TOWARDS CORRECTING SOURCE STRUCTURE FOR AN IMPROVED K-BAND (24 GHz) CELESTIAL REFERENCE FRAME.

The AGN that define the radio Celestial Reference Frame (CRF) are not perfect stable point sources and are known to vary in both flux density and structure on timescales of months to years. The variations in structure can lead to significant errors in astrometric Very Long Baseline Interferometry (VLBI) measurements. Ideally, the effects of source structure should be accounted for in the VLBI analysis, but such modelling requires an ongoing imaging effort for all CRF sources. Observing at 24 GHz, higher than the traditional-used frequencies below 10 GHz, allows for better resolution and astrometric accuracy.