HR: 1330h
AN: G22B-0311    [PDF]
TI: Determination of Forced Diurnal Polar Motion Using Large Ring Lasers Gyroscopes
AU: * Rothacher, M
EM: rothacher@bv.tum.de
AF: Forschungseinrichtung Satellitengeodaesie, TU Munich, Arcisstrasse 21, Munich, D-80290 Germany
AU: Schreiber, U
EM: schreiber@wettzell.ifag.de
AF: Forschungseinrichtung Satellitengeodaesie, TU Munich, Arcisstrasse 21, Munich, D-80290 Germany
AU: Kluegel, T
EM: kluegel@wettzell.ifag.de
AF: Bundesamt fuer Kartographie und Geodaesie, Fundamental Station Wettzell, Koetzting, D-93444 Germany
AU: Stedman, G E
EM: g.stedman@phys.canterbury.ac.nz
AF: Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch, 8020 New Zealand
AU: Hurst, B
EM: bob.hurst@canterbury.ac.nz
AF: Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch, 8020 New Zealand
AB: In October 2001, a very large ring laser gyroscope with an area of 16~m$^2$ was inaugurated at the Fundamental Station in Wettzell, Bavaria. Large gyroscopes with areas of 1~m$^2$, 16~m$^2$, and 367~m$^2$ are also operational at the University of Canterbury in Christchurch, New Zealand. These ring lasers, measuring the frequency difference between two counter-rotating laser beams, are now approaching a precision of 10~ppb for geophysical signals with periods of less than 2~days and therefore allow the monitoring of variations in Earth rotation (polar motion and length of day) in the high-frequency spectrum. For the first time, forced diurnal polar motion (also called "Oppolzer terms", caused by the gravitational attraction of Sun and Moon) with variations up to 20~mas (60~cm on the Earth's surface) can directly be measured. This is a novelty, because with the space geodetic techniques like VLBI, GPS, SLR/LLR, and DORIS, nutation and forced diurnal polar motion cannot be separated. With a few months of data stemming from the two most accurate ring lasers, the amplitudes of the largest terms of forced diurnal polar motion have been determined with a precision of about 1~mas. The results are discussed and compared to theoretical models.
UR: http://www.wettzell.ifag.de
DE: 1210 Diurnal and subdiurnal rotational variations
DE: 1239 Rotational variations
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: 2003 Fall Meeting