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The European Southern Observatory (ESO) is preparing to upgrade VISIR, the mid-IR imager and spectrograph at the
VLT. The project team is comprised of ESO staff and members of the original consortium that built VISIR: CEA Saclay
and ASTRON. The goal is to enhance the scientific performance of VISIR and to facilitate its use by the ESO
community. In order to capture the needs of the user community, we collected input from the users by means of a webbased
questionnaire. In line with the results of the internal study and the input from the user community, the upgrade
plan calls for a combination measures: installation of improved hardware, optimization of instrument operations and
software support. The limitations of the current detector (sensitivity, cosmetics, artifacts) have been known for some
time and a new 1k x 1k Si:As Aquarius array (Raytheon) will be the cornerstone of the VISIR upgrade project. A
modified spectroscopic mode will allow covering the N-band in a single observation. Several new scientific modes (e.g.,
polarimetry, coronagraphy) will be implemented on a best effort basis. In addition, the VISIR operational scheme will be
enhanced to ensure that optimal use of the observing conditions will be made. Specifically, we plan to provide a means
to monitor precipitable water vapour (PWV) and enable the user to specify it as a constraint set for service mode
observations. In some regions of the mid-IR domain, the amount of PWV has a fundamental effect on the quality of a
given night for mid-IR astronomy. The plan also calls for full support by ESO pipelines that will deliver science-ready
data products. Hence the resulting files will provide physical units and error information and all instrumental signatures
will have been removed. An upgraded VISIR will be a powerful instrument providing diffraction-limited performance at
an 8-m telescope. Its improved performance and efficiency as well as new science capabilities will serve the needs of the
ESO community but will also offer synergy with various other facilities such as ALMA, JWST, VLTI and SOFIA. A
wealth of targets for detailed study will be available from survey work done by VISTA and WISE. Finally, the upgraded
VISIR will also serve as a pathfinder for potential mid-IR instrumentation at the European Extremely Large Telescope
(E-ELT) in terms of technology as well as operations.
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