A method for determining the acceleration due to gravity is suggested. Two falling interferometer reflectors illuminated by a laser are used. The falling reflectors are separated by a AT and thus have a constant velocity differential, this generates a frequency linearly proportional to acceleration ( g = kf ) Thus, the metrology of measuring g is simplified by having g linearly proportional to frequency.
L. D. Ballard,
W. S. Epstein,
E. R. Smith,
"A Suggestion for Determining g by a Two Interferometer Technique," Optical Engineering 9(5), 905166 (1 July 1971). https://doi.org/10.1117/12.7971579