Toward an interferometer at Dome C, Antarctica: measurement of the atmospheric coherence time

Aglaé Kellerer

doi:10.1117/12.723038

1 November 2006 Toward an interferometer at Dome C, Antarctica: measurement of the atmospheric coherence time

Aglaé Kellerer

Proceedings Volume 6522, Thirteenth Joint International Symposium on Atmospheric and Ocean Optics/ Atmospheric Physics; 65220G (2006) https://doi.org/10.1117/12.723038
Event: Thirteenth Joint International Symposium on Atmospheric and Ocean Optics/ Atmospheric Physics, 2006, Tomsk, Russian Federation

Abstract

Dome C, a summit on the Antarctic Ice Sheet, is a potential site for a projected astronomical interferometer. Measurements of the atmospheric time constant , τ0 - which characterizes the performance of ground-based interferometers - have been performed on January 31st and February 1st 2005 at daytime. The atmospheric time constant was assessed through the motion of the image formed in the focal plane of a Fizeau interferometer. Insufficient temporal and spatial samplings did not permit the direct determination of τ0, but a lower limit was, nevertheless, obtained by studying the decay rate of the correlation between successive fringes. Coherence times were found to exceed 10 ms, i.e. they are at least three times larger than the median coherence time measured at the site of Paranal (3.3ms). The instrumental set-up used at DomeC is sensitive to the wind direction and this intrinsically limits the precision that can be reached in the determination of τ0. We review other current techniques for measuring the atmospheric time constant, and show that an adequate technique to monitor τ0 is still lacking. A new method based on the fast variations of defocus is outlined.

Citation Download Citation

Aglaé Kellerer "Toward an interferometer at Dome C, Antarctica: measurement of the atmospheric coherence time", Proc. SPIE 6522, Thirteenth Joint International Symposium on Atmospheric and Ocean Optics/ Atmospheric Physics, 65220G (1 November 2006); https://doi.org/10.1117/12.723038

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