Reference Systems

Our group organized a summer school and workshop bringing together more than 100 participants for lectures, practical training, and research discussions on astrometry, reference systems, and Earth rotation.

VLBI celestial pole observations provide a consistent estimate of the Earth’s dynamical flattening for precession and nutation and recover long-term J₂ variations broadly consistent with satellite laser ranging.

An RFC–Gaia study showing that redshift trends in optical astrometry and radio-optical offsets are largely linked to magnitude and source-population effects, while VLBI properties show no significant redshift dependence.

APSG VLBI observations strengthen the Asia-Pacific geodetic network and improve station-motion estimates, reducing velocity formal uncertainties at several stations by up to 25%.

We investigate the astrometric properties of CatWISE2020 relative to Gaia DR3 and show that, after correcting systematic errors, it can serve as an infrared realization of the International Celestial Reference System.

Asteroid-based tie between Gaia-CRF3 and DE440 shows ~10 mas orientation offset; adding Gaia into orbit solutions reduces it to ~0.2 mas.

An assessment of AllWISE astrometry and its use as an infrared celestial reference frame through comparison with Gaia DR3.

Oleg Titov and Feng-Chun Shu visit our group for academic discussions, with presentations on future improvements to the ICRF and the OCCAM VLBI analysis software.

A simulation-based assessment of the CSST sky survey’s potential to extend the Gaia celestial reference frame.

We discovered a new term of secular aberration drift due to the changing line of sight, affecting stellar proper motions measured by Gaia.