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30 January 2003 Atmospheric-induced wavefront distortion and compensation on large-aperture millimeter-wave telescopes
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In the troposphere water vapor plays a fundamental role in radio propagation. The refractivity of water vapor is about 20 times greater in the radio range than in near-infrared or optical regimes. As a consequence, phase fluctuations at frequencies higher than about 1 GHz are predominantly caused by fluctuations in the distribution of water vapor. On filled-aperture telescopes radio seeing shows up as an anomalous refraction (AR), i.e. an apparent displacement of a radio source from its true position. The magnitude of this effect, as a fraction of the beam width, is bigger on larger telescopes. I will thus present a model study of AR effects, obtained producing numerical simulations of two-dimensional phase screens. I will finally discuss the basic concept and requirements of a tip-tilt compensation system at millimeter wavelengths, and will also describe a proposed design based on a scanning microwave radiometer as a wave front sensing device.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Luca Olmi "Atmospheric-induced wavefront distortion and compensation on large-aperture millimeter-wave telescopes", Proc. SPIE 4840, Future Giant Telescopes, (30 January 2003);


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