Plans for the Third Realization of the International Celestial Reference System and its Link to the ITRF

Abstract:

The International Celestial Reference Frame has been accepted as the closest realization of a quasi-inertial reference system proper. Its last version, the ICRF-2, was compiled with geodetic/astrometric VLBI observations until 2009.2 and is now due for a general overhaul planned to be ready by 2018. The new realization, the ICRF-3, is being prepared not only with more observations but also with addressing two completely new features. The first one is an extension of the observing frequency range, the second one is an attempt to rigorously combine individual VLBI solutions. In a further step, the combined VLBI data set may be rigorously linked to the other space-geodetic techniques, GNSS, SLR, and DORIS. With this multi-step combination, a consistent realization of TRF, EOP, and CRF will be possible.

The combinations are carried out primarily on the basis of datum-free normal equation systems (NEQ). The first step is an accumulation of all solutions for IVS and VLBA Calibrator Survey observations at X/S band. For the second combination step, a special Ka/X band solution with fully populated covariance matrix has to be converted to an NEQ, and the third step is the combination of the final VLBI solution with that of the other space-geodetic techniques. In this presentation, we will briefly elaborate on the methodology and show first results of the combinations.