Project Diana

Project Diana, named for the Roman moon goddess Diana, was a project of the US Army Signal Corps to bounce radio signals off the moon and receive the reflected signals. Today called EME (Earth-Moon-Earth), this was the first attempt to "touch" another celestial body. From a laboratory at Camp Evans (part of Fort Monmouth), near 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, and the antenna (a "bedspring" dipole array) 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 transmission was made on 10 January 1946 at 11:58am local time.

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 Ocean-Monmouth Amateur Radio Club, where they sometimes operate an amateur radio station as a special event.

References

* Radar Echoes From the Moon, January 1946, By Jack Mofenson, Evans Signal Laboratory, Belmar N.J. [http://www.infoage.org/diamof.html]
* IEEE Virtual Museum [http://www.ieee-virtual-museum.org/collection/event.php?id=3456980&lid=1]
* Butrica, Andrew J. To See the Unseen: A History of Planetary Radar Astronomy. (NASA SP4218, 1996) [http://history.nasa.gov/SP-4218/ch1.htm]