• PDF / 254,808 Bytes
• 9 Pages / 439.37 x 666.142 pts Page_size
• 20 Downloads / 204 Views

DOWNLOAD

REPORT

---

Improvement in GPS Orbit Determination at GFZ Grzegorz Michalak, Daniel König, Karl-Hans Neumayer and Christoph Dahle

Abstract Precise orbits of the GPS satellites are required at GFZ for generation of Earth’s gravity field models, precise determination of baselines between Low Earth Orbiters (LEOs) such as TerraSAR-X and TanDEM-X, for processing of various LEO radio occultation data as well as in research following the integrated approach where ground and space-borne GPS data are used together to estimate parameters needed for determination of a geodetic terrestrial reference frame. For this GFZ has implemented many GPS modelling improvements including GPS phase wind-up and attitude model, improved ambiguity fixing, absolute antenna phase centre offsets and variations, global constrains for the terrestrial reference system, frame transformation according to IERS Conventions 2010, higher order ionospheric corrections and improvements in the parameterization of the solar radiation pressure model. In this paper the influence of all these modelling improvements on the accuracy of the GPS orbits is presented. It is shown, that the application of the new models reduced the mean 3D difference of our orbits from 7.76 to 3.01 cm when compared to IGS final orbits. Keywords GPS orbits · Modelling improvements

2.1 Reference Processing To demonstrate the impact of the modelling improvements we started from the GPS orbits generated using modelling standards close to that used in the Release 04 (or RL04) of the GFZ GRACE gravity field modelling (Flechtner et al. 2010). These orbits were generated using EPOS-OC (Earth Parameter and Orbit System—Orbit G. Michalak (B) · D. König · K.H. Neumayer · Ch. Dahle GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany e-mail: [email protected]

F. Flechtner et al. (eds.), Observation of the System Earth from Space - CHAMP, GRACE, GOCE and Future Missions, Advanced Technologies in Earth Sciences, DOI: 10.1007/978-3-642-32135-1_2, © Springer-Verlag Berlin Heidelberg 2014

9

10

G. Michalak et al.

Computation module) software package (Zhu et al. 2004) and the applied background models include: • • • • • • • • • • • • • • • • • • • •

Earth gravity potential model: EIGEN-6C (Shako et al. 2013), Lunar gravity field model: Ferrari (1977), Sun, Moon and planets ephemeris: JPL DE421, Earth Tide model: Wahr (1981), Nutation and precession models: IERS Conventions 2003 (McCarthy and Petit 2004), Earth Orientation Parameters (EOP): EOP04C05, Ocean Tide model: EOT11 (Savcenko and Bosch 2012), Ocean pole tide model: Desai (2002), Atmospheric Tide model: Biancale and Bode (2006), Relative station antenna phase centre offsets and variations: igs_01.pcv, Solar radiation pressure: GPS model ROCK 4 (Fliegel et al. 1992), Tropospheric delay estimated with the Vienna Mapping Function 1, Empirical periodic accelerations (1/rev), unconstrained cosine and sine in transversal and normal direction, Post-Newtonian relativistic corrections, Lense-Thirring and deSitter effect, E