2009A&A...507.1739S


Query : 2009A&A...507.1739S

2009A&A...507.1739S - Astronomy and Astrophysics, volume 507, 1739-1757 (2009/12-1)

The PRIMA fringe sensor unit.

SAHLMANN J., MENARDI S., ABUTER R., ACCARDO M., MOTTINI S. and DELPLANCKE F.

Abstract (from CDS):

The fringe sensor unit (FSU) is the central element of the phase referenced imaging and micro-arcsecond astrometry (PRIMA) dual-feed facility and provides fringe sensing for all observation modes, comprising off-axis fringe tracking, phase referenced imaging, and high-accuracy narrow-angle astrometry. It is installed at the Very Large Telescope Interferometer (VLTI) and successfully served the fringe-tracking loop during the initial commissioning phase. To maximise sensitivity, speed, and robustness, the FSU is designed to operate in the infrared K-band and to include spatial filtering after beam combination and a very-low-resolution spectrometer without photometric channels. It consists of two identical fringe sensors for dual-star operation in PRIMA astrometric mode. Unique among interferometric beam combiners, the FSU uses spatial phase modulation in bulk optics to retrieve real-time estimates of fringe phase after spatial filtering. The beam combination design accommodates a laser metrology for pathlength monitoring. An R=20 spectrometer across the K-band makes the retrieval of the group delay signal possible. The calibration procedure uses the artificial light source of the VLTI laboratory and is based on Fourier transform spectroscopy to remove instrumental effects. The FSU was integrated and aligned at the VLTI in July and August 2008. It yields phase and group delay measurements at sampling rates up to 2kHz, which are used to drive the fringe-tracking control loop. During the first commissioning runs, the FSU was used to track the fringes of stars with K-band magnitudes as faint as mK=9.0, using two VLTI auxiliary telescopes (AT) and baselines of up to 96m. Fringe tracking using two Very Large Telescope (VLT) unit telescopes was demonstrated. The concept of spatial phase-modulation for fringe sensing and tracking in stellar interferometry is demonstrated for the first time with the FSU. During initial commissioning and combining stellar light with two ATs, the FSU showed its ability to improve the VLTI sensitivity in K-band by more than one magnitude towards fainter objects, which is fundamental for achieving the scientific objectives of PRIMA.

Abstract Copyright:

Journal keyword(s): instrumentation: interferometers - techniques: interferometric - astrometry

Simbad objects: 17

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Number of rows : 17
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 HD 4803 PM* 00 49 58.2191287200 -16 10 03.262310436   9.75 9.09     G2V 13 0
2 HD 10067 * 01 38 03.4126681152 -22 25 31.287085428   10.49 9.35     K1/2III 6 0
3 HD 15520 PM* 02 28 10.7645987496 -50 18 09.792484524   8.10 6.97     K1III 12 0
4 HD 17967 * 02 52 36.9872708352 -19 37 17.723275464   11.01 10.31     G2V 4 0
5 HD 18558 PM* 02 58 04.2966604080 -30 57 46.455827868   10.50 9.83     G5V 9 0
6 HD 18829 * 02 59 34.5498121152 -53 54 30.786891696   8.10 6.85     K2III 11 0
7 HD 19349 * 03 06 33.4943946528 -06 05 18.779128836   6.808 5.256     M2/3II 44 0
8 HD 23747 ** 03 46 14.8322111448 -33 28 54.735891096   10.629 10.294 10.399   A9V 10 0
9 * ome CMa Be* 07 14 48.6538664 -26 46 21.609714 2.90 3.64 3.82 3.80 3.90 B2.5Ve 351 0
10 V* GP Vel HXB 09 02 06.8608812864 -40 33 16.899168060 6.85 7.37 6.87 6.31 6.05 B0.5Ia 1493 0
11 * iot Ant PM* 10 56 43.0512189504 -37 08 15.962675568 6.47 5.63 4.60 3.85 3.32 K0III 52 0
12 HD 100091 PM* 11 30 42.1906683504 -42 34 43.484078928   10.52 9.94     G0V 6 0
13 EQ 1315-330 * 13 18 22.4046265632 -33 15 48.041592876   11.5       G2 2 0
14 HD 116714 * 13 26 08.4825701616 -40 45 53.215969032   10.62 10.08     G0V 4 0
15 TYC 7830-1237-1 TT* 15 14 47.4804223896 -42 20 15.034384644   12.200 11.297 11.084   K1IV 19 0
16 HD 157591 * 17 25 42.2763379824 -35 45 18.468543132   9.65 8.16     K0III 10 0
17 HD 206647 * 21 44 01.3654111944 -19 30 31.165172352   9.09 8.11     K0III 10 0

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