Atmosphere-like turbulence generation with surface-etched phase-screens.

We built and characterized an optical system that emulates the optical characteristics of an 8m-class telescope like the Very Large Telescope. The system contains rotating glass phase-screens to generate realistic atmosphere-like optical turbulence, as needed for testing multiconjugate adaptive optics systems. In this paper we present an investigation of the statistical properties of two phase-screens etched on glass-plate surfaces, obtained from Silios Technologies. Those etched screens are highly transmissive (above 85%) from 0.45 to 2.5 microm. From direct imaging, their Fried parameter r0 values (0.43+/-0.04 microm and 0.81+/-0.03 microm, respectively, at 0.633 microm) agree with the expectation to within 10%. This is also confirmed by a comparison of measured and expected Zernike coefficient variances. Overall, we find that those screens are quite reproducible, allowing sub-millimetre r0 values, which were difficult to achieve in the past. We conclude that the telescope emulator and phase-screens form a powerful atmospheric turbulence generator allowing systematic testing of different kinds of AO instrumentation.

[1]  Roberto Ragazzoni,et al.  MAD the ESO multi-conjugate adaptive optics demonstrator , 2003, SPIE Astronomical Telescopes + Instrumentation.

[2]  Elena Masciadri,et al.  G-SCIDAR measurements on Mt. Graham: recent results , 2006, SPIE Astronomical Telescopes + Instrumentation.

[3]  Brent Ellerbroek,et al.  Advances in Adaptive Optics II , 2006 .

[4]  Michel Tallon,et al.  Focusing on a Turbulent Layer: Principle of the “Generalized SCIDAR” , 1998 .

[5]  J. Conan,et al.  Wave-front temporal spectra in high-resolution imaging through turbulence , 1995 .

[6]  Jean Vernin,et al.  Generalized SCIDAR Measurements at San Pedro Mártir. II. Wind Profile Statistics , 2006 .

[7]  Remko Stuik,et al.  Optimizing wavefront sensing for extreme AO , 2004, SPIE Astronomical Telescopes + Instrumentation.

[8]  E. Fedrigo,et al.  Multiple field of view layer-oriented adaptive optics Nearly whole sky coverage on 8 m class telescopes and beyond , 2002 .

[9]  M. Kasper,et al.  Simultaneous Measurements of the Fried Parameter r_0 and the Isoplanatic Angle theta_0 using SCIDAR and Adaptive Optics - First Results , 2001, astro-ph/0101474.

[10]  John M. Hill,et al.  LBT facility SCIDAR: recent results , 2003, SPIE Astronomical Telescopes + Instrumentation.

[11]  Wenli Xu,et al.  Phase screens for astronomical multiconjugate adaptive optics: application to MAPS , 2003, SPIE Astronomical Telescopes + Instrumentation.

[12]  Thomas Henning,et al.  The MPIA multipurpose laboratory atmospheric turbulence simulator MAPS , 2006, SPIE Astronomical Telescopes + Instrumentation.

[13]  A. Glindemann,et al.  Multi-Conjugate Adaptive Optics with Two Deformable Mirrors – Requirements and Performance , 2001 .

[14]  Jc Dainty,et al.  Profiling of atmospheric turbulence strength and velocity using a generalised SCIDAR technique , 1998 .

[15]  A. Kolmogorov.  The local structure of turbulence in incompressible viscous fluid for very large Reynolds numbers , 1991, Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences.

[16]  Robert K. Tyson,et al.  Adaptive Optical System Technologies , 1998 .

[17]  Andrei Tokovinin,et al.  Seeing Improvement with Ground‐Layer Adaptive Optics , 2004 .

[18]  Bernhard Delabre,et al.  MAPS: a turbulence simulator for MCAO , 2004, SPIE Astronomical Telescopes + Instrumentation.

[19]  Wenli Xu,et al.  Broadband, static wave-front generation: Na-Ag ion-exchange phase screens and telescope emulation. , 2004, Applied optics.

[20]  Jean Vernin,et al.  Generalized Sciadr measurements at San Pedro martir : II wind profiles statistics , 2006 .

[21]  V. I. Tatarskii,et al.  Atmospheric turbulence and the resolution limits of large ground-based telescopes: comment , 1993 .