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NASA Goddard Geophysical and Astronomical Observatory

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Co-Location Survey System Development at GGAO

Space geodetic techniques are now making measurements over global distances to mm precision,but one of the fundamental problems with the co-location regime is the measurement of the vector between the invariant reference points (intersection of axes, GPS antenna reference points, etc.) on the co-located instruments. Sub-mm accuracy of space geodesy system measurments may require a monitoring component in order to understand what is happening in real or near real-time. Small motions may corrupt measurements and subsequently the realization of the reference frame.

Automated measurement of inter-instrument vectors is an essential aspect of an integrated space geodesy station. Measurements provide closure between terrestrial reference frames derived from different space geodesy techniques. Tests of technologiesand currently available systems are underway at GGAO.

A workshop was held in September 2008 to evaluate use of terrestrial laser scanners for automated measruement of co-location vectors. Other techniques currently under study include robotic total station survey systems with a local network of ground reference pillars.

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