The Secular Aberration Drift and Future Challenges for VLBI Astrometry

TL;DR

The paper discusses the impact of the Solar system's acceleration due to the Galaxy's gravity on VLBI astrometry, highlighting the need to revise celestial reference frames to account for secular aberration drift.

Contribution

It identifies the secular aberration drift as a significant factor affecting high-precision astrometry and proposes methods to incorporate this effect into reference frame realizations.

Findings

Secular aberration drift affects celestial reference frames.

Current models neglect Solar system acceleration effects.

Revised models can improve astrometric accuracy.

Abstract

The centrifugial acceleration of the Solar system, resulting from the gravitational attraction of the Galaxy centre, causes a phenomenon known as 'secular aberrration drift'. This acceleration of the Solar system barycentre has been ignored so far in the standard procedures for high-precision astrometry. It turns out that the current definition of the celestial reference frame as epochless and based on the assumption that quasars have no detectable proper motions, needs to be revised. In the future, a realization of the celestial reference system (realized either with VLBI, or GAIA) should correct source coordinates from this effect, possibly by providing source positions together with their proper motions. Alternatively, the galactocentric acceleration may be incorporated into the conventional group delay model applied for VLBI data analysis.