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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 559448.0, MPI für Astronomie / Publikationen_mpia
Status of PRIMA for the VLTI or the quest for user-friendly fringe tracking
Authors:Schmid, C.; Abuter, R.; Ménardi, S.; Andolfato, L.; Delplancke, F.; Derie, F.; di Lieto, N.; Frahm, R.; Gitton, Ph; Gomes, N.; Haguenauer, P.; Lévêque, S.; Morel, S.; Müler, A.; Phan Duc, T.; Pozna, E.; Sahlmann, J.; Schuhler, N.; van Belle, G.
Place of Publication:Bellingham, Wash.
Date of Publication (YYYY-MM-DD):2010
Title of Proceedings:Optical and Infrared Interferometry II
Start Page:77340F-77340F
End Page:13
Title of Series:SPIE
Volume (in Series):7737
Name of Conference/Meeting:Optical and Infrared Interferometry II
Review Status:not specified
Audience:Experts Only
Abstract / Description:The Phase Referenced Imaging and Micro Arcsecond Astrometry (PRIMA) facility for the Very Large Telescope Interferometer (VLTI), is being installed and tested in the observatory of Paranal. Most of the tests have been concentrated on the characterization of the Fringe Sensor Unit (FSU) and on the automation of the fringe tracking in preparation of dual-field observations. The status of the facility, an analysis of the FSU performance and the first attempts towards dual-field observations will be presented in this paper. In the FSU, the phase information is spatially encoded into four independent combined beams (ABCD) and the group delay comes from their spectral dispersion over 5 spectral channels covering the K-band. During fringe tracking the state machine of the optical path difference controller is driven by the Signal to Noise Ratio (SNR) derived from the 4 ABCD measurements. We will describe the strategy used to define SNR thresholds depending on the star magnitude for automatically detecting and locking the fringes. Further, the SNR as well as the phase delay measurements are affected by differential effects occurring between the four beams. We will shortly discuss the contributions of these effects on the measured phase and SNR noises. We will also assess the sensitivity of the group delay linearity to various instrumental parameters and discuss the corresponding calibration procedures. Finally we will describe how these calibrations and detection thresholds are being automated to make PRIMA as much as possible a user-friendly and efficient facility.
Comment of the Author/Creator:Date: 2010, July 1, 2010
External Publication Status:published
Document Type:Conference-Paper
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL: [ID No:1]
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