Enabling a linear model for the IMGC-02 absolute gravimeter

Measurement procedures of most rise-and-fall absolute gravimeters have to resolve singularity at the apex of the trajectory caused by the discrete fringe counting in the Michelson-type interferometers. Traditionally the singularity is addressed by implementing non-linear models of the trajectory, but they introduce problems of their own, such as bias, non-uniqueness, and instability of the gravity estimates. Using the IMGC-02 gravimeter as an example, we show that the measurement procedure of the rise-and-fall gravimeters can be based on linear models which successfully resolve the singularity and provide rigorous estimates of the gravity value. The linear models also facilitate further enhancements of the instrument, such as accounting for new types of disturbances and active compensation for vibrations.