ERIS (Enhanced Resolution Imager and Spectrograph) is an instrument for diffraction limited imaging, coronography and spectroscopy on the Cassegrain focus of VLT UT4 in the 1 to 5µm spectral range to be commissioned in late 2017. 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.

In 2006 ESO decided to upgrade the VLT UT4 by an adaptive optics (AO) facility which includes a deformable secondary mirror and four laser guide stars. At the time when this facility will be installed, the existing instruments SINFONI and NACO become obsolete. Since NACO is reaching the end of its lifetime, it will be decommissioned, and its focal station will be occupied by the new ESO instrument MUSE. However, the high spatial resolution imaging and spectroscopy modes of NACO and SINFONI are indispensable for the VLT. Therefore ESO decided to build ERIS which makes use of the new AO facility and is composed of three main components:

  • an upgraded version of SPIFFI
  • a near infrared camera (J, H, K, L, M) which provides the most important observing modes of CONICA
  • a wavefront sensor module feeding the AO facility.

MPE has been involved in the ERIS phase A study which ended in May 2012. The concept emerging from this study is presented in the figures below:

The upper brown structure interfaces to the telescope flange and carries the wavefront sensor module (dark blue and cyan) and the near infrared camera (green); on its bottom side, SPIFFI (the large cylindrical vessel) is attached by an upgraded cyostat lid (light blue). Four yellow boxes mounted around SPIFFI house the instrument electronics. The blue tripod is attached to the telescope frame and carries the cable wrap. The wavefront sensor module is fed with the visible telescope beam via a dichroic beam splitter. The IR beam either feeds SPIFFI directly or can be deflected into the camera. The calibration source unit is shown in light green.

In December 2012 ESO issued a call for proposal for the upgrade of SPIFFI, the ERIS camera, and subunits of the wavefront sensor module. MPE applied for the first two items and has been selected by ESO in March 2013 to provide both. The ERIS project leadership is with ESO and MPE acts as main partner on these two subsystems. The infrared group at MPE (Principle Investigator: Frank Eisenhauer) collaborates with a team at ETH Zürich (Co-Investigator Michael Meyer) on the ERIS camera. MPE is responsible for optics, mechanics, cryo-vacuum equipment, testing and verification of the entire camera subsystem. ETH will provide it with filter, aperture and pupil wheels as well as with all required filters and masks. ESO will supply the 2k x 2k detector, all electronics and the instrument software. The modification of SPIFFI from SINFONI to ERIS is a collaboration between MPE and ESO only and covers all changes to adapt to the new optics, to replace aged components and to eventually exchange electronics by a light-weight new generation system. In addition MPE has proposed to provide upgrades to include a high resolution grating and a sky spider modification including software algorithms to facilitate a significant improvement on the sky subtraction (e.g. OH lines).

The ERIS project at ESO: ERIS at ESO

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

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