Some of the decrease is obtained through accumulating and subsequently implementing information on high frequency components in the solar radiation torques, which show to be systematic and predictable. As such, it decreases the degrees of freedom in the a posteriori reconstruction. The dynamic modelling is expected to give a more accurate representation of the satellite's attitude than was obtained with a pure mathematical modelling. The method is tried out on the Hipparcos data and is shown to reduce the noise for the along-scan attitude reconstruction for that mission by about a factor two to three. This method, referred to as the fully-dynamic approach, explores the possibility to describe the satellite's attitude as that of a rigid body subject to continuous external torques. We present a new method for a high-accuracy reconstruction of the attitude for a slowly spinning satellite. This theoretical result allows one to solve b and s (or v) simultaneously. In the resulted induction equation of the perturbed magnetic field b caused by nutation, it is shown that the spheroidal and toroidal part of b are decoupled with each other, although both of them involve the steady part of B and the nutational displacement s (or velocity v) field. In this work, the magnetic induction equation and the Lorentz force density in the motion equation are derived to scalar format in GSH. This is especially the case when the ellipticity of the interior structures and boundaries are considered. In the studies of Earth nutation involving electro-magnetic coupling at the core boundaries inside the Earth, it is convenient to express the magnetic induction equation and the Lorentz force density, as well as the magnetic field (B) itself, in generalized spherical harmonics expansion (GSH). Experiences gained with this first ever space astrometry mission are considered in relation to a follow up mission for Hipparcos. The data quality verifications are reviewed and guidelines to the proper use of the Hipparcos data are provided, followed by some of the first scientific results of the mission. Astrometric and photometric data for a selection of 48 minor planets, the Jovian moon Europa and the Saturnian moons Titan and Iapetus were also obtained. The Hipparcos mission was complemented by the Tycho experiment, providing a complete all-sky survey of astrometric and photometric parameters for one million stars down to magnitude 11, though with lower accuracies than obtained for the main mission. This has led to the discovery of thousands of variable stars. The mission results comprise not only outstanding astrometric data on both single and double stars, but also an unique all-sky photometric survey which has been used for variability investigations. Data files presented in the catalogues are described in the context of the data reductions, and explained in content and usage. This is followed by a description of the input data streams and a summary of the data reductions. It presents a brief review of the satellite, the aims of the mission with their relation to ground-based astrometry, and the mission history. The emphasis is on those aspects that have or may have influenced the data as presented in the catalogues. A review is presented of the European Space Agency's astrometric satellite project Hipparcos, for which the final data catalogues were published in June 1997.
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