Omega-E: Establishing the instantaneous Earth rotation vector by inertial rotation sensing

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Operations of the large G ring laser have improved to the point that Earth rotation can be routinely monitored at the level 5*10-9 < 'Earth rotation changes' < 10-8. Unfortunately this is only a single component gyroscope. With the construction of the ROMY ring laser it was possible to build the first large 4 component optical gyroscope for applications in seismology and space geodesy. The scale factor of ROMY is two times larger than that of the G ring laser and it has been constructed as a heterolithic structure. This research proposal attempts to operate the ROMY structure phase locked in a weak multimode regime in order to stabilize the cavity sufficiently to observe diurnal retro-grade polar motion. This signal is not directly detectable with the geometric techniques of space geodesy such as GNSS, SLR and VLBI. The development of suitable models for the geophysical processes causing this signal is another important part of this research proposal as well as the appropriate fusion of ring laser observations with measurements of VLBI and GNSS. The comparison between the G ring laser and ROMY structure finally helps to distinguish local from global rotation.