Balance for Measuring Mass Under Microgravity Conditions

A method for efficiently and accurately measuring mass under conditions of weightlessness is proposed using the law of conservation of momentum. In this method, the velocities of two different uniform motion states of an object and the reference mass are measured highly accurately using an optical interferometer. For the preparatory experiments on earth, an instrument, with which linear motion of constant velocity is realized using pneumatic linear bearings, is developed. The combined standard uncertainty in mass measurements from 4 to 18 kg by a single collision is estimated to be about u c = 0.012 kg, which corresponds to 0.07% (7 x 10 -4 ) of the maximum value of 18 kg. For a mass-measurement instrument employed under microgravity conditions, a design for the instrument and a measurement procedure are proposed.