Consistent Adjustment of Combined Terrestrial and Celestial Reference Frames

Today, the realization of the International Terrestrial Reference System (ITRS) and the International Celestial Reference System (ICRS) is performed separately. Consequently, the two realizations are not fully consistent and show differences in the network geometry and the realized scale of the terrestrial reference frame (TRF) and in the simultaneously estimated Earth Orientation Parameter (EOP) series. The paper deals with the common adjustment of the Terrestrial Reference Frame (TRF), the Celestial Reference Frame (CRF) and the linking EOP. It presents a computation strategy, which is based on the combination of normal equations. The main focus of the paper is on the impact of a combination of different space geodetic techniques on the CRF, which was not in detail studied so far. The influence of the local tie handling as well as the impact of the EOP combination are studied. The results show, that the combination leads only to small but partly systematic changes of the CRF. The maximum systematic effect is about 0.5mas for source positions derived in regional networks only.