This computer-generated image depicts NASA’s Juno spacecraft firing its Leros-1b main engine – credit NASA

Radio amateurs around the world took part in an experiment with NASA’s Juno spacecraft as it did a flyby of Earth.

SDR display showing 28 MHz transmissions taken by Dmitry Pashkov UB4UAD

NASA’s Juno spacecraft flew past Earth on Wednesday, October 9, 2013 to receive a gravity assist from our planet, putting it on course for Jupiter.

To celebrate this event, the Juno mission invited amateur radio operators around the world to say “HI” to Juno in a coordinated Morse Code message that would be detected by Juno’s radio and plasma wave experiment, called Waves.

Radio amateurs transmitted Morse (CW) signals on a range of frequencies between 28.001 and 28.450 MHz. To give a random spread the precise frequency used depended on the last character of each stations call sign. The natural signals the team expect to measure at Jupiter will consist of a large number of discrete tones, so spreading the signals out in this manner was a good approximation to the signals Juno is expected to detect. But at Jupiter, they don’t expect to be able to decode CW in the telemetry!

The Waves instrument is sensitive to radio signals in all amateur bands below 40 MHz. However, experience with the University of Iowa instruments on the Galileo and Cassini Earth flybys showed significant shielding by the ionosphere at lower frequencies, so the 28 MHz band was chosen for the experiment.

Juno’s antenna consists of a pair of tapered 2.8 meter long titanium tubes, deployed from the bottom deck of the spacecraft under the +X solar array and magnetometer boom. A high impedance radiation resistant preamp sits at the base of the antenna and buffers the signals from 50 Hz to 45 MHz. The elements are deployed with an opening angle of about 120 degrees. 28 MHz is above the resonant frequency of the antenna and NEC analysis indicates a lobe generally along the spin axis of the spacecraft. This will be good for detection on the inbound part of closest approach to Earth.

The Waves instrument uses four receivers to cover the frequency range of 50 Hz to 41 MHz. Signals up to 3 MHz are bandpass filtered, sampled by A/D converters and FFT processed into spectra using a custom FFT processor developed by The University of Iowa under a grant from the Iowa Space Grant Consortium.

Among those taking part were students at Virginia Tech using their club station K4KDJ.

Watch Hi Juno de K4KDJ (Virginia Tech)

Dmitry Pashkov UB4UAD said Hi to Juno http://tinyurl.com/UB4UAD-Hi-Juno

Roland PY4ZBZ – Hi Juno http://tinyurl.com/PY4ZBZ-Hi-Juno

University of Iowa radio club hams it up with Jupiter probe
http://www.desmoinesregister.com/article/20131010/NEWS/310100078/U-radio-club-hams-up-Jupiter-probe

JPL Hi Juno page http://www.jpl.nasa.gov/hijuno/

NASA’s Juno probe to be Humankind’s fastest ever thing
http://www.theregister.co.uk/2013/10/09/juno_spacecraft_set_for_earth_flyby/