Effects of Atmospheric Water Vapor on Infrared Interferometry

September 2004 • 2004PASP..116..876C

Authors • Colavita, M. Mark • Swain, Mark R. • Akeson, Rachel L. • Koresko, Christopher D. • Hill, Reginald J.

Abstract • Water vapor, while usually a small contributor to the atmospheric refractive index for astronomical observations at IR wavelengths, is highly dispersive and can introduce optical path length errors affecting high-precision interferometer observing modes. The refractive index of atmospheric water vapor can be computed from a summation over the various IR resonances, and we present values over a range of 1.2-13.5 μm. The dispersion of water vapor introduces phase errors across the instrument passband and produces excess noise in interferometer group delay, residual errors in cophasing using a different source wavelength, and coherence loss over broad optical bandwidths. We quantify these effects for the J through N bands, discuss means of amelioration, and consider their implications for differential phase and nulling observing modes.

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• PDF https://iopscience.iop.org/article/10.1086/424472/pdf
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