Citation
Abstract
Galactic aberration drift (GAD), also commonly referred to as secular aberration drift (SAD), is the distance-independent dipolar proper-motion feld of celestial objects induced by the long-term acceleration of the Solar System barycenter in the Milky Way potential [1,2]. Although the efect is only a few microarcseconds per year, it accumulates over multi-decade very long baseline interferometry (VLBI) time spans and must be treated consistently to preserve the quasi-inertial character of the International Celestial Reference Frame (ICRF) [3,4]. This article reviews the physical origin and expected sky signature of GAD, summarizes a vector-spherical-harmonic (VSH) formulation for representing low-degree proper-motion felds, and surveys the principal observational routes used to constrain the corresponding Galactic aberration constant, including Galactic-tracer astrometry, Gaia quasar astrometry, and extragalactic geodetic VLBI [3, 5]. Practical estimation strategies in VLBI (global multi-session versus session-wise/time-series approaches) are then discussed, with emphasis on robustness diagnostics required for microarcsecond-per-year global-mode recovery, given that individual-source apparent motions are frequently dominated by source-structure variability and other analysis-dependent systematics [3,4]. Finally, the study identifes several practical directions for improving future GAD estimates: expanding southern-sky coverage, using controlled higher frequency multi-band observations as consistency checks, and maintaining more homogeneous long-term a priori products, including Earth-orientation inputs. These improvements would strengthen the estimation of GAD and would also beneft global geodetic products by ensuring that this deterministic low-order signal is treated consistently [3, 6].
Keywords
Details
- Volume
- 42-246
- Published
- August 15, 2026
- Pages
- 1–23
- File Size
- 2.0 MB