The ICRF3 is here
The ICRF3 is the most recent realization of the ICRS and was calculated by an IAU working group consisting of resea
rchers from all over the world. The Vienna VLBI Center was an active part of this group with Johannes Böhm as an working group member and David Mayer as an PhD student working on this topic. The ICRF3 was finished in 2018 and was approved by the IAU as the new standard celestial reference frame.
More than 4500 sources are listed in the ICRF3. For the first time it is a multi wavelength catalog with most of the positions in X/S band and some in higher frequency bands (K and X/Ka). The noise level of this catalog is 30 µas which is equivalent to seeing a tennis ball on the surface of the moon. At such a level of accuracy even tiny effects can distort positions and therefore have to be modeled. A tiny effect which was not modeled in the ICRF2 but was modeled in the ICRF3 is the so called galactic aberration which is an effect from the rotation of our solar system about the galactic center.