Juno’s launch vehicle was capable of giving the spacecraft only enough energy to reach the asteroid belt, at which point the sun’s gravity pulled it back toward the inner solar system. Mission planners designed the swing by Earth as a gravity assist to increase the spacecraft’s speed relative to the sun, so that it could reach Jupiter. (The spacecraft’s speed relative to Earth before and after the flyby is unchanged.)Juno is carrying a radio receiver called the Waves receiver; the receiver tunes more than the entire HF (shortwave) radio spectrum; from 3 to 40 MHz for monitoring natural radio emissions from the giant planet. The lead engineer on the project, Don Kirchner, had an idea for an interesting way to test that receiver. Don is a radio amateur - a ham, KD0L, and immediately realized that the receiver tunes across all the HF amateur bands, but that one of them offered good conditions for a test of the receiver. If he could only get hams all around the world to send very slow, synchronized Morse code to the satellite in the 10 meter (28-29.6 MHz) band.
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