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Binocular Space Telescope in the Works
museumpeace writes "ABCNews.com's technology pages have a story about NASA's plans to orbit a binocular telescope. Similar in concept to the Arizona telescope reported in /., this new variable baseline interferometer would be able to operate in the UV which is unavailable to terrestrial intstruments. The telescope would have the resolving power of a 120 foot diameter conventional telescope."
It makes a big difference. The aim of the game is to increase your angular resolution, and interferometry is a way of combining two separate telescopes to get the angular resolution of one larger telescope.
You cannot take one image, wait a few seconds to get a baseline, and then take another image. For the technique to work, you need the two images to be recorded with phase information, and for wavelengths shorter than radio waves, you cannot easily and efficiently do that.
For a 8.4m single mirror, the 125 feet separation increases the angular resolution by a factor of 6.25. That's a very useful improvement.
The problem is that the light from the two mirrors has to be cophased to within 1/10 of a single wavelength of UV light. Those tolerances are absolute bastards to achieve, even in outer space.
Dr Fish
They're not really using it for "binocular vision", they're using it to do "aperture synthesis" or optical interferometry where the separation of two telescopes whose optical paths are combined (with sub wavelength (like 550nanometers for green) precision maintenance of the optical path) effectively allows it to have the resolution of one humongous telescope whose mirror is as big as the separation between the two smaller telescopes or "baseline". Radio telescopes are combined in the VLBA or very long baseline array like this, except that they are not connected to eachother as they make observations (at least not until recently) so they record the phase of the radio waves as correlated to a high precision atomic clock standard, then combine the (usually terabytes of) data from each dish later on supercomputers. None of this comes across terribly clearly in the article because the journalist who wrote it is an idiot("SPIRIT telescope since it will be detecting infrared light, which is a light form of heat." uhhhh yeah.).
- "Hear that?! The percolations are imminent! Cease your ingress!"
from looking at the sunshades, I'd guess that they plan to put Spirit in an L2 or earth trailing orbit, most likely L2-- it's close enough for high bandwidth communication, and it actually takes slightly less energy to get there than earth trailing.
The other mission they mentioned, SIM, won't do spectroscopy. It's a very high precision interferometer for astrometry-- it will measure positions of stars to a microarcsecond or so. I can't remember the down to earth comparison information, but it will be capable of detecting planets of a few earth masses in their stars' habitable zones around the nearest 250 or so stars. It will also remove the sin(i) ambiguity of the radial velocity measurements of the planets already known. There are also a bunch of other science programs covering stellar astrophysics, and some extragalactic stuff, too.
This seems to come up every time there's a space telescope article. The moon's not that great a place-- it's not as stable as you think, it's dirty, you get cycled in and out of full sunlight, and you have to land everything softly in a nasty gravity well without any atmosphere to use for braking.
I'm going to have to put in a journal entry or something with why the moon is overrated for space telescopes.