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Superconducting Gravimeter Data from Helgoland - Level 1

The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy IAG. IGETS continues the activities of the Global Geodynamics Project (GGP) between 1997 and 2015 to provide support to geodetic and geophysical research activities using superconducting gravimeter (SG) data within the context of an international network. As part of this network, the Helgoland Gravimetric Observatory Germany (HELGOG) was established by the GFZ German Research Centre for Geosciences in March 2020. Continuous time-varying gravity and atmospheric pressure data from the iGrav SG at HELGOG are integrated in the IGETS data base hosted by GFZ. HELGOG is located in the basement of the Biological Institute Helgoland (BAH) of the Alfred Wegener Institute (AWI), Helmholtz Centre for Polar and Marine Research. The operation and maintenance of the HELGOG instrumentation is jointly done by staff of AWI and GFZ. The iGrav SG is directly installed on the concrete floor of the basement. The distance from the iGrav SG to the North Sea is only 10 m. Being located at sea level (H=2.059 m), the iGrav SG is predominantly sensitive to vertical displacements. Helgoland is Germany’s only island in the open sea 50 km away from the mainland. The gravimetric observations enable the analysis of ocean tides and non-tidal mass redistributions, especially in connection with storm surges in the North Sea (see also Weise et al. 2020). Next to the iGrav SG, there is space for absolute gravimeters (first measurements in July 2020 by Ludger Timmen from Leibniz Universität Hannover) and other instruments. The nearby continuous Global Navigation Satellite Systems (GNSS) stations HELG and HEL2 are operated by BKG (Federal Agency for Cartography and Geodesy). HELGOG is also part of the Observation Platform Helgoland including seismometers, infrasound, spring gravimeters and tiltmeters. HELGOG is equipped with the iGrav SG 047 manufactured by GWR Instruments. The time series of gravity and barometric pressure from the iGrav SG 047 starts in March 2020. The SG is active and the time series is kept up to date regularly with a time delay of a few months. The time sampling of the raw gravity and barometric pressure data of IGETS Level 1 is 1 second and 1 minute. For a detailed description of the IGETS data base and the provided files see Voigt et al. (2016, http://doi.org/10.2312/GFZ.b103-16087).

Superconducting Gravimeter Data from Sutherland - Level 1

The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy IAG. IGETS continues the activities of the Global Geodynamics Project (GGP) between 1997 and 2015 to provide support to geodetic and geophysical research activities using superconducting gravimeter (SG) data within the context of an international network. As part of this network, the South African Geodynamic Observatory Sutherland (SAGOS) was established by the GFZ German Research Centre for Geosciences during the years 1998 and 2000 based on an Agreement on Cooperative Activities between the National Research Foundation (NRF) and GFZ signed in August 1998. Continuous time-varying gravity and atmospheric pressure data from the SGs at SAGOS are integrated in the IGETS data base hosted by GFZ.The SAGOS observatory is located at the site of the South African Astronomical Observatory (SAAO) approximately 350 km northeast of Cape Town (longitude: 20.81 E, latitude: 32.38 S, height above MSL: 1755 m). The operation and maintenance of the SAGOS instrumentation is jointly done by staff of SAAO and GFZ. The shortest distance to the South Atlantic coastline is approximately 200 km. The area is located in a tectonically quiet zone far away from the African rift. Geologically, the setting is a huge dolerite plateau with a several kilometres thick layer of dolerite. This bedrock allows a good coupling of the SG pillars to the ground. The environment is a remote area with no industry and low seismicity. The climate at this place is determined by the border between summer and winter rainfall zones so that temperature fluctuations are not too rough. The observatory is built into the ground to protect it against environmental effects like strong winds and temperature changes. All rooms are thermally insulated. An air-conditioning system controls the temperature inside the measurement chamber, which is equipped with three concrete pillars embedded into the dolerite bedrock. Two of the pillars are constructed for SGs or other geophysical instruments. The third pillar is dedicated for absolute gravimeters for the calibration of the SGs. In the vicinity of the observatory four further pillars were set up for various other geodetic antennas and instrumentation.SAGOS is a high precision geodynamic observatory comprising space techniques and ground instruments. Presently, the observatory is equipped with one SG manufactured by GWR Instruments (SG D037). The second SG operating in parallel until September 2017 was installed at mountain Zugspitze in September 2018 (Voigt et al. 2019, http://doi.org/10.5880/igets.zu.l1.001). The time series of gravity and barometric pressure from the dual sensor gravimeter SG D037 starts in February 2000 and is interrupted from July 2008 to November 2009 due to an upgrade of the electronics package. The time series of SG 052 begins in August 2008 and ends in September 2017 without interruption. The SG D037 is active and the time series is kept up to date regularly with a time delay of a few months. The time sampling of the raw gravity and barometric pressure data of IGETS Level 1 is 1 minute. Starting in January 2016, raw data with a time sampling of 1 second is provided additionally. For a detailed description of the IGETS data base and the provided files see Voigt et al. (2016, http://doi.org/10.2312/GFZ.b103-16087).In addition, SAGOS is equipped with auxiliary data supporting the interpretation of the SG measurements, which is, however, not provided in the IGETS data base due to their complexity. These are a local network of hydrological and meteorological sensors as well as a permanent GNSS (Global Navigation Satellite Systems) station as a core station of the International GNSS Service (IGS) with the ID SUTM.

Superconducting Gravimeter Data from LNE-SYRTE Trappes - Level 1

The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy. IGETS continues the activities of the Global Geodynamics Project (GGP) between 1997 and 2015 to provide support to geodetic and geophysical research activities using superconducting gravimeter (SG) data within the context of an international network. As part of this network, the Trappes station (code TR) was established in 2013 by LNE-SYRTE. Continuous time-varying gravity and atmospheric pressure data from TR are integrated in the IGETS data base hosted by ISDC (Information System and Data Centre) at GFZ. LNE-SYRTE is responsible for primary metrology missions of gravimetry in France. The gravimetry laboratory is located at 30 km at the West of Paris (longitude: 1.98 E, latitude: 48.76 N, height above MSL: 170 m) [Merlet et al. 2008, doi:10.1088/0026-1394/45/3/002] in the French National Metrology Institute LNE-Trappes. It has been designed to accommodate other gravimeters for metrological comparisons tests and calibrations and is located close to the LNE Kibble Balance for which an absolute value of g is needed [Thomas et al. doi.org/10.1088/1681-7575/aa7882]. For that purpose an absolute quantum gravimeter has been developed [Louchet-Chauvet et al. 2011, doi:10.1088/1367-2630/13/6/065025, Karcher et al. 2018, doi.org/10.1088/1367-2630/aaf07d]. To evaluate its long term sensitivity, to ensure redundancy and to guarantee the continuity of the gravity signal in case of displacement of the reference gravimeter, an SG manufactured by GWR Instruments, the iGrav#005, has been installed in the gravimetry laboratory at the beginning of 2013. With the quantum gravimeter, it allows for Planck constant determination and now for the implementation of the new definition of the kilogram [Thomas et al. doi.org/10.1088/1681-7575/aa7882]. Research activities are aimed at both improving the accuracy of the quantum instrument, of 20 nm.s-2 currently, to a level below 10 nm.s-2, and its long term sensitivity, of 0.6 nm.s-2 currently, to a level below 0.1 nm.s-2. The time series of gravity and barometric pressure from the gravimeter iGrav-005 starts in February 2013. It interrupted 3 times: from 25 of may 2018 to 4 of July 2018 due to a coldhead maintenance problem of the manufacturer; from 14 of August 2019 to 1st of October 2019 and from 1st of January 2020 to 4th of March 2020 for a CPU problem. The time sampling of the raw gravity and barometric pressure data of IGETS Level 1 is both 1 minute and 1 second. For a detailed description of the IGETS data base and the provided files see Voigt et al. (2016, http://doi.org/10.2312/GFZ.b103-16087). Moreover the laboratory is also equipped with a permanent GNSS (Global Navigation Satellite Systems) antenna LNE1 belonging of the RENAG network (RESIF-RENAG French National Geodetic Network, RESIF – Réseau Sismologique et Géodésique Français, https://doi.org/10.15778/resif.rg, 2017) which is the French contribution to EPOS for the Seismology and Geodesy components.

Superconducting Gravimeter Data from Membach - Level 1

The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy (IAG). IGETS continues the activities of the Global Geodynamics Project (GGP, 1997-2015) to provide support to geodetic and geophysical research activities using superconducting gravimeter (SG) data within the context of an international network. The Membach station is located near the river Vesdre. It consists of a 130 m long gallery excavated in the side of the valley that rises to the Hautes Fagnes plateau. At the end of the gallery, there are two rooms, located at ~45 m below the ground surface. Room 1 is dedicated to absolute gravity and seismic measurements; room 2 houses the superconducting gravimeter. The structure of the gallery and the rooms is in reinforced concrete. It was built in the early 1970s to monitor the seismic activity in the vicinity of the Gileppe and Eupen water reservoirs. Works were performed contemporeanously with the raising of the Gileppe dam. The gallery has been excavated in low-porosity argillaceous sandstone with quartzitic beds. As a function of rainfall and seasonal effects, gravity variations up to 40 nms-2 have been observed, and are mostly due to groundwater changes in the vadose zone above the underground laboratory (Van Camp et al., 2006). Strong rainfall induces rapid gravity decreases (Meurers et al 2007; Delobbe et al., 2019). At the surface, a beech forest. Absolute gravity measurements have been performed on average every month since 1996, using the FG5#202 gravimeter and the station is also the reference point for the Belgian gravity network. The SG GWR#C021 has been operating continuously since 1995 August so that, since 2017 September 18, it holds both records for the longest continuous time spent measuring gravity variations in the same place and for the longest superconducting levitation of an artefact (Van Camp et al., 2017). For high precision works like Earth tides analysis on long time series, data should not be used before 1998 June 12, when the original "TIDE" card in the SG electronics was replaced by the "GGP" one. Filters are different, and so are the transfer functions. Moreover, in this early period, the SG suffered from numerous technical issues, causing several changes in the amplitude and phase calibrations and making it difficult to ensure that the data are as reliable as after 1998 June.

Superconducting Gravimeter Data from Zugspitze - Level 1

The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy IAG. IGETS continues the activities of the Global Geodynamics Project (GGP) between 1997 and 2015 to provide support to geodetic and geophysical research activities using superconducting gravimeter (SG) data within the context of an international network. As part of this network, the Zugspitze Geodynamic Observatory Germany (ZUGOG) was established by the GFZ German Research Centre for Geosciences in September 2018. Continuous time-varying gravity and atmospheric pressure data from the SG at ZUGOG are integrated in the IGETS data base hosted by GFZ.The ZUGOG observatory is located in the European Alps on the summit of mountain Zugspitze, Germany's highest peak, at an altitude of 2938 m above MSL. The operation and maintenance of the ZUGOG instrumentation is jointly done by staff of the Umweltforschungsstation Schneefernerhaus (UFS) and GFZ. The shortest distance to the North Sea coastline is approximately 700 km. The area is close to the seismically active area of the Inn valley/Ester mountains. ZUGOG is located in the research catchment Zugspitze (RCZ; Bernhardt et al. 2018, https://doi.org/10.1007/s00506-018-0510-8) covering an area of 11.4 km² located in the Northern Limestone Alps. Its main characteristics are an annual precipitation of more than 2000 mm at an average temperature of -4.5°C. The altitudes vary between 2962 m (summit of mountain Zugspitze, Germany’s highest peak) and 1430 m at Partnach spring where the catchment is drained solely due to the special geological situation. The catchment is therefore regarded as lysimeter and especially suitable for studies on water balance. Germany’s highest and largest glaciers - the Northern and Southern Schneeferner – are also located in the RCZ as well as permafrost rock walls in mountain Zugspitze.The observatory is a former laboratory of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. The special architecture of the lab prevents snow accumulation on the roof above the sensor. Due to the high altitude, the gravimetric footprint can be largely increased. The room has a ventilation system, and the SG is additionally insulated in a box with heaters. The first concrete pier is occupied by the SG, while the second one is intended for absolute gravimeters (first measurements in Oct 2018, second measurements in Sep 2019 both by Ludger Timmen from Leibniz Universität Hannover) and other instruments. A continuous GNSS station is installed nearby as well as a snow balance and 5 snow height sensors for the monitoring and modelling of near-field effects.ZUGOG is a high precision geodynamic observatory comprising space techniques and ground instruments. Presently, the observatory is equipped with the SG 052 manufactured by GWR Instruments, one of the two SGs operating in parallel at Sutherland, South Africa, until September 2017 (Förste et al., 2016, http://doi.org/10.5880/igets.su.l1.001). The time series of gravity and barometric pressure from the SG D037 starts in September 2018, however, with a malfunction in the beginning until 29 December. The SG is active and the time series is kept up to date regularly with a time delay of a few months. The time sampling of the raw gravity and barometric pressure data of IGETS Level 1 is 1 second and 1 minute. For a detailed description of the IGETS data base and the provided files see Voigt et al. (2016, http://doi.org/10.2312/GFZ.b103-16087).In addition, ZUGOG is equipped with auxiliary data supporting the interpretation of the SG measurements, which is, however, not provided in the IGETS data base due to their complexity. These are a local network of hydrological and meteorological sensors as well as a permanent GNSS (Global Navigation Satellite Systems) station.

Superconducting Gravimeter Data from Rochefort - Level 1

The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy (IAG). IGETS continues the activities of the Global Geodynamics Project (GGP, 1997-2015) to provide support to geodetic and geophysical research activities using superconducting gravimeter (SG) data within the context of an international network. In 2014 December the Royal Observatory of Belgium installed the iGrav #019 at the surface site of the Rochefort "Lorette" cave laboratory. The Lorette cave is one of several cavities that belong to the Wamme–Lomme karst system, a 10 km long karst area. At the surface of the site, a small and solid building, located at the border of a large sinkhole, hosts the gravity laboratory, which is thermally stabilized at ~25°C by a heater, excepted during a few days each summer when the temperature may increase above that level. The iGrav #019 is installed directly on the bedrock (limestone) in a 1 m deep shaft. Two meters away from the iGrav there is a pillar of cement (60% sand, 40% cement, no iron nor stones) founded 1 meter deep on the bedrock and on which absolute gravity measurements are performed 10 times or more per year with the FG5#202 absolute gravimeter. See description in Fig A7 in Van Camp et al., 2017. As this instrument was installed among others to investigate flash floods in the caves, it regularly monitors sudden changes in gravity reaching 50-100 nm/s², especially during the winter (Watlet et al., 2020). This should be considered when performing e.g. tidal analyses.

Superconducting Gravimeter Data from Rustrel (LSBB) - Level 1

The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy. IGETS continues the activities of the Global Geodynamics Project (GGP) between 1997 and 2015 to provide support to geodetic and geophysical research activities using superconducting gravimeter (SG) data within the context of an international network. As part of this network, the Rustrel station (code RU) was established in 2015 thanks to the financial support of the EQUIPEX MIGA (Matter wave-laser based Interferometer Gravitation Antenna) ANR-11-EQPX-0028 and by the European FEDER 2006-2013 “PFM LSBB - Développement des qualités environnementales du LSBB”. Continuous time-varying gravity and atmospheric pressure data from RU are integrated in the IGETS data base hosted by ISDC (Information System and Data Centre) at GFZ. The operation and maintenance of the RU instrumentation is done by staff at EOST/IPG Strasbourg. The RU station is located about 500 m beneath the surface in the underground research laboratory of the LSBB (« Laboratoire Souterrain à Bas Bruit ») built in 1997. The LSBB is located within the Regional Natural Park of Luberon (longitude: 5.4837 E, latitude: 43.9411 N, height above MSL: 499.3 m). The LSBB gallery is located in the unsaturated zone of the Fontaine de Vaucluse karst hydrosystem. There is no industry around the site so the anthropogenic noise is very low. The time series of gravity and barometric pressure from iOSG-24 starts in October 2015 and is going on. The time sampling of the raw gravity and barometric pressure data of IGETS Level 1 is 1 minute. For a detailed description of the IGETS data base and the provided files see Voigt et al. (2016, https://doi.org/10.2312/GFZ.b103-16087).

Superconducting Gravimeter Data from Buchholz, Eifel - Level 1

The International Geodynamics and Earth Tides Service (IGETS) was established in 2015 by the International Association of Geodesy IAG. IGETS continues the activities of the Global Geodynamics Project (GGP) between 1997 and 2015 to provide support to geodetic and geophysical research activities using superconducting gravimeter (SG) data within the context of an international network. As part of this network, the Eifel Gravimetric Observatory Germany (EIGOG) was established by the GFZ Helmholtz Centre for Geosciences in August 2025. Continuous time-varying gravity and atmospheric pressure data from the SG at EIGOG are integrated in the IGETS data base hosted by GFZ. The EIGOG observatory is located at the Buchholz Provostry (Propstei Buchholz) in the municipality of Burgbrohl. It is part of a multiparameter station for the monitoring and analysis of seismic and volcanic signals within the Central European Volcanic Province Observatory (CVO) in the Eifel region. Additional sensors at Buchholz are GNSS, InSAR corner reflector, seismometer, tiltmeter, groundwater level and a weather station. The operation and maintenance of the EIGOG instrumentation is done by staff of the GFZ. EIGOG is a high precision gravimetric observatory with the dual-sphere OSG D037 manufactured by GWR Instruments as core instrument, one of the two SGs operating at Sutherland, South Africa, until December 2024 (Förste et al., 2016, http://doi.org/10.5880/igets.su.l1.001). The time series of gravity and barometric pressure from the OSG D037 starts in August 2025. The SG is active and the time series is kept up to date regularly with a time delay of a few months. The time sampling of the raw gravity and barometric pressure data of IGETS Level 1 is 1 second and 1 minute. For a detailed description of the IGETS data base and the provided files see Voigt et al. (2016, http://doi.org/10.2312/GFZ.b103-16087).

Superconducting Gravimeter Data from Pecný - Level 1

The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy (IAG). IGETS continues the activities of the Global Geodynamics Project (GGP, 1997-2015) to provide support to geodetic and geophysical research activities using superconducting gravimeter (SG) data within the context of an international network. The Geodetic Observatory Pecný (GOPE) is located in the Czech Republic, about 40 km south-east of Prague, in the Central Bohemian hilly land at the elevation of about 500 m. It is surrounded by a mixed wood. Except for one local road the next nearest local road is about 1 km apart, the nearest railway is 5.2 km, the nearest village 1 km (Ondřejov). The bigger river (Sázava) flows through the valley at a distance of 5 km from the observatory at the height of about 300 m. No construction or other technological works (mines, industrial plants etc.) run either in the close surroundings or at longer distance. The hill Pecný is in the old metamorphic paleozoic synclinal zone of the Čerčany Chlum neighbouring with the Central Bohemian granitic massif and the perm massif of Černý Kostelec. From the geological point of view, GOPE was established in very stable region. GOPE is operated by the Research Institute of Geodesy, Topography and Cartography (RIGTC) and was established in 1957. GOPE has been involved in tidal observations with spring gravimeters since the early seventies of the last century, cooperation with the International Center for Earth Tides (ICET) has been dated since 1990. GOPE belongs to the core stations of ECGN - European Combined Geodetic Network, established by the EUREF IAG Subcommission. Since February 2007, the observatory type of one sphere superconducting gravimeter OSG-050 was running in the old gravimetric laboratory (OGL) of GOPE located in the cellar of the main building of GOPE (Latitude: 49.9137 N, Longitude: 14.7856 E, Elevation: 534.58 m), about 1.8 m under the ground of the surrounding relief. Almost uninterrupted 10-year time series of gravity record with OSG-050 has been carried out till October 2017, when the OSG-050 has been moved to the new gravimetric laboratory (NGL) situated in the top of the hill Pecný, less than 100 m from OGL. NGL (Latitude: 49.9141 N, Longitude: 14.7868 E, Elevation: 545.10 m) provides 3 concrete pillars in the ground level, which are founded to the bedrock (4 m below the ground). Two pillars are used for repeated observations with absolute gravimeters (AG) and in the third pillar, located in a separate room, the OSG-050 is running continuously. All rooms are thermally stabilized by air-conditioning systems. Due to the excellent stability of the station and the facilities to inter-compare different AGs, the GOPE was developed as a regional comparison site which serves as a reference for the Czech Gravimetric Network. Since 2001, repeated absolute measurements with interval of one month have been carried out in OGL and later in NGL to achieve continuous drift-free gravity time series by combination of absolute and superconducting data. At the area of the station, meteorological (precipitation, air temperature, humidity, air pressure) and hydrological (ground water and soil moisture) parameters are measured by different sensors. These data are available through auxiliary data in the IGETS database. Raw gravity and local atmospheric pressure records sampled at second and the same records decimated at 1‐minute samples are provided as Level 1 products of the IGETS network.

Superconducting Gravimeter Data from Strasbourg - Level 1

The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy. IGETS continues the activities of the Global Geodynamics Project (GGP) between 1997 and 2015 to provide support to geodetic and geophysical research activities using superconducting gravimeter (SG) data within the context of an international network.As part of this network, the Strasbourg station (code ST) was established in 1996 thanks to the financial support of INSU-CNRS France. Continuous time-varying gravity and atmospheric pressure data from ST are integrated in the IGETS data base hosted by ISDC (Information System and Data Centre) at GFZ.The ST station is the unique permanent station in France belonging to the geophysical observatories funded by INSU-CNRS. The operation and maintenance of the ST instrumentation is done by staff at EOST/IPG Strasbourg.The ST station is located in an old bunker built in 1875 (called J9) which is 10 km away from Strasbourg city (longitude: 7.684 E, latitude: 46.622 N, height above MSL: 180 m). The area is located in the sediments of the Rhine graben and the local environment is agricultural with no close industry. The observatory is partly underground with a loess layer of about 1 m thick above it.An air-circulation system controls the humidity and temperature in all the rooms inside the bunker and there are about 10 pillars available. One room is dedicated to the absolute gravity measurements done regularly with FG5#206 operated by EOST Strasbourg. SG C026 manufactured by GWR Instruments was installed in 1996 and stopped in November 2018. The new SG iOSG#23 was installed in February 2016. Both meters ran side by side between February 2016 and November 2018 in order to perform an intercomparison in terms of noise level (Rosat & Hinderer 2018) and instrumental drift.The time series of gravity and barometric pressure from SG C026 starts in July 1996 and ends in November 2018. The time series of gravity and barometric pressure from iOSG#23 starts in February 2016 and is going on.The time sampling of the raw gravity and barometric pressure data of IGETS Level 1 is 1 minute. Raw data with a time sampling of 1 second will be provided additionally on the seismological IRIS Data Management Center (http://ds.iris.edu/mda/SG/ST).For a detailed description of the IGETS data base and the provided files see Voigt et al. (2016, http://doi.org/10.2312/GFZ.b103-16087).In addition, ST station is equipped with auxiliary data supporting the interpretation of the SG measurements, which is, however, not provided in the IGETS data base due to complexity. These are a local network of hydrological and meteorological sensors as well as a permanent GNSS (Global Navigation Satellite Systems) station belonging to the RENAG network (http://renag.resif.fr/).

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