ERIS (Enhanced Resolution Imager and Spectrograph) is an instrument for diffraction limited imaging, coronagraphy and spectroscopy on the Cassegrain focus of VLT UT4 in the 1 to 5µm spectral range to be commissioned in 2020. It will combine the existing integral field spectrograph SPIFFI with a new near infrared camera and a wavefront sensor module for the ESO adaptive optics facility.

ESO has upgraded the VLT UT4 by an adaptive optics (AO) facility which includes a deformable secondary mirror and four laser guide stars. Together with this exciting new facility, the existing instruments SINFONI and NACO are becoming obsolete. However, the high spatial resolution imaging and spectroscopy modes of NACO and SINFONI are indispensable for the VLT. Therefore ESO decided to build the ERIS instrument which makes use of the new AO facility and is composed of four main components:

  • an upgraded version of SPIFFI with better throughput and higher spectral resolution
  • a near infrared camera called NIX to provide imaging in J, H, K, L, M bands as well as high contrast imaging in L and M bands (K as a goal)
  • long slit spectroscopy at a resolution of R~450 in L-band (M as a goal)
  • a wavefront sensor module that uses the AOF and provides much higher strehl than currently available
  • a calibration unit for spectral, spatial and photometric calibration of all sub-systems

The ERIS instrument thus provides similar functionality compared to NACO and SINFONI but significantly better performance, to last beyond 2030.

MPE has been involved in the project since the ERIS phase A study. End of 2014 a consortium has been formed under leadership of MPE to start the preliminary design phase of ERIS. Both ESO reviews along the development cycle of a VLT instrument have been succssfully passed (Preliminary Design Review: 2016, Final Design Review 2017). Since then, the project is proceeding through its manufacturing, assembly and integration phase at all its consortium sites.

The final design of the instrument is presented in the figures below:

Left: Optical concept of the instrument.
Right: View of the CAD model providing an overview of the final mechanical design and its sub-systems.
CAD view of the instrument mounted on the UT4 telescope

The responsibilities within the ERIS project and sub-systems are distributed among the consortium partners:

  • Principle Investigator (R. Davies), project management, system engineering: MPE
  • SPIFFI upgrade to SPIFFIER: MPE
  • Central mechanical structure, system electronics and IR detectors: MPE
  • NIX camera system: UK Astronomy Technology Centre in Edinburgh (ATC)
  • NIX filter, pupil and aperture wheels including all filters and masks: ETH-Zürich, NOVA (Leiden)
  • Adaptive optics and warm optics: INAF-Arcetri
  • Calibration unit: INAF-Teramo
  • Instrument control software: INAF-Padua (lead) in collaboration with ATC and MPE
  • Pipeline software: MPE (SPIFFIER), ATC (NIX)
  • Wavefront sensor cameras, adaptive optics real time computer, detector procurement and testing, ERIS handling tool: ESO

Major schedule milestones for the ERIS project:

  • End 2014: Formation of consortium
  • Feb 2016: Preliminary design review
  • Spring 2017: Final design review
  • 2020: Integration at MPE
  • Q1/Q2 2021: European acceptance
  • Q1 2022: Begin of commissioning phase

The ERIS project at ESO: ERIS at ESO

Picture credits: 1: ESO; 2, 3, 4 : MPE;

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