The Amazing Technology Of Pico Balloons

If there was anything good about three or four days of obsessing over unidentified balloons last weekend, it’s that we all learned about a fascinating niche of amateur radio that marries tiny radio transmitters to featherweight hydrogen balloons capable of sailing around the globe—sometimes many times.

In this hour-long video—really a published Zoom conference—radio amateur Brian Basura explains the fascinating hobby of pico ballooning, a unique marriage of physics, meteorology, electronics and radio communication. The sport came to light when an Illinois-based pico club revealed that one of its balloons was in the same area that an F-22 shot down an unidentified flying object on Feb. 11. The Northern Illinois Bottlecap Balloon Brigade isn’t claiming its pico was splashed by the Raptors, but the coincidence suggests that it could have been.

So what is a pico balloon? (That’s pronounced pee-coh, not pye-coh, and refers to the size of the thing: small.) As Basura explains, a pico balloon is an ultra-lightweight plastic balloon suspending a tiny, lightweight amateur radio transmitter. The envelope is filled with a breath of hydrogen, which is used in place of helium because it leaks less. The balloon has a free lift capacity of about 15 or 16 grams—a little over half an ounce. When launched, it appears to be barely inflated but expands to a larger sphere when it reaches planned stasis altitude of about 40,000 feet. Basura explains that the difference between too little inflation and too much is barely a squirt of hydrogen. It’s determined by careful weighing on a gram scale.

The electronics package, which dangles under the balloon on a light filament, is called the tracker. It consists of a transmitter, a GPS chip and a small computer with programing instructions. Total weight? Just under a half ounce, including a light solar array to power the system. The device trails a long dipole antenna made of 0.005-inch fine wire.

Pico balloons communicate through various protocols, but two popular ones are called APRS and WSPR. The Automatic Packet Reporting System is a kind of single-frequency network system that allows any ham to check on local activities in that region. There are numerous APRS nets in the U.S. and many countries have some version of it. In the U.S., it operates on 144.39 MHz in the 2-meter band, but on different frequencies elsewhere in the world so the transmitters have to be smart enough to adapt. The balloon trackers transmit continuously when the sun is up to energize their solar arrays and report position, altitude and other parameters that the bandwidth allows. APRS is integrated with the internet.

So is WSPR or Weak Signal Propagation Reporting, pronounced whisper. It’s a software protocol designed for sniffing out very low-powered one-way signals. It has miniscule bandwidth and reports station power and position by grid reference. With WSPR, it takes 110 seconds to transmit 50 characters at 1.46 baud. That might be so 1970s, but it gets the job done with the low-powered transmitters pico balloons have. Some countries don’t allow transmissions from balloons, so picos following the rules have to be emissions geo-fenced. And by the way, pico balloons, by dint of their light weight, are exempt from 14 CFR 101 that regulates balloons. Picos typically transmit at about 10 milliwatts—1/50^th the power of a Christmas tree light. Still, explains Basura, transmit distances of up to 5000 miles have been achieved and 1200 to 2000 miles are routine.

Success with a pico balloon is anything but. Sometimes they never reach altitude or don’t survive the first night. They can develop leaks and sink out of the stratosphere or just disappear without a trace. On the other hand, when this video was recorded last April, Basura had been tracking one of his balloons for 51 days and 4.5 global circumnavigations. Not bad. This site tracks known pico launches, but doesn’t claim to be complete.

Pilots naturally wonder if pico balloons represent a threat to aircraft. Politics being what they are, the Pentagon thought so and ordered three of what may or may not have been pico or research balloons shot down. The first question to ask, however, is are standard NOAA radiosondes a threat because they’re 30 times heavier and far more numerous? In the conterminous U.S. alone, some 138 are launched daily from 69 sites. The little Styrofoam box containing the hardware weighs about 17 ounces, max. It has a parachute and a return address.

No crashes have been caused by aircraft/weather balloon collisions in the U.S., but one was recorded in Russia in 1970 when an AN-24 airliner collided with a radiosonde just after takeoff. There were no survivors. The size of the radiosonde doesn’t appear in accident reports.

For amazing as pico technology is, just as astonishing is that U.S. radar can find such a thing and an AIM-9X can target it and bring it down.

If, indeed, that actually happened.