Site Positions and Velocities

A prime ILRS end-product is SLR site positions/coordinates and velocities. Coordinate solutions are produced independently by ILRS analysis centers and have been combined by the ILRS combination centers to produce the official IERS contribution to the International Terrestrial Reference Frame (ITRF). SLR coordinate solutions are used as the definition of the ITRF origin and its linear rate of change. In addition, the ITRF scale and its linear rate of change was defined by the combination of SLR and VLBI coordinate solutions.

The responsibility of combining coordinate solutions from a given space geodetic technique (i.e. SLR, GPS, VLBI, DORIS) will migrate from the ITRS to the respective geodetic services (i.e. ILRS, IGS, IVS, IDS). The ITRS will still generate the combined ITRF coordinate solution, but will only accept one solution from each geodetic service. This task of generating the single combined SLR coordinate solution resides with the ILRS Analysis Working Group (AWG).