Sensitivity of the Drop Length in a Rise and Fall Absolute Gravimeter: Simulation and Data from the IMGC-02 Instrument Operating in Different Measurement Sites

In ballistic absolute gravimeters, the length of the analyzed trajectory of the falling object plays a crucial role in the accuracy and the precision of the determination of the gravity value. The effect is generated by different known and unknown sources. They depend both on the instrument setup, e.g. mechanical systems or fringe signal processing, and the measurement site, namely the stiffness of the floor. The dominant aspect concerns the recoil which appears at the start of the drop. In the case of rise and fall method, as for the IMGC-02 apparatus, the magnitude of such recoil is higher with a respect to the freefall one. A detailed analysis of the sensitivity of the drop length for this absolute gravimeter was never done before. The goal of the study is to evaluate how the variation of drop length can affect the measurement of the free fall acceleration, in order to achieve best solution to minimize the perturbation without reduce the resolution. The solution must be found as a function of the different measurement site and its associated uncertainty were evaluated.