International reference framework contributions
VLBI is the only technology that permits determination of positions on Earth with a direct relationship to a celestial reference system. The International Celestial Reference Frame (ICRF) is an inertial frame of reference with fundamental importance for astronomy and geodesy. It is determined using extragalactic radio sources (quasars), whose locations in space have proven to be very stable when measured with VLBI. The International Terrestrial Reference Frame ITRF), which rotates with the earth, is defined by a globally distributed measurement network on the earth’s surface. The rotation of the earth plays a key role in linking the terrestrial and celestial systems. The task of updating global reference systems involves continuous determination of all the parameters that define the celestial and terrestrial reference systems (ICRF, ITRF), including the Earth Orientation Parameters (EOP).
As one of two VLBI stations in Antarctia, O’Higgins plays an important role. As part of the 'International VLBI Service' (IVS), four to eight 24 hour sessions are conducted each year during six- to eight-week campaigns. Most monitoring sessions (OHIG series) are undertaken to improve the southern reference frame and are undertaken together with radio telescopes in Fortaleza (Brazil), Hartebeesthoek (South Africa), Hobart (Tasmania), Kokee Park (Hawaii, USA), Syowa (Antarctica) and Concepcion (Chile). O'Higgins also participates in so-called T2 sessions, which contribute to the global terrestrial reference framework and involve 15-20 stations worldwide. Since the beginning of regular observations in 1993, 140 sessions have been conducted at O'Higgins.
The GNSS stations at O'Higgins have regularly provided data since 1995 as part of the 'International GNSS Service' (IGS) global network. These data are processed at the IGS analysis centres to generate products like station coordinates and earth orientation parameters. Thus, as one of ten IGS stations in the Antarctic O'Higgins makes an important contribution to the stability of the international reference frame.
