On Uncertainties of Laser Interferometric Absolute Ballistic Gravimeters Due to Magnetic Effects in the Free-Fall Gravity Measurements

At present, the uncertainty in measurements of free fall acceleration (FFA) by the designed absolute ballistic gravimeter (ABG), developed in VNIIM, attains microgal values (1 Gal = 1 cm/s2). At such a high level of accuracy, the effects of the interaction of a test body (TB) falling in the vacuum chamber of the ABG in the geomagnetic field could comprise sources of systematic errors. Furthermore, individual units and systems of the ABG itself also can be sources of the magnetic field (MF). We report about more rigorous calculations of the possible effects than those performed in the past. A consecutive self-consistent method of calculation of the desired correction to the FFA has been developed. It results in the differential equation, including not only the field itself, but also its vertical first and second derivatives and variation of the velocity along the trajectory. The desired correction is obtained by its numerical solution on the basis of the parameters of the field generated by the magnet of the stepper motor. The derived correction proved to be at the level of a tenth part of microgal.