Progress Towards ICRF4 at X/S and K Bands

In the nearly 6 years since ICRF3, considerable progress has been made with the X/S and K band catalogs. The X/S dataset has increased by ∼40% and the number of sources has increased by ∼25%. And the precision for the ICRF3-X/S sources has improved by ∼25%. At K band, the amount of data has increased more than five-fold and the number of sources has increased by ∼60%. And precision for the ICRF3-K sources has improved by ∼40%. Work will continue over the next three years aimed at generating ICRF4 catalogs at X/S and K bands for presentation and approval at the 2027 IAU General Assembly.