The advantages of getting a single telescope into space might be.
- The ability to see wavelengths normally absorbed by the atmosphere.
- Lack of atmospheric turbulence leads to a crisper, sharper image.
Very little of that changes though, between LEO and 'deep space'.
Once a single telescope has gone far enough, it does enable us to see different perspectives on local objects. E.G. This picture of Saturn taken by NASA’s Voyager 1 spacecraft in 1980.
It does also raise the possibility to pass directly behind the planet and view the upper reaches of the atmosphere as they filter the light from the Sun. I believe this can aid in determining the composition of the atmosphere.
Saturn eclipsing the sun, seen from behind from the Cassini orbiter.
Having said that, I suspect the atmospheres of most objects in the Solar System is pretty well quantified, and getting such images would add little to our existing knowledge.
When it comes to groups of telescopes the situation changes for at least one, possibly two, more abilities.
1. Parallax measurement
Parallax measurements. Sending a pair of telescopes into deep space, or a single scope with an Earth(/Earth orbit) based counterpart, would allow us to view the 3-D nature of the galaxy to a greater distance/depth.
Pair with one in Earth orbit, the other in orbit about another planet
Baselines for parallax measurements for pairs of telescopes, assuming the images are taken at the same moment as opposed to '6 months apart' as is done to get the maximum parallax possible from a single point on Earth.
Maximum baseline advantage between Earth orbit and the orbits of other
planets, when in opposition. Approximate, given the distances are the
average of the elliptical orbits.
Planet Dist. Total Advantage
Mars 1.5 2.5 1.25
Jupiter 5.2 6.2 3.1
Saturn 9.54 10.54 5.27
Uranus 19.18 20.18 10.09
Neptune 30.06 31.06 15.53
Minimum baseline when both planets are on the same side of the sun.
Planet Dist. Total Advantage
Mars 1.5 0.5 0.25
Jupiter 5.2 4.2 2.1
Saturn 9.54 8.54 4.27
Uranus 19.18 18.18 9.09
Neptune 30.06 29.06 14.53
The Lagrangian points formed by two massive objects.
The L2/L3 Lagrange points would be most optimal. Since these are on the opposite side of the sun by
definition, the baseline will change much less over time. The baselines are (very) approximately as much larger than those of Earth's L2/L3 distance, directly in proportion to the orbital radii of the other planet.
I wrote "(very) approximate" above because the L2 point is very much affected by the mass of the planet (bigger mass leads to further away from the planet) and distance from the Sun (larger orbital radius leads to larger planet/L2 distance).
2. Astronomical interferometry
WikiPedia on Astronomical interferometry.
An astronomical interferometer is an array of telescopes or mirror segments acting together to probe structures with higher resolution by means of interferometry. The benefit of the interferometer is that the angular resolution of the instrument is nearly that of a telescope with the same aperture as a single large instrument encompassing all of the individual photon-collecting sub-components. The drawback is that it does not collect as many photons as a large instrument of that size. Thus it is mainly useful for fine resolution of the more luminous astronomical objects, such as close binary stars.
Would it be possible to power such a device?
Quite possible with nuclear power generation. The main power drains would be:
- Realigning the scope(s) for different objects.
- Keeping the core areas where the circuitry is located warm enough to avoid failure (which can sometimes be done purely as a side effect of the waste heat produced by the power generator).
- The power to transmit high quality images (what's the point if we only get a grainy image?) over vast distances.
Would such a device be so expensive as to become inviable?
I have little idea of the cost, and even less of what is considered viable.