Around the same time that Dewitt was building his lunar radar at the Army’s signal laboratory, a young Navy electrical engineer named James Trexler was also preoccupied with the moon. Fresh out of Southern Methodist University where he had spent his time experimenting with reflecting radio waves off of meteor ionization trails, Trexler had joined the Navy Research Laboratory as a junior radio engineer and quickly rose through its ranks.
Although most of Trexler’s day-to-day work involved refining military radar technology, he couldn’t help thinking bigger—much, much bigger.
In a notebook entry dated January 28, 1945, Trexler described a transcontinental communication system that would establish a radio link between Washington, DC and Los Angeles by bouncing the signal off the moon. Trexler did some back of the envelope calculations that showed how such a system might work, but he didn’t tell anyone about his idea for years. Instead, he focused on his work at the NRL, which was increasingly concerned with the phenomenon of so-called “anomalous signals.”
For decades, military receivers had been picking up seemingly random signals from all over the world. Under certain conditions, signals from Japan, Europe, and other far flung locales seemed to bounce off the ionosphere and reflect back toward Earth. In 1947, an NRL radio engineer named Howard Lorenzen called Trexler into his office to float a “rather interesting” idea: What if they built a system that could intercept anomalous radio signals as a form of intelligence gathering?
So Lorenzen and Trexler cobbled together a receiver from old Nazi antennas the NRL had lying around from the war, and began running experiments at the NRL Blue Plains site near Washington. Their primary objective was to determine the direction of anomalous radio waves. The project was chugging along until June 1948, when Trexler happened to read a paper published by three researchers working in a corporate communications laboratory run by International Telephone and Telegraph. The researchers hypothesized that the moon might have an ionosphere, which would reflect certain radio wavelengths back toward Earth with much higher fidelity than bouncing them off the surface.
Trexler immediately grasped its implications for his own work. Rather than searching for the directions of random signals bouncing off the ionosphere, the Navy could enlist the moon itself to eavesdrop on Soviet communications and intercept radar signals. It would be like having a big ear in the sky.
Within a few days of reading the paper, Trexler had calculated that trying to intercept signals bounced off the moon was both feasible and desirable. His bosses at NRL agreed and so Trexler and Lorenzen built a couple of experimental antennas at Blue Plains in the hopes of detecting Soviet radar signals reflected off the moon. The project—codenamed “Joe” in honor of Joseph Stalin—consumed the pair for the next two years.
STUMPED AT STUMP NECK
Early successes with the scrappy antennas at Blue Plains demonstrated to the NRL that the project had a lot of potential as an intelligence platform. In 1950, the Navy allotted the project enough funding to build a new radar at Stump Neck, Maryland and christened it with a new name: the Passive Moon Relay or PAMOR. The project’s new dish was built directly into the Earth and was oriented to maximize observations in the direction of the Soviet Union. It briefly held the distinction of being the largest parabolic radio dish in the world, a testament to the Navy’s enthusiasm for the project.
The Navy maintained utmost secrecy about the purposes of its new radar. PAMOR was top secret, but when the dish wasn’t used for military observations it was passed off to astronomers. This proved to be an effective cover for the project, and marked the beginning of a close relationship between Trexler’s intelligence unit and the astronomical community.
The Stump Neck telescope allowed Trexler and Lorenzen to scale up their efforts at detecting Soviet signals with the moon, but it was a chance event in October 1951 that really captured the Navy’s attention. That day, Trexler and Lorenzen decided to send some short radio pulses toward the moon and listen for a response. When they heard back, everyone working on PAMOR was surprised by the quality of the reflection. It got the group thinking—in addition to using the moon for passive surveillance, perhaps it could also be used as a secure communication channel. No matter what happened on Earth—war, electromagnetic storms, whatever—the moon could always be used to send a signal around the globe even if all the telecommunications infrastructure was destroyed.
And so the Communication Moon Relay project was born. Unlike PAMOR, which remained top secret, CMR was unclassified and a point of pride for the military. It envisioned using the moon for all sorts of things like communicating with aircraft and submarines, or broadcasting public messages to half the world at a time. On July 24, 1954, after years of experiments transmitting toward the moon, Trexler sat down at a microphone and delivered a short monologue into a microphone. There are no records of what was said, but two-and-a-half seconds later a speaker in the room echoed his message back to him. It was the first time in history that a human voice left the planet and returned again.
But using the moon to talk to yourself didn’t have much utility for the military. The real prize would be sending a message between two distant locations using the moon as a relay. Only a few months after Trexler’s historic transmission, the Navy made it happen. On November 29, 1954, Franz Kurie, the associate director of the NRL and one of the inventors of radar, sent a message from Stump Neck to his colleagues on the West Coast. His message was simple: “Lift up your eyes and behold a new horizon.”
The Navy was, understandably, ecstatic about their new toy. No longer was CMR just a curiosity; now it was a bonafide part of military communication infrastructure. The Navy had conscripted the moon. Following Kurie’s broadcast, the Navy leaned into the project and began developing communication systems that could be deployed on warships and receive lunar messages. The NRL doubled down on its efforts to boost the power of its transmitters and sensitivity of its receivers.
The existence of CMR was revealed to the world in 1960. A photo transmitted from the USS Hancock (CV 19), to Washington, DC, featured sailors arranged on the deck of the aircraft carrier in order to spell out two words: “MOON RELAY.” The stunt generated a lot of publicity, but by then the military was on to bigger things. The Soviet Union had stunned the world when it launched Sputnik in 1957, and it didn’t take the Navy long to realize the future of communication was artificial satellites, not moon bounces.
The premature death of the CMR project might have been a blow to Trexler and Lorenzen had they not been so preoccupied with other problems. As the Navy operationalized the moon bounce system, the pair had resumed work on PAMOR at Stump Neck. But after some early successes, it became clear that intercepting Soviet radar signals would require a bigger antenna—a lot bigger.