Benefits of SLR in epoch reference frames

In the actual terrestrial reference frame realizations the station motions are approximated by linear velocities (multi-year reference frames). But this parameterization is not adequate, since we know that the station movements include not modeled non-linear parts due to various geophysical effects. One possibility to overcome this deficiency in the modeling is to estimate the station positions more frequently by computing epoch reference frames in addition to the conventional multi-year reference frames. SLR is the primary technique to determine the origin of the reference frame (i.e., center of mass) together with station coordinates, EOP and gravity field parameters. To combine the station coordinates of the different techniques (SLR, GPS, VLBI), stations with at least two techniques available (colocation sites) are used. The coordinates of the different techniques at the colocation sites are tied together using terrestrial difference vectors (local ties). The quality of the transfer of the origin information from SLR to the other techniques depends strongly on the connection of the different station networks within the combination. Therefore and because of the different accuracies of the local ties, the selection of the local ties, which should be used, is one crucial part of the combination process. In this study we analyze the quality of the datum realization by comparing the obtained epoch reference frames with a multiyear solution. Furthermore we discuss the impact of the temporal resolution on the datum realization. The coordinates of the terrestrial pole are validated w.r.t. the International Earth Rotation and Reference Systems Service (IERS) 08 C04 time series.