I realize this is one of those sorta fuzzy questions, but I am wondering if there are any other good examples of space telescopes with a similar mission to Hubble. Not really things like compton, Chandra, soho or things built for a single primary purpose.


Basically: General purpose or broad mission, optical telescopes using visible light, or UV or near visible IR, but excluding telescopes especially designed only for work in the lower thermal IR range, x-ray telescopes... that sort of thing.

Yes, it is a blurry line, but basically stuff with a lens and CCD and optical sensors, as opposed to a scintillation imager or something similar. And intended for broad use for stars, galaxies etc etc.

What is there to compare hubble to? I know it's pretty much the biggest and best, but are there any others in this nitch? were there?

The only thing that comes to mind ATM is some of the stuff on Skylab...

At the moment, as far as I know, there are no such telescopes in orbit other than HST. When JWST is launched, it will operate in this general manner (though it won't have much optical capability, concentrating on the near-IR).

The Joint Dark Energy Mission (JDEM) is a collaboration between NASA and DOE to put into space some sort of telescope + detector which can study dark energy. Some of the ideas proposed for JDEM involve roughly 2-meter optical telescopes with boatloads of optical and/or near-IR detectors. JDEM's mission is supposed to be focused on one goal, so it shouldn't have general observing by a wide pool of applicants; on the other hand, the type of survey it should carry out seems to change over time ...

JDEM may never be funded or built or launched. If it does go into space, it probably won't be for 6-10 years.

Not sure how Spitzer fits in your classification scheme, Drbuzz0.

It may be said to occupy a niche in the IR that is complementary to that of the HST in the optical ...

Also, how about Galex? Not at all a competitor to the HST (so different in so many ways), but it does have "basically stuff with a lens and CCD and optical sensors, as opposed to a scintillation imager or something similar. And intended for broad use for stars, galaxies etc etc."

From the viewpoint of someone who's been collecting information for a book on the history of space astronomy - no, not really. The major difference from the other wavelength bands - UV, X- and gamma-rays, IR - is that there was little point to building an optical space telescope much less capable than Hubble, as most of the science could be done from the ground (sometimes using a different approach) at maybe 1% of the cost. There were many predecessors to HST's UV capability - two OAOs in the late 1960s, experiments on Salyut 1, Skylab, Apollo 16, Soyuz 13, Mir, the International Ultraviolet Explorer, Astron... To be sure Hubble harvested what was learned form most of these. I'd agree that GALEX comes close, since a deep UV survey has such broad scientific value. And it's a very healthy thing that we've been learning to tear down the traditional boundaries between wavelength regions, all set by our detection limits and techniques, and use whichever gets us the scientific conclusions.

Looking at the short-wavelength limits of instruments currently manifested for JWST, one could make the argument that there is no other such general-purpose optical space telescope seriously planned at the moment either... The reason is that the compelling science cases for studying the formation of planets, stars, and galaxies all agreed on the value of a large IR-optimized space instrument, so that realy is the obvious next step.

Yes I realize that it's a very poorly defined category when I simply say "General purpose optical" telescope. I don't mean to sound like I don't know what I'm an idiot: I just don't know how to say it better than that. I guess spritzer would.

As I think of all the things that the HST has been part of and all the now-iconic images and the discoveries, it's almost unbelievable. I guess my best interpretation is that the HST is really the only real example of it's type.


I'd love to see the Hubble be replaced by something even more capable. Of course, I'd love even more to see it be augmented by something more capable and remain in service as long as possible. I'd also love to see four HST type telescopes in operation... or for that matter seven ... or maybe 18. (I'm sure there are plenty of things to keep them all busy at. Yes it would be expensive... but... it's not like there aren't a few examples of more expensive investments that returned less than a single space telescope has).


Also, there is a fringe benifit of an optical telescope:

When Joe non-astronomer says

"What the hell have you got to show me for all my tax money and spent up there with that there space rocket and your moon men walking around"

the reply "Well, we now have a much better idea of how nebula form new stars and how galaxies move relative to each other. And it looks like *THIS*"

He is likely to respond "Oh ok. Well... er.. keep that up. oh and also...can I get a poster of that for my rec room?"

There are many optical telescopes similar to Hubble orbiting the Earth, some considerably larger, but they all point in the wrong direction.

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But you just trying getting observing time on those!

GALEX has much lower resolution than HST (4" vs. 0.02"). The now-dead ACS still has the best resolution for any optical to near-UV camera in operation, in space or on the ground (though ESO is getting pretty close)

I was at a talk about some of the JDEM missions, and they brought up the observing time/cost comparison: with a ground-based telescope, you've got at *best* less than half the year available for observing (night), and even at the best sites, usually more like 1/5 or less, due to bad weather and seeing. So a space-based telescope can do a lot more observations in a given amount of time. So if a space telescope costs 10x as much, and runs for the same amount of time, it is still a decent value, monetarily.

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