Seventy Years Ago, We Bounced Signals Off the Moon for the First Time

Before there were Moon landings, there were Moon bounces.

The Moon exerts a tidal force on Earth, but it also holds a similar sway over the human imagination. Few objects have inspired as much speculation and worship than our beaming silver satellite, and the drive to reach it is a cornerstone of civilizations spanning continents and millennia.

But it wasn't until 70 years ago, on January 10, 1946, that this relentless dream finally came to fruition. At 11:58AM that day, military scientists based at Camp Evans, New Jersey shot UHF radio signals at the Moon, and received a bounceback from the lunar surface 2.5 seconds later.

The left pulse shows the transmitted signal, while the right pulse shows the bounced back received signal. Image: Radio News Magazine

The experiment, dubbed Project Diana after the Roman goddess of the Moon, marked the first time humans had ever actively probed another celestial body, and some even regard it as the birth of the American space program. It was, at the very least, the fundamental bedrock upon which space communication and radar astronomy was built.

Indeed, the name Diana was selected not only for its lunar-friendly connotations, but because lead engineer John H. Dewitt Jr., wanted to play up the virgin angle. "The Greek [sic] mythology books said that she had never been cracked," DeWitt said, according to the history Earth Sound Earth Signal by Douglas Kahn, alluding to Diana's virginity in Roman myth.

Admittedly, that's kind of a weird way of fetishizing the lunar surface—does DeWitt mean that the Moon lost its virginity to a bunch of Jersey-based light waves? Best not to think about it. The point was that Project Diana had demonstrated, for the first time, that it was possible to transmit information to objects in space, and to learn about the properties of celestial bodies by bouncing light off of them.

This would have obvious applications for subsequent spaceflight missions, particularly the Apollo Moon landings, but from the team's vantagepoint in 1946, that was on neither their figurative or literal radars.

"At the time, the handful of scientists working on the project did not feel it was of great long range importance towards putting a man on the Moon," according to this US Army history of Camp Evans activities between 1907 and 2007. "The first thought, according to [Project Diana mathematician] Walter S. McAfee, was to see if it was possible to bounce an electronic signal. If that could be done, he concluded it would be useful in propagating sound waves."

"People were not thinking of going to the Moon in those days, according to McAfee."

As a side note, it's worth mentioning that McAfee was denied credit for his crucial role in in Project Diana at the time, possibly because he was African-American, though histories seem to dance around that assumption—including McAfee's own account.

"Sometime later, somebody connected with publicity at the Army was talking with me and said, 'I looked at all those early [press releases] and I don't find you anywhere," McAfee said in an interview with the New York Historical Commission. "I said, 'I can tell you why, but I don't care to get into a discussion about it.'"

Postcard commemorating Project Diana. Image: US Army

Whatever the reason, his contributions, which included the calculation of the relative motions of Earth and the Moon, weren't acknowledged until much later. It might be pertinent to also mention that Camp Evans served as the Ku Klux Klan's New Jersey headquarters less than a decade before McAfee worked there. I'm not drawing conclusions—just sayin'.

Regardless, thanks to McAfee and the other specialists involved in Project Diana, humanity was able to take its first tangible step towards exploring the Moon...from the Jersey Shore, of all places.

Today, the same techniques have been used to explore distant planets, operate vast constellations of satellites, and estimate the Moon's distance from Earth to within a millimeter—an incredibly precise measurement considering the two bodies have, on average, about 384,400 kilometers between them. Project Diana was a modest experiment at the time, but in retrospect, it opened up the skies.