AGGO: Concept and realization of a geodetic observatory in South-America

Geodetic observatories form the backbone of global geodetic reference frames. This article reviews the definition of the global geodetic reference system in terms of its origin, orientation, and scale, and its realization through reference frames. At geodetic observatories, reference points are materialized by instruments and survey markers. To achieve the highest possible accuracy, complementary measurement techniques are employed, often operating near the limits of what is technically feasible. Accordingly, a geodetic observatory brings together complex instruments, including a radio telescope for very long baseline interferometry (VLBI), a satellite laser ranging (SLR) system, receiving stations for global navigation satellite systems (GNSS), atomic clocks, absolute and superconducting gravimeters, and complementary sensors. The spatial relationships between the reference points of these instruments are determined through precise local surveys (local ties). The current instrumentation of the Argentine-German Geodetic Observatory (AGGO) is described as an example of the range of measurement techniques needed to establish and maintain a reference site within the global geodetic reference frame. Measurement data collected at AGGO are made freely available through international services.