Modern meteorology depends hugely on radiosondes, and hundreds of these balloon-borne instrument packages are released daily from weather stations all over the world. The sonde collects data up to a height of 18 miles (30 km), while being tracked in position using radar. The real-time data is continuously transmitted back to Earth by radio and the position of the sonde as time passes indicates the wind speed. Rising at the rate of about 0.2 miles (0.3 km) per minute, the flight usually takes about two hours.
Silk weather balloons were first used to collect data in 1892 by the French scientist Gustave Hermite. In 1901 these were replaced by sealed rubber balloons. These burst when they reached a height of 12 miles (20 km), and the instrument package parachuted to the ground. The rest was left somewhat to chance because the flight records were picked up when, or if, someone happened to find them.
Military requirements during World War I stressed the need for more instant data. But the radiosondes' requirement of a cheap, low weight, reliable radio system and a transducer that could convert the recorded temperature, pressure, and humidity into radio signal modulations had to wait until 1930. The Russian Pavel Molchanov (1893-1941) is generally credited with the development of this system, and the instrument was quickly adopted by the meteorological offices of a number of countries.
Modern neoprene balloons burst when the ambient pressure falls to about 10 millibar, this being at a height of around 23 miles (37 km). The weight of the whole package is a few pounds.
