EME

Earth-Moon-Earth is a radio communication which relies on the propagation of radio waves from an earth based transmitter directed via reflection from the surface of the moon back to an earth based receiver.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

As the albedo of the moon is very low, and the path loss over the 770,000 kilometre return distance is extreme, this means that high power and high gain antennas must be used. In practice, this limits the use of this technique to the spectrum at VHF and above.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The technique was developed by the United States Military in the years after World War Two, with the first successful reception of echoes off the moon being carried out at Fort Monmouth, New Jersey on January 10, 1946 by John DeWitt. This was followed by more practical uses, including a teletype link between the naval base at Pearl Harbor, Hawaii and United States Navy headquarters in Washington, DC. In the days before communications satellites, a link free of the vagaries of ionospheric propagation was revolutionary.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Later, the technique was used my non-military commercial users, and the first amateur detection of signals from the moon took place in 1953.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Recent advances in digital signal processing have allowed EME contacts, admittedly with low data rate, to take place with powers in the order of 100 Watts and a single Yagi antenna.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Moon: :For other moons in the solar system see natural satellite. For the astrological meaning of the Moon, see Solar system in astrology. For other uses see Moon (disambiguation)....

Albedo: The albedo is a measure of reflectivity of a surface or body. It is the ratio of electromagnetic radiation (EM radiation) reflected to the amount incident upon it. The fraction, usually expressed as a percentage from 0% to 100%, is an important concept in climatology and astronomy. This ratio depend...

Path loss: Path loss: In a communication system, the attenuation undergone by an electromagnetic wave in transit between a transmitter and a receiver....