After nine months of effort, the incredible team of Curious Marc, Ken Shirriff and Mike Stewart have revived my 50+year-old Apollo S-Band communications system, using my ground support equipment and the vintage Apollo CSM transponder. In the most recent episode, they powered it up and got the Apollo transponder to lock bidirectionally, with the original NASA test transmitter and receiver, which we both restored to their original Apollo frequencies. Cue “Ground Control to Major Tom”

The original “USB” (Unified S-Band) was the sole deep space communication channel used during the Apollo missions. With just 20 Watts, they could communicate with Houston from the moon (across 239,000 miles). And a single antenna combined voice, television, command, tracking and ranging. They even used it to study the lunar surface, with the aid of the Stanford Dish.

You can see the black art of microwave RF design as they disassemble my Apollo CSM transponder, travelling wave tube amplifier and the various ground panels used for communications. They even had to have a custom crystal made, to undo modifications made post-Apollo to adjust the ground test equipment for a mystery application (deduced to be the GEOS-3 satellite in 1975).

I will be loaning these panels to SETI to decorate their new HQ with the heroes of our deep space communications systems. In addition to the Apollo S-Band suite, I will be loaning the panels for Viking (the first Mars landers, which failed to find the signatures of alien life), the docking adapter for the Apollo-Soyuz Test Project (the symbolic end of the last space race), and various Saturn V rocket engine monitoring and communications systems.

Here is the complete video playlist, with 13 episodes so far, and more items in the FV space collection.

4 responses to “Reviving the Apollo USB Communications System”

  1. jurvetson Avatar
    jurvetson

    Earth on the left; Apollo CSM on the right:The big picture:and the frequency bands. C = Cycles/Sec = Hz and in this case, the center band is 2.1 GHz for the up-link: Location in the Apollo CM: More on the Apollo USB transponder hereApollo Command Module Unified S-Band Ranging Transponderand the 20W tube amp that powered the Earth-Moon link, hereApollo Command Module USB TWT Amplifier

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  2. jurvetson Avatar
    jurvetson

    And by amazing coincidence, my Apollo Transponder and Motorola equipment was made in the 60’s at their Scottsdale, AZ facility. I was conceived in Canada, but my Dad was recruited by Motorola -Scottsdale in 1966, making me a U.S. citizen as I was born there.

    That unit was acquired by General Dynamics, and they recount here:

    “ONE SMALL STEP FOR MAN. ONE GIANT LEAP FOR MANKIND.

    These iconic words from Neil Armstrong during his Moon landing were heard by more than 600 million people thanks in part to the engineering accomplishments in Scottsdale, AZ.

    The Apollo missions were incredibly complex with multiple space vehicles performing intricate maneuvers in deep space which required accurate tracking at extreme distances. The equipment had to be designed to withstand the extreme cold, heat and radiation they would experience and for Apollo 11, they also needed to transmit more data than previous NASA missions, including television and video.

    Hundreds of employees in Scottsdale, AZ began developing the Unified S-Band Transponder in 1962, a new system that would accurately track the Apollo spacecraft, transmit and receive telemetry signals, communicate between ground stations and the spacecraft, and provide the link for the historic broadcast from the surface of the moon. The formal contract was awarded in 1963 to Motorola’s Government Electronics Division, a legacy company of General Dynamics.

    Once the spacecraft reached a distance 30,000 miles from Earth, the astronauts completely relied on the Unified S-Band Transponder to stay connected. The Transponder was their only link to mission control and transmitted all voice and video communications, spacecraft status, mission data, distance, the astronauts’ biomedical data and emergency communications."

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  3. Jim Somsel Avatar
    Jim Somsel

    Incredible story, Steve. Glad I kept reading to see your very personal tie-in. Thanks for sharing this!

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  4. jurvetson Avatar
    jurvetson

    You’re welcome! Also, it’s on display and operating at DesignCon this evening. Here’s a video of the setup in preparation.

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