Improvements of the MPG-2 transportable absolute ballistic gravimeter

The MPG-2 (Max-Planck-Gravimeter) is a transportable absolute gravimeter built on a classical free-fall scheme to measure the local gravity value. With significant improvements and further investigations in recent years, the standard deviation of the mean for a typical measurement over 12 h to 24 h is 1.0 µGal to 3.0 µGal (1 µGal = 10 −8  m s −2 ), and the combined standard uncertainty is estimated to be less than 10 µGal. The major improvements include the new interferometer design and alignment, longer drop length, reduced recoil effects and demagnetization of the falling body. The revised uncertainty budget and new measurement results of MPG-2 are reported. The results of observations at the reference gravity station Bad Homburg confirmed the revised uncertainty budget.