MATISSE is foreseen as a mid-infrared spectro-interferometer combining the beams of up to four UTs/ATs of the Very
Large Telescope Interferometer (VLTI) of the European Southern Observatory. The related science case study
demonstrates the enormous capability of a new generation mid-infrared beam combiner.
MATISSE will constitute an evolution of the two-beam interferometric instrument MIDI. MIDI is a very successful
instrument which offers a perfect combination of spectral and angular resolution. New characteristics present in
MATISSE will give access to the mapping and the distribution of the material (typically dust) in the circumstellar
environments by using a wide mid-infrared band coverage extended to L, M and N spectral bands. The four beam
combination of MATISSE provides an efficient UV-coverage : 6 visibility points are measured in one set and 4 closure
phase relations which can provide aperture synthesis images in the mid-infrared spectral regime.
Long baseline interferometry now faces two main challenges. The first one is the image reconstruction from interferometric data. Indeed, the reduced information on the phase of the object Fourier transform during an observation makes image reconstruction quite critical. The second challenge is the improvements of the
overall sensitivity. Strong improvement are expected from double field interferometry : For instance, double field
interferometry enables phase referencing which is a way to obtain information on phases. In addition, double
field interferometry increases the sensitivity of an interferometer.
In this paper we present simulations of double field interferometry. Our simulations take into account; the turbulence conditions, the detection noise, the fringe tracking error. For simulated double field data, we perform an image reconstruction using the coaddition of fringes in the image plane. Since the performances of a double field interferometer are very closely related to and dependent on the site characteristics we studied the results for two different locations: Paranal and Dome C. The comparison shows that Dome C offers much better results, and that it is probably the best site on Earth to build a double-field interferometer.
The amdlib AMBER data reduction software is meant to produce AMBER data products from the raw data files
that are sent to the PIs of different proposals or that can be found in the ESO data archive. The way defined
by ESO to calibrate the data is to calibrate one science data file with a calibration one, observed as close in
time as possible. Therefore, this scheme does not take into account instrumental drifts, atmospheric variations
or visibility-loss corrections, in the current AMBER data processing software, amdlib.
In this article, we present our approach to complement this default calibration scheme, to perform the final
steps of data reduction, and to produce fully calibrated AMBER data products. These additional steps include:
an overnight view of the data structure and data quality, the production of night transfer functions from the
calibration stars observed during the night, the correction of additional effects not taken into account in the
standard AMBER data reduction software, and finally, the production of fully calibrated data products. All these new features are implemented in the modular pipeline script amdlibPipeline, written to complement the amdlib software.
Recent site testing (see: http://www-luan.unice.fr/Concordiastro/indexantartic.html) has shown that Dome C in Antarctica might have a high potential for stellar interferometry if some solutions related to the surface atmospheric layer are found. A demonstrator interferometer could be envisioned in order to fully qualify the site and prepare the future development of a large array. We analyse the performances of a prototype interferometer for Dome C made with 3 telescopes of 40 cm diameter. It assumes classical Michelson recombination. The most recent atmospheric and environmental conditions measured at Dome C are considered (see K. Agabi "First whole atmosphere night-time seeing measurements at Dome C, Antarctica"). We also study the possible science reachable with such a demonstrator. Especially we evaluate that even such small aperture interferometer could allow the detection and low resolution spectroscopy of the most favorable pegaside planets.
PRIMA, the Phase-Referenced Imaging and Micro-arcsecond Astrometry facility for the Very Large Telescope Interferometer, is now nearing the end of its manufacturing phase. An intensive test period of the various sub-systems (star separators, fringe sensor units and incremental metrology) and of their interactions in the global system will start in Garching as soon as they are delivered. The status and performances of the individual sub-systems are presented in this paper as well as the proposed observation and calibration strategy to reach the challenging goal of high-accuracy differential astrometry at 10 μas level.