curiousmarc
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Stanford Dish Visit
🕑 Added 2022-04-17 00:51:54 +0000 UTCWell, wouldn't you know it, Steve M., the current engineer for the nearby SRI space antenna, better known as the Stanford Dish, is watching the channel. This thing is a mere 10 minutes from where I live, and I had always wondered about it. So imagine my surprise when Steve recently contacted me, wondering about the role of the Dish in the Apollo program. He could find some traces of Apollo related equipment in the warehouse and observation notes in the log books, but nobody at SRI remembered what it did then.
He sent me a photo of this piece of equipment entitled "Apollo S-Band receiver" with an Apollo 16 patch.
It turns out, on this document about Apollo 16, the Stanford Dish is prominently mentioned on p. 61, as performing a bistatic radar experiment.
What's a bistatic radar you might ask? That's one where the transmitter is at different location from the receiver. In this case, the transmitter was Apollo's command module own transponder, and one of the receivers was the Stanford Dish (apparently, another one was the Goldstone antenna). The antenna would get both the direct signal from the spacecraft, and the same signal bounced off the surface of the moon. By comparing the two signals, they could get radar information about the moon's surface.
Steve was able to corroborate that this was it, and did later find old memos from when the program was awarded. And for our good deed, he got SRI management approval to get us a inside the dish for a visit. We couldn't wait!
Up close, the thing is monstrous. It did not quite fit in my camera field of view.
At 150 ft diameter, it is much larger than the 82 ft antennas that were used to normally communicate with the spacecraft, but smaller than the gigantic 210 ft antennas at Goldstone (California) and Parkes (Australia) that were sometimes made available to the program and helped considerably in hairy situations, namely the Apollo 11 landing and the Apollo 13 communication in low power mode. When we eventually climbed on the Stanford Dish, I was more than a little queasy from the absurd height and the howling wind in the antenna mesh.
The control building, which is nestled underneath the antenna and rotates with it, houses the huge 30 kW klystron amplifier, straight out of the early 1960's. Made by nearby klystron's inventor Varian, of course. All original tube electronics inside, complete with the Tektronix integrated scope in the control panel.
We got to see the logbooks with the Apollo annotations.
We even moved the Dish from the original command console, complete with the Apollo-era Twist-Lite illuminated buttons. Sadly it does not have the original Nixie indicators nor the PDP straight-8 controller anymore. But not too far off, it runs from an old PC with Windows 95. That gets brownie points in my book.
I would call that a good field day!
Marc
Comments
MVVblog
I wish I had been with you, what a great day!
CuriousMarc
I think they finally got rid of the PDP-8. And then Win95 could still run DOS, in which they ran FORTRAN, and could recompile their old code... But they are going to get a brand new modern commercial antenna control system to replace all this. Which may be good, but is also kind of sad. I would have resurrected the PDP-8 and added the Nixie tubes back in. ;-)
