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The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation adaptive optics near-IR imager and
spectrograph for the Cassegrain focus of the Very Large Telescope (VLT) Unit Telescope 4, which will soon make full
use of the Adaptive Optics Facility (AOF). It is a high-Strehl AO-assisted instrument that will use the Deformable
Secondary Mirror (DSM) and the new Laser Guide Star Facility (4LGSF). The project has been approved for
construction and has entered its preliminary design phase. ERIS will be constructed in a collaboration including the Max-
Planck Institut für Extraterrestrische Physik, the Eidgenössische Technische Hochschule Zürich and the Osservatorio
Astrofisico di Arcetri and will offer 1 - 5 μm imaging and 1 - 2.5 μm integral field spectroscopic capabilities with a high
Strehl performance. Wavefront sensing can be carried out with an optical high-order NGS Pyramid wavefront sensor, or
with a single laser in either an optical low-order NGS mode, or with a near-IR low-order mode sensor. Due to its highly
sensitive visible wavefront sensor, and separate near-IR low-order mode, ERIS provides a large sky coverage with its 1’
patrol field radius that can even include AO stars embedded in dust-enshrouded environments. As such it will replace,
with a much improved single conjugated AO correction, the most scientifically important imaging modes offered by
NACO (diffraction limited imaging in the J to M bands, Sparse Aperture Masking and Apodizing Phase Plate (APP)
coronagraphy) and the integral field spectroscopy modes of SINFONI, whose instrumental module, SPIFFI, will be
upgraded and re-used in ERIS. As part of the SPIFFI upgrade a new higher resolution grating and a science detector
replacement are envisaged, as well as PLC driven motors. To accommodate ERIS at the Cassegrain focus, an extension
of the telescope back focal length is required, with modifications of the guider arm assembly. In this paper we report on
the status of the baseline design. We will also report on the main science goals of the instrument, ranging from exoplanet
detection and characterization to high redshift galaxy observations. We will also briefly describe the SINFONI-SPIFFI
upgrade strategy, which is part of the ERIS development plan and the overall project timeline.
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