The giant radio telescope that NASA wants to build on the far side of the Moon

3 LCRT crater view

Humanity has a fleet of space and terrestrial observatories that allow us to study the universe in a wide range of spectra. Although cosmic rays and neutrinos offer valuable information, the main one is electromagnetic in a wide range of possibilities. However, the resolution or sensitivity of these instruments is limited by their size, such that NASA seeks to convert a lunar crater into the largest radio telescope in the solar system.

Illustration of the structure of the Lunar Crater Radio Telescope, as well as its orientation with respect to the Sun and Earth.

Tidal coupling

In its perpetual dance around the Earth, the Moon shows, with slight variations, the same face to the planet. In a process known as tidal coupling, the period of lunar rotation and translation are approximately equal.

A huge advantage of the far side of the Moon is that it serves as a great shield against signal contamination. That is, radio emissions, both from the Sun and the Earth, will be blocked almost entirely. Furthermore, during the lunar night there is a perfectly dark sky for observations at other wavelengths, without an atmosphere that absorbs or distorts part of the light received.

perpetual isolation

In the past, the Apollo 16 mission carried the first interplanetary telescope. It was deployed on the Moon and allowed the Earth to be studied, stars, cumulus clouds, nebulae and the Large Magellanic Cloud in the ultraviolet rangeto. Obtaining images that could not be obtained from the planet.

A proposal that has resonated in the scientific community in recent years is to convert a lunar crater, with a diameter of at least one kilometer, into a radio telescope. This would be able to hear at frequencies between 6 and 30 MHz, a range completely unexplored from Earth.

Diagram of three possible methods for deploying the antenna and the different related equipment.

The so-called LRCT, for the acronym in English of Radio Telescope in a Lunar Crater, aims to study what is known as the Dark Age of the Universe, which covers part of the beginning of the cosmos and whose light has been stretched to the radius range.

Moon construction

Transforming a lunar crater into a radio telescope is not a simple task. Although the environment itself is already used to mold the shape of the disk, it is necessary to deploy a series of networks and a receiver to turn it into something useful.

Diagram of the LCRT deployment process. a) Landing of the equipment b) Preparations for installation c) Deployment of the rovers and anchoring to the support lines d) Deployment of the entire radio telescope disk and anchoring to the edge of the crater.
Sample of the DuAxel rovers, made up of pairs of Axel rovers. The latter are capable of moving easily over uneven terrain or large slopes.

Given the limitations of machinery, equipment and personnel available, construction would be carried out by robots. A first probe would be responsible for carrying the receiver and the main component of the dish. The latter would be folded, inspired by the techniques used in origami, and later deployed on the lunar surface.

Although there are different methods to deploy all the necessary equipment, the most feasible is to use a series of rovers in charge of extending the radio telescope disk and subsequently anchoring it to the lunar soil. In any scenario, this project involves medium-term work and the development of new technologies to make it feasible.

Reference: P. McGarey et al. “A Concept for the Deployment of a Large Lunar Crater Radio Telescope Using Teams of Tethered Robots.” JPL Open Repository (2022).

Francisco Andrés Forero Daza