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| Titel |
POD improvements of GALILEO satellites through the measurement of their non-gravitational accelerations by means of an onboard accelerometer |
| VerfasserIn |
Roberto Peron, David M. Lucchesi, Francesco Santoli, Valerio Iafolla, Emiliano Fiorenza, Carlo Lefevre, Marco Lucente, Carmelo Magnafico, Maciej Kalarus, Janusz Zielinski |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250135141
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| Publikation (Nr.) |
 EGU/EGU2016-15970.pdf |
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| Zusammenfassung |
| The Precise Orbit Determination (POD) of the satellites of the Global Navigation Satellite
Systems (GNSS) represents the basic prerequisite in order to provide refined ephemerides for
their orbit, aimed at providing a precise and accurate positioning on the Earth. An important
factor that impacts negatively in the POD of these satellites is the limited modeling of the
accelerations produced by the non-gravitational accelerations. These, indeed, are subtle and
generally complex to model properly, especially in the case of a complex in shape spacecraft,
with solar panels and antennae for microwave link and the mutual shadowing effects among
the many surfaces involved. We have to notice that their modeling has an important impact
in the determination of a number of geophysical parameters of interest, such as
stations coordinates, Earth’s geocenter and orientation parameters. In the case of
GNSS satellites, the main NGP acceleration is the one produced by the direct solar
radiation pressure, with non-negligible contributions due to Earth’s albedo, thermal
effects and power radiated by the antennae. The models developed so far for these
perturbative effects have shown many limits, as pointed out in the literature. Currently,
the models developed for the NGPs are mainly based on empirical blind models
(with the goal of absorb unknowns quantities) and more recently with the use of
wing-box models, that try to provide a finite-elements approach to the modeling.
The European Space Agency (ESA) — in the context of the development of the
GALILEO constellation, and especially in view of the next generation of GALILEO
spacecraft — besides being interested in possible improvements of the NGPs models, is
also envisaging the use of an onboard accelerometer to directly measure them in
order to improve the POD of each spacecraft of the constellation. We have been
involved in this study by means of a proposal to ESA denominated GALileo and
ACcelerometry (GALAC) led by the Space Research Centre (SRC) of the Polish
Academy of Sciences (PAS) of Warsaw. The GALAC main objective is to provide the
characteristics and performance of an onboard accelerometer able to improve the POD with
respect to the current best results obtained through the modeling of the NGPs. The
starting point of our activities has been the ISA accelerometer developed for the ESA
BepiColombo mission to Mercury. We will present our results of a preparatory work for
GALAC concerning a first characterization of the main NGPs acting on the GALILEO
spacecraft of second generation, including their (main) spectral content. Such results are
used to preliminary fix the accelerometer measurement band, its sensitivity and
physical characteristics in order to fit with the GALILEO spacecraft environment. |
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