Project Diana: Bouncing Radio Waves Off The Moon

In the history of space exploration and communication technology, Project Diana holds a special place. Conducted by the United States Army Signal Corps in 1946, it was the first successful attempt to bounce radio waves off the Moon and receive their echo back on Earth. This groundbreaking experiment not only proved that communication with objects beyond Earth was possible, but it also laid the foundation for radar astronomy and space communications as we know them today.


Credit: Pierre PRESTAT

The Birth of Project Diana

At the end of World War II, scientists and engineers were eager to apply radar technology to new frontiers. Under the leadership of John H. DeWitt Jr., a team at Fort Monmouth, New Jersey, began working on a bold idea: using radar to detect and reflect signals from the Moon. They named the experiment Project Diana, after the Roman goddess of the Moon.

The challenge was immense. Radio signals had to travel nearly 500,000 miles round trip, overcoming atmospheric interference and the Moon’s weak reflective properties. The team used a modified SCR-271 radar system, operating at 111.5 MHz with a power output of 3 kilowatts. The antenna array, made up of 24 dipoles, was carefully aligned to track the Moon’s movement.

The radar antenna used for Project Diana. Credit: www.projectdiana-eme.com

The site of the experiment. Credit: www.projectdiana-eme.com

The Historic Achievement

On January 10, 1946, Project Diana achieved success. The team transmitted a series of radar pulses toward the Moon and, after 2.5 seconds, detected faint but clear echoes returning to Earth. This was the first time humanity had intentionally sent a signal into space and received a response, proving that the Moon could act as a passive reflector.

The experiment confirmed several key scientific concepts:

• Earth’s atmosphere does not block high-frequency radio waves.

• Two-way communication with outer space is possible.

• Radar astronomy can be used to study celestial objects.
  
  
  Oscilloscope display showing the radar signal. The large pulse on the left is the transmitted signal, the small pulse on the right is the return signal from the Moon. Credit: www.projectdiana-eme.com

Impact on Science and Technology

Project Diana’s success marked the dawn of radar astronomy. Scientists realized they could use radar to study the size, shape, and distance of planets and other objects in the solar system. This technology later contributed to the mapping of Venus, Mercury, and asteroids.

It also paved the way for the space race and modern satellite communications. The idea that signals could be transmitted beyond Earth led directly to innovations in space telemetry, satellite navigation, and even deep-space communication used by NASA today. Without Project Diana, achievements like the Apollo Moon landings or the Voyager spacecraft signals might not have been possible.

Legacy of Project Diana

Today, Project Diana is remembered as a milestone in human achievement. It transformed radar from a wartime tool into a scientific instrument for exploring the universe. The experiment also inspired generations of engineers and astronomers to look beyond Earth for answers.


Jack Mofenson, Harold Webb, John DeWitt, King Stodola, and Herbert Kauffman. Credit: www.projectdiana-eme.com

In summary, Project Diana: Bouncing Radio Waves Off The Moon was more than just a scientific test. It was a bold step into the future of space exploration and communication, proving that Earth was no longer isolated. From that moment in 1946, humanity’s voice had truly reached the stars.