An idea first proposed by a British communications engineer in 1940 celebrates 73 years of successful implementation on Jan. 10, 1946. The results of this experiment have powered various practical applications, including communication between distant ground receivers. The work also laid the basis for radio astronomy.

W.J. Bray, an engineer with the British General Post Office, posited a microwave signal could be transmitted from Earth, bounced off the moon and received at another point on Earth. In the aftermath of World War II, several nations showed great interest in using the moon as a passive communications satellite. Two separate Project Diana antenna at Fort Monmouth, New Jersey, used to bounce a signal off the moon.Project Diana antenna at Fort Monmouth, New Jersey, used to bounce a signal off the moon.groups — the U.S. military and a team in Hungary — worked to prove Bray’s proposition after World War II. The U.S. group from the Army Signal Corps succeeded first, receiving echoes of its transmission from Fort Monmouth, New Jersey, to the moon at 11:58 a.m. The Hungarian group, led by theoretical physicist Zoltan Bey, followed less than a month later, on Feb. 6, 1946. This path from the Earth to the moon and back is formally known as Earth-Moon-Earth (EME), or informally as moonbounce.

After this initial success, the military attempted to develop a few different communications systems based on moonbounce. The first system was intended to eavesdrop on the Soviet Union’s military. PAMOR, for Passive Moon Relay, started in 1950 and was ultimately abandoned in 1962. A somewhat more successful program dubbed Communication Moon Relay, or Operation Moonbounce, carried military communications, including a link between Hawaii and Washington, D.C.

With the advent of purpose-built communications satellites, the U.S. government abandoned EME communications. Since 1953, amateur radio operators have used moonbounce for two-way communications, despite significant challenges due to inherent signal weakness.

Although EME did not become a game-changing espionage or communications system, Project Diana, the research effort that produced the first successful signal, also formed the basis of radio astronomy. In another significant achievement, Project Diana proved that radio signals can pierce the ionosphere. Proof that radio waves can travel outside earth’s atmosphere enabled the development of communications to support unmanned satellites and manned space missions. The project also tested continuous wave FM Doppler radar, a technology developed during World War II. This radar allows detection of potential airborne threats.