Impact of Different ITRS Realizations on VLBI Combined EOP and Scale

In this paper we investigate the impact of using the three ITRS realizations DTRF2014, ITRF2014, and JTRF2014 as a priori TRF for the VLBI combination on EOP and scale. The scale factor between the IVS routine combined solution and DTRF2014, ITRF2014, and JTRF2014 shows a significant offset of −0.59 ppb with respect to ITRF2014 and of 0.19 ppb with respect to JTRF2014. No significant offset was found for the DTRF2014-based solution. The investigation of the EOP of all four TRF-based solutions (DTRF2014-, ITRF2014-, JTRF2014- and VTRF2015q2-based) shows specific effects when comparing to the reference time series IERS 14C04, IGS, and ILRS. Relative to the VTRF2015q2-based solution, x-pole differences with respect to the DTRF2014-based solution (positive trend) and JTRF2014-based solution (scatter and negative trend), as well as an offset concerning the y-pole for all three TRF-based solutions with an additional scatter for the JTRF2014-based solution are recognized. No significant differences were found for pole rates, nutation, and LOD, but using ITRF2014 or JTRF2014 leads to marginal larger scatter with respect to the VTRF-based EOP series for LOD. In addition, a significant impact was found when comparing dUT1. All three TRF-based solutions show a significant offset comparing to IERS 14C04, whereas no offset is detected for the VTRF2015q2-based solution.