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We present the design, capabilities and applications of a cryogenic test facility for astronomical instrumentation located at ETH Zurich, Switzerland. This facility was designed, built, and commissioned with the purpose to support opto-mechanical performance measurements of cryo-mechanisms for astronomical instruments. In particular, the facility was developed initially to test the opto-mechanical stability and repeatability of the wheel-mechanisms for the ERIS/VLT instrument that are developed in house. However, the facility has a generic application portfolio and can be used for other development projects as well. The unique setup allows optical access from the warm end with short working distance to the cold elements of only a few millimeters. Electrical, mechanical, and liquid feedthroughs provide a flexible infrastructure for a large variety of thermal, mechanical, electrical and optical tests. To provide maximum mechanical stability, the cooling is provided by a low vibration pulse tube cooler that cools the facility down to approximately 8 K.

We present a solution to the challenges of interfacing the ELT’s METIS to the telescope using a steerable hexapod structure. To guide the architectural choices, lumped physical models were derived from inverse kinematics in order to address the load distribution in each arm. Complete FE Analysis is carried on the optimal solutions of these models. The hexapod arms, which are high precision heavy duty linear actuators enduring forces in the excess of 30 tons, are designed using standard components whenever possible. An overall fully functional support structure design, satisfying the ESO/ELT and METIS requirements, is described.

We present the design and measured performance of the Aperture Wheel and the Pupil and Filter Wheel mechanisms for the NIX camera of the VLT/ERIS instrument. Both mechanisms were developed for high opto-mechanical precision and stability while operating at 70 K. We summarise the design constraints and considerations. Further, we have developed a dedicated cryo-test facility to allow measuring the position repeatability under nominal operational conditions. We demonstrate that the wheel mechanisms perform as designed and provide the measurement methodology and results of the opto-mechanical tolerances.

ERIS is an instrument that will both extend and enhance the fundamental diffraction limited imaging and spectroscopy capability for the VLT. It will replace two instruments that are now being maintained beyond their operational lifetimes, combine their functionality on a single focus, provide a new wavefront sensing module that makes use of the facility Adaptive Optics System, and considerably improve their performance. The instrument will be competitive with respect to JWST in several regimes, and has outstanding potential for studies of the Galactic Center, exoplanets, and high redshift galaxies. ERIS had its final design review in 2017, and is expected to be on sky in 2020. This contribution describes the instrument concept, outlines its expected performance, and highlights where it will most excel., 12 pages, Proc SPIE 10702 "Ground-Based and Airborne Instrumentation for Astronomy VII"

ERIS will be the next-generation AO facility on the VLT, combining the heritage of NACO imaging, with the spectroscopic capabilities of an upgraded SINFONI. Here we report on the all-new NIX imager that will deliver diffraction-limited imaging from the J to M band. The instrument will be equipped with both Apodizing Phase Plates and Sparse Aperture Masks to provide high-angular resolution imagery, especially suited for exoplanet imaging and characterization. This paper provides detail on the instrument’s design and how it is suited to address a broad range of science cases, from detailed studies of the galactic centre at the highest resolutions, to studying detailed resolved stellar populations.