Simulation of the Goce Gravity Field Mission
GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) is one of the four selected ESA Earth Explorer Missions (Phase A has started in summer 1998). The main objective of GOCE is the determination of the Earth’s gravity field with high spatial resolution and with high homogeneous accuracy. For this purpose, two observation concepts will be realized. Satellite-to-Satellite Tracking (SST) in high-low mode will be used for orbit determination and for retrieval of the long-wavelength part of the gravity field. Satellite Gravity Gradiometry (SGG) will be employed for the recovery of the medium/short- wavelength parts of the gravity field. The measurement principles and the relation between the various instruments are explained by means of a Flow Chart.
For its realization, a GPS receiver, a 3-axis gradiometer and further instruments are needed; e.g. star trackers to control the orientation of the spacecraft or thrusters for attitude and drag-free control. Each instrument shows its own error behavior which affects the measurements and the final products in a specific way. Here, the corresponding error Power Spectral Densities (PSD), due to several error sources, are shown.
Error PSD’s represent the stochastic model in the spectral domain. In connection with frequency-wise modeling of the observables (through the lumped coefficient approach) leastsquares error simulation can be performed. Thus the PSD’s are propagated to spherical harmonic error spectra, geoid heights and gravity anomaly accuracies to assess effects of instrument and measurement errors on the gravity field determination.
KeywordsPower Spectral Density Gravity Field Gravity Gradient Geoid Height Spherical Harmonic Coefficient
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