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On the Hipparcos Link to the ICRF derived from VLA and MERLIN radio astrometry

Walter, H. G.; Hering, R.

Positions and proper motions obtained from observations by the very large array (VLA) and the multi-element radio-linked interferometer network (MERLIN) are used to establish the link of the Hipparcos Celestial Reference Frame (HCRF) to the International Celestial Reference Frame (ICRF). The VLA and MERLIN data are apparently the latest ones publi…

Prediction of Earth orientation parameters by artificial neural networks

Ulrich, M.; Müller, J.; Schuh, H. +2 more

Earth orientation parameters (EOPs) [polar motion and length of day (LOD), or UT1-UTC] were predicted by artificial neural networks. EOP series from various sources, e.g. the C04 series from the International Earth Rotation Service and the re-analysis optical astrometry series based on the HIPPARCOS frame, served for training the neural network fo…

Linear drift and periodic variations observed in long time series of polar motion

Schuh, H.; Nagel, S.; Seitz, T.

Two long time series were analysed: the C01 series of the International Earth Rotation Service and the pole series obtained by re-analysis of the classical astronomical observations using the HIPPARCOS reference frame. The linear drift of the pole was determined to be 3.31 - 0.05 milliarcseconds/year towards 76.1 - 0.80° west longitude. For the le…