Automated IVS Reference Point Monitoring - First Experience from the Onsala Space Observatory

The realization of the International TerrestrialReference Frame (ITRF) builds upon acombination of results derived from several geodeticspace techniques, such as Very Long Baseline Interferometry(VLBI), Satellite and Lunar Laser Ranging(SLR and LLR) or Global Navigation Satellite Systems(GNSS). To combine the different techniques andtheir results in a meaningful way, co-location sites areimportant where equipment for several techniques islocated reasonably close to each other. The relativegeometries (local tie vectors) between the geometricreference points of the different techniques can bederived by terrestrial survey at these co-locationsites. Within the Global Geodetic Observing System(GGOS) the requirements in terms of e.g. accuracyand frequency of local survey campaigns have beenincreased to guarantee that the local tie vectors reachan utmost level of global accuracy. In response tothis request we developed a concept to achieve automatedand continuous monitoring of radio telescopereference points. This concept was realized and testedin 2012 at the Onsala Space Observatory where anautomated monitoring system was installed for acontinual determination of the reference point ofthe 20 m radio telescope. The results confirm thatuncertainties on the sub-mm level can be achieved withthis approach