The University of Bonn and the state of NRW jointly operate a geodetic observatory near Todenfeld, a beautiful Eifel village about 30 km east of Bonn. The observatory hosts a range of seismometers and, since two years, one of the world's finest superconducting gravimeters. The gravimeter is operated by Jürgen Kusche and Basem Elsaka from the Geodesy Institute just across the street and can measure changes in the Earth's gravitational potential at the level of one in a billion.
The research group of Simon Stellmer now installed a commercial fiber-optic gyroscope right next to the gravimeter as a test system for the home-built ring lasers. Already now, they can sense slow changes in rotation at the level of a few 10 nrad per second, that's about one revolution per year. Both the gravimeter and the gyroscope are sensitive to tilt, which might become the next joined project of the two research groups. Luckily, a suitable tiltmeter with sub-nrad resolution is already operational in the basement of the physics institute.