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).