De la conception instrumentale
à l’exploitation des observables


The workhorse instruments of the 8-10m class observatories are their multi-object spectrographs (MOS), providing comprehensive follow-up to ground-based and space-borne imaging. With the advent of deeper imaging surveys from, e.g., HST, VISTA, JWST and Euclid, there will be a plethora of targets for ELT spectroscopy. We believe there is a strong and compelling case for a MOS as one of the first E-ELT instruments. By exploiting the excellent image quality across the full focal plane of the telescope, combined with its tremendous light-gathering power, we will be able to obtain the large samples necessary to tackle some of the key scientific drivers of the E-ELT project, ranging from studies of stellar populations out to the highest-redshift galaxies.

E-ELT overview

More details on our instrument, its conception, science cases and team are available on our website :

MOSAIC (formerly ELT-MOS) is a multi-object and multi-integral field spectrograph that will use the widest possible field of view provided by the E-ELT. The MOSAIC top-level requirements have been based on a comprehensive White Paper summarizing the very numerous scientific cases for a multi-object spectrograph on the ELT.

MOSAIC optical path

MOSAIC will have three operating modes : a high multiplex mode (HMM) covering the visible and near-infrared domain ; a high definition mode (HDM) that will provide spatially resolved observations in the near-infrared ; and a multi light bucket integral field mode for the Inter-Galactic Medium mode (IGM).

The conceptual design of MOSAIC, a powerful multi-object spectrograph for the ELT, will conclude in late 2017. The design combines high-multiplex near-IR and visible spectroscopy, together with AO-corrected spectroscopy in the near-IR that exploits the fantastic angular resolution of the E-ELT across a large field of view. These capabilities will enable MOSAIC to tackle fundamental questions that are simply out of reach of other facilities. In cosmology, MOSAIC will lift the veil on how matter is distributed in distant galaxy haloes, including dark matter and missing baryons. It will also result in a leap forward in our understanding of how present-day galaxies assemble. This includes detecting nearby primordial stars and the very first galaxies at the epoch of reionisation, the most exhaustive dynamical survey of distant galaxies ever undertaken and the detailed study of the stellar populations.

Next MOSAIC Congress : Spectroscopic Surveys with the ELT : A Gigantic Step into the Deep Universe

On October 17th to 20th 2017, a colloquium will take place in Toledo, Spain, in order to discuss several scientific topics related to the MOSAIC instrument. Co-Organized by the Complutense Universidad in Madrid and the GEPI laboratory in...

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