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2016年7月12日 德国慕尼黑工业大学Schreiber教授学术报告

发布时间:2016-07-08          来源:办公室           浏览次数:


Ulrich Schreiber


Technische Universitaet Muenchen

Forschungsreinrichtung Satellitengeodaesie

Geodetic Observatory Wettzell







Variations  of Earth Rotation from Ring Laser Gyroscopes:

One Hundred  Years of Rotation sensing with Optical Interferometry



Earth Rotation and  Orientation are providing the link between the terrestrial (ITRF) and  celestial reference frames (ICRF). Traditionally the Earth orientation  parameters (EOPs) are observed by radio interferometry. The fixed positions  of the quasars, along with measurement redundancy of a sufficiently large  network, provide the long-term stability of the observations. For the  short-term and the access to the instantaneous rotation axis of the Earth,  VLBI is depending on suitable models, which still have some deficiencies.  Optical interferometric rotation sensing with ring lasers in contrast provide  direct access to the Earth rotation axis, a high resolution in the shortterm,  but are suffering from tiny non-reciprocal laser behavior causing drift in  the long-term.

Now, one hundred years after  George Sagnac’s important paper published in Comptes Rendus in 1913 the tools  of modern quantum optics have matured to a point where they make ring lasers  more than 12 orders of magnitude more sensitive than the early  instrumentation in this field. The single component prototype ring laser G in  Wettzell now resolves rotation rates of 10e-12 rad/s after one hour of  integration and has demonstrated an impressive sensor stability over several  month. This is in particular unique since we use a single local sensor to establish  a global quantity.

The combination of VLBI and  ring laser measurements offers an improved sensitivity for the EOPs in the  shortterm and the direct access to the Earth rotation axis. At the same time  the progress in controlling the backscatter coupling in ring lasers has succeeded  to reach the domain of 3 parts per billion for the relative uncertainty of  the measured Earth rotation. Since the Earth itself represents the turntable  for our interferometer we can also study dynamic processes on the Earth  itself. This talk explores the prospects of optical Sagnac Interferometry in Geodesy  and Geophysics at the Centennial of the Sagnac effect.



Karl Ulrich Schreiber received  his Ph.D. in applied physics in Göttingen in 1988. Since then he works for  the Technische Universitaet Muenchen (TUM) in the field of Space Geodesy. His  interests are in Satellite and Lunar Laser Ranging (SLR/LLR) and in particular  in Sagnac Interferometry, which is applied to the highly resolved monitoring  of Earth Rotation variations. His large ring laser gyroscopes seeded the  research on rotations in seismology. He habilitated in 1999 and is Professor (extraordinary)  at the Forschungseinrichtung Satellitengeodaesie and an adjunct Professor at  the University of Canterbury in Christchurch, New Zealand. He received the  Huygens research medal (for significant progress in geoscientific  instrumentation) of the European Geoscience Union in 2016.



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