A radiosonde is a group of instruments for simultaneous measurement and radio transmission of meteorological data, including temperature, pressure, and humidity of the atmosphere. It is usually carried into the upper atmosphere by balloon. As it travels upward, it transmits meteorological measurements to ground stations. Radiosondes measure temperature with a thermometer, humidity with a hygrometer, and air pressure with a barometer. Radiosondes are attached to helium-filled neoprene balloons that are designed to burst when they reach a specified altitude. They can operate up to around 100,000 feet (30,000 meters).
Radiosondes’ advantage over other types of meteorological instruments is that they do not have to be returned to Earth for their data to be retrieved.