A Flaw the JWST Doesn't (Have to) Have?

On 15/07/2011 5:58 PM, Quadibloc wrote:
On Jul 15, 3:09 pm, Yousuf wrote:

The reason for having adaptive optics on ground telescopes is to deal
with atmospheric blurring. In space, they won't have any of those
problems, obviously.

Yes, but it has a *segmented mirror*, and keeping the segments aligned
presents problems which are analogous to those of adaptive optics, so
there might be a similar limitation.

The original idea behind segmented mirrors was to make a reflector that
doesn't sag under its own weight, and therefor allows you to make bigger
telescopes. They found that it helped in compensating for atmospheric
blurring too.

A space telescope doesn't have to worry about blurring, nor does it
really need to worry about sagging, so it's just the bigger telescope
aspect that's relevant here. If they made the telescope large enough to
fit into a rocket nosecone, the telescope would still be the size of the
Hubble or the Herschel space telescopes.

Don't worry, they'll make the images available for you to see in
wavelengths you recognize.

Oh, of course the images will be available in false-color.

Most of the images coming from the Hubble are false color too. They come
into the scope as discrete bands of black'n'white images which are then
combined and colorized in computers on the ground. Hubble was able to
see ranges that our eyes couldn't see such as near-infrared and
ultraviolet, and they too were all false-colored into our range.

But because the Hubble will eventually be retired, the limitation of
the JWST to wavelengths of 600 nm and longer will mean that data at
shorter wavelengths will not be obtainable. I think that's a lack.

I think it's been shown that visible light astronomy has nothing new
left to offer, and all of the really amazing stuff comes in other
wavelengths, especially Far Infrared, Gamma, and X-Ray. They all are
able to escape through dust clouds. Other wavelengths like Radio can be
done entirely from the ground. If we still need visible light images,
then it seems as if the modern ground telescopes are doing a better job
than Hubble.

These days its seems that something like a gamma-ray burst occurs, a
space telescope is the first to detect it, and then a network of optical
scopes on the dark side of the planet get herded together to take
after-images of something the space telescope discovered. Basically just
clean-up hitters.

Yousuf Khan