Transosonde

an automatic aerostat equipped with scientific apparatus and designed for prolonged horizontal flights in the upper troposphere and the stratosphere.

A transosonde consists of a helium-filled plastic envelope from which are suspended an instrument payload, a programmed control device, radio and navigational equipment, and electric power supplies. Transosonde measurements are transmitted to the earth by means of an ultrashort-wave transmitter either directly or by relay through an artificial earth satellite. In flight the geographic coordinates of a transosonde are determined by means of ground-based or satellite-based direction finding; in some types of transosondes, direction finding is carried out with an onboard autonavigator. The flight altitude of a transosonde may be constant or be varied by signals from the ground or an onboard programmed control unit. A portion of the gas is released from the envelope to make a transosonde descend, and solid or liquid ballast is jettisoned to make the transosonde ascend. A transosonde may remain aloft for up to several tens of days and may make several revolutions about the earth. In September 1968, an American transosonde with an envelope having a volume of 810,000 m³ reached an altitude of 48,160 m.

Transosondes are used to study planetary-scale atmospheric processes—for example, air currents—over otherwise inaccessible regions, such as Antarctica and the oceans, and to collect data on atmospheric radioactivity and the gaseous and aerosol composition of the air. Several transosondes are usually launched from a given point for simultaneous measurements at different altitudes.