Project Diana



Project Diana, named for the Roman moon goddess Diana — goddess of the hunt, wild animals and the moon — was an experimental project of the US Army Signal Corps in 1946 to bounce radio signals off the moon and receive the reflected signals. This was the first experiment in radar astronomy and the first attempt to actively probe another celestial body. It was the inspiration for later EME (Earth-Moon-Earth) communication techniques.

At a laboratory at Camp Evans (part of Fort Monmouth), in Wall Township, New Jersey, a large transmitter, receiver and antenna array were constructed for this purpose. The transmitter, a highly modified SCR-271 radar set from World War II, provided 3,000 watts at 111.5 MHz in 1/4 second pulses, applied to the antenna, a "bedspring" reflective array antenna composed of an 8x8 array of half wave dipoles in front of a reflector which provided 24 dB of gain. Reflected signals were received about 2.5 seconds later, with the receiver compensating for Doppler modulation of the reflected signal. The antenna could be rotated in azimuth only, so the attempt could be made only as the moon passed through the 15 degree wide beam at moonrise and moonset, as the antenna's elevation angle was horizontal. About 40 minutes of observation was available on each pass as the moon transited the various lobes of the antenna pattern.

The first successful echo detection came on 10 January 1946 at 11:58am local time by John H. DeWitt and his chief scientist E. King Stodola.

Project Diana marked the birth of the US space program, as well as that of radar astronomy. It was the first demonstration that artificially-created signals could penetrate the ionosphere, opening the possibility of radio communications beyond the earth for space probes and human explorers. It also established the practice of naming space projects after Roman gods, e.g., Mercury and Apollo.

Today, the Project Diana site is maintained by the Infoage Science/History Learning Center.