Atmospheric Turbulence Measurements with the Palomar Testbed Interferometer

Abstract

Data from the Palomar Testbed Interferometer, with a baseline length of 110 m and an observing wavelength of $2.2\mu \mathrm{m}$, were used to derive information on atmospheric turbulence on 64 nights in 1999. The measured two-aperture variance coherence times at $2.2\mu \mathrm{m}$ ranged from 25 msec to 415 msec (the lower value was set by instrumental limitations---the interferometer could not operate when the coherence time was lower than this). On all nights, the spectrum of the short time scale ($<600$ msec) delay fluctuations had a shallower spectrum than the theoretical Kolmogorov value of 5/3. On most nights, the mean value of the power law slope was between 1.40 and 1.50. Such a sub-Kolmogorov slope will result in the seeing improving as the $\approx 0.4$ power of wavelength, rather than the slower 0.2 power predicted by Kolmogorov theory. On four nights, the combination of delay and angle tracking measurements allowed a derivation of the (multiple) wind velocities of the turbulent layers, for a frozen-flow model. The derived wind velocities were all $\le 4\mathrm{m}{\mathrm{s}}^{-1}$, except for a small $10\mathrm{m}{\mathrm{s}}^{-1}$ component on one night. The combination of measured coherence time, turbulence spectral slope, and wind velocity for the turbulent layer(s) allowed a robust solution for the outer scale size (beyond which the fluctuations do not increase). On the four nights with angle tracking data, the outer scale varied from 6 to 54 m, with most values in the 10-25 m range. Such small outer scale values cause some components of visibility and astrometric errors to average down rapidly.

25 pages (including 9 figures), accepted by Ap.J

References in corpus (1)

• The Palomar Testbed Interferometer

Cited by in corpus (14)

• Quantum Physics Exploring Gravity in the Outer Solar System: The Sagas Project
• Infrared Observations During the Secondary Eclipse of HD 209458 b II. Strong Limits on the Infrared Spectrum Near 2.2 Microns
• A coherent optical link through the turbulent atmosphere
• Data reduction methods for single-mode optical interferometry - Application to the VLTI two-telescopes beam combiner VINCI
• Stabilized free-space optical frequency transfer
• Lasers for coherent optical satellite links with large dynamics
• OSS (Outer Solar System): A fundamental and planetary physics mission to Neptune, Triton and the Kuiper Belt
• Impact of Atmospheric Chromatic Effects on Weak Lensing Measurements
• The Optical/Infrared Astronomical Quality of High Atacama Sites. I. Preliminary Results of Optical Seeing
• Wavelength Dependent PSFs and their impact on Weak Lensing Measurements
• The PRIMA fringe sensor unit
• Constraining the Adaptive Optics Point-Spread Function in Crowded Fields: Measuring Photometric Aperture Corrections
• Methods for coherent optical Doppler orbitography
• Direct Measurements of Giant Star Effective Temperatures and Linear Radii: Calibration Against Spectral Types and V-K Color