Building the Celestial Grid: The ICRF and Global VLBI Collaboration

• Autores: de Witt, A.
• Año de publicación: 2025
• Idioma: inglés
• Tipo de recurso: documento de conferencia
• Materia: Ciencias Astronómicas; International Celestial Reference Frame (ICRF); Very Long Baseline Interferometry (VLBI); Gaia reference frame
• Institución: Universidad Nacional de La Plata

The International Celestial Reference Frame (ICRF) is the fundamental realization of the International Celestial Reference System (ICRS), providing a quasi-inertial coordinate system anchored by precise positions of extragalactic radio sources. Realized through Very Long Baseline Interferometry (VLBI), the ICRF underpins all high-precision astrometry, Earth orientation studies, geodesy, and spacecraft navigation. This talk provides an overview of the evolution of the ICRF from its first realization in 1998 to the current multi-frequency ICRF-3, adopted by the I AU in 2018. ICRF-3 incorporates nearly 40 years of dual-frequency S/X VLBI data, as well as independent realizations at K-band and X/Ka-band, achieving positional accuracies at the 30 micro-arcsecond level. Key challenges -such as source structure effects, Southern Hemisphere coverage, and frequency-dependent offsets - are addressed through global collaboration, targeted observations, and improved modeling. The ICRF is also increasingly integrated with the optical Gaia reference frame, and future efforts are focused on developing a multi-wavelength realization. Particular attention will be given to the growing role of Africa in VLBI and its contributions to the celestial reference frame.
Facultad de Ciencias Astronómicas y Geofísicas