Time to scrap the Hubble telescope?

http://smh.com.au/articles/2003/07/2...244488651.html

"Andrew Nowicki" wrote in message
...
http://smh.com.au/articles/2003/07/2...244488651.html

Aren't modern ground-based telescopes with adaptive optics superiour to
Hubble, especially when they are linked up? I thought I heard that these new
telescopes can produce pictures every bit as good as Hubble.

On Mon, 28 Jul 2003 16:42:27 +0200, "Ultimate Buu"
wrote:

"Andrew Nowicki" wrote in message
...
http://smh.com.au/articles/2003/07/2...244488651.html

Aren't modern ground-based telescopes with adaptive optics superiour to
Hubble, especially when they are linked up?

No. Where although adaptive optics greatly help it is the case that
the atmosphere still blurs things.

They use special computer software to pull it mostly back together.

I thought I heard that these new
telescopes can produce pictures every bit as good as Hubble.

I have yet to see any.

Still these days there are other space based telescopes just as
powerful as hubble, but not in the same frequency range.

Cardman.

In article ,
Ultimate Buu wrote:
Aren't modern ground-based telescopes with adaptive optics superiour to
Hubble, especially when they are linked up?

No. In principle, they can do *some things* better... although those are
mostly still "Real Soon Now!" promises rather than demonstrated facts.
However, in other areas Hubble retains an inherent advantage that is not
going to go away.

Hubble can take much longer exposures, given targets in the right parts
of the sky, because its sky isn't full of scattered sunlight half the time.

And it works farther into the infrared, and much farther into the
ultraviolet, than any ground-based scope can.

And it has a much darker sky background, which matters when working on
very faint objects.

And it can point closer to the Sun, although its cautious operating
policies limit that.

And it can observe rapid time variations without a lot of superimposed
atmospheric noise.

And -- minor but not entirely insignificant -- it has a clear view of the
entire sky, something that is quite difficult to achieve from any single
point on Earth.

And, finally, although its high resolution has been exceeded by adaptive
optics and interferometry on the ground, its high resolution comes with
many fewer ifs, ands, and buts. Adaptive optics requires either nearby
bright guide stars, or still-experimental laser guide stars. Imaging
interferometry can observe only bright sources, because you need a fair
number of photons per millisecond to detect interference fringes.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

Andrew Nowicki wrote in message ...
http://smh.com.au/articles/2003/07/2...244488651.html

For $600 million, could you build an launch a service module which
would

1. Tansport Hubble to the Earth Sun L4 or L5 point, perhaps with
electric propulsion
2. Provide effective communications with Earth
3. Have a wide angle telescope for target finding

This would then be used to locate NEOs for possible resource
exloitation, or as part of the Space Guard Project.

"Henry Spencer" wrote:
In article ,
Ultimate Buu wrote:
Aren't modern ground-based telescopes with adaptive optics superiour to
Hubble, especially when they are linked up?

No. In principle, they can do *some things* better... although those are
mostly still "Real Soon Now!" promises rather than demonstrated facts.
However, in other areas Hubble retains an inherent advantage that is not
going to go away.

[long list of stuff snipped]

And, finally, although its high resolution has been exceeded by adaptive
optics and interferometry on the ground, its high resolution comes with
many fewer ifs, ands, and buts. Adaptive optics requires either nearby
bright guide stars, or still-experimental laser guide stars. Imaging
interferometry can observe only bright sources, because you need a fair
number of photons per millisecond to detect interference fringes.

This is the kicker, and it's why Hubble is still worth its weight
in gold. In many ways ground based telescopes can match some of
Hubble's capabilities under the right circumstances. But Hubble
doesn't need much setup to reach its maximum capabilities. Some
ground observatories have the ability to match some of Hubble's
abilities some of the time, but Hubble has them on tap, available
basically 24/7. So in many respects, once you factor in the
timeliness and duty cycle and availability and all that jazz,
Hubble adds up to around several VLTs or Kecks (I'd hate to guess,
I'd guess around a dozen or more world class ground based
telescopes, averaging out various factors). Hubble costs about
the same as several world class observatories, but on a science
basis it has proven to be worth it.

"Duncan Young" wrote:
Hubble's ACS/WFC has a field of view of about 200 arcseconds (less
than a tenth the angular size of the moon as seen from Earth)... a bit
narrow for rock hunts. Given that, I dont see the need for HST for
Space Guard - you can just fly your platform with the wide angle
telescope (much cheaper) and do any follow up from earth or HST.

Hubble isn't even remotely optimized for such a mission. For
one, it's sensors tend to have too many googaws for sorting
out spectral information, and that's not really needed for
rock hunting. I'd imagine you'd want something somewhat
similar to (though completely differently utilized than)
Kepler's "precision photometer", or a similar monster CCD
array (circa 100 megapixels). Incidentally, I'd imagine that
Kepler will find a decent number of new, faint asteroids and
comets as a byproduct of its investigation.

(Henry Spencer) wrote


In article ,
Ultimate Buu wrote:
Aren't modern ground-based telescopes with adaptive optics superiour to
Hubble, especially when they are linked up?

No. In principle, they can do *some things* better... although those are
mostly still "Real Soon Now!" promises rather than demonstrated facts.
However, in other areas Hubble retains an inherent advantage that is not
going to go away.


[Catalogue of virtues snipped.]

One thing that I wonder about is the wisdom of viewing NGST (JWST?)
as a replacement for Hubble, rather than as a separate instrument
intended for different, if complementary tasks. IIRC, NGST isn't
meant to operate at wavelengths shorter than 600 nm, which doesn't
even include all of the visible part of the spectrum, let alone the
UV.

If so, and since HST shows no sign of slowing down in its
production of outstanding science, why not consider launching a
modernized but essentially similar Hubble-2? Doubtless LockMart
would be glad of the business, and might even have some spare KH-11
hardware around that could be used.

"Christopher M. Jones" wrote in message ...
"Duncan Young" wrote:
Hubble's ACS/WFC has a field of view of about 200 arcseconds (less
than a tenth the angular size of the moon as seen from Earth)... a bit
narrow for rock hunts. Given that, I dont see the need for HST for
Space Guard - you can just fly your platform with the wide angle
telescope (much cheaper) and do any follow up from earth or HST.

Hubble isn't even remotely optimized for such a mission. For
one, it's sensors tend to have too many googaws for sorting
out spectral information, and that's not really needed for
rock hunting. I'd imagine you'd want something somewhat
similar to (though completely differently utilized than)
Kepler's "precision photometer", or a similar monster CCD
array (circa 100 megapixels). Incidentally, I'd imagine that
Kepler will find a decent number of new, faint asteroids and
comets as a byproduct of its investigation.

My specific interest is more composition and orbit determination for
resourc e usage, rather than space guard. Would the spectral "sorting"
enable any of that?

The aim would also not be to find all NEOs within a region, but to
randomly identify a few that could then be analysed for material
composition and rendezvous profile, a few y

"Christopher M. Jones" wrote in message ...
"Duncan Young" wrote:
Hubble's ACS/WFC has a field of view of about 200 arcseconds (less
than a tenth the angular size of the moon as seen from Earth)... a bit
narrow for rock hunts. Given that, I dont see the need for HST for
Space Guard - you can just fly your platform with the wide angle
telescope (much cheaper) and do any follow up from earth or HST.

Hubble isn't even remotely optimized for such a mission. For
one, it's sensors tend to have too many googaws for sorting
out spectral information, and that's not really needed for
rock hunting. I'd imagine you'd want something somewhat
similar to (though completely differently utilized than)
Kepler's "precision photometer", or a similar monster CCD
array (circa 100 megapixels). Incidentally, I'd imagine that
Kepler will find a decent number of new, faint asteroids and
comets as a byproduct of its investigation.

My specific interest is more composition and orbit determination for
resourc e usage, rather than space guard. Would the spectral "sorting"
enable any of that?

The aim would also not be to find all NEOs within a region, but to
randomly identify a few that could then be analysed for material
composition and rendezvous profile, a few y