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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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