FARSIDE

NASA is investigating building a radio telescope on the far side of the moon which would allow us to see very faint signals that background noise from the Earth and the Sun make impossible to discern now. For the money, it would probably be a better way to advance our understanding of fundamental physics than a new next generation particle collider.

The current state of the art is EDGES which has revealed that primordial radio wave backgrounds from around 228 million years after the Big Bang (redshift z=17) contradict the LambdaCDM prediction.

The 21cm EDGES result is one of the most striking failures of the "Standard Model of Cosmology" at the cosmology scale, in addition to its many problems at a "large scale structure" galaxy scale.  A few other cosmology scale problems with LambdaCDM are the "impossible early galaxy" problem, the Hubble tension, and deviations from the cosmological principle.

Modified gravity theories can resolve all of these cosmology issues and reproduce the Cosmic Microwave Background (CMB) peaks used as Exhibit 1 as evidence in favor of LambdaCDM, as well as its many large scale structure issues. 

The new instrument would be able to view primordial radio wave backgrounds from around 6 million years after the Big Bang (z=200).

An array of low-frequency dipole antennas on the lunar farside surface will probe a unique, unexplored epoch in the early Universe called the Dark Ages. It begins at Recombination when neutral hydrogen atoms formed, first revealed by the cosmic microwave background. This epoch is free of stars and astrophysics, so it is ideal to investigate high energy particle processes including dark matter, early Dark Energy, neutrinos, and cosmic strings. 

A NASA-funded study investigated the design of the instrument and the deployment strategy from a lander of 128 pairs of antenna dipoles across a 10 km x 10 km area on the lunar surface. The antenna nodes are tethered to the lander for central data processing, power, and data transmission to a relay satellite. The array, named FARSIDE, would provide the capability to image the entire sky in 1400 channels spanning frequencies from 100 kHz to 40 MHz, extending down two orders of magnitude below bands accessible to ground-based radio astronomy. 

The lunar farside can simultaneously provide isolation from terrestrial radio frequency interference, the Earth's auroral kilometric radiation, and plasma noise from the solar wind. It is thus the only location within the inner solar system from which sky noise limited observations can be carried out at sub-MHz frequencies. Through precision calibration via an orbiting beacon and exquisite foreground characterization, the farside array would measure the Dark Ages global 21-cm signal at redshifts z~35-200. It will also be a pathfinder for a larger 21-cm power spectrum instrument by carefully measuring the foreground with high dynamic range.

Jack Burns, et al., "A Lunar Farside Low Radio Frequency Array for Dark Ages 21-cm Cosmology" arXiv:2103.08623 (March 15, 2021) (response to DOE request for information on lunar farside radio telescope to explore the early universe).