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EP: Fachverband Extraterrestrische Physik
EP 10: Planeten-III
EP 10.3: Vortrag
Freitag, 1. März 2013, 10:00–10:15, SR 113
Gravity field estimation of the nucleus of 67P/Churyumov-Gerasimenko by the Rosetta Radio Science experiment — •Matthias Hahn1, Martin Pätzold1, Silvia Tellmann1, Bernd Häusler2, and Tom Andert2 — 1Rheinisches Institut für Umweltforschung, Abteilung Planetenforschung, Cologne, Germany — 2Institut für Raumfahrttechnik, Universität der Bundeswehr, Munich, Germany
The perturbed Doppler frequency shift of the radio signal transmitted by the spacecraft will be used to reconstruct the flown orbit. The gravitational potential of the nucleus shall be estimated from this reconstruction. These parameters are the mass and 2nd degree and order gravity field coefficients. The accuracy of these parameter estimations depends on various error sources. The measurement is superimposed by thermal and plasma frequency noise. Another uncertainty will be the poorly known outgassing rates of the nucleus. The gravitational parameters, however, cannot be estimated independently. The uncertainties of the mass, for example, will be reflected in the errors of the 2nd degree and order coefficients, and vice versa. Various orbit trajectories are analyzed to estimate the accuracy with which the parameters GM, C20 and C22 can be measured. Therefore, simulated measurements are generated by using a complex force model, including all gravitational and non-gravitational forces. An artificial noise will be added to these simulations. A least squares adjustment to the simulated data including considered parameters will give the errors to be expected for the true measurements.