Celestial Reference Frame
The Celestial Reference Frame is defined by the ICRF3 S/X catalog, which was adopted by the IAU effective January 2019. ICRF3 also has CRF catalogs at K and X/Ka bands. The analysis center regularly monitors and maintains the Celestial Reference Frame using VLBA and IVS sessions at S/X bands and VLBA and southern hemisphere sessions at K band. We also periodically make global VLBI solution updates of the Celestial Reference Frame at S/X and K bands. The latest S/X source solution can be downloaded here and contains precise positions of > 5200 compact extragalactic radio sources.
Also provided here is a source time series generated by the USNO IVS VLBI Analysis Center. This file contains the positions of the sources in each of > 6700 S/X VLBI sessions. This file can be used to study the positional stability of > 5200 quasar radio sources at S/X bands.