Atmospheric phase measurements with the Mark III stellar interferometer.

Area of Science:

• Astronomy and Astrophysics
• Atmospheric Science

Background:

• Stellar interferometers are vital for high-precision astrometry.
• Atmospheric turbulence significantly impacts astrometric accuracy.
• The Mark III interferometer is a phase-coherent instrument designed for astrometry.

Purpose of the Study:

• To review the effect of atmospheric phase fluctuations on astrometric accuracy.
• To present phase measurements from the Mark III interferometer.
• To characterize atmospheric turbulence using astrometric data.

Main Methods:

• Utilized the Mark III interferometer with a 12-m baseline at Mt. Wilson.
• Collected phase fluctuation data across a frequency range of 0.001-100 Hz.
• Compared measurements to Kolmogorov spatial spectrum predictions.

Main Results:

• Phase measurements align with Kolmogorov spectrum predictions.
• Estimated the atmospheric turbulence outer scale to be greater than 2 km.
• Calculated astrometric measurement standard deviation: ~0.14 arcsec for absolute, with reduced error for relative measurements.

Conclusions:

• The Mark III interferometer effectively detects atmospheric phase fluctuations.
• Turbulence characteristics derived are consistent with existing models.
• Findings inform strategies for improving astrometric precision in turbulent conditions.