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#11
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Why Hubble was cancelled, and what to do now
In article ,
Henry Spencer wrote: If you've got a system that could do a servicing visit in lunar orbit, then with a bit less propulsion and a bit more life support, it could do one at L2. It's significantly hard but not ridiculous, if the cost is low enough. Well, maybe the discussion isn't ridiculous, but for the time being the mission itself would be. Don't worry, there will be no moon base, no astronauts on Mars, and no lunar or L2 "servicing visits" in the next 15 years. ...Hubble is like an old computer data center with a 20-year service contract. Sure, they might get upgrade the memory and even the CPU now and then. Of course what people really want is completely new computers every few years. And likewise astronomers want completely new telescopes. Keck must be on its last legs by now, to say nothing of ridiculous antiques like almost everything on Mount Palomar. Keck is still a competitive telescope, but yes, they want a bigger one. The proposed TMT dwarfs Keck, and in comparison Hale looks like a hand mirror: http://www.astro.caltech.edu/observa...s/3Mirrors.jpg Anywhere [other than in space], it may not be right at the leading edge any more, but it remains in service. As an afterthought. The Hale telescope on Mount Palomar used to be the big great telescope of American astronomy. But now it only carries a small fraction of astronomy research, even though it is by far the best of the old telescopes. On the contrary. The new ones are built as extensions of the old ones whenever possible -- e.g., the Tevatron is fed by the original Fermilab ring (and yes, there have been proposals to do similar things with Hubble!) -- and even when that's not done, often the older machines are rebuilt for secondary roles. "Secondary roles" is a good phrase and it's also the best that you can hope for with yesterday's experimental technology. So space is a little different - the old telescopes aren't recycled. Recycling is laudable, but sometimes it's not worth it. -- /\ Greg Kuperberg (UC Davis) / \ \ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/ \/ * All the math that's fit to e-print * |
#12
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Why Hubble was cancelled, and what to do now
"Greg Kuperberg" wrote in message ... "Secondary roles" is a good phrase and it's also the best that you can hope for with yesterday's experimental technology. So space is a little different - the old telescopes aren't recycled. Recycling is laudable, but sometimes it's not worth it. I just think your analogy wasn't that great. Rather, compare it to an old airliner being retired. Sure, you could keep flying it, but eventually you have to replace it with something new, even though you've investing millions in it. Bruce |
#13
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Why Hubble was cancelled, and what to do now
Greg Kuperberg wrote:
First of all JWST will be farther away than the moon. Thus, so-called "service missions" are out the window... Henry Spencer wrote: If you've got a system that could do a servicing visit in lunar orbit, then with a bit less propulsion and a bit more life support, it could do one at L2. Are there any plans to make JWST serviceable? If it isn't designed to be worked on by astronauts, it doesn't matter if NASA develops the ability to send manned missions to L2 during JWST's lifetime. Last week I went to a talk by John Logsdon on The Future of Human Space Flight. (See http://www.philsoc.org/2004Spring/2171abstract.html) Someone in the audience objected to the risk and expense of manned space flight, claiming that the science return from robots is better. When someone brought up the Hubble maintenance missions, he claimed that a second Hubble could have been launched for less than the cost of fixing the first one. Instead of disagreeing about science return, as you (Henry) do, John Logsdon conceded that space exploration wasn't primarily about science at all. Keck must be on its last legs by now, to say nothing of ridiculous antiques like almost everything on Mount Palomar. Indeed, telescopes made by Alvin Clark over 120 years ago are still being used for real science. Only in space is it accepted that you throw out a hugely expensive observatory after a few years of use. Anywhere else, it may not be right at the leading edge any more, but it remains in service. I'd like to see a *permanent* Mars rover. Well, ok, not literally permanent, but one with a lifetime measured in decades, not weeks. One capable of being driven all the way around the planet, multiple times. As for accelerators, it's plausible to me that one would soon do all the science it's capable of. But a telescope can be pointed in a vast number of directions, plus new things are all the time happening in the sky (comets, supernovas, etc.). And a rover has a whole lot of Mars (or Moon, or Venus, or whatever) to explore. Getting back to Hubble, nobody answered my question as to whether any useful science can be done with the backup low precision gyros. Why are the high precision gyros failing, anyway, and will this problem be resolved on JWST? Thanks. -- Keith F. Lynch - - http://keithlynch.net/ I always welcome replies to my e-mail, postings, and web pages, but unsolicited bulk e-mail (spam) is not acceptable. Please do not send me HTML, "rich text," or attachments, as all such email is discarded unread. |
#14
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Why Hubble was cancelled, and what to do now
In article ,
Keith F. Lynch wrote: Are there any plans to make JWST serviceable [by astronauts]? Not remotely. Steve Beckwith, the director of the institute that manages Hubble and JWST, gave an interesting speech about space telescope costs in 1999: http://nem-srvr.stsci.edu/~svwb/ChallengeofNGST.htm The JWST team has (or had) a budget ceiling of $500 million dollars, the result of which is that they cut corners and prune away features at every turn. As Beckwith explains, the cost of any spacecraft is dominated by an insane degree of quality assurance. They need the quality assurance for any hope of the machine working in space. Simply man-rating JWST for any astronaut interaction would add hundreds of millions of dollars to its cost, even without adding serviceability to the design. In the "faster, better, cheaper" environment of the designers, I'm sure that they would despise man-rating. One reason that they would hate it is that NASA won't actually send any astronauts to L2. Right now they are too chicken even to send astronauts to service Hubble. L2 is to LEO as K2 is to Kit Carson Peak. Indeed, telescopes made by Alvin Clark over 120 years ago are still being used for real science. I'm not going to say that no one can think of any research use for these old telescopes. There is little reason to tear them down and they have significant popular and educational value. Still, you'd have to be pretty far down the research totem pole to be excluded from much better telescopes. -- /\ Greg Kuperberg (UC Davis) / \ \ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/ \/ * All the math that's fit to e-print * |
#16
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Why Hubble was cancelled, and what to do now
In article ,
Derek Lyons wrote: [Hale] only carries a small fraction because it's one of many instruments, looking at only a fraction of the wavelengths of interest to astronomers today. Which is the same as saying that it's not that great of a telescope anymore. Before the era of space telescopes and active optics, Hale was the best telescope in the world. And now it just isn't. In a way it's amazing that it's still as useful as it is. It's the Empire State Building of telescopes. Even so, I doubt that another passive mirror the size of Hale will ever be built. (Okay, the Bolshoi mirror is even bigger than Hale, but not better. That's the Soviets for you.) Active optics is a superior technology for large mirror telescopes. (Not to mention adaptive optics and interferometry.) Which brings us back to Hubble and JWST. Maybe because it was designed in the 1970s, Hubble is another passive mirror. Active mirrors are also a better idea than passive mirrors in space, in principle, although for slightly different reasons. That's why JWST will have an active, articulated mirror. It's a bold proposal, because it's a new technology for space, and maybe it's a foolish proposal. But for those who want technological innovation in space, JWST is it, more so than Hubble. The astronaut servicing plan committed NASA to a fixed mirror technology for decades. If not for the astronaut distraction, a JWST-type telescope might have been launched a long time ago. In my opinion, if the save-the-Hubble leaders were clever, they would parlay sympathy for Hubble into better support for JWST. Yes, JWST is moving along. Yes, O'Keefe has expressed his continued support for it. But I don't think that O'Keefe can set his promise in stone. In any case JWST might well benefit from a funding bonus. -- /\ Greg Kuperberg (UC Davis) / \ \ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/ \/ * All the math that's fit to e-print * |
#17
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Why Hubble was cancelled, and what to do now
In article ,
(Greg Kuperberg) wrote: As an afterthought. The Hale telescope on Mount Palomar used to be the big great telescope of American astronomy. But now it only carries a small fraction of astronomy research, even though it is by far the best of the old telescopes. If you're talking about cutting-edge research you might be right, but otherwise I suspect the astronomers who use it would probably disagree with you: "Scientific research at Palomar Observatory since 1948 has been remarkably productive. The Hale Telescope has been used on virtually every clear night to provide astronomers with the information they need to pursue their investigations. The scope of this work ranges from studies of asteroids and comets within the solar system, to the stars that comprise our Milky Way Galaxy, out to the uncounted galaxies beyond our own, and finally to the quasars--beacons in the universe so distant that the light collected from them with the Palomar telescopes has been billions of years in transit to the Earth." --http://www.astro.caltech.edu/observatories/palomar/overview.html As the above webpage goes on to note, the telescope & its tools are "constantly being improved". "Because of these improvements, the 200-inch Hale Telescope can now be used to attack research problems that would have been impossible just a few years ago." If anything might eventually doom the 200-inch scope it will probably be light pollution from southern California rather than its age. -- Stephen Souter http://www.edfac.usyd.edu.au/staff/souters/ |
#18
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Hubble
I was curious if anyone here thought there would be enough interest in
the private/university sector to keep Hubble up. The reason for decommissioning Hubble has nothing to do with it becoming obsolete it’s simply that NASA feels it can’t safely repair Hubble with the shuttle according to the guidelines put forth by the Columbia accident investigation board. Hubble as far as I know can be maintained for a good while longer if it could have regular maintenance and a modest funding stream. Hubble was designed to be maintained by humans performing spacewalks but there is no reason a robotic satellite could not dock with Hubble and perform the needed maintenance/orbital boost, it would probably be infinitely cheaper than the multi-billion dollar launch of the shuttle to do so. Also, as far as I know the replacement parts have already been procured by NASA for testing at Goddard before they were to fly on the next service mission. It would just seem to me that well organized amateurs along with universities and private investment could build a maintenance satellite boost it up with a commercial launcher and maintain the Hubble with the pre-existing parts. ----== Posted via Newsfeed.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeed.com The #1 Newsgroup Service in the World! 100,000 Newsgroups ---= 19 East/West-Coast Specialized Servers - Total Privacy via Encryption =--- |
#19
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Why Hubble was cancelled, and what to do now
"Stephen Souter" wrote in message ... In article , (Greg Kuperberg) wrote: As an afterthought. The Hale telescope on Mount Palomar used to be the big great telescope of American astronomy. But now it only carries a small fraction of astronomy research, even though it is by far the best of the old telescopes. If anything might eventually doom the 200-inch scope it will probably be light pollution from southern California rather than its age. Heck, folks seem to forget that backyard astronomers are often the ones finding comets. In other words, bigger is not always better. Calling something obsolete just because there's something "bigger" doesn't mean it can't be repurposed. Hubble may be too expensive to run, but obsolete, hardly, I'm sure there are plenty of astronomers out there who'd love to get time on it. -- Stephen Souter http://www.edfac.usyd.edu.au/staff/souters/ |
#20
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Why Hubble was cancelled, and what to do now
In article ,
Greg D. Moore \(Strider\) wrote: Heck, folks seem to forget that backyard astronomers are often the ones finding comets. Yes, and I'm all for that, but it isn't going to be very good research. If you want to know the comets, the way to do it is with an enormous sky survey with a wide-angle telescope, followed by massive data processing. People without computers can't compete with people with computers for a task like this. Yes, you can still find a few comets with your own telescope, but it's like hunting for seashells at the seashore. Yes, it is a great way to learn science. If you're talented, it can even be a good practice run at research. But it has nothing to do with NASA's money, which is this real topic of this thread. If NASA wants to launch tools for astronomers, it shouldn't pretend that space telescopes are just like ground telescopes. It shouldn't spend billions to "service" one passive mirror over and over again, when the major interest is in completely new instruments. In other words, bigger is not always better. That's true, of course, and Hale is still a valuable telescope. There's no reason to mothball it. Even in space, WMAP, which is a much smaller mission and already had its run, ran away with the Oscar last year. My real point is that research requires new instruments because it's about seeing new things. After you get the new photo one or two times, it's not research any more. In every area of science, old instruments are destined to play only a supporting role. -- /\ Greg Kuperberg (UC Davis) / \ \ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/ \/ * All the math that's fit to e-print * |
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