My Apollo CSM transponder with the cover removed is on the right. They has to build custom wire harness connectors, as everything was custom back then.

It also has interesting ranging circuitry: NASA sent a pseudo-random ranging sequence to the spacecraft and this box amplified and returned the signal. On the ground, they measured how long the signal took (by correlating the returned signal with the sent signal), which gave them an accurate distance to the spacecraft.

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 locked bidirectionally, with the original NASA test transmitter and receiver, which we both restored to their original Apollo frequencies: youtu.be/hBKHNADtNPs

3 responses to “The Curious Marc Apollo USB Revival”

  1. jurvetson Avatar
    jurvetson

    I found this fascinating description of an experiment that involved this USB system and the Stanford Dish, unmistakable to me as I used to climb it like a big jungle gym for atavistic adults:This comes from the "Apollo 16 Preliminary Science report." This Radar Experiment also used the Apollo CSM transponder, comparing to moon reflection.

    I discovered that I have a bunch of documents on the Apollo 16 “S-Band Transponder Experiment” where they used the doppler shift of a signal sent, multiplied the frequency by 240/221 and then returned from the lunar orbiting CSM to deduce gravitational variation, and boy, were there a lot (the masscons as we call them, for mass concentrations).

    Earth cone and PM Tx Rx

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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. 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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