THE US AIRFORCE MAY HAVE SHOT DOWN AN AMATEUR RADIO PICO BALLOON OVER CANADA
Since the famous takedown of a suspected Chinese spy balloon, US jets have shot down a total of three more unidentified balloon objects, now confirmed to have been 'commercial or benign'. There is speculation that at least one these three objects may have been an amateur radio 'pico' balloon.

One part of the amateur radio hobby is launching high altitude balloons with various radio and other payloads. Larger amateur radio balloons launched in the USA require FAA clearance, need a radar reflector attached, and usually continually transmit APRS telemetry before naturally popping and falling back to earth after a few hours, just like a weather balloon.

However there is also the simpler 'pico' ballooning hobby, which involves the use of mylar helium party balloons to launch small solar powered payloads that are only a few grams in weight. They typically transmit low power WSPR at HF frequencies and can only transmit whenever there is sufficient solar power available. Amateur radio or SDR hobbyist stations around the world can pick up these transmissions, and report them on amateur.sondehub.org and/or wsprnet.org. Well built balloons can totally circumnavigate the globe several times over several months before degrading.

While termed 'pico', the party balloons used can still be roughly a meter in diameter on the ground, with some latex balloons potentially expanding further at high altitudes due to the low atmospheric pressure. These balloons can be legally launched from almost anywhere in the world. In particular in the USA there is no FAA clearance required to launch them due to their payload being much less than the limit of 4 lbs (1.8kg).

There is speculation that at least one of the objects shot down over Canada, Yukon by a US Air Force jet may have been amateur radio pico balloon K9YO-15 which was launched from Illinois on October 10 2022. It was on it's seventh circumnavigation of the globe after being aloft for 123 days.

The launch blog post indicates that the K9YO-15 balloon was flying a silver mylar 32" sphere SAG balloon which appears to be this one from balloons.online. Unlike latex or rubber weather balloons which inflate and stretch as they rise into lower atmospheric pressures, these mylar balloons can't stretch, so their fully inflated ground size will be the same as their size at high altitudes, meaning the pico balloon won't get much bigger than 32". The payload was a GPS module, Arduino, SI5351 used as a WSPR and APRS transmitter and a solar panel, all together weighing 16.4 grams. A pentagon memo notes that the object shot down over Canada was a "small metallic balloon with a tethered payload" which fits the description of the pico balloon exactly.

The K9YO-15 balloon ceased all WSPR telemetry transmissions while flying just below Alaska since Feb 11 00:18 UTC (just before sunset in Alaska when the solar panels would stop working).

By using NOAA wind models and the last known location by Alaska, K9YO-15 was projected to have been over Yukon when the US Air Force shot down the unknown balloon object at Feb 11 20:41 UTC (3:41 PM EST / 1:41 PM Yukon time according to Canadian Defense Minister Anand). Reports put the altitude of the shot down object at approximately 40,000ft (~12000 meters), which matches the projected ~11500 meters of K9YO-15. Based on the previous days transmission times, it is suspected that if it were operational, the balloon would have begun transmitting again sometime later in the Yukon afternoon when the sun was stronger, but no transmissions have been seen.

Over on Twitter @ikluft (KO6YQ) has been reporting on this speculation, and has been keeping an eye on K9YO-15, awaiting telemetry transmission. We recommend following his account for further updates.



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Originally Posted By Procta⏩