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Onsala Space Observatory

Superconducting Gravimeter In June 2009, a permanently operating superconducting gravimeter has been taken into operation at Onsala Space Observatory. The main purpose of the facility is to be seen in conjunction with projects that determine gravity change in Fennoscandia, e.g. the Nordic Geodetic Commission's Working Group for Geodynamics. A dominating effect of graivty change in the form of a secular trend is for instance related to the post-glacial isostatic adjustment, an after-effect of the latest great ice sheet in the Pleistocene and its disappearance about 10,000 years ago. The Superconducting Gravimeter can monitor temporal changes of gravity and thus provide visiting teams operating absolute gravimeters (free-falling prisms) with measurements of perturbations. These perturbations relate most often to the changing ground water masses near the observing point. But also the attraction and loading effects of the - coupled - system atmospere and ocean are fairly complicated at the near-by coast of Kattegat. The constellation of facilities for GNSS and VLBI observations at OSO provides a full-fledged setting for a gravimeter calibration site. It helps us meet the requirements for multicomponent observing sites for the Global Geodetic Observing System (GGOS), and affords us the role of a Fundamental Geodetic Station. Also, gravity change due to glacial isostatic adjustment here at a station peripheral to the Pleistocene ice sheet is expected to enhance some of the second-order effects of mass redistribution in the earth interior and the ocean. The costs for the equipment and the laboratory building has been funded by the Committee for Infrasturcture of the Swedish Research Council (VR-KfI). An invitation: If you like to know more, e.g. what kind of gravity and surface acceleration signals the instrument has been catching, you are invited to visit the NEWS page.

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