The Mark III interferometer is a phase-coherent stellar interferometer designed for astrometry. Operating through the turbulent atmosphere, the instrument is also a sensitive detector of atmospheric phase fluctuations. The effect of phase fluctuations on astrometric accuracy is reviewed, and phase measurements obtained with the instrument at Mt. Wilson using a 12-m base line are presented. These measurements agree well with the predictions of a simple Kolmogorov spatial spectrum over the frequency range of 0.001–100 Hz. From these measurements, the outer scale of turbulence for propagation through the entire atmosphere is estimated to be >2 km. The standard deviation for an absolute astrometric measurement estimated from these measurements is ∼0.14T−1/6 sec of arc for long integration times for conditions of 0.5-sec of arc seeing. For star-switched relative measurements, this error should decrease as the square root of the number of switching cycles.
© 1987 Optical Society of America
Original Manuscript: April 29, 1987
Published: October 1, 1987
M. Mark Colavita, Michael Shao, and David H. Staelin, "Atmospheric phase measurements with the Mark III stellar interferometer," Appl. Opt. 26, 4106-4112 (1987)