more than most other dimensions.

I'd suggest computing matters more.

The SSCO would have been crippled by the sensor and computing technology available at the time. It would have been able to make very small things go "boink" a lot, but it would have had problems capturing a fat enough stream of data to record the results.

LHC wins because signals are statistical, and the more data you have the more reliably you can say "Uh huh - that's a real signal and not just one of those random things that happens sometimes."

See also the current debate about whether or not something real is going "boink" at 750GeV.

Re: The James Webb Telescope, the largest science project in US government history

#25

Post by jessriedel »

madaxe_again wrote: post #19
jjoonathan wrote: post #13

Earlier quoted context omitted.

Bet you a dollar that you've got an unmodulated electromagnetic audio signal not two feet from where you're sitting (if not stuck directly into your ears). More importantly: I think it's fair to assume that someone reading an EM spectrum has the knowledge to figure out what they mean.

I'm a physicist and I have absolutely no idea what you mean by an "electromagnetic audio signal". I think what you mean is an EM wave which happens to carry an amplitude-modulated audio signal , which is not an audio wave. Audio waves are compressional waves formed in a medium, and require a medium for transmission through, such as air, or rock, or water, or even interstellar gas. Electromagnetic waves require no med…

> I have absolutely no idea what you mean by an "electromagnetic audio signal". I think what you mean is an EM wave which happens to carry an amplitude-modulated audio signal

...So you did know what they mean.

Re: The James Webb Telescope, the largest science project in US government history

#26

Post by gaur »

madaxe_again wrote: post #7

Nice article, but the diagram halfway down that shows the EM spectrum.... I'm scratching my head over why "Audio" is apparently now electromagnetism.

"Audio sideband" is a common term for AM or FM sidebands from dc to a few tens of kilohertz or a few hundred kilohertz. Not exactly the same as calling a 10-km wavelength EM wave an audio wave, though.

Re: The James Webb Telescope, the largest science project in US government history

#27

Post by kjs3 »

jgalt212 wrote: post #23
kjs3 wrote: post #11

Earlier quoted context omitted.

Claiming we'd have learned everything the LHC taught us a generation ago also doesn't make much sense, considering the vast improvements in sensor technology and data handling that happened between the last generation and this. It's just as likely we'd have seen little or nothing because our "eyes" weren't sensitive enough or we couldn't find the needle in the data haystack.

Perhaps, but in high energy physics, size matters. Or at least size matters more than most other dimensions.

Only with respect to generating events, not with respect to detecting and analyzing them.

Re: The James Webb Telescope, the largest science project in US government history

#28

Post by jjoonathan »

madaxe_again wrote: post #19
jjoonathan wrote: post #13

Earlier quoted context omitted.

Bet you a dollar that you've got an unmodulated electromagnetic audio signal not two feet from where you're sitting (if not stuck directly into your ears). More importantly: I think it's fair to assume that someone reading an EM spectrum has the knowledge to figure out what they mean.

I'm a physicist and I have absolutely no idea what you mean by an "electromagnetic audio signal". I think what you mean is an EM wave which happens to carry an amplitude-modulated audio signal , which is not an audio wave. Audio waves are compressional waves formed in a medium, and require a medium for transmission through, such as air, or rock, or water, or even interstellar gas. Electromagnetic waves require no med…

> I'm a physicist

Useless nitpicking gives us a bad name. Please stop.

Re: The James Webb Telescope, the largest science project in US government history

#29

Post by mturmon »

The cryocooler for the infrared imager has proven to be the toughest design issue with JWST, at least so far, and AFAIK it's still on the critical path for the mission. (http://spacenews.com/northrop-grumman-at-last-set-to-ship-tr...)

I was surprised the cryocooler was not mentioned in the article. The sunshade is there, but that's not nearly as big an engineering challenge.

Re: The James Webb Telescope, the largest science project in US government history

#30

Post by mturmon »

drzaiusapelord wrote: post #21
tfm wrote: post #3

"Putting an astronomical telescope in space was a natural solution, and it followed directly—and, according to some, very directly—from the spy satellite program." Can anyone expand upon this? I know the NRO has recently donated some of its old gear to NASA, but is there much cross-pollination between the space-operating agencies?

I also have trouble with this claim. Its been documented several times that problems NASA stuggles with have sometimes been solved by the DoD, but due to classification cannot be shared with NASA. No, this isn't some evil conspiracy, but NASA is open-ish and the contractors that do their work don't do so under classification, so anything given to NASA would quickly fall into the hands of America's enemies. That said,…

Let's suppose you were an expert in optical design for space systems -- lenses, mirrors, coolers, detectors, electronics, thermal design -- and worked at NASA on a space telescope.

When that space telescope (say it was Hubble or Spitzer) was launched, you would be looking for another project. That's a small world. Maybe you would talk to a friend who works for intelligence agencies and find out what they are looking for.

And the reverse happens too. If you've explored the design space for an intelligence agency, you would be well-positioned to re-use that knowledge for a space telescope. You mention the classification barrier, but the basic physics drivers will be more apparent the second time around.

Case in point: Larry James (http://www.jpl.nasa.gov/about/bio_james.php), who is the Deputy Director for JPL, but who used to be Air Force Deputy Chief of Staff for Intelligence, Surveillance and Reconnaissance at the Pentagon, and who before that was a Shuttle payload specialist. He's a technical executive, but there are pure technical examples as well.

OK, and a second example, of a segmented mirror demonstrator: http://www.nps.edu/About/News/NPS-New-Home-for-Giant-Segment... ("NASA’s James Webb Space Telescope, named for the former NASA administrator and scheduled for launch in 2014 [erp!], will deploy the next generation of SMT technology on a mission to image light from the earliest galaxies in the universe.")

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