High-precision laser gravimeter.

A ballistic gravimeter has been constructed using a laser interferometer to measure the vertical distance traversed by a free-falling body and a rubidium frequency standard to measure elapsed time. The error in distance and time measurement are estimated to be less than 2 x 10(-8) and 2 x 10(-11) respectively. The systematic error in measuring gravitational acceleration, after corrections have been made, does not exceed 0.02 mgal.