OTD In Space – January 10: Radar Astronomy Is Born

On January 10, 1946, the U.S. army bounced radar signals off of Earth's moon for the first time ever.

Known as "Project Diana," this was the first experiment in radio astronomy. They set up a large transmitter, receiver and antenna at a laboratory in New Jersey and blasted short radio pulses in the direction of the moon. Then 2.5 seconds later, the reflected radio signals were detected. So it took 2.5 seconds for the radio waves to make the 477,000-mile round trip to and from the moon. With this successful experiment, Project Diana marked the birth of radio astronomy.