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July 19, 2019

T-MINUS 1 DAY: Motorola Delivered the First Words from the Moon Via the S-Band Transponder

In honor of the 50th anniversary of the first manned moon landing, we are revisiting our archives to reflect on our history of “firsts” and how it has shaped our commitment to innovation through mission-critical communications.

One of Motorola’s most notable contributions to the Apollo 11 mission was the unified S-Band transponder that carried the first words from the moon to Earth. The contract for the “vital communications link between earth and the Apollo space capsule” was awarded to Motorola Military Electronics Division in Scottsdale, Arizona, in 1963.   

Motorola was tasked with building a compact radio transmitter-receiver unit, called a transponder, to provide voice, television and telemetry communications between the Apollo spacecraft and Earth. The electronic device was a radio transmitter and phase-lock receiver built into one unit.

There were a number of technical requirements to design and develop a coherent transponder. One key element was that it had to be lightweight. According to a 1964 Motorola news release, it took 100 pounds of thrust to send one pound of payload into space flight, so it was imperative that the communications equipment did not exceed a certain weight. The transponder also required less power to communicate from the moon to Earth than the power used by a refrigerator light bulb.

"Pictures, voice and digital communications will be coming through the exceptionally small and lightweight electronic devices being produced by Motorola, especially for the lunar mission," said Joseph A. Chambers, vice president and general manager of Motorola's Military Electronics Division, in a 1964 Motorola news release.

The transponder delivered all communications into a composite signal for transmission. Once the spacecraft reached a distance of 30,000 miles from Earth, the astronauts completely relied on the unified S-Band transponder to stay connected.


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