Author Topic: Cold times for NASA's new telescope  (Read 6606 times)

Offline hektor

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Re: Cold times for NASA's new telescope
« Reply #20 on: 09/14/2006 05:46 PM »
I am really rooting for an Ariane 5 with a NASA logo on the fairing...

Offline Bruce H

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Re: Cold times for NASA's new telescope
« Reply #21 on: 09/14/2006 06:34 PM »
Would that be a first on the NASA Logo and Ariane 5 ECA?

Offline Justin Space

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Re: Cold times for NASA's new telescope
« Reply #22 on: 08/11/2008 08:58 AM »

Offline rdale

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Re: Cold times for NASA's new telescope
« Reply #23 on: 08/11/2008 11:16 AM »
Are you asking about that problem? Or JWST in general?

Looks like that issue was cleared out...

http://www.jwst.nasa.gov/newsletter4.html

If it's JWST - UMSF probably has more updated information on the overall platform...

Offline Fequalsma

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Re: Cold times for NASA's new telescope
« Reply #24 on: 08/13/2008 02:22 AM »
meiza, do you still have this document?  If so, can you post it here or provide an active link to it?  I tried to look for it, but no luck.
Thanks in advance!
F=ma

On a remotely related note, I accidentally hit this story about composites development for the submillimeter telescope in the late eighties, and the mess that happened around it at JPL. Of course, it is written by only one involved party, but the story seems juicy.

http://mars-lunar.net/archives/The%20PSR%20Story.pdf

nobodyofconsequence

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Re: Cold times for NASA's new telescope
« Reply #25 on: 08/13/2008 03:38 AM »
the mirror coatings and focal point are for infrared
Actually IR scope design issues include mirror quality (1/40 wave IR is not  good enough for visible), material integrity (warping/alignment), and structural issues. To make JWST work like Hubble is beyond our abilities.

There is nothing like Hubble in the works. Cross fingers for a long life and 100% success on the servicing mission.

Offline Blackstar

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Re: Cold times for NASA's new telescope
« Reply #26 on: 08/13/2008 10:39 AM »
Yes they are doing it to cut down costs for NASA, and Europe and the USA have already done joint mission with Soho and Cassini-Huygens. JWST had a cost overrun reported on the order of $1 billion, NASA then planned save money by getting a free launch on an Ariane 5 in exchange for observing time on JWST.

The launch is worth approximately $300 million.  Turns out that when NASA announced plans to launch on an Ariane V, US launch vehicle providers protested.  This resulted in a delay.  That delay cost approximately $300 million.  No savings.

Offline synchrotron

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Re: Cold times for NASA's new telescope
« Reply #27 on: 08/13/2008 01:27 PM »
With all the hubub about this telescope not having a visible light camera, whats the difficulty (or why isn't it being done) in adding a visible light camera to go along with the infrared one?

I'm a huge HST fan.  But this question perplexes me somewhat. We don't walk up to Hubble and put our eye to an eyepiece.  We have layers of sensors and avionics and data reduction equipment on the ground which act as intermediaries for us to see what Hubble sees.  Does it matter if the original wavelength is in the narrow optical spectrum available to human eyesight?
Once we have the IR detected, we can shift the spectra digitally to see what JWST can see.  The pictures will be inspiring whether the science drives us to IR or visible.


nobodyofconsequence

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Re: Cold times for NASA's new telescope
« Reply #28 on: 08/13/2008 04:22 PM »
With all the hubub about this telescope not having a visible light camera, whats the difficulty (or why isn't it being done) in adding a visible light camera to go along with the infrared one?

I'm a huge HST fan.  But this question perplexes me somewhat. We don't walk up to Hubble and put our eye to an eyepiece.  We have layers of sensors and avionics and data reduction equipment on the ground which act as intermediaries for us to see what Hubble sees.  Does it matter if the original wavelength is in the narrow optical spectrum available to human eyesight?
Once we have the IR detected, we can shift the spectra digitally to see what JWST can see.  The pictures will be inspiring whether the science drives us to IR or visible.



Two answers  - the science and the imagery

The science at IR is not the science in visible and UV - different physics entirely. They are all quite different. Look at the results from Spitzer and compare them to Hubble for a (limited) example. The point here is that JWST does not replace Hubble, you still need as much (perhaps even more) Hubble time. The hope has been to replace Hubble in visible with ground based adaptive  optics (like the LBT). This may just be becoming possible, as telescopes are coming online and researchers are starting to make optical AO possible (using MEMS).

[By the way, you don't use one as a finder for the other - you overlay the results instead.]

Imagery from the Hubble has had a powerful public outreach effect, mostly because people can understand traditional visible "true" color photos than anything else. You can look in a amateur telescope for some of these objects and tell that the Eagle Nebula and the Hubble "Pillars of Creation" are of the same object! That connects the public to the Hubble as something they "get".

Offline iamlucky13

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Re: Cold times for NASA's new telescope
« Reply #29 on: 08/14/2008 01:11 AM »
To follow up on the science part of nobody's post:

There's light coming in across the entire gamut of the electromagnetic spectrum. From gamma rays measured in exohertz (quintillion cycles per second) down to "audio" ranges. They come from a variety of sources, so things that you see in infrared not only tell you something different from what you see in visible light...they might not even appear to be there in visible light.

For example, star-forming regions tend to be bright in infrared as protostars begin to warm up, but aren't hot enough to shine visibly. Dust clouds may block visible light but let certain infrared wavelengths through. Cold hydrogen that is otherwise undetectable glows weakly in the microwave, quite close in fact to GPS  broadcasts. Astronomers have charted huge clouds of free hydrogen by looking for that. On the other end of the spectrum, x-rays and gamma rays suggest active black holes, quasars, and supernovae.

So Hubble sees some of these. Spitzer sees others. GLAST sees still others. The upper end of JWST, I think overlaps slightly with the bottom end of Hubble's ability, but because of the desire to see objects billions of light years away that have been red-shifted down to the mid-infrared range, it can't simply mimic Hubble.

There will be some loss of capability when Hubble is retired. It won't be as bad as some make out, and obviously Hubble is hitting a lot of the high priority targets now and generating enough data to keep astronomers busy for years. Adaptive optics have made it so ground-based telescopes can accomplish a lot of what Hubble does in the visible range despite the distortion of the atmosphere. Their big drawback, however, is because of the earth's rotation they can't do really long observations necessary for the deep field views from Hubble that have been most revealing. Fortunately that's right in line with what JWST will specialize at.

Offline nomadd22

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Re: Cold times for NASA's new telescope
« Reply #30 on: 08/14/2008 01:27 AM »
 JWST will actually go a bit into the visible range. It goes up to 700nm. It overlaps Hubble quite a bit. WFC3 goes down to 1400nm and NICMOS to 2500nm.

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