Time to scrap the Hubble telescope?
Andrew Nowicki
Ultimate Buu
"Andrew Nowicki" <and...@nospam.com> wrote in message
news:3F251A38...@nospam.com...
> http://smh.com.au/articles/2003/07/27/1059244488651.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.
Cardman
<majjinbuu@dragonball.z> wrote:
>"Andrew Nowicki" <and...@nospam.com> wrote in message
>news:3F251A38...@nospam.com...
>> http://smh.com.au/articles/2003/07/27/1059244488651.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.
Henry Spencer
Ultimate Buu <majjinbuu@dragonball.z> 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! | he...@spsystems.net
Alex Terrell
> http://smh.com.au/articles/2003/07/27/1059244488651.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.
Duncan Young
> Andrew Nowicki <and...@nospam.com> wrote in message news:<3F251A38...@nospam.com>...
> > http://smh.com.au/articles/2003/07/27/1059244488651.html
>
> For $600 million, could you build an launch a service module which
> would
>
> 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.
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.
Duncan
Christopher M. Jones
> In article <3f2536ef$0$133$1b62...@news.wanadoo.nl>,
> Ultimate Buu <majjinbuu@dragonball.z> 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.
>
>
> 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.
Christopher M. Jones
> 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.
Greg D. Moore (Strider)
"Christopher M. Jones" <spic...@dualboot.net> wrote in message
news:bg52ru$khcim$1...@ID-137880.news.uni-berlin.de...
>
> 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.
>
All the more reason to dig out the Kodak mirror, grab the old equipment
already removed from Hubble and build a Hubble II. Toss it into a high
orbit, assume once it breaks it breaks and now you've got another world
class sat for a miniscule cost of the original. The bigger problem I think
would be funding the ground operations after launch.
Allen Thomson
> In article <3f2536ef$0$133$1b62...@news.wanadoo.nl>,
> Ultimate Buu <majjinbuu@dragonball.z> 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.
Greg D. Moore (Strider)
"Allen Thomson" <thom...@flash.net> wrote in message
news:501f9880.03072...@posting.google.com...
>
> 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.
In a word: Money.
Alex Terrell
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
Alex Terrell
My specific interest is more composition and orbit determination for
Allen Thomson
> > 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.
> In a word: Money.
Well, yes. But say that money were an explicit constraint: could a
much-like-Hubble Hubble-2 be built and launched in five years for
two to four gigabucks total, we-really-mean-it-do-not-exceed cost?
Say the price of a half to one STS launch per year for those five
years? It doesn't seem too absurd for an agency that is funded at
$15G/yr to scrounge up that kind of money for a kind instrument that
has been proven to produce staggeringly wonderful results and shows
no signs of stopping.
Christopher M. Jones
> All the more reason to dig out the Kodak mirror, grab the old equipment
> already removed from Hubble and build a Hubble II. Toss it into a high
> orbit, assume once it breaks it breaks and now you've got another world
> class sat for a miniscule cost of the original. The bigger problem I think
> would be funding the ground operations after launch.
Bad idea. Hubble might be one of a kind and highly valuable now,
but it's design is grossly obsolete, even with updated
instruments. The Nexus side / sub project (which, sadly I think,
got axed) of NGST showed a better and cheaper way to get Hubble
class optics. Hubble was designed and built at a time of great
change in telescope systems, especially optics. The type of
monolithic mirror used on Hubble has been surpassed by perhaps
more than one full generation of optical designs (depending on
how you count). If they were redesigning a spacecraft today to
match Hubble's capabilities it would be lighter and cheaper and
probably much more capable even in the same basic package. It's
almost too bad that ESA hasn't succumbed to the classic "well if
they're doing it, we're doing it!" behavior and designed a
Hubble class next generation space telescope on the cheap (and
it could be done, easily). But I suppose they haven't because
they've already got an in with NGST / JWST and they've still got
a decent stake in Hubble, while it lasts.
Oh, and the mirror is a relatively minor cost of any observatory,
the big costs are in instrumentation and other systems. It's
easy to think "mirror = observatory", but that's not the case
and simply having a free mirror around would not really
substantially decrease the cost of a new space telescope. In
fact, the needs of having to design the telescope around the
"free mirror" would probably cost more than a from scratch
design.
Christopher M. Jones
> 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
Here's the funny part. Hubble has a lot of decent capability
for multi-spectral imaging and even some basic spectrometers,
but spectroscopy is much more forgiving, generally, to things
like atmospheric disturbance. So it really pays just to have
the biggest light-bucket you can get, and that means, for now,
ground based telescopes. And indeed, spectroscopy is where
the big ground based telescopes excell. That's why things
like the cosmological supernova searches, which nailed down the
accelerating expansion of the universe, or doppler velocity
planet searches are done using big ground based telescopes
(both are spectroscopic studies).
Christopher M. Jones
> Well, yes. But say that money were an explicit constraint: could a
> much-like-Hubble Hubble-2 be built and launched in five years for
> two to four gigabucks total, we-really-mean-it-do-not-exceed cost?
> Say the price of a half to one STS launch per year for those five
> years? It doesn't seem too absurd for an agency that is funded at
> $15G/yr to scrounge up that kind of money for a kind instrument that
> has been proven to produce staggeringly wonderful results and shows
> no signs of stopping.
You're far behind the times. NGST won't cost near that
much, even if it overruns its budget by a huge margin.
And really a new Hubble replacement could just about fit
within one of those new fangled New Frontiers mission
budgets (depending on design, of course).
This is one of the classic problems of publically funded
science. There's often a tendency to chase after the
"edge" and eschew the fundamentals or "retreading" what's
been done, even when you can do so at relatively little
cost in comparison.
Allen Thomson
> "Allen Thomson" <thom...@flash.net> wrote:
> > Well, yes. But say that money were an explicit constraint: could a
> > much-like-Hubble Hubble-2 be built and launched in five years for
> > two to four gigabucks total, we-really-mean-it-do-not-exceed cost?
> You're far behind the times. NGST won't cost near that much, even if
> it overruns its budget by a huge margin.
Wanna bet? Maybe, just to be current, we should open a futures market
on what the NGST/JWST is actually going to cost by the time it gets on
orbit. :-) (See, BTW, http://us.newsfutures.com/home/home.html , which
got there before DARPA almost did.)
> This is one of the classic problems of publically funded science.
> There's often a tendency to chase after the "edge" and eschew the
> fundamentals or "retreading" what's been done, even when you can do
> so at relatively little cost in comparison.
Very true, and somewhat hard to balance. I'm all in favor of pushing
the outer edge, but also support wringing as much as possible out of
what has already been shown to be productive. Perhaps it would be
worth discussing how to allocate money between such things.
I'm also in favor of dumping things that have been shown not to work,
and/or have no reasonable prospect of returning worthwhile results.
(Not to name any names, of course.)
Andrew Nowicki
Jason Rhodes
"Devlin" <dev...@nospam.spam> wrote in message
news:300720031929541580%dev...@nospam.spam...
> In article <501f9880.03072...@posting.google.com>, Allen
> Thomson <thom...@flash.net> wrote:
>
> > 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.
>
> wouldn't its successor need to be on the drawing boards soon?
Some information here:
http://www.aura-astronomy.org/hsl/
Stephen Souter
Jones" <spic...@dualboot.net> wrote:
> "Greg D. Moore (Strider)" <moo...@greenms.com> wrote:
> > All the more reason to dig out the Kodak mirror, grab the old equipment
> > already removed from Hubble and build a Hubble II. Toss it into a high
> > orbit, assume once it breaks it breaks and now you've got another world
> > class sat for a miniscule cost of the original. The bigger problem I think
> > would be funding the ground operations after launch.
>
> Bad idea. Hubble might be one of a kind and highly valuable now,
> but it's design is grossly obsolete, even with updated
> instruments. The Nexus side / sub project (which, sadly I think,
> got axed) of NGST showed a better and cheaper way to get Hubble
> class optics. Hubble was designed and built at a time of great
> change in telescope systems, especially optics. The type of
> monolithic mirror used on Hubble has been surpassed by perhaps
> more than one full generation of optical designs (depending on
> how you count). If they were redesigning a spacecraft today to
> match Hubble's capabilities it would be lighter and cheaper and
> probably much more capable even in the same basic package.
That's all very well and true, but until a new gee-whiz replacement
actually gets built and flown any superiority the replacement might have
over Hubble is pretty much irrelevant. You can't do useful things with a
mission that only exists on paper! If nobody is prepared to fund a Hubble
2 that pretty leaves two options: making do with the hardware you already
have in space, obsolete or not, or doing without Hubble *and* any
replacement.
--
Stephen Souter
s.so...@edfac.usyd.edu.au
http://www.edfac.usyd.edu.au/staff/souters/
William C. Keel
There seems to be a consensus among folks who build these things that
one could build and launch a Hubble-class (2-2.5m) telescope with
acquisition/guiding plus a single science instrument for the
surprisingly small level of <500M (some proposals come in well
below by taking advantage of special opportunities, but NDRs
probably mean I can't be any more specific). For example, the
optical systems are now basically admitted to be reconnaissance-satellite
clones.
This only translates into "doable for NASA" if one can make a case for
a new kind of science (wide field, IR sensitivity, multispectral
capability). This is an agency that has shown little compunction in
the past about shutting down functional satellites past their
primary missions. Actually, given resources in high demand and
new and powerful science capabilities coming along (i.e. JWST vs HST),
it can't help being a tough decision.
Note to Ed Weiler - guess that makes me a Hubble hugger...
Bill Keel