Fringe tracking optimization with 4 beams: application to GRAVITY

K. Houairi; F. Cassaing; G. Perrin; F. Eisenhauer; W. Brandner; C. Straubmeier; S. Gillessen

doi:10.1117/12.790967

28 July 2008 Fringe tracking optimization with 4 beams: application to GRAVITY

K. Houairi, F. Cassaing, G. Perrin, F. Eisenhauer, W. Brandner, C. Straubmeier, S. Gillessen

Proceedings Volume 7013, Optical and Infrared Interferometry; 70131B (2008) https://doi.org/10.1117/12.790967
Event: SPIE Astronomical Telescopes + Instrumentation, 2008, Marseille, France

Abstract

GRAVITY, a VLTI second generation instrument, requires a fringe tracker combining four beams. Its design is driven by the observation of the Galactic Center and implies stringent fringe sensor specifications. We present the simulations of the fringe tracking closed-loop performance with an optical path difference (OPD) turbulence spectrum using a Kolmogorov model of the atmosphere for typical seeing conditions at VLTI (r₀ = 0.95 m, t₀ = 47 ms at 2.2 μm). We show that the total residual OPD standard deviation can be as low as λ/12 at a sampling frequency of 350 Hz on a guide star with a magnitude of mK = 10. To obtain this performance, we compared several 4-beam pairwise co-axial combination conceptual architectures and show that the optimal 4-beam combination is the one measuring the OPD on the six baselines.

Citation Download Citation

K. Houairi, F. Cassaing, G. Perrin, F. Eisenhauer, W. Brandner, C. Straubmeier, and S. Gillessen "Fringe tracking optimization with 4 beams: application to GRAVITY", Proc. SPIE 7013, Optical and Infrared Interferometry, 70131B (28 July 2008); https://doi.org/10.1117/12.790967

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