Tilt effects on GWR superconducting gravimeters |
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| Institution: | 1. Dipartimento di Scienze della Terra, Università “Federico II” di Napoli, L.go S. Marcellino 10, 80138 Naples, Italy;2. Institut de Physique du Globe de Strasbourg (UMR 7516 CNRS-Université de Strasbourg), 5 rue René Descartes, 67084 Strasbourg Cedex, France;3. Planetary Geodynamics Laboratory, Mail Code 698, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA;1. Department of Neurosurgery, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi Province, P.R. China;2. Department of Neurosurgery, Renji Hospital, School of Medicine of Shanghai Jiao Tong University, Shanghai, P.R. China;3. Department of Neurosurgery, Fudan University Huashan Hospital, Shanghai, P.R. China;1. Department of Urology, Kantonsspital Winterthur, 8400 Winterthur, Switzerland;2. Department of Surgery, Kantonsspital Frauenfeld, Frauenfeld, Switzerland;1. Plastic Surgery Department, King Edward Medical University, Mayo Hospital Lahore, Lahore, Punjab, Pakistan;2. Department of Biostatistics, King Edward Medical University, Mayo Hospital Lahore, Lahore, Punjab, Pakistan;3. Department of Medicine, University of Tennessee College of Medicine at Chattanooga, Chattanooga, TN;1. Gynecology Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, New York;2. Head and Neck Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, New York;3. Department of Anesthesiology and Critical Care Medicine, Memorial Sloan Kettering Cancer Center, New York, New York;4. Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, University of California Irvine Medical Center, Orange, California;5. Department of Obstetrics and Gynecology, Weill Cornell Medical College, New York, New York;1. Cuschieri Skills Centre, Dundee, UK;2. Department of General Surgery, Ninewells Hospital & Medical School, Dundee, UK |
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| Abstract: | The superconducting gravimeters (SGs) are the most sensitive and stable gravity sensors currently available. The low drift and high sensitivity of these instruments allow to investigate several geophysical phenomena inducing small- and long-period gravity changes. In order to study such topics, any kind of disturbance of instrumental origin has to be identified and possibly modelled. A critical point in gravity measurement is the alignment of the gravimeter to the local vertical. In fact a tilt of the instrument will lead to an apparent gravity change and can affect the instrumental drift. To avoid these drawbacks, SGs are provided with an “active tilt feedback system” (ATFS) designed to keep the meter aligned to the vertical. We analyse tilt and environmental parameters collected near Strasbourg, France, since 1997 to study the source of the tilt changes and check the capability of the ATFS to compensate them. We also present the outcomes of a calibration test applied to the ATFS output to convert the Tilt Power signals into angles. We find that most of the observed signal has a thermal origin dominated by a strong annual component of about 200 μrad. Nevertheless, our analysis shows that even the tilt due to different geophysical phenomena, other than the thermal ones, can be detected. A clear tidal signal of about 0.05 μrad is detectable thanks to the large data stacking (>11 years). We conclude that (i) the ATFS device compensates the tilt having a thermal origin or coming from any sources and (ii) no significant tilt changes alter the gravity signal, except for the high frequency (>1 mHz) perturbations. |
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