The VLTI fringe sensors: FINITO and PRIMA FSU

FINITO is the first generation VLTI fringe sensor, optimised for three beam observations, recently installed at Paranal and currently used for VLTI optimisation. The PRIMA FSU is the second generation, optimised for astrometry in dual-feed mode, currently in construction. We discuss the constraints of fringe tracking at VLTI, the basic functions required for stabilised interferometric observations, and their different implementation in the two instruments, with remarks on the most critical technical aspects. We provide an estimate of the expected performance and describe some of their possible observing and calibration modes, with reference to the current scientific combiners.

[1]  Andreas Glindemann,et al.  Phase-referenced imaging and micro-arcsecond astrometry with the VLTI , 2000, Astronomical Telescopes and Instrumentation.

[2]  Sebastien Morel,et al.  VLTI technical advances: present and future , 2004, SPIE Astronomical Telescopes + Instrumentation.

[3]  Leonardo Corcione,et al.  Models for VLTI fringe sensor units: FINITO and PRIMA FSUs , 2004, SPIE Astronomical Telescopes + Instrumentation.

[4]  Leonardo Corcione,et al.  Near IR Fringe Tracking for VLTI: the FINITO Detection System , 2004 .

[5]  Samuel A. Leveque.  Metrology for phase-referenced imaging and narrow-angle astrometry with the VLTI , 2000, Astronomical Telescopes and Instrumentation.

[6]  Romain G. Petrov,et al.  Astrophysical potential of the AMBER/VLTI instrument , 2003, SPIE Astronomical Telescopes + Instrumentation.

[7]  Sebastiano Ligori,et al.  Ten-micron instrument MIDI: getting ready for observations on the VLTI , 2003, SPIE Astronomical Telescopes + Instrumentation.

[8]  Leonardo Corcione,et al.  The FINITO Fringe Sensor for VLTI , 2002 .

[9]  James W. Beletic,et al.  Scientific Detectors for Astronomy , 2004 .