Author Topic: Spacecraft distance measurement  (Read 5093 times)

Offline molesworth

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Spacecraft distance measurement
« on: April 24, 2022, 06:10:33 PM »
Being a computer nerd I thought I'd seen everything to do with the guidance, telemetry, data handling etc. for the Apollo missions, but I've just discovered this fascinating and ingenious system which was used to measure the spacecraft distance and velocity.  I'm sure a few folks here will be familiar with it already, but I love finding stuff like this, and it really brings home the amazing efforts which went into the design and implementation of these systems.  Hats off to whoever came up with this idea!

Long-ish Twitter thread -

Related YouTube video -
Days spent at sea are not deducted from one's allotted span - Phoenician proverb

Offline bknight

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Re: Spacecraft distance measurement
« Reply #1 on: April 24, 2022, 07:50:45 PM »
I didn't know this information and procedure existed when I was arguing with Apollo "lack of computing power" with some ignorant individuals.  But I did know that the bulk of computation was done by ground computers leaving guidance to the onboard computers.
Cool stuff.
Truth needs no defense.  Nobody can take those footsteps I made on the surface of the moon away from me.
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Offline smartcooky

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Re: Spacecraft distance measurement
« Reply #2 on: April 25, 2022, 02:49:02 AM »
This concept appear to be almost like a secondary* radar altimeter.

* For those not familiar with this term, "primary" radar is where the primary broadcast signal is reflected by the target and the returnes picked up by the receiver (for example, search radar & weather radar), while "secondary" radar is where the target is equipped with a a transponder that rebroadcasts the primary signal (for example IFF).

If you're not a scientist but you think you've destroyed the foundation of a vast scientific edifice with 10 minutes of Googling, you might want to consider the possibility that you're wrong.