Hello,

I really believe a very large balloon, on the far side of the Moon, would make the ultimate Radio Telescope location. Since, the moon is Tidally locked to have one side face us, the other side remains shielded from the Radio Noise, we keep making here on Earth. Several Parabolic Balloon Stations on the Moon, would make quite the interferometer. The gravity, is so low, that you really could make a really big balloon, and as far as unmanned missions are concerned, that would be a great one. Solar panels still get daylight, and the batteries could run for years. One side of the balloon, is RF reflective. Keeping it inflated, well, I'd use a large molecule gas because, the sun's radiation will be making microscopic holes in it. So, a fat gas molecule, may be more ideal. X and Y, could be controlled by anchored belts, rather than gears.

Doesn’t there need to be an atmosphere in order for a balloon to rise.

---

Doesn’t there need to be an atmosphere in order for a balloon to rise.

Rise yes. Make a sphere, no.

---

How do you focus a ballon to a patch of sky? How do you collect the waves? Where is the detector?

How do you focus a ballon to a patch of sky? How do you collect the waves? Where is the detector?

Look at Arecibo. It uses a spherical dish.

---

It's not spherical, it's only a small part of a sphere, and it's not a balloon.

A few concerns come to mind.
1.) maintaining the 'figure' of the spherical-section reflector would presumably be complicated by a certain amount of sagging of a very large balloon, under gravity, even when it is fully inflated.
2.)The expansion and contraction of the inflating gas, due to the very wide swings in temperature on the Moon's surface would also have to be compensated for in some way, possibly by cycling the gas between the balloon and storage tanks.
3.)Micro-meteorites could make for an increasingly leaky balloon. These would presumably be much larger than the largest available gas molecules for inflating the balloon.
4.) Since the focal area of the reflector would be inside the balloon, suspending the feed there, without its weight causing deformation of the balloon, should prove an interesting challenge.

The wavelength of radio is measured in cm so it's possible an inflated reflector could achieve tolerances.

The idea is to coat the bottom segment of the sphere with reflective material while the top remains transparent to radio.

You could make it self sealing by using a membrane consisting of a viscous layer sandwiched between two plies of mylar. It wouldn't last forever but maybe "long enough".

The secondary could be another inflatable part inside the main cell that reflects the beam to an external detector.

I think a non-inflatable radiotelescope would be more easy to orient and maintain, more precise, more stable, durable, etc. It can even
be constructed inside a crater. Anyway, if you can construct a big radiotelescope in the Moon, you should be capable of doing the same in space (for example in L2), and then you will have a more stable environment and a more steerable telescope.

I think a non-inflatable radiotelescope would be more easy to orient and maintain, more precise, more stable, durable, etc. It can even
be constructed inside a crater. Anyway, if you can construct a big radiotelescope in the Moon, you should be capable of doing the same in space (for example in L2), and then you will have a more stable environment and a more steerable telescope.

Yes, but you also don't have a large hunk of rock (the moon) between your receiver and all the damn terrestrial transmitters.

As to building it, no matter where the building supplies have to come from earth, so weight is the number one concern.

---

...and the collected data returned to earth

---

Bob Smith
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?