ERIS - Enhanced Resolution Imager and Spectrograph

ERIS, the Enhanced Resolution Imager and Spectrograph, is a 1-5 μm instrument for the Cassegrain focus of UT4 at the VLT, the telescope that will be equipped with the Adaptive Optics Facility (AOF).

Builders
Project manager Lieselotte Jochum (ljochum@eso.org)
Project scientist
Harald Kuntschner (hkuntsch@eso.org)
Instrument approval October 17, 2012
Project Status Beginning Phase B
Instrument Science Team Jean-Charles Augereau (Institut de Planétologie et d’Astrophysique de Grenoble, France)
Giovanni Cresci (INAF Arcetri, Italy)
Natascha Förster Schreiber (MPE, Germany)
Harald Kuntschner (ESO, chair)
Sylvestre Lacour (Observatoire de Paris, France)
Franck Marchis (SETI Institute, USA)
Almudena Prieto (IAC, Spain)
Sascha Quanz (ETH, Switzerland)
Rainer Schödel (Instituto de Astrofísica de Andalucía, Spain)
Location Cassegrain focus of UT4

Status

  • First light at the telescope – end 2017
  • Final Design Review (FDR) goal – 1Q2015
  • Preliminary Design Review (PDR) goal – 2Q2014
  • Project partner selection concluded - March 2013
  • ESO internal project approval – October 17, 2012 
  • Phase A study review meeting – May 24, 2012 

Instrument Phase A Description

ERIS, the Enhanced Resolution Imager and Spectrograph, is a 1-5 μm instrument for the Cassegrain focus of UT4 at the VLT. It will benefit from the Adaptive Optics Facility (AOF) including the deformable secondary mirror (DSM).

In its baseline incarnation (see Figure 1), ERIS consists of three main instrumental modules:

  • The AO module, which will use the AOF Deformable Secondary Mirror (DSM), and one AOF laser, providing NGS and LGS visible wavefront sensing with real-time computing capabilities. The baseline choice for the NGS wave front sensor (WFS) is a pyramid design that also serves as a low order WFS to be used with the LGS. The LGS WFS is a Shack-Hartmann. The AO module will allow for single-conjugate adaptive optics (SCAO) operations. Both science instruments, the imager and ERIS-SPIFFI are fed by the AO module through a dichroic beamsplitter.
  • The imager providing diffraction limited imaging, sparse aperture masking (SAM) and pupil plane coronagraphy capabilities from 1-5 μm (i.e. J-Mp), either in “standard” observing mode or with “pupil tracking” and “cube” readout mode. The imager is a cryogenic instrument and its 2k×2k detector is cooled at 40K by means of a closed cycle cooler (CCC).
  • The spectrograph ERIS-SPIFFI is a refurbished version of SPIFFI, the 1-2.5 μm integral field unit currently on-board SINFONI, slightly modified to be integrated into ERIS. Its observing modes are identical to those of SINFONI.

ERIS uses and depends on the AOF infrastructure to perform the AO correction. The ERIS concept maximizes the re-use of existing sub-systems and components. In particular, the AO correction is provided by the AOF Deformable Secondary Mirror (DSM) and the artificial Laser Guide Star (LGS) is generated by the 4LGSF system. The wavefront sensor camera detectors are identical to the ones used for GALACSI and GRAAL (the two GLAO systems of the AOF) and the Real-Time Computer (RTC) is a modified version of SPARTA.

Figure 1: Chart showing the main components of the ERIS baseline design. The coloured boxes are for sub-systems belonging to ERIS, the white ones are external to the instrument.

Baseline Specification

Requirement

Imager

Spectrograph (IFU)

Wavelength range

J – Mp

J, H, K

AO performance (Strehl)

>75% in K-band, on-axis, visible NGS AO sensing at MR=8

>60% in K-band, on-axis, Na LGS + visible on axis TT ref-star at MR=12

FoV

27” x 27”, 54” x 54”

8" x 8", 3.2" x 3.2" and 0.8" x 0.8"

Pixel scale

0.013mas/pix, 0.027 mas/pix

250mas/spaxel, 100mas/spaxel and 25mas/spaxel

Modes

Imaging, APP coronagraphy, Sparse Aperture Masking

Integral field spectroscopy

Scientific Objectives

The main scientific drivers for ERIS are drawn from experiments benefitting from near-diffraction (8m) limited imaging and spectroscopy in the near to mid IR. Naturally, science programs span a wide range including, for example:

  • Solar system science – measurements of asteroid shapes, sizes and SED’s; characterization of satellites around giant planets (e.g. volcanism on Io at Jupiter, or cloud formations on Titan at Saturn)
  • Stellar disk science – studying the circumnuclear disks of young forming stars from the primordial stages to debris disks
  • Exoplanet studies – basic characterization of exoplanet SEDs, specifically in the L- and M-bands
  • Initial Mass Function (IMF) determinations – direct investigations of the IMF in AO-resolved starburst clusters
  • Galactic Centre science – Monitoring of stellar orbits around Sagittarius A* to measure the distance to and mass of the black hole (BH) to percent-accuracy. Constraining the physics of the accretion flow and investigating the star-formation in the central pc potentially influenced by the BH.
  • Centres of nearby galaxies – characterization of the circumnuclear regions at the highest possible spatial scales and the influence of the BH on star-formation in nearby (active) galaxies 
  • Medium to high redshift (z=0.4 to 2) galaxies – studying the structure, content and kinematics of distant galaxies in order to address fundamental questions on galaxy formation and evolution, and the role of BHs therein            

ERIS, installed at the Cassegrain of UT4 and thus benefitting from the AOF, will combine state-of-the-art near IR imaging and spectroscopy with an advanced SCAO system to deliver superb on-axis Strehl ratios. The increased sensitivity of wave front sensors together with powerful (20W) laser-driven AO, allow for the use of fainter TT-stars further away from the science target therefore giving access to a larger number of targets. ERIS is designed to replace several of the most important NaCo capabilities, perhaps most importantly diffraction limited imaging of the Galactic Center.

Given that ERIS combines a general purpose near to mid IR camera and a versatile J-K-band integral field spectrograph with a powerful AO system, we expect that it will not only fulfill its main scientific objectives, but will also be used for a wide variety of other science cases with hopefully new and unexpected results.

Documents

  •  ERIS folder in the ESO BSCW

If you need access to these pages please contact Lieselotte Jochum.