Geodetic Observatory Wettzell
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The Geodetic Observatory Wettzell is located atop the 616 meter-high mountain Wagnerberg, west of the village Wettzell in the German district Cham in the Bavarian Forest.


Tasks

It is operated for the purpose of geodesy by the
Federal Agency for Cartography and Geodesy The Federal agency (Germany), Federal Agency for Cartography and Geodesy (german: Bundesamt für Kartographie und Geodäsie, links=no, BKG) is Germany's national mapping agency. It is located in Frankfurt, with a branch in Leipzig. It operates t ...
together with the Technical University of Munich and is today one of the most important geodetic observatories in the world. As observing station, the Geodetic Observatory Wettzell has the task of gathering measuring data for the geodetic space techniques VLBI, SLR, GNSS and DORIS. These data are used for realizing global coordinate reference systems that form the basis for numerous issues in the field of geosciences (e.g. continental drift, sea level rise), in aerospace, but also in areas of everyday life (e.g. surveying, navigation). These global tasks can today only be solved through international cooperation. The activities like observations, data flow, data analysis and provision of results are coordinated by the international services of the IAG, e.g.
IERS The International Earth Rotation and Reference Systems Service (IERS), formerly the International Earth Rotation Service, is the body responsible for maintaining global time and reference frame standards, notably through its Earth Orientation Pa ...
, IVS (International VLBI Service), ILRS (International Laser Ranging Service), IGS (International GNSS Service) and IDS (International DORIS Service). The Federal Georeference Data Act (German: ''Bundesgeoreferenzdatengesetz'') is the legal basis for that. Wettzell also supports the operation of the observatories AGGO in
La Plata La Plata () is the capital city of Buenos Aires Province, Argentina. According to the , it has a population of 654,324 and its metropolitan area, the Greater La Plata, has 787,294 inhabitants. It is located 9 kilometers (6 miles) inland from th ...
/ Argentina and GARS O'Higgins in Antarctica.


Measurement equipment

At the site with an approximate size of 300 by 150 meters, you find all modern observation techniques of satellite or space geodesy and complementary measuring techniques, especially * a
laser telescope A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The firs ...
for ranging to satellites and the moon (WLRS) * a
laser telescope A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The firs ...
for distance measurements to low-flying satellites with high temporal resolution (SOS-W) * a 20 m
radio telescope A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...
for intercontinental VLBI measurements (RTW) * a twin system consisting of two 13 m
radio telescope A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...
s, also for VLBI measurements (TTW-1 and TTW-2) * several Multi- GNSS receivers for continuous satellite measurements * a high-precision time system with several atomic clocks and hydrogen masers and a fibre-optic time distribution system with delay compensation * a ring laser in an underground observatory for monitoring the
Earth's rotation Earth's rotation or Earth's spin is the rotation of planet Earth around its own Rotation around a fixed axis, axis, as well as changes in the orientation (geometry), orientation of the rotation axis in space. Earth rotates eastward, in retrograd ...
* a beacon for the French Doppler system DORIS * a superconducting gravimeter * complementary measuring equipment for ground and atmosphere monitoring (seismometer, tiltmeter, hydrological sensors, climate station, water vapour radiometer, temperature profiler, cloud detector) * and facilities for administration and maintenance. The reference points of the single measuring systems are linked by a local surveying network in order to obtain coordinate differences for a combination of the different techniques. This characteristic determines a geodetic fundamental station.


History

The Geodetic Observatory Wettzell was founded nearby the former
Iron Curtain The Iron Curtain was the political boundary dividing Europe into two separate areas from the end of World War II in 1945 until the end of the Cold War in 1991. The term symbolizes the efforts by the Soviet Union (USSR) to block itself and its s ...
to former Czechoslovakia and to Germany's Air Defense Identification Zone in 1970 in order to have a night sky as dark as possible with only low light pollution and have to take little consideration of air traffic for Satellite and Lunar Laser Ranging. The beginnings of the satellite observing station Wettzell go back to an early research project of the Technical University of Munich and the
Institute for Applied Geodesy An institute is an organisational body created for a certain purpose. They are often research organisations (research institutes) created to do research on specific topics, or can also be a professional body. In some countries, institutes can ...
for optical observation and orbit determination of geodetic Earth satellites. The field of satellite geodesy newly arisen at that time promised great progress for global geodesy. The optical observations carried out until the end of the 1970s included images of satellite passages with the ''Zeiss Double Astrograph'' and the ballistic measuring camera ''Zeiss BMK 75'' for satellite triangulation and observations with a circumzenithal and the ''Danjon
Astrolab An astrolabe ( grc, ἀστρολάβος ; ar, ٱلأَسْطُرلاب ; persian, ستاره‌یاب ) is an ancient astronomical instrument that was a handheld model of the universe. Its various functions also make it an elaborate inclin ...
'' for astronomical longitude and latitude determination. In cooperation with the German Test and Research Institute for Aviation and Space Flight (DFVLR, today's DLR), a first laser distance measuring system consisting of an
anti-aircraft Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...
gun carriage A gun carriage is a frame and mount that supports the gun barrel of an artillery piece, allowing it to be maneuvered and fired. These platforms often had wheels so that the artillery pieces could be moved more easily. Gun carriages are also used ...
and a ruby laser, was put in operation in 1972. With that, on 8 April 1973, the distance to a satellite (GEOS-1) was measured for the first time in Germany by laser. But only with the following, computer-adjusted systems SRS (Satellite Ranging System, 1977–1991) and WLRS (Wettzell Laser Ranging System, since 1991) large numbers of routine observations became possible. In addition, distances to the reflectors located at the moon were already measured with the WLRS. In the mid-seventies, the station was extended by microwave measuring techniques. Since 1974, Doppler measurements to satellites of the “Navy Navigational Satellite System” (N.N.S.S. or Transit) were performed regularly for point determination in geodesy. The first measurements to the satellite navigation system NAVSTAR GPS were already performed during the test phase 1979–1981 with Wettzell as one of four tracking stations worldwide. In 1993 the Doppler measurements ended, after the N.N.S.S. was replaced with the full development of GPS. With implementing a
radio telescope A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...
in 1983, the satellite observation station turned into a fundamental station of geodesy, where the various space geodetic techniques VLBI, SLR and GNSS are combined in one place. Since 2012, the observatory has two further so-called twin telescopes, in order to take account of technical progress and the increasing observation tasks. ''Die Arbeiten des Sonderforschungebereiches 78 Satellitengeodäsie der Technischen Universität München'', Astronomisch-Geodätische Arbeiten, issues 32–48.


See also

* List of astronomical observatories


References


External links


Geodetic Observatory Wettzell (in German)

Flyer “Geodetic Observatory Wettzell”

Friends' association “Geodetic information centre Wettzell” (in German)
{{Portal bar, Germany, Astronomy, Stars, Spaceflight, Outer space, Solar System, Education, Science Radio telescopes Astrometry Astronomical observatories in Germany Cham (district) Buildings and structures in Bavaria Geodesy organizations