Self-consistent treatment of tidal variations in the geocenter for precise orbit determination: Fid-Bau Portal

Self-consistent treatment of tidal variations in the geocenter for precise orbit determination

Desai, Shailen D. / Bertiger, Willy / Haines, Bruce J.

Abstract We show that the current levels of accuracy being achieved for the precise orbit determination (POD) of low-Earth orbiters demonstrate the need for the self-consistent treatment of tidal variations in the geocenter. Our study uses as an example the POD of the OSTM/Jason-2 satellite altimeter mission based upon Global Positioning System (GPS) tracking data. Current GPS-based POD solutions are demonstrating root-mean-square (RMS) radial orbit accuracy and precision of $${<}1$$ cm and 1 mm, respectively. Meanwhile, we show that the RMS of three-dimensional tidal geocenter variations is $${<}6$$ mm, but can be as large as 15 mm, with the largest component along the Earth’s spin axis. Our results demonstrate that GPS-based POD of Earth orbiters is best performed using GPS satellite orbit positions that are defined in a reference frame whose origin is at the center of mass of the entire Earth system, including the ocean tides. Errors in the GPS-based POD solutions for OSTM/Jason-2 of $${<}4$$ mm (3D RMS) and $${<}2$$ mm (radial RMS) are introduced when tidal geocenter variations are not treated consistently. Nevertheless, inconsistent treatment is measurable in the OSTM/Jason-2 POD solutions and manifests through degraded post-fit tracking data residuals, orbit precision, and relative orbit accuracy. For the latter metric, sea surface height crossover variance is higher by $$6~\hbox {mm}^{2}$$ when tidal geocenter variations are treated inconsistently.