This is the millionth article on lunar far-side telescopes I've seen that conveniently fails to explain why you'd want to place a radio telescope on the surface

This is the millionth article on lunar far-side telescopes I've seen that conveniently fails to explain why you'd want to place a radio telescope on the surface rather than just at the Earth-Moon L2 Lagrange point (i.e., the point on the far side of the Moon that orbits with the Moon around the Earth and keeps the Moon between itself and the Earth). I'm sick of not having this obvious question answered, so I dug into it. Like the lunar surface, a telescope at L2 keeps the Moon permanently between itself and the Earth to block incoming radio waves. For a fixed telescope size, going down into the Moon's gravity well increases costs tremendously. And, although doing construction in a vacuum is never easy, it's a lot easier when you're in zero-g and you don't need a crane! Unlike the far-side surface, L2 has exposure to sunlight for power for ~90% of the time. (You would still need a relay satellite in a different lunar orbit for communications, of course, just like the far-side surface.) As far as I can tell from browsing the article https://arxiv.org/abs/2009.12689 https://arxiv.org/abs/2009.12689 and the much more helpful analysis of the lunar radio environment that they cite https://sci-hub.st/https://arc.aiaa.org/doi/pdf/10.2514/6.IAC-06-D4.1.01 https://sci-hub.st/https://arc.aiaa.org/doi/pdf/10.2514/6.IA... the only benefits to going to to the surface is (1) you get better shielding of the extremely low frequencies (≲ 1 kHz) which are long enough wavelength to diffract around the Earth, but don't think those are detectable unless you have a telescope that's many kilometers in size. (2) you avoid radio signals from satellites in geostationary orbits, but these should be very small since the transmitters are pointing toward the Earth. Indeed, the faculty member who is advising the undergraduate intern lead author says > “The first SETI observations that are done from the lunar farside will be done from orbit, there’s no question about that,” says Andrew Siemion, the director of the Berkeley SETI Research Center and the second author on the paper. “I think eventually we absolutely want to do something on the surface because we want to build a very large aperture telescope, but even when we’re at that point I don’t think that would negate the utility of doing things from orbit as well.” and I think he's downplaying how tremendously costly going to the surface would be for very little benefit. EDIT: Note that the FARSIDE array on the surface they mention is much better justified, but it's not SETI, it's an array, the surface benefits from solar storm shielding, and it probably only makes sense because it piggybacks on high bandwidth connection for the NASA Lunar Gateway. More details here: https://www.lpi.usra.edu/leag/white-papers-astronomy/FARSIDE_190710_Final.pdf https://www.lpi.usra.edu/leag/white-papers-astronomy/FARSIDE... https://twitter.com/di_goldene_pave/status/1312391572407955457 https://twitter.com/di_goldene_pave/status/13123915724079554...