Evaluation of the Orbital-Based terrestrial reference frame realized by autonomous orbit determination based on BDS-3 inter-satellite link measurements

Based on the broadcast ephemeris of a global navigation satellite system (GNSS) uploaded from the ground, an orbital-based terrestrial reference frame (TRF) can be produced in consistence with the ground-based TRF. High-precision inter-satellite link (ISL) ranging technology makes satellite autonomous orbit determination (AOD) possible. Therefore, if the broadcast ephemeris cannot be uploaded, the GNSS satellites can independently maintain the accuracy of the orbital-based TRF. In this paper, orbital-based TRF realized by the autonomous orbit determination (AOD) based on BDS-3 ISL measurements is compared with the ITRF2014. The accuracy of the orbital-based TRF realized by the AOD is evaluated. The comparison between the AOD orbits and the post-processed precise orbits over 60 days via the 7 parameters Helmert transformation shows that the maximum differences of the three-axis translation between the orbital-based TRF and ITRF2014 are 1.25 m, 1.32 m and 0.47 m, and the maximum difference of the scale is 6.2 ppb. The differences of the three-axis rotation parameters between the orbital-based TRF and ITRF2014 are related to whether the orientation correction method is applied. Since the long-term orbit prediction (OP) generated by the orbit dynamics models can predict the right ascension of the ascending node (RAAN) and the inclination accurately in Geocentric Celestial Reference System (GCRS), in the orientation correction method, the long-term OP is used as the reference to constrain the rotation differences. If the orientation correction method is not applied, the maximum differences of the three-axis rotation parameters are 65.0 mas, 77.1 mas, 122.5 mas; however, if the orientation correction method is applied, the maximum differences of the three-axis rotation parameters are reduced to 32.5 mas, 46.9 mas and 67.1 mas. Part of the residual rotation differences are caused by the prediction errors of the rapid Earth rotation parameters (ERPs) from International Earth Rotation and Reference Systems Service (IERS) bulletin A. Over 60 days, the differences between the rapid ERPs from IERS bulletin A and the final estimated ERPs from IERS bulletin B are equal to 2.56 mas, 15.03 mas and 84.12 mas in X, Y, Z axis, respectively. The influence of the orbit prediction accuracy on the orbit-based TRF based on the AOD method is also analyzed. If precise satellite orbits with an accuracy of 0.10 m are applied as long-term orbit prediction, the accuracy of the orbital TRF is improved significantly. During 60 days, the maximum differences of the three-axis translation are reduced to 0.10 m, 0.10 m, and 0.12 m, the maximum differences of the three-axis rotation are reduced to 3.03 mas, 3.47 mas, and 4.94 mas, and the maximum difference of the scale is reduced to 1–2 ppb.