Measurement of the absolute acceleration due to gravity using a laser ballistic gravimeter

A unique device is described for highly accurate measurement of the absolute acceleration due to gravity using a ballistic method. Using stabilized lasers, a rubidium frequency standard, and a computercontrolled high-speed electronic counting system, it was possible to achieve a relative error of 4×10^–9 with an output of 5000 measurements per twenty four hours. Results are presented of determinations of the absolute acceleration due to gravity at international initial and reference gravimetric points and to investigate tidal and nontidal (secular) variations in gravity.