Geodetic Datum Realization Using SLR‐GNSS Co‐Location Onboard Galileo and GLONASS

Abstract

AbstractModern satellites of Global Navigation Satellite Systems (GNSS) are equipped with laser retroreflector arrays for Satellite Laser Ranging (SLR). Laser range observations to GNSS satellites allow for the co‐location of two space geodetic techniques onboard navigation satellites. We search for the best network constraining strategy for the SLR and GNSS stations to realize the geodetic datum using combined microwave‐GNSS and SLR‐to‐GNSS measurements. We find that consistent imposing of no‐net‐translation and no‐net‐rotation for the unified GNSS and SLR network provides the best quality of station coordinates and the best common realization of the terrestrial reference frame (TRF). We employ the space ties using solely space geodetic techniques for the SLR and GNSS station coordinates and confront them with the ground‐based measurements, that is, local ties, conducted at the SLR‐GNSS co‐located sites. The common processing of the GNSS and SLR observations allows for the realization of the TRF using space ties that are independent of the a priori coordinates and independent of the errors in local tie measurements. The agreement of space ties with ground measurements is at the level of 1 mm in terms of long‐term mean values for the co‐located station in Zimmerwald, Switzerland. We also revise the approach for handling the SLR range biases which now considers the impact of the SLR observations to GNSS and LAGEOS satellites. The updated SLR range biases improve the agreement between space ties and local ties from 4.4 to 2.4 mm for the co‐located station in Wettzell, Germany.