Overall, Earth’s atmosphere is divided into five layers based on properties such as barometric pressure, temperature, and composition, consisting primarily of nitrogen and oxygen. The stratosphere extends between 15 and 50 kilometers above the Earth’s surface, it is also called near space. The stratosphere contains the vital ozone layer, where ultraviolet radiation is absorbed and converted into heat.
Below that is the troposphere, which contains almost all of the water in the atmosphere. Clouds also form in this layer, daily weather occurs at this altitude. The troposphere has different heights – at the poles it is lower by about seven kilometers. Air travel also takes place in the troposphere, at an altitude of about ten to twelve kilometers.
ORF/Sandra Schober Weather or surveillance balloons usually move in the stratosphere
After the stratosphere, the very cold (down to -180 degrees Celsius) mesosphere begins at about 50 kilometers and the very hot thermosphere (up to 1,500 degrees) after about 85 kilometers. From 500 kilometers onwards, the upper layer of the atmosphere and the boundary of space, the exosphere, follow.
1,800 weather balloons launched daily
Flying objects such as balloons fly at a height of up to 36 kilometers, that is, in the stratosphere. Weather balloons are particularly common. According to the US Weather Service, a weather balloon is launched twice a day from 900 locations around the world, which is more than 600,000 annually. About 20 percent of measuring instruments are salvaged.
During the ascent, the weather balloon, which is filled with hydrogen or helium, expands up to 15 meters due to the decrease in air pressure. When the balloon finally pops, the attached radiosonde flies back to the ground with a parachute. Weather balloons must be registered before taking off to ensure they don’t disrupt air traffic – in Austria this is done by Austro Control.
GeoSphere Austria/Daniel Auer Important data can be collected in the stratosphere with the help of weather balloons
With the help of radiosondes, balloons transmit data on air pressure, temperature and humidity, for example, built-in GPS transmitters also make it possible to calculate the direction and speed of high-altitude winds. However, other scientific measurements such as turbulence, energetic particles from space and the electrical charge of clouds can also be recorded with modified weather balloons.
The data obtained is shared internationally, which makes it possible to create weather forecasts, for example – and the data is also an important indicator of global warming for climatology. The Federal Institute of Geology, Geophysics, Climatology and Meteorology (Geosfera Austria) also raises a weather balloon twice a day on the Hohe Warte in Vienna.
the wind problem
Unlike weather balloons, which only travel for a relatively short time, spy and surveillance balloons can also move in the atmosphere for several weeks. These balloons are usually equipped to record ground images or receive electronic communications and information.
The same technology used in satellites could also be used in balloons, Stilianos Vidalis, deputy head of computer science at the University of Hertfordshire, told the Financial Times (“FT”). Unlike satellites in high orbits, balloons offer the advantage that the data transmission time to the ground is significantly shorter. They are also significantly cheaper than satellites.
APA/AFP/Loren Elliott balloons are also used for surveillance, like this balloon in 2018 at the US-Mexico border
One drawback, however, is that balloons are at the mercy of strong winds. Even if the winds can be predicted, it can happen that the trajectory of a balloon is miscalculated. Comparing the trajectory of an airplane, it is easy to see that balloons follow much more turbulent routes.
Too much “heavenly garbage”?
In addition to governments and research institutions, private companies also send balloons and flying objects into the stratosphere. Until two years ago, Google, for example, sent hundreds of self-navigating balloons into the atmosphere to beam internet to rural areas.
For the “Loon” project, balloons were built that could rise and fall to catch a favorable wind. In 2021, the project was discontinued for financial reasons and partially sold. On the Flightradar24 website, where aircraft can be tracked, there is even a dedicated icon for balloons – this also made the Google balloons visible.
How much “heavenly junk” is moving through the atmosphere right now? A lot, Brad Tucker, an astrophysicist and astronomer at the Australian National University, told the Guardian. It could be anything that went up on purpose, like balloons and high-flying drones, but also junk like plastic bags and party balloons that got caught in the chains.
At the same time, the amount of flying objects lost in the stratosphere cannot be compared with the amount of space debris floating around in the orbit of disused satellites.