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| Honeysuckle, this is Houston | Jan 21, 2011 3:46 PM PST | url |
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Added 1 new A* page:If you watched that short NASA documentary on Apollo 13 that I embedded/linked a few days back, you probably heard those characteristic periodic high-pitched beeps in the background of the radio dialogue between mission control and the spacecraft. If you need a refresher, here's an Apollo radio dialogue with a bunch of the beeps: listen (specifically, this is a transmission system test between the NASA Mission Control Center in Houston, Texas ("Houston") and their Honeysuckle Creek Tracking Station near Canberra, Australia ("Honeysuckle")). ("Honeysuckle is go!")
Turns out those beeps have a name! They're Quindar tones, named after the manufacturer of the tone generation/listening equipment. There are two of them: one triggered when ground control pushes a button to open their microphone channel to the spacecraft, and a slightly lower one triggered when ground control finishes talking and releases that button to close the transmission.
The beeps were actually a signal to NASA's worldwide network of transmitting stations to open or close the broadcast channel, so it only stayed open while mission control was actually talking to the astronauts; without that system, that channel would have to have been left open all the time, subjecting the astronauts to static and mission control background noise 24/7. So while the somewhat shrill tones are a little annoying, in theory they probably saved the astronauts from a lot of headaches! Or "save," rather, because they're still in use in use in half-duplex UHF Space Shuttle transmissions--at least until the shuttle program ends later this year.
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