Untitled - Laboratoire d'Astrophysique de l'Observatoire de Grenoble

Figure 11.5: Image of the binary star λ Virginis obtained by aperture synthesis with the IONIC3 instrument
on IOTA. At the bottom, the beam combiner IONIC3. From Monnier et al., 2004, ApJ, 602, L57.
11.2.2 The innovative integrated optics: IONIC on the IOTA and VLTI interferometers
LAOG has developed in a close partnership with the Harvard-Smithsonian Center for Astrophysics the focal
instrument (called IONIC3) combining three telescopes of the IOTA Interferometer (Traub et al., 2004, SPIE,
5491, 482). This instrument, whose first light has occurred in 2002, uses the integrated optics techniques developed
by LAOG with its local partners (IMEP and LETI) and significantly financed by the CNES. IONIC3 is the
more sensitive and the more accurate imaging instrument operating in the near infrared range. It is now used
by about ten American and European teams and provides scientific results in the field of imaging of multiple
systems (Figure 11.5), pre-main sequence stars, evolved stars (Kraus et al., 2005, AJ, 130, 246). J.-P. Berger
is the main responsible for this activity at LAOG.
LAOG has also delivered two integrated optics beam combiners to ESO to equip the focus of the VINCI
instrument. The first one, made by ion-exchange technique and operating in H band, has been tested at
Paranal during the summer 2002 (Le Bouquin et al., 2004, A&A, 424, 719). The second one, made by silica-onsilicon
etching technique and operating in K band, has been installed in Paranal during the summer 2004. The
latter is routinely used with VINCI for VLTI test such as for the first combination of the Auxiliary Telescopes
(Figure 11.6).
11.2.3 Combining up to eight telescopes of the VLTI array: VITRUV
In the framework of the European Interferometry Initiative (EII) within the FP6 OPTICON program (see
”European involvement” chapter in this report), we have conducted the concept study for a second generation
instrumentation for the VLTI. It consists of a spectro-imager based on the integrated optics techniques aimed
at combining 4 to 8 beams from the VLTI to produce aperture synthesis images in one single night. The work
consisted in several R&D developments financed by the CNES and the BQR of UJF University (4-way beam
combiners, 4T/8T workbenches, end-to-end lab and numerical modeling, system studies, image reconstruction,
...) but also the preparation of the science cases in collaboration with P. Garcia in Porto (chair of the Science
group).
This concept and all related studies have been presented at the ESO Workshop The Power of Optical/IR
Interferometry: Recent Scientific Results and 2nd Generation VLTI Instrumentation, held in Garching in April
2005. This project has been recommended by the Science Council of the EII to ESO, but is still waiting for the
beginning of a phase A study. F. Malbet is responsible for this activity.
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