Annual Report 2011 Max Planck Institute for Astronomy

IV.3 MatiSSe – Interferometric Imaging in the Mid-Infrared
MatiSSe – the Multi Aperture Mid-Infrared SpectroScopic
Experiment – is one of two second generation instruments
which had been selected by eSo for the VLTI at
Paranal. Thus MatiSSe is in a sense the successor of
Midi, the Mid-Infrared Interferometric Instrument, which
has been built at MPIA and which is working on Paranal
since 2003.
Matisse will combine the beams of up to four of the 8 m
UTs (Unit Telescopes) or of up to four of the 1.8 m ATs
(Auxiliary Telescopes) and thus will be able to measure
in “closure phase mode”, i.e. it offers an efficient capability
for image reconstruction with a spatial resolution
of up to 7 milliarcsec. The instrument will work at three
wavelength bands: L (3.2 – 3.9 μm), M (4.5 – 5 μm), and
N (8 – 13 μm), where the L and M band observations are
performed simultaneously to the N band.
With the three different spectroscopic resolutions in
the range of R 30 – 1500 it will provide the basis for
a fundamental analysis of the composition of gas and
dust grains in various astrophysical environments. Key
science programs for the ATs cover for example the formation
and evolution of planetary systems, the birth of
massive stars as well as the observation of the highcontrast
environment of hot and evolved stars. With the
UTs selected astrophysical programs such as the study
of Active Galactic Nuclei and Extrasolar Planets shall
be possible.
Matisse is developed and built by a collaboration
of the Observatoire de la Cote d’Azure, the MPIA, the
MPI for Radio Astronomy in Bonn and two institutions
(astron/Dwingeloo and Leiden University) from the
Netherlands. In this consortium MPIA is responsible for
the cryogenics system, the entire control electronics, and
the instrument control software.
After the successful Preliminary Design Review
(PDR) in December 2010 the year 2011 was dominated
by the preparations for the first part of the Final Design
Fig. IV.3.1: Pulse tube cooler PTC 410 from Cryomech. The two
copper plates mark the two stages.
Fig. IV.3.2: Head of Pulse tube cooler with damping system on
test set-up.
Review (FDR) in September 2011, where the cryogenic system and the design of the optics were reviewed by
eso. For the development of the cryostats several tests
Table. IV.3.1: The characteristic parameters of Matisse.
Number of beams/
telescopes
4 (2 or 3 possible)
Field of view 2 arcsec
Spectral resolution L/M N
Low 20 R 40 20 R 40
Medium 200 R 400 200 R 400
High 750 R 1250
Spatial resolution 0.007 arcsec 0.02 arcsec
had to be performed. By using an auxiliary cryostat we
specified the characteristics of the selected Pulse Tube
Cooler PT410 from Cryomech (Fig. IV.3.1). With using
such a device the induced vibrations are typically factors
of 10–50 lower than with normal Closed Cycle Coolers
of similar cooling power.
Besides the vibrations inside and outside of the test
cryostat we also tested for the minimum temperatures to
be reached with this kind of cooler at its first and second
stage and for the temperature variations caused by the
cooler when connected to a dummy cold optical bench
(first stage) and a dummy detector (second stage). Here
the copper braid used for this connection had to be opti-
Credit: U. Graser
Credit: U. Graser
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