Naslov
Kinematic Orbits for LEO Satellites - a New Product

Autori
Švehla, Dražen ; Rothacher, M.

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

Skup
10 Years of IGS, Workshop and Symposium

Mjesto i datum
Bern, Švicarska, 01.03.2004. - 05.03.2004

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
CHAMP; POD; LEO; IGS products

Sažetak
The CHAMP satellite mission opened a new era in the high precision orbit determination (POD) of LEO satellites. The high performance of the Blackjack GPS receiver on-board present geodetic missions allows for the first time a purely kinematic orbit determination of LEO satellites with the same level of accuracy (2-3 cm) as that of the common reduced-dynamic approach. Kinematic orbit determination can be defined as an estimation of satellite positions epoch by epoch using solely GPS measurements without making use of any information on satellite dynamics or force models. Therefore, kinematic POD is fully independent of orbit height and forces acting on the satellite, e.g. gravity field, air-drag, solar radiation, albedo etc. From this point of view and considering the high accuracy, kinematic POD is a very appropriate POD strategy for Earth observing satellites, where air-drag and gravity field perturbations become more difficult to model or estimate. We determined CHAMP kinematic orbits for a period of one year. A considerable number of groups already uses these kinematic positions for validation of dynamic orbits and models and, for the first time, several groups estimate Earth gravity field coefficients based on our kinematic CHAMP positions together with the corresponding variance-covariance information, making use of the energy balance approach or the boundary value method rather than the classical numerical integration schemes. 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 raw 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. In this contribution we present and discuss our POD approaches based on zero- and double-differences with and without ambiguity resolution from the point of view of accuracy and efficiency. We show how our one year of CHAMP kinematic orbits can be used for Earth gravity field determination and discuss kinematic POD in the framework of LEO missions like GRACE and GOCE. In the case of GRACE, kinematic and dynamic results for the inter-satellite baseline in space will be presented including ambiguity resolution with simulated and, if available, with the real GRACE data. Finally, we discuss the importance of IGS products for kinematic LEO POD and kinematic LEO orbits as a new product, maybe even an IGS product.

Izvorni jezik
Engleski

Znanstvena područja
Geodezija

POVEZANOST RADA