Astrometry

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.

An all-sky assessment of nine plate models shows that plate-solution uncertainty can contribute at the metre-per-second level to stellar-aberration-based navigation.

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.

Inverse phase-referencing VLBI astrometry measures nearly bias-free core shifts in BL Lacertae with 5–30 μas precision, providing constraints on opacity and physical conditions in the inner jet.

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.

Nearly 50 years of satellite laser ranging observations support a parabolic model of Earth’s long-term $J_{2}$ variation. Incorporating this variation into the precession equations yields an updated solution with improved agreement with VLBI celestial pole offsets.

A statistical study of more than two million LQAC-6 quasars examines their sky distribution, astrometric uncertainties, redshift consistency, and optical luminosities, with implications for celestial reference frames.

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