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Description
In this paper, we present a new theory of motion for Hyperion, defined like in TASS1.6 for the other Saturn's satellites (Vienne & Duriez, 1995A&A...297..588V), by the osculating saturnicentric orbital elements referred to the equatorial plane of Saturn and to the node of this plane in the mean ecliptic for J2000.0. These elements are expressed as semi-numerical trigonometric series in which the argument of each term is given as an integer combination of 7 natural fundamental arguments (Table 3). These series (Tables 4 to 7) collect all the perturbations caused by Titan on the orbital elements of Hyperion, whose amplitudes are larger than 1km in the long-period terms and than 5km in the short-period ones. Taking also account of the perturbations from other satellites and Sun (Table 8), these series have been fitted to 8136 Earth-based observations of Hyperion in the interval [1874-1985]. The resulting series allows to produce new ephemerides for Hyperion, which have been compared to those previously given by Taylor (1992A&A...265..825T): Using the same set of observations and the same way to weight them, the root mean square (o-c) residual of the present theory is 0.156-arcseconds while the ephemerides of Taylor gives 0.203-arcseconds.
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