Towards the next multi-waveband realization of the International Celestial Reference Frame

The presentation reviews the current status of the VLBI frames at 8 GHz (X band), 24 GHz (K band) and 32 GHz (Ka band) in preparation for the next realization of the International Celestial Reference Frame (ICRF) which will be multi-waveband. As such, the next ICRF will incorporate the optical frame derived from the Gaia data in addition to those from the three above radio bands. Potential frames that may emerge at other radio frequencies in the coming years, namely at 43 GHz (Q band) or with the VLBI Global Observing System of the International VLBI Service for geodesy and astrometry, are also considered. Questions relating to the construction of such a multi-waveband frame like inhomogeneity in sky distribution, treatment of Galactocentric acceleration, alignment of the frames in the different bands, along with considerations regarding wavelength and time-dependent source positions are discussed. The targeted date for completion of the next ICRF, as envisioned by the IAU Multi-waveband ICRF Working Group in charge of producing the frame, is 2027, meaning a possible adoption by the IAU General Assembly that will take place the same year.