The idea of using balloons to aid in the study of the atmosphere was first explored by the French when, in 1784, a hot air balloon was used for this purpose. It took a long time, however, before the practice came into common use. More commonly thought of as a “weather balloon,” radiosondes (“sonde” is French for “probe”) are collections of weather-detecting instruments attached to a balloon that is released into the upper atmosphere. They were first used in Europe during the 1920s and 1930s. Radiosondes typically measure temperature, moisture, and wind speeds, and they often include small, battery-powered motors. More modern radiosondes—called “rawinsondes”—include a radar reflector so they can be more easily tracked.

Radiosondes reach elevations that can take them into the stratosphere. Once it reaches its maximum height, the balloon will burst and the instrument package will be carried safely down on a parachute. Another way to deploy a radiosonde is by dropping it from an airplane. When this is done, the device is called a dropsonde. Rocketsondes—weather probes mounted on rockets, as one might guess—may also be used on occasion. There are over 800 radiosonde launch sites around the world, with the probes being launched at midnight and noon. Data is generally shared by meteorologists around the world.