Hams Collaborate to Greet Juno Spacecraft on Flyby; Results Are Pending
Radio amateurs around the globe greeted NASA’s Juno spacecraft October 9 as it looped past Earth for a gravity-assisted boost on its way to Jupiter. Participants were invited to spread out across 10 meters to transmit “HI” in very slow speed CW (1/25 WPM), sending 30 second dits punctuated by 30 second spaces and 90 seconds between the two characters. The experiment involved 16 identical rounds or cycles and ran a bit longer than 2-1/2 hours all told (1800 to 2040 UTC). The object of the experiment was to see if Juno’s onboard “Waves” experiment would be able to detect the collective RF. One possible glitch was that the spacecraft’s systems went into “safe mode” at some point. University of Iowa researcher and Waves Principal Engineer Don Kirchner, KDØL, believes the unexplained switchover will not prove to be a problem for the Say “HI” to Juno experiment.
“Safe mode entry was late enough that we likely have data taken from the event,” Kirchner told ARRL. "[Project managers] are carefully working through their standard procedures, which take priority over downlinking the science telemetry that should be stored on board. I am still hopeful that we will have enough data to determine whether or not our instrument was able detect amateur signals.”
Among stations participating were operators at the Virginia Tech Amateur Radio Club’s K4KDJ, who posted video of their activity on YouTube.
Whatever the outcome, Kirchner said, he and the Juno team “would like the thank the operators that took part in this experiment.” He said reports came in from all over the world. Anyone who took part can request a QSL card that acknowledges their help.
“Indications are that we had very large and enthusiastic participation,” he added.
At the time of the experiment the Juno spacecraft was within 50,000 kilometers from Earth, and the Waves team determined that would be the best opportunity for the wide-band receiver to detect Amateur Radio signals. Spreading out participants on a wide range of 10 meter frequencies was intended to improve the chance of the Waves instrument’s hearing the ham signals. The detector has a bandwidth of 1 MHz.
“The natural signals we expect to measure at Jupiter will consist of a large number of discrete tones,” a pre-experiment announcement explained, “so spreading the signals out in this manner is a good approximation to the signals we expect to detect. But at Jupiter, we don't expect to be able to decode CW in our telemetry!”
Despite the government shutdown two websites were available to guide participants when to key down and when to stop transmitting. Numerous operators were monitored who, apparently not having read or fully understood the instructions, transmitted “HI” and their call signs at normal CW speeds. The very slow speed CW was necessary because the Waves instrument samples the spectrum just once per second. As the website explained, “By spreading the signal out in time, we can average to reduce the noise level. In addition, the spacecraft spins at 2 RPM, so a 30 second ‘dit’ time gives us a full spin to see if there is any spin modulation.”
Organizers were actually hoping for poor conditions on 10 meters, so that signals from Earth would pass through the ionosphere for the most part, allowing the spacecraft a better chance of detecting them.