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.