Radio Telescope in a Carpet

The lunar farside would be a splendid place to do radio astronomy. First, the cacophony of the Earth would be silenced by up to 2,160 miles of rock. Second, lacking an atmosphere, a radio telescope located on the lunar surface would be able to detect radio waves at frequencies that are absorbed or reflected back into space by the Earth’s ionosphere.

Radio waves below a frequency of 10 MHz (λ ≥ 30 m) cannot pass through the ionosphere to reach the Earth’s surface. The Earth’s atmosphere is variably opaque to radio waves in the frequency range of 10 MHz to 30 MHz (λ = 10 to 30 m), depending upon conditions. The Earth’s atmosphere is mostly transparent to frequencies between 30 MHz (10 m) and 22 GHz (1.4 cm).

Not surprisingly, electromagnetic radiation of a non-terrestrial origin having wavelengths longer than 10 meters has been little studied. If we look, we might discover new types of objects and phenomena.

The best part is the lunar radio telescope wouldn’t have to be a steerable parabolic dish, but instead could be a series of dipole antennas (simple metal rods or wires) imbedded into a plastic carpet that could easily be rolled out onto the lunar surface. This type of radio telescope is “steered” (pointed) electronically through phasing of the dipole elements.

Even though the ever-increasing number of lunar satellites should be communicating at wavelengths far shorter than 10 meters, care must be taken to minimize their impact (both communication and noise emissions) upon all lunar farside radio astronomy.