MODEL RELEASED. Weather balloon. Meteorologist launching a weather balloon at night. The balloon,which is made of rubber and filled with helium,carries aloft a radiosonde. A group of instruments for measurement and radio transmission of meteorological data,including temperature,pressure and humidity. As the balloon gains altitude,and the local pressure drops,the balloon expands. Eventually,at around 35,000 metres,the balloon bursts and the radiosonde is returned to Earth by a small parachute. Although helium is used for night launches,hydrogen gas is used during the day. Photographed at the Arctic Research Centre,Sodankyla,Finnish Lapland |