# What are the advantages and disadvantages of sending a telescope into deep space? [closed]

When I first heard of the Voyager missions I thought this: why not do the same, only make it a telescope? I thought it would surely see a lot of things we can't see from Earth or the inner Solar System. I just thought that when you're in a place that's sufficiently different, you start to see different things or the same things differently.

Now I'm not sure the outer reaches of the Solar System are far enough to produce enough change in what's visible.

What are the possible significant advantages of sending a telescope out of the solar system? Would it be possible to power such a device? I know Voyagers were still sending information to the Earth when they were extremely far from it, but I'm guessing a useful telescope might need significantly more power. Would such a device be so expensive as to become inviable?

• This is definitely a "bad" list question. See Meta.SO. – called2voyage Sep 9 '13 at 17:58
• It's not that this question is opinion based, but that there are a lot of equally valid yet different answers. – called2voyage Sep 9 '13 at 18:00
• @ymar, can you try and narrow the scope of the question? – James Jenkins Sep 11 '13 at 10:44

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.

## Multiple telescopes

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


Lagrange points

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.

## Other questions.

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.

Yes, there is at least one advantage to a deep-space telescope. That would be getting away from our Sun's dust cloud to avoid the reflected Zodiacal light. In fact, such missions have been proposed in order to study the Extra-Galactic Background Light which is blocked by Zodiacal light. They would ideally like to get out to 5 AU and well above or below the ecliptic.

Such telescopes do not have to be very large, nor transmit very much data in order to improve on our current ability to see the EBL by a few orders of magnitude. That sort of increase gets astronomers very excited.

Technologically, we could certainly do it. We could power such a telescope using nuclear cells.

However, as you mention! you would have to send these things a long ways just to produce the most minute change in our perspective. Since we are talking about hundreds of thousands of light years, the distance to the outside of the solar system wouldn't be close to enough.

By the time you got a telescope far enough to produce a real change in what we can observe, it would be next to impossible to communicate with it, and latencies would be upwards of months.

The main advantage of such a telescope would be the ability to look through space without an atmosphere in the way - and the Hubble telescope already has almost all of that advantage.

• I suggest looking up gravitational microlensing. This is the only known justification of sending telescopes far away into the nowhere, short of sending them directly to other systems. – Deer Hunter Sep 6 '13 at 14:58

For infra-red astronomy, operating anywhere near the sun can be problematic. Even the James Webb Space Telescope design has issues in that the sun shield is expected to degrade over time causing a gradual increase in the telescope's operating temperature and corresponding decrease in the telescope's effectiveness.

An IR telescope launched into deep space would be free of any meaningful source of heat and would be able to operate at optimal temperatures pretty much indefinitely. Indefinitely, in this case, being defined by the lifespan of the telescopes critical hardware components.

There is no actual technology to receive data from such telescope.

Look at the picture. This is SETI@home's radio telescope. It is situated in Puerto Rico. There is no technology on the Earth, to move all amount of data by radio or wires to Berkeley, California, but physically, with whole of storage, magnetic tapes in that case.

It is about 6,000 km, only.

wiki: Sneakernet

The SETI@home project uses a sneakernet to overcome bandwidth limitations: data recorded by the radio telescope in Arecibo, Puerto Rico is stored on magnetic tapes which are then shipped to Berkeley, California for processing. In 2005, Jim Gray reported sending hard drives and even "metal boxes with processors" to transport large amounts of data by postal mail.

However, radio telescope in Arecibo, is a largest one.

Probably, it is hard to win anything with deep space's telescope, because data received from it, will not be so preciseness.