Naslov
Two Years of CHAMP Kinematic Orbits for Geosciences

Autori
Švehla, Dražen ; Rothacher, M.

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Geophysical Research Abstracts, Vol. 6. ISSN:1029-7006 / - Nica : European Geosciences Union (EGU), 2004

Skup
1st General Assembly, European Geosciences Union

Mjesto i datum
Nica, Francuska, 25.04.2004. - 30.04.2004

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
Kinematic POD; GPS; CHAMP; LEO

Sažetak
Kinematic precise orbit determination (POD) can be defined as an estimation of epoch-by-epoch satellite positions using solely GPS measurements without making use of any information on satellite dynamics or force models. Using GPS data from the CHAMP satellite we showed for the first time that a LEO orbit can be estimated kinematically with the same level of accuracy (1-3 cm) as with the widely applied dynamic approaches and therefore kinematic POD turned out to be a new method in orbit determination. This CHAMP kinematic POD experiment initiated the computation of kinematic orbits for a longer time period, namely one year, in order to see the potential of LEO geometrical positions for the determination of, e.g., gravity field or atmosphere density parameters and for orbit comparisons and the validation of dynamic orbits and models. For the first time, several groups estimated Earth gravity field coefficients and studied their temporal variations using these CHAMP kinematic positions together with the variance-covariance information and making use of energy balance approach or boundary value method rather than classical numerical integration. The validation of gravity field models computed in such a way showed that CHAMP kinematic positions contain high-resolution gravity information and that the accuracy of the derived gravity models is comparable to that of official CHAMP models, if not better. Kinematic positions with the corresponding variance-covariance information are an extremely attractive interface between the LEO GPS data and gravity field models or other interesting information that can be derived from satellite orbits, because the simultaneous adjustment of model parameters (e.g. gravity field coefficients) and a huge amount of global GPS parameters, like GPS satellite clocks and orbits, zero or double-difference ambiguities, station coordinates, troposphere parameters, Earth rotation parameters, etc. can be avoided. CHAMP kinematic and dynamic orbits, estimated for the period of two years, are presented here. We show strategies to compute kinematic LEO orbits from the point of view of accuracy and efficiency. We present the type of applications possible with our one- and two-year CHAMP kinematic orbits, especially for the determination of Earth gravity field parameters as already performed by various groups, and discuss the role of kinematic POD in the framework of the GRACE, GOCE and other LEO missions. For a period of the high solar activity in 2003, the impact of higher order ionosphere terms on the GPS phase measurements and kinematic POD has been studied. The results were obtained using CHAMP magnetometer measurements and the recently developed 9th-Generation International Geomagnetic Reference Field.

Izvorni jezik
Engleski

Znanstvena područja
Geodezija

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