Gravity Field Error Assessment for the Cartwheel Formation via the Semi-Analytical Approach
19/09/2016 | 17:00 | Session 1: Current and future satellite gravity missions
Author(s): Huishu Li, Markus Antoni, Tilo Reubelt, Nico Sneeuw, Min Zhong and Zebing Zhou
Huishu Li, Markus Antoni, Tilo Reubelt, Nico Sneeuw, Min Zhong and Zebing Zhou
Past and current gravimetric satellite missions have contributed drastically to our knowledge of the Earth's gravity field. Nevertheless, several geoscience disciplines push for even higher requirements on accuracy, homogeneity and time- and space-resolution of the Earth's gravity field. Apart from better instruments or new observables, alternative satellite formations could improve the signal and error structure. With respect to other methods, one significant advantage of the semi-analytical approach is its effective pre-mission error assessment.
The semi-analytical approach builds a linear analytical relationship between the Fourier spectrum of the observables and the spherical harmonic spectrum of the gravity field. The spectral link between observables and gravity field parameters is given by the transfer coefficients, which constitute the observation model. In connection with a stochastic model, it can be used for pre-mission error assessment of gravity field missions.
The cartwheel formation is formed by two satellites in the same plane but in different elliptic orbits. In a rotating frame, the two satellites circuit their barycenter in an ellipse as well. In opposite to GRACE, the observation contains components in along-track and radial directions. The time-dependent ranging is considered via Fourier expansions and their convolutions with the transfer coefficients of orbit perturbation. The final transfer coefficients are applied to assess the error patterns of the gravity field coefficients, which are caused by different orientations of the cartwheel for range-rate and range-acceleration. The different orientations of the cartwheel are investigated to find the optimal orientation with minimal formal errors and the most isotropic solution.