Finally, a sensible solution to the Hubble debate - ... that we can all agree on...maybe.

GCNRevenger · 2005-05-06 07:32:29

from Houston Chronicle
NASA Administrator Michael Griffin has asked agency experts to take a fresh look at an astronaut mission to extend the life of the Hubble Space Telescope.
Griffin has directed NASA's Goddard Space Flight Center in Greenbelt, Md., to begin planning for a mission that could launch by mid-2007 and extend the life of the observatory by five years. He was careful not to promise the mission is a go.
http://www.chron.com/cs/CDA/ssistory.mp … 79]Article link
A launch by mid-2007 if delayed may not be soon enough as its expected to expire late-2007.
I did not like the articles following quote...
Columbia was downed by damage caused when foam insulation from the fuel tank fell off and struck the left wing at launch. Discovery's mission is being delayed to give shuttle engineers more time to reduce such hazards.
Discovery's crew would take refuge on the space station if damage occurred again, an option not available to astronauts headed for Hubble.
It makes it sound as if every mission into space should head for a safe haven - we'll never get to Mars with that attitude!
Graeme

Now hold on here... getting to Mars is going to be a risk, no doubt about it, but shouldn't we at least see what we get in return for our risk?

If the mission suceeds, we get another few years of HST operation, maybe and we no longer have those $200M worth of parts to build Hubble Origins with nor the $1.3-1.5Bn it cost for the mission to build it with... Versus the new reliable telescope which will do much more and last twice as long or more.

I have no problem with taking risks... but taking foolish risks for no good reason I am not okay with.

And, I think there is a risk that if Shuttle were lost for the same reason as Columbia, that there would be a terrible political price that NASA would pay... NASA has now lost two Shuttles and over a dozen souls because of its bad judgement about Shuttle, if they were to strike a third time, it could be very bad.

Just imagine for a moment... if word got out that the astronauts were stranded and doomed since rescue could not possibly come in time. Can you imagine the round-the-clock coverage that would get for the brave astronauts final hours as their fuel cells ran out? ...And then after its over, the real pain would begin. "NASA killed a THIRD crew by putting them in a vehicle they KNEW had a flimsy heat shield... and for what? They could have just built a NEW telescope, and then they would be alive today." Etcetera etcetera. NASA might not even survive the controversy as a manned spaceflight entity. As least with the ISS, it is something unique that only Shuttle can do, and the risk is cut in half with the availability of a safe haven.

GCNRevenger · 2005-05-06 07:37:11

Or haul its own safe haven with it on each flight. How hard would it be to design a bale out surviability capsule? Even if it were very cramp just to come down and nothing fancy or special.
He may want to do this just to stop all the risk assements of using the shuttle.
So far all ships that will leave Earth orbit for future CEV have no safe haven or return capability if apollo 13 style damage does occur. So unless that is a creteria of design then the risk is what it is and we must live with it and not in fear of it.

Nope, NASA has already looked at that option. The modifications to Shuttle would be too radical (airlock especially) to be done by 2007 most likly.

Other NASA ships that are not the Space Shuttle have some things that makes all the difference though: no flimsy heat shields, launch-escape capability, and they don't carry three huge high-pressure high-RPM turbopump engines in the back.

The reason why the Apollo 13 crew didn't die is that they had a second life support system in the LEM. So, what we do it we put -two- independant LSS units in the CEV, and you have the same safety net.

SpaceNut · 2005-05-06 07:40:28

Yup put out the cans for funds for Nasa rescue mission and see what happens, ask for help from our partners ect...
Thou as dooming as another acident would be to both crew and to Nasa some good would become of it thou I think.
It would possibly give the much needed push for proper funding for CEV developement now, not later.

GraemeSkinner · 2005-05-06 21:47:26

Now hold on here... getting to Mars is going to be a risk, no doubt about it, but shouldn't we at least see what we get in return for our risk?
If the mission suceeds, we get another few years of HST operation, maybe and we no longer have those $200M worth of parts to build Hubble Origins with nor the $1.3-1.5Bn it cost for the mission to build it with... Versus the new reliable telescope which will do much more and last twice as long or more.
I have no problem with taking risks... but taking foolish risks for no good reason I am not okay with.
And, I think there is a risk that if Shuttle were lost for the same reason as Columbia, that there would be a terrible political price that NASA would pay... NASA has now lost two Shuttles and over a dozen souls because of its bad judgement about Shuttle, if they were to strike a third time, it could be very bad.
Just imagine for a moment... if word got out that the astronauts were stranded and doomed since rescue could not possibly come in time. Can you imagine the round-the-clock coverage that would get for the brave astronauts final hours as their fuel cells ran out? ...And then after its over, the real pain would begin. "NASA killed a THIRD crew by putting them in a vehicle they KNEW had a flimsy heat shield... and for what? They could have just built a NEW telescope, and then they would be alive today." Etcetera etcetera. NASA might not even survive the controversy as a manned spaceflight entity. As least with the ISS, it is something unique that only Shuttle can do, and the risk is cut in half with the availability of a safe haven.

You missed the point either on purpose or not I don't know. Going to the ISS is a risk, but I'm yet to be convinced it has any value other than being a drain on NASA's funds (but I won't gripe about the ISS )
You painted a scenario of astonauts stranded in space receiving round the clock news coverage - this would not change regardless of its destination, there would still be questions a-plenty by the gen. public whether the goal was a temp. fix of HST or a new sock order for the ISS - this is purely because the average Jo on the street does not know the difference between a ISS run and a HST repair. If NASA did send a crew out in a sub-standard unsafe vehicle regardless of its destination they should be shot, a safe haven at the end does not make it a worthwhile risk if they know in advance of as you say a flimsy heat shield, risk is inevitable yes, but knowingly sending a crew out with a sub-standard vehicle is not a reasonable risk.

Palomar · 2005-05-09 07:23:46

*Adaptive optics (vs. Hubble's abilities) have been mentioned a couple of times in this thread. Thought I'd drop this brief abstract (The]http://www.spaceref.com/news/viewsr.html?pid=16558]("The Limits of Adaptive Optics for High-Contrast Imaging") here.

--Cindy

dicktice · 2005-05-09 12:38:44

Why not just present the abstract, so we can judge for ourselves? Oh, alright, I'll do it for you:

Limits of Adaptive Optics for high contrast imaging
Authors: Olivier Guyon (Subaru Telescope)
The effects of photon noise, aliasing, wavefront chromaticity and scintillation on the point spread function (PSF) contrast achievable with ground based adaptive optics (AO) are evaluated for different wavefront sensing schemes. I show that a wavefront sensor (WFS) based upon the Zernike phase contrast technique offers the best sensitivity to photon noise at all spatial frequencies, while the Shack-Hartmann WFS is significantly less sensitive. In AO systems performing wavefront sensing in the visible and scientific imaging in the near-IR, the PSF contrast limit is set by the scintillation chromaticity induced by Fresnel propagation through the atmosphere. On a 8m telescope, the PSF contrast is then limited to 1e-4 to 1e-5 in the central arcsecond. Wavefront sensing and scientific imaging should therefore be done at the same wavelength, in which case, on bright sources, PSF contrasts between 1e-6 and 1e-7 can be achieved within 1 arcsecond on a 8m telescope in optical/near-IR. The impact of atmospheric turbulence parameters (seeing, wind speed, turbulence profile) on the PSF contrast is quantified. I show that a focal plane wavefront sensing scheme offers unique advantages, and I discuss how to implement it. Coronagraphic options are also briefly discussed.

Now, to compare THAT with the limitations of the Hubble Telescope optics. Let's see, hm-mm ...

Palomar · 2005-05-09 13:56:58

???

Sorry, dicktice.

Was it really going to harm anyone to click on a hyperlink?

???

--Cindy

dicktice · 2005-05-09 20:39:56

No, and I hope no hard feelings. It just struck me that from the title: "Limits of Adaptive Optics ..." my initial impression was that adaptive optics weren't all they're cracked up to be. And then, when I read the abstract and understood the author's intention was to cover every known aspect, I had to laugh. Hence, my cheeky post. If you had gone on to discuss, say, "The effects of photon noise, aliasing, wavefront chromaticity and scintillation on the point spread function (PSF) contrast achievable with ground based adaptive optics (AO) are evaluated for different wavefront sensing schemes," I would have shut up. I was okay until "... scintillation on the point spread function ..." and then my interest in the telescope began to fade. The Hubble at least is just a bigger amateur telescope than any of us ever ground and figured, in the garage. It just happens to be located in orbital space, and (sob) I wuv it.

Palomar · 2005-05-09 21:00:00

No, and I hope no hard feelings. It just struck me that from the title: "Limits of Adaptive Optics ..." my initial impression was that adaptive optics weren't all they're cracked up to be. And then, when I read the abstract and understood the author's intention was to cover every known aspect, I had to laugh. Hence, my cheeky post. If you had gone on to discuss, say, "The effects of photon noise, aliasing, wavefront chromaticity and scintillation on the point spread function (PSF) contrast achievable with ground based adaptive optics (AO) are evaluated for different wavefront sensing schemes," I would have shut up. I was okay until "... scintillation on the point spread function ..." and then my interest in the telescope began to fade. The Hubble at least is just a bigger amateur telescope than any of us ever ground and figured, in the garage. It just happens to be located in orbital space, and (sob) I wuv it.

*No problem, and thanks for explaining. It's sometimes very difficult to know how to interpret something on the internet. I thought perhaps you were irked or annoyed. I feel -very- relieved that's not the case.

--Cindy

John Creighton · 2005-05-09 23:40:41

dicktice I don't know if this is obvious to you or not but the trick for an article like cindy posted is to read the conclusion first and then decide later if you want to go though all the details.

8. Conclusion
A thourough comparison of the fundamental
contrast limits of AO has shown that visible wave-
front sensing doesn’t allow high accuracy correc-
tion of near-IR wavefront aberrations: chromatic
e_ects then limit the PSF contrast to 104 to 105
within the central arcsecond. Wavefront sensing
should therefore be performed at the same wave-
length as imaging to reach the contrast limit im-
posed by photon noise (about 10^-6 to 10^-7 in the
central arcsecond).
An AO system optimized for high contrast,
with wavefront sensing and imaging at the same
wavelength, can still greatly benefit from a first
stage AO correction with a shorter wavelength
(visible) WFS:
. If residual aberrations are small, a FPWFS
can be used e_ciently. This WFS o_ers
unique advantages: no non-common path er-
rors, no aliasing, high sensitivity. It there-
fore appears to be the ideal solution for high
contrast AO.
. If wavefront correction were perfect at the
shorter wavelength, the chromatic residu-
24
als that the second WFS needs to measure
would be small and relatively slow (same
speed as the uncorrected turbulence). The
PSF contrast achievable in this case could be
better than the limits derived in this work,
as more photons are used.
This solution is especially attractive since low-
noise fast visible detectors exist, while near-IR de-
tectors currently o_er lower performance. Theo-
retically, combining a fast high sensitivity visible
WFS (preferably a ZWFS) with a slower near-IR
WFS (preferably a FPWFS) is not as advanta-
geous for red sources as it is for bluer (spectral
type G or bluer) sources.
The PSF contrast estimates derived in this pa-
per represent a limit which is hard to reach, as
many optimistic hypothesis have been made: ob-
servation at zenith, perfect telescope and detec-
tors, perfect DM, high system throughput, favor-
able atmospheric conditions, perfect coronagraph,
bright mv = 5 source, no time delay for AO con-
trol. On a 8m telescope, PSF contrast up to 10.6
may be reached in the central arcsecond if devi-
ation from these optimistic assumptions is mini-
mal. Even on a 100m telescope, the corresponding
contrast (about 10^-8) is two orders of magnitude
short of what is required to detect an Earth-size
planet orbitting a solar-type star. Direct imag-
ing of extrasolar planets is therefore bound to rely
heavily on e_cient calibration of the speckle noise
(through di_erential imaging techniques for exam-
ple).
The author is thankful to the referee, Ren´e
Racine, for his detailed and thorough look at this
work, which led to many useful suggestions.

I found this quote the most interesting

Even on a 100m telescope, the corresponding
contrast (about 10.8) is two orders of magnitude
short of what is required to detect an Earth-size
planet orbitting a solar-type star.

Clearly we are never going to build a 10 km telescope on earth so I would think space telescopes should always have a future. I found it interesting that they may get the adaptive optics down to the level of the photon noise. I am partly left to wonder if noise is the limiting factor why can’t they just do a longer exposure? Obviously this isn’t a good way to do detection but if you can detect the plant by another means then it would make sense for follow-up study.

dicktice · 2005-05-10 09:51:50

Well, Cindy, thanks. I'm irked and annoyed with myself. Re. space telescope optics vs. atmospheric adaptive optics on Earth, ask yourselves: If we had followed through post Saturn and, by now, capable of arrays of optical as well as radio telescopes spread over great distances, coupled together by means of laser technology ... would we be the least bit interested in developing adaptive optic telescopes, here on Earth, at the present time?

Palomar · 2005-05-10 10:11:16

Well, Cindy, thanks. I'm irked and annoyed with myself. Re. space telescope optics vs. atmospheric adaptive optics on Earth, ask yourselves: If we had followed through post Saturn and, by now, capable of arrays of optical as well as radio telescopes spread over great distances, coupled together by means of laser technology ... would we be the least bit interested in developing adaptive optic telescopes, here on Earth, at the present time?

*I can only imagine how frustrating it must be, to have been an adult in the 1950s and 1960s (even into the mid-70s), seeing so much genuine potential coming to fruition and actual goals being achieved. So many developments unfurling before your eyes -- and the real sense that it can only continue/gain momentum from here!

And then the belly flop.

It's annoying and frustrating to me, coming from a child's memory (only 7 in 1972 -- last of the Apollo missions).

Yeah, I hear you.

Mediocrity is the rule of the day, currently. As is conformity, complacency...I'll stop here.

Back on topic. Just had to make those comments!

--Cindy

GCNRevenger · 2005-05-10 18:30:16

No, no we wouldn't... people keep talking of Saturn like it was this visionary long-term human expansion into space.

Nonsense. Apollo was built for one and only one reason... to beat the Commies. It just happend to involve building a rocket of similar scale needed for such an expansion's early steps. There was no serious "after Apollo" plan... So, there wouldn't have been any mega space telescopes.

Anyway, back to the present... yes, there things that Adaptive Optics-based scopes' can't do that a space telescope can. One ability imparticularly, wide-field imaging, will probobly never be very practical... So, all the more reason to eliminate any consideration of Hubble SM4 and start work on HOP immediatly.

John Creighton · 2005-05-10 23:43:57

I wonder if you could build an array of adaptive optics telescopes. Maybe that would be the way to get the 10 km mirror needed to resolve earth like planets on distant stars.

Dook · 2005-05-11 06:34:32

Last I read the outgoing NASA Administrator, O'Keefe, put in the NASA budget a request of $300 million for a de-orbiting device for the Hubble.

Since we are planning to go to the moon to stay what if we instead used the $300 million for a device that boosts the Hubble into an orbit around the moon. Then, when we want to build our interferometer (lunar telescopic array) we capture the Hubble and land it on the dark side of the moon and use it as the center of our interferometer.

I'm sure by then it would need some replacement of it's on board equipment but it's large (8 ft wide) mirror would be very useful.

EDIT: In addition the James Webb space telescope due to be launched in 2011 is destined for a very high orbit (L2). It's expected to last 5 years but hoped that it will last 10. If and when this telescope dies we could do the same thing to it.

With it's 21 foot mirror joined with Hubbles on the moon we could slowly be building an incredible interferometer on the dark side.

GCNRevenger · 2005-05-11 08:21:34

For our readers who aren't interested in flipping back through all the posts in this thread, the Hubble Origins Probe (aka "Hubble-II or HOP) is a replacement telescope that is basically a copy of the original Hubble but with modernized parts, using the new cameras intended for Hubble, and the ultra-wide-field imager camera which is not compatible with Hubble. This is a unique and powerful capability that neither the current Hubble nor any ground based telescope with adaptive optics could do.

The simple fact of the matter is that repairing Hubble will be so expensive that you really, literally, might as well build a new one instead.

As far as putting Hubble into a high orbit for long-term storage, that isn't going to be very helpful since when Hubble's batteries die then its electronics will freeze and be perminantly ruined. Putting Hubble on the Moon to salvage its main mirror is silly, since you would need a huge rocket and a big lander to get it there, and then have to rip it apart (which astronauts really can't do in space suits well), and hoist the ultradelicate main mirror out... No way. You really should instead just build an array of multisegment mirrors brought from Earth.

Same with JWST. Being that it is not designed to support its own weight, trying to salvage its mirror without breaking it is impractical, and it is an infra-red mirror, not optical like Hubble.

dicktice · 2005-05-11 08:33:39

Excuse me, but infrared is just as "optical" as visual. I can't allow you to mislead the great unwashed (i.e. non-physicists) like that. Otherwise, you're right on.

GCNRevenger · 2005-05-11 12:03:15

Excuse me, but infrared is just as "optical" as visual. I can't allow you to mislead the great unwashed (i.e. non-physicists) like that. Otherwise, you're right on.

Um. No its not... Visible electromagnetic energy has a wavelength in the range of ~100-1,000nm, but Infrared is around 1,000-1,000,000nm. The JWST mirrors are optimized for the latter, while Hubble's for the former. JWST doesn't really have any practical optical capability, and Hubble doesn't have much practical IR capability.

John Creighton · 2005-05-11 13:49:45

Perhaps it is a matter primarily of material science and how large a range of frequencies a mirror can be built for.

dicktice · 2005-05-11 18:33:50

My tiny point, since you are such a stickler for accuracy: The statement "it is an infra-red mirror, not optical like Hubble" just doesn't make sense. "Infrared" refers to the band of EM wavelengths adjacent to the band of "visual" wavelengths, each of which can be delt with, telescopically using appropriately chosen and configured "optical" elements. So, your statement should have concluded: "... not visual like Hubble." If you weren't so bright, I wouldn't be so critical. But since we seem to be dealing with a variety of telescope optics, covering a variety of wave bands, maybe it was warranted after all. Sorry if I have offended.

GCNRevenger · 2005-05-11 21:02:33

Now you are just being petulant Dicktice, and you certainly have offended. And actually, the better part of the infrared spectrum isn't practical to image in any traditional sense as you would with conventional telescope optics, and sits somewhere between optical and radio astronomy.

dicktice · 2005-05-12 09:04:44

Aw ... but if the term "optical" is understood to include the so-called "Far Infrared" energies down to 10 micrometres, I'm comfortable with that limitation in its coverage. Time to pull up our socks and move on, wouldn't you say?

SpaceNut · 2005-05-26 09:45:59

New hope for the troubled Hubble; But is servicing the space-based telescope affecting other high-priority initiatives as NASA funding gets tighter.

Now, Hubble's prospects are brightening. What was to be a $175 million effort to "deorbit" Hubble has become a $291 million program to keep alive the option of servicing and upgrading the telescope so it can continue functioning at least until 2010. A robotic mission could cost as much as $1.5 billion. An expendable-rocket rendezvous brought the price tag down to about $750 million. While no formal cost estimate has been submitted yet for using the shuttle, Beckwith suggests that the complete servicing mission 8could run about $600 million. In exchange, he says, astronomers would get a telescope more powerful, more efficient than today's Hubble lasting into the next decade and at a price that undercuts the nearest competitors for a deorbit-motor-only mission.

All of which the final desicion to fly the shuttle to Hubble hinges on the sucess of the return to flight to the ISS.
Which is being delayed again...

GCNRevenger · 2005-05-26 13:34:26

The numbers still don't add up

Say a Shuttle mission -does- only cost $600M, with a lower marginal price for the additional launch, and the rest of the money spent on Hubble spares discounted from the total mission cost.

$600M to orbit the new Hubble cameras and to maybe squeeze another four or five years out of the old bird, or:

$900M, which includes Atlas-V launch vehicle and substantial budget cusioning in the event of overrun, to orbit HOP with both the new HST cameras and the superwide-field imager donated from JAXA that will operate for at least ten years.

No risk of astronauts, no disruption of ISS schedule, much less risk of Hubble simply dying in the next few years... HOP is still the obvious choice.

Grypd · 2005-05-26 15:28:30

We have seen that Griffin will no matter what follow Bush's instructions and finish the shuttle in 2010. With the ISS still to complete and with all the delays the shuttle has to its return we can only take it that there will not be any time for a repair mission to Hubble.

We can debate it all we like but NASA has no time left now to do the mission so the JWT is all that is left.

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Re: Finally, a sensible solution to the Hubble debate - ... that we can all agree on...maybe.

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