Advancements and Innovations in the Korean VLBI Network (KVN) for mm-VLBI Astrometry and Geodesy

The Korean VLBI Network (KVN) is distinguished by its unique multi-frequency receiving system, allowing simultaneous observations across four bands (18-26, 35-50, 85-116, 124-142 GHz). This capability greatly enhances our broadband observational capabilities in radio astronomy and geodesy. Overcoming atmospheric phase fluctuations, a major challenge in millimeter VLBI (mm-VLBI), is made possible through KVN's innovative calibration technique known as Frequency Phase Transfer (FPT). Consequently, multi-frequency astrometry at mm-VLBI, extending up to 130 GHz, has become feasible, together with the detection of the largest number of sources at this frequency by KVN. These broadband multi-frequency radio observations open up new avenues for VLBI astrometric and geodetic studies. In this presentation, I will introduce our recent advancements and innovations, including: (1) the first geodetic observation results at 22/43/86/129GHz, (2) the development of a photonic instrumental phase calibration system, and (3) the establishment of common time/frequency standards across the KVN through a fiber network. I will also discuss the synergies and future prospects from these developments for astrometry and geodesy.