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Modeling the gravitational field by using CFD techniques
Yin, Zhi; Sneeuw, Nico
A harmonic scalar field has a Laplacian (i.e., both source-free and curl-free) gradient vector field and vice versa. Despite the good performance of spherical harmonic series on modeling the gravitational field generated by spheroidal bodies (e.g., the Earth), the series may diverge inside the Brillouin sphere enclosing all field-generating mass. …
Improved Fourier modeling of gravity fields caused by polyhedral bodies: with applications to asteroid Bennu and comet 67P/Churyumov-Gerasimenko
Wu, Leyuan; Chen, Longwei; Wu, Bin +2 more
This paper presents an improved algorithm for the 2D and 3D Fourier forward modeling of gravity fields caused by polyhedral bodies with constant and exponential density distributions. Three modifications have been made to the Fourier forward algorithm introduced in a previous paper. First, vertex-based Fourier-domain expressions are used instead o…
Determination of Phobos' rotational parameters by an inertial frame bundle block adjustment
Willner, Konrad; Oberst, Jürgen; Burmeister, Steffi +1 more
A functional model for a bundle block adjustment in the inertial reference frame was developed, implemented and tested. This approach enables the determination of rotation parameters of planetary bodies on the basis of photogrammetric observations. Tests with a self-consistent synthetic data set showed that the implementation converges reliably to…
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…