I have thought about this idea since I was a kid. Now it appears possible to set up a radio telescope on the far side of the moon and it also appears, with the passage of time, what frequencies would best be served by the location - frequencies of 30MHz and lower.
After NASA ditched the idea of landing Apollo 17 on the far side of the moon, the forbidden fruit is being sought once again. Not by astronauts this time, but by astronomers seeking a quiet spot from which to observe the universe’s “dark ages“.
This was an epoch in the development of the cosmos, which lasted for a few hundred million years after the big bang, before the stars and galaxies began to form. The only way to observe the dark ages is to look for faint radio signals from neutral hydrogen – single protons orbited by single electrons – which filled the early universe.
Telescopes on Earth, such as the Murchison Wide Field Array in Western Australia, are searching for such signals, at frequencies above 100 megahertz. This can probe the universe back to 400 million years after the big bang.
To explore even earlier times, telescopes need to receive radio waves at frequencies below 100 megahertz. Interference from radio sources on Earth like FM radio and the planet’s ionosphere can interfere with these signals. “You get to the point where the ionosphere is just a hopeless barrier,” says Dayton Jones of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “You have got to go to space, and the most promising location by far is the far side of the moon.”
According to Saptarshi Bandyopadhyay of the NASA Jet Propulsion Laboratory:
"An ultra-long-wavelength radio telescope on the far-side of the Moon has tremendous advantages compared to Earth-based and Earth-orbiting telescopes, including: (A) Such a telescope can observe the universe at wavelengths greater than 10m (i.e., frequencies below 30MHz), which are reflected by the Earth's ionosphere and are hitherto largely unexplored by humans, and (B) the Moon acts as a physical shield that isolates the lunar-surface telescope from radio interferences/noises from Earth-based sources, ionosphere, Earth-orbiting satellites, and Sun’s radio-noise during the lunar night. We propose to deploy a 1km-diameter wire-mesh using wall climbing DuAxel robots in a 3-5km-diameter lunar crater on the far-side, with suitable depth-to-diameter ratio, to form a spherical cap reflector.
This Lunar Crater Radio Telescope (LCRT), with 1km diameter, will be the largest filled-aperture radio telescope in the Solar System! LCRT could enable tremendous scientific discoveries in the field of cosmology by observing the early universe in the 10– 50m wavelength band (i.e., 6–30MHz frequency band), which has not been explored by humans till-date."
Why would you want to get a billions year old message anyway? We would still be alone if they no longer exist, and we did not exist when the message was sent. Suppose it's closer and we find a message and respond and it gets there in 100 years, and they respond back. 200 years to say hello.
SETI meant well but it was and is a waste of money
The far side antenna is a great idea. I'm sure SETI ad CETI would want time on it. I would be much more interested in the HF frequency spectrum and what it looks like. After all this time, it would be a real hoot to find intelligent signals there. But here's the thing. THz and above signals are detected because of their high intensities. They are flux. Many multiple emitters. Lower frequency signals have to be singular or uniform accelerations for long periods of time. For any kind of intensity....compared to the light source intensities. I.E......long durations of control of a lot of power. So, it would indeed be surprising, no matter how one looks at it.
It would be most impressive, and a little scary. It's a lot of controlled power.
If we can fly shoe box satellites in formation, we can install HF antennas out in space very cheaply using tethers. An adjustable size and direction disk.