<P> The balloon is usually filled with hydrogen due to lower cost, though helium can also be used . The ascent rate can be controlled by the amount of gas with which the balloon is filled . Weather balloons may reach altitudes of 40 km (25 miles) or more, limited by diminishing pressures causing the balloon to expand to such a degree (typically by a 100: 1 factor) that it disintegrates . In this instance the instrument package is usually lost . Above that altitude sounding rockets are used, and for even higher altitudes satellites are used . </P> <P> Weather balloons are launched around the world for observations used to diagnose current conditions as well as by human forecasters and computer models for weather forecasting . About 800 locations around the globe do routine releases, twice daily, usually at 0000 UTC and 1200 UTC . Some facilities will also do occasional supplementary "special" releases when meteorologists determine there is a need for additional data between the 12 - hour routine launches in which time much can change in the atmosphere . Military and civilian government meteorological agencies such as the National Weather Service in the US typically launch balloons, and by international agreements almost all the data are shared with all nations . </P> <P> Specialized uses also exist, such as for aviation interests, pollution monitoring, photography or videography and research . Examples include pilot balloons (Pibal). Field research programs often use mobile launchers from land vehicles as well as ships and aircraft (usually dropsondes in this case). In recent years weather balloons have also been used for scattering human ashes at high - altitude by companies such as Stardust Ashes, founded by Chester Mojay - Sinclare . </P> <P> The Weather balloon was also used to create the fictional entity' Rover' during production of the 1960s TV series' The Prisoner' in Portmeirion, Gwynedd, North Wales, UK in September 1966 . This was retained in further scenes shot at MGM Borehamwood UK during 1966 - 67 . </P>

Where do weather balloons fly in the atmosphere