Radiosonde
A radiosonde is used in meteorology and Aerology for measuring parameters of the Earth's atmosphere at altitudes of about 20 to 30 km ( stratosphere ). It is supported by a weather balloon and transmits the measured values ( air temperature and its gradient, vapor pressure, winds aloft, etc.) wirelessly to a ground station. The amount of provision is usually by continuous measurement of the air pressure and GPS.
Balloon -borne probes are also used in other disciplines - see the balloon probe (measuring instrument) that reach even greater heights in part. The altitude record for radiosondes is about 39 km or 2.5 hPa ( German Weather Service ).
History
Since the early 1890s contributed unmanned weather balloons self-registering instruments in the free atmosphere. Compared with manned ballooning this had a significant cost advantage. Moreover heights were reached, which were not accessible to people in an open basket despite oxygen supply. The measured values could be read but only delayed, and even if the floor has returned to the instrument has also been found. One of the pioneers of the atmosphere probing with weather balloons was the German meteorologist Hugo Hergesell. As head of the International Commission for Scientific Aeronautics, he called for the construction of lighter balloon USEFULLY instruments. The potential of wireless telegraphy early knowing he introduced as early as 1908 attempts at transferring records -registering balloon instruments via radio, but failed because of the still insufficient technological possibilities. The name " radiosonde " goes back to Hergesell.
In 1917 it succeeded Max Robitzsch and send Herath Friedrich ( 1889-1974 ) in Germany and Pierre Idrac ( 1885-1935 ) in France, readings from instruments which were mounted on weather dragons on the dragon wire to the ground. But dragons you could not bring in the achievable level of weather balloons, and they were not used in any weather.
1921 Paul began Duckert ( 1900-1966 ) at the Aeronautical Observatory Lindenberg, whose head was now Hergesell to deal with the development of the radiosonde. A first step was 1926 Doppelanpeilung a balloon attached to the radio transmitter to determine its trajectory and speed. Similar experiments were also performed by William Blair in the United States. At the end of the 1920s, several meteorologists worked with first prototypes of radiosondes.
On January 7, 1929, succeeded Robert Bureau ( 1892-1965 ) in Trappes first time, to receive the signals of a radiosonde, provided the temperature values from the free atmosphere. In the spring of the same year he completed the probe to a barometer. As the inventor of the radiosonde but the Soviet meteorologist Pavel Molchanov (1893-1941) is often regarded, the first time on January 30, 1930 successfully launched radiosonde became the standard for future development. The probe measured temperature and pressure and radioed the values encoded as a Morse code to the receiver. On May 22, 1930 Duckert followed with an independently developed probe in addition to temperature and pressure could also measure the humidity. The probe sent readings to the bursting of the balloon to over 15 km altitude.
On the Arctic voyage of Zeppelin LZ 127 Molchanov launched several radiosondes in July 1931. For an extensive and systematic use of new technology, it came during the International Polar Year 1932 / 33rd The Finn Vilho Väisälä, who had started his first radiosonde on December 30, 1931, began in 1936 with commercial production.
A further development in the radiosonde in 1942 by the Berlin Josef Graw. The conversion of the measured values in Morse characters made in the Graw probe by the fact that the pointer of the measuring devices, a pattern scanning of conductive material that is applied to a rotating roller, the roller Grawsche Morse.
Technology
Probe to the radiosonde measure temperature, pressure and humidity as the balloon rises into the air. Periodically, the collected data is sent by radio ( in Germany at about 400 MHz) to the ground station.
The probes are housed for thermal insulation in a foam -polystyrene housing, the outside are only a wire antenna and sensors. The probe consists of at least a battery, sensors for pressure ( barometric height measurement), temperature, humidity, etc., and a telemetry transmitter.
The displays shown at right sensor and encoding part of a radiosonde (DDR, 1960 )
- Temperature sensor (top, bimetal)
- Pressure cell ( left under the metal bracket )
- Time base ( pocket watch movement, far right)
- Encoder for temperature and humidity (red PVC cylinder with contact wire helical )
- Encoder for air pressure ( Pertinax bar with contact strips, right behind the cylinder )
The humidity sensor ( hair hygrometer ), the battery and the telemetry transmitter ( UHF transmitter tube with a triode) are not seen in the picture.
Today Vaisala SGPD disposable radiosondes are used, a finder's fee will be paid only for ozone sondes. In the GDR times, a finder's fee of five marks was paid. A radiosonde ascent costs with wasserstoffgefülltem balloon and radiosonde today about 300 € and with a 1.8 m³ helium fill about 400 €.
The position of a radio probe can be determined by radar, this is helpful to determine the wind direction of the upper winds, which in turn is immensely important in the weather forecast. The probe shall make a due to the low weight of existing with reflective foil coated paperboard radar reflector which reflects the transmitted radio waves again and thus allows conclusions to the position. Current radiosondes use for position determination, however, a GPS receiver, whose raw data transmitted by radio and are translated at the receiving station to the position. Other modern radiosondes work with a full GPS receiver whose processed position data are transmitted directly.
The MeteoSwiss respectively. the Swiss army does not use GPS bearing for their weather probe SRS400. The reasons for this are that the radar - bearing is more accurate than the GPS bearing and one is not dependent on the GPS operators. Whether or not but sometime GPS will prevail, is still uncertain.
The probe to slide on a parachute to the ground. However, it has been found that the small parachute usually of little use and is often tied with the strings and not deployed. It is said that it must be used for insurance purposes anyway.
Special ozone probes can also measure the ozone concentration. These data are necessary for the observation of the ozone hole.
Regular soundings
Many stations can be every twelve hours a probe rise, mostly noon and midnight. In Germany this is done at twelve stations ( three of which are fully automatic). The previous probe at this time is usually no longer active, ie already on the ground.
Thus, the probe can fly at all, a large helium -filled flaccid or hydrogen balloon made of latex is attached to it. With increasing altitude, the balloon is getting plumper by the decreasing air pressure and finally bursts, since the gas has expanded to a multiple of the volume inside the ground.
Now the probe begins to fall back to Earth. So they do not just hitting the floor, it is often equipped with a small parachute.
" Probe hunter "
Some people make the fun and trouble to observe the flight of the probes to track them and pick up after falling down as possible. Partly it comes to downright head-to -head race this so-called probe hunter.
In the evening light the probes appear as a bright star first size, sometimes as bright as Venus. In binoculars the balloon shape is usually seen as the moment of bursting ( 20-30 km in height) and the reduced floating parts.
The distance from the starting point of a radiosonde for landing point is an average of about 100 km, but can reach up to 300 km. For the probe hunting a good knowledge about radio and direction finding is useful because there are many difficulties (reflections of the radio waves to trees, buildings, etc. ).
Radio probes on other planets
The Soviet spacecraft Vega sat two radiosondes from 1984 in the atmosphere of Venus, which could be followed over a two day period.