Dave Akerman

In light of the intense recent interest in what hitherto was an almost unknown hobby, I thought it would be a good idea to answer some questions and correct some misunderstandings that I’ve seen in social media lately.

So was an “pico balloon” shot down by an F22?

The circumstantial evidence very strongly suggests that this is the case. One of these balloons has not been seen on the amateur tracking map since the USAF shot down an object matching the description in the area that the balloon was known to be. It was launched in the USA in October 2022 and was about to complete its 7’th circumnavigation of the globe before it went missing from the tracking map.

And what are “pico” balloons?

This is the name given to them by the high altitude balloon community. They are small, plastic (often silvered) balloons, with very light payloads of the order of 10-20 grams. By using plastic with a small amount of helium, instead of bursting they float near the top of the troposphere, for days or sometimes months.

Are these a new thing?

No, they’ve been flown for several years now. What appears to have happened (this is conjecture, not necessarily fact) is that after the Chinese balloon was shot down over the Atlantic, RADAR settings were adjusted to look for other balloons of the same sort. Since pico balloons have several properties that match those balloons – slow moving, high altitude, not ascending/descending – and because the silver coating makes for a very good RADAR reflector, then they would very likely show up with such filtering.

Are they legal?

Yes. They are legal to launch and it is legal for them to fly over other countries for meteorological purposes.

Do launchers need permission for pico balloons?

No, for launches from the USA or Europe (other territories may have different rules). The rules vary across territories, but pico balloons are small and lightweight and this generally excludes them from the rules pertaining to larger/heavier balloons. If you wish to launch any balloon anywhere, check your current local regulations and don’t rely on what I said here being correct.

What about other types of amateur balloon?

The majority of amateur flights use latex balloons, and these flights differ from pico flights in several ways. First, they do burst, typically within an hour or two of being launched. A typical latex flight will take around 90-120 minutes to ascend, and 30 minutes or so to descend, so the overall flight time is measured in hours instead of months. These balloons expand as they ascend, starting at 1-2m diameter at launch, bursting at 7-11m diameter at an altitude of 30-40km. Also, they ascend very quickly, with the majority of the flight time being well above aircraft altitudes.

In the UK, such flights do need permission and a NOTAM, but as I understand it permission is not required in the USA for flights under 4 lbs. In the UK we apply to the CAA with at least 28 days notice, during which time the CAA check the requested launch location for nearby airports, flight paths and other airborne activities. They then issue the launcher a permission/exemption certificate, which depending on the launch location may stipulate only launching with certain wind directions, and/or may require coordination with local ATC (Air Traffic Control). The CAA also issue a NOTAM (Notice To Air Missions) so that pilots know in advance of the activity. Again I should stress, if you wish to launch any balloon anywhere, check your current local regulations and don’t rely on what I said here being correct.

Is there a benefit of amateur balloons?

Very much so. There’s a huge benefit in STEM education at schools and universities, with balloon projects increasing interest in science and engineering. In the UK I have seen many school students who started with their own balloon flight, then used their experience and knowledge to get into a top university, and then move on to jobs in the space industry which, in the UK alone, was worth £16.5 billion in 2019/20.

Do these balloons carry GPS trackers?

Yes; there’s no point in launching one if you can’t track it. A tracker contains a GPS receiver so that the balloon’s position is known, and small radio transmitter to relay this position to the ground. The radio communication includes the balloon callsign so that we know which balloon is where.

Receivers around the world receive these transmissions and feed the balloon data to one or more maps, one of which (Sondehub/amateur) collates data from the other maps, so is a single point of reference for the vast majority of amateur balloons.

Is it just amateur balloons up there?

No. The vast majority of high altitude balloons are weather balloons, launched by meteorological offices several times a day from locations around the world. Compare the approx 1800 such balloons launched every day with maybe 1-200 amateur launches per year. Balloons are also launched by the likes of NASA and SpaceX prior to rocket launches, and by universities, companies and space agencies for research purposes. Some of the latter are very large, as the Chinese balloon was, and stay aloft for months.

Are those weather balloons tracked?

The launchers track their own balloons, but don’t make their positions publicly available. However, there is an amateur network of receivers that connect to the Sondehub system.

Why don’t balloons carry ADS-B transponders like aircraft?

Weight and cost. Weight would make pico balloons impossible, and cost would mean that amateur flights would essentially cease, with only commercial outfits able to meet the cost spread over a number of flights.

Not every aircraft carries ADS-B anyway. For example in the UK gliders and small aircraft typically carry FlARM or OGN trackers.

So if there’s an object in the sky, how to know what it is?

Check the maps for aircraft, amateur balloons or met office weather balloons. It wouldn’t be beyond the wit of man to integrate these into a single map to save time; in fact the Sondehub system already has data feeds set up for amateur and met office balloons, ready for such integration.

Any other comments?

This hobby has been operating quietly, legally and safely for decades now until an errant (or otherwise) foreign balloon was seen over USA soil. Leaving aside the immediate result of a $100 balloon project apparently being prematurely ended by a pair of $400,000 missiles, we now have the very real risk of the hobby being curtailed or even ended completely in the USA and beyond. I was quoted last week by the Washington Post that I feared “a knee jerk reaction” and sadly it looks like this might happen.

Let’s hope that common sense prevails.