What's a Tiny sound cone
Got to Do with a Tiny DSN antenna, Dr. Marc?

Dr. Marc explains Like waves in the ocean, sound makes waves in the air. Air jostles back and forth as the sound energy waves pass.

If you put something like paper in the path of the sound wave, it will also vibrate quite a lot. If you give this paper surface the right shape, the sound waves will be funneled to a point. So your super sound cone is a sound funnel!

The same sort of idea makes NASA's giant dish antennas work. These antennas listen for signals from the planetary spacecraft now exploring space far from Earth.

Deep Space Network 34-M antenna at Canberra, Australia

The antenna dish in this picture is 34 meters (about 110 feet) across. This antenna is in Australia. See how tiny the sheep look as they graze peacefully beneath its attentive ear.

 

         
         

We can't just build a spacecraft, tell it to phone home once in a while, then launch it to Mars or Jupiter! We must have a way to hear its tiny voice and talk to it when it is very far away.

Of course, no spacecraft actually communicates by sound. Messages wouldn't get very far, since sound waves can't travel in the vacuum of space! But the spacecraft do send out radio waves, which can travel practically forever. The trouble is, the radio waves spread out and get weaker and weaker the farther they travel.

So NASA's radio wave "ears" must be very big indeed!

Some of the Deep Space Network antennas are twice as big as the one watching over the sheep above!

These dish antennas don't look much like your sound cone, do they? But the path the radio signals take once they hit the dish is like a folded up cone. Once the signal hits the focus (like the small end of your cone), electronic instruments take over to turn up the volume even more.

Cassegrain antenna signal path

Then we can begin to decode the message and figure out what the spacecraft has to show and tell us!

 

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