Paris, Tuesday 3rd October 2017

The MOSAIC multi-object spectrograph will be the workhorse instrument for the future Extremely Large Telescope (ELT), the biggest visible/infrared telescope in the world. It will be the world-leading multi-object spectrograph well into the 2020s, contributing to most fields of contemporary astronomy. Scientists from across the world are meeting in Toledo to explore the unprecedented capabilities of MOSAIC in tracking the earliest ‘first-light’ structures in the Universe, and to refine plans for observations that will uniquely trace the amounts of dark and invisible matter in the deep Universe (see video).

The MOSAIC team* is now finalising the design concept for a versatile multi-object spectrograph at the ELT. It will provide spectra of astronomical objects in both the visible and near-infrared parts of the electromagnetic spectrum, using optical fibres to relay light from the telescope to an array of spectrographs. In addition to enabling observations of hundreds of objects simultaneously, it will provide a mode where several targets of particular interest can be observed at finer spatial resolution via correction from wide-field adaptive optics.

When combined with the world’s largest collecting area at these wavelengths, MOSAIC will be able to observe the tiny spectral features arising from cold, warm and hot gas in the halos of galaxies in the deep Universe, looking back some 12 billion years. Using advanced tools that take into account the properties of the astronomical objects, the effects of Earth’s atmosphere, and the performance of the telescope and the instrument, young scientists will show a suite of new simulations in Toledo, Spain. These will demonstrate how MOSAIC will obtain the first rotation curves of the most distant galaxies, allowing astronomers to test if their dark matter content was already in place, or has changed with time. Beyond this flagship case, MOSAIC on the ELT will also provide unique observations of the first galaxies and possibly the first generation of stars, the early formation of massive black holes, and numerous mysteries in the distant and nearby Universe.

Figure 1 – Overview of the instrument. Spectrographs are shown on the left of the focal plate to select targets. MOSAIC development will generate several innovative and smart developments which will trigger a huge leverage effect on several areas, e.g., Deformable Mirrors, Optical Systems, fibre assemblies, detectors for both science and wave-front sensing, and real time computers.

(*) The MOSAIC Consortium includes five Leading Countries (France, the UK, the Netherlands, Brazil and Germany), and six Associated Partners (Austria, Finland, Italy, Portugal, Spain, and Sweden). The team includes François Hammer, Pascal Jagourel (Observatoire de Paris), Chris Evans (UK-ATC, Edinburgh), Mathieu Puech (Observatoire de Paris), Gavin Dalton (RAL & Oxford Univ.), Myriam Rodrigues (Observatoire de Paris), Ewan Fitzsimons (UK-ATC, Edinburgh), Simon Morris (Durham Univ.), Beatriz Barbuy (IAG, Sao Paulo), Jean-Gabriel Cuby (LAM, Marseille), Lex Kaper (Amsterdam Univ.), Martin Roth (AIP, Potsdam), Gérard Rousset (Observatoire de Paris), Richard Myers (Durham Univ.), Olivier Le Fèvre (LAM, Marseille), Alexis Finogenov (Helsinki Univ.), Bruno Castilho (LAN, Itajuba), Goran Ostlin (Stockholm Univ.), Jesus Gallego (Madrid, Computense Univ.), Iglesias-Paramo (IAA, Spain), Fabrizio Fiore (Roma Observatory), Bodo Ziegler (Vienna Univ.), Jose Afonso (Lisboa Univ.), Marc Dubbledam (Durham Univ.), Marc Close (Durham Univ.), Phil Parr Burman (UK-ATC), Tim Morris (Durham Univ.), Fanny Chemla (Observatoire de Paris), Fatima De Frondat (Observatoire de Paris), Andreas Kelz (AIP, Potsdam), Isabelle Guinouard (Observatoire de Paris), Ian Lewis (Oxford Univ.), Kevin Middleton (RALSPACE, Oxford), Ramon Navarro (NOVA), Marie Larrieu (IRAP, Toulouse), Johan Pragt (NOVA), Annemieke Janssen (NOVA), Kjetil Dohlen (LAM, Marseille), Kacem El Hadi (LAM, Marseille), Yanbin Yang (Observatoire de Paris), Sylvestre Taburet (Observatoire de Paris), Mickael Frotin (Observatoire de Paris), Claire Bouillet (Observatoire de Paris).

17-19th October 2017 – Toledo, Spain

Scientific Rationale

The European Extremely Large Telescope (E-ELT) will be the world's largest optical/IR facility for at least a generation. It will have an immense collecting area, equivalent to gathering together all the current large telescopes in use today. Multi-object spectroscopy will be a key capability of the observatory, immediately able to harness its unprecedented sensitivity to deliver unique surveys which address a broad range of important topics in contemporary astrophysics.

The conceptual design of MOSAIC, a powerful multi-object spectrograph for the E-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, e.g. pertaining to the formation and evolution of galaxies, which are simply out of reach of other facilities.

This colloquium is timed to discuss the scientific opportunities of surveys with MOSAIC, focussing in particular on simulated performances from the conceptual design. It will also take stock of other developments that will influence surveys envisaged for the late 2020s.

The next important meeting for MOSAIC will be the MTR (Mid-Term Review) meeting in Garching - Germany (near Munich) at the ESO headquarters (European Southern Observatory). This meeting will take place on Tuesday 21st and Wednseday 22nd of March 2017. You can follow the news on the E-ELT project at this adress on the ESO web page.

On March 18, 2016, during the MOSAIC kick-off meeting at the Paris Observatory in the presence of the team(*) led by François Hammer, The European Southern Observatory has signed a phase A study contract with the MOSAIC consortium. The multi-object spectrograph will be the workhorse instrument for the E-ELT, being the biggest telescope in the world with its 39m diameter primary mirror.

MOSAIC will be the world-leading MOS facility, contributing to all fields of contemporary astronomy, from extra-solar planets, to the study of the halo of the Milky Way and its satellites, and from resolved stellar populations in nearby galaxies out to observations of the earliest ‘first-light’ structures in the Universe.

The ESO contract has been signed by the CNRS-INSU (Leading Institute of the MOSAIC Consortium). The Consortium includes five Leading Countries

  • France,
  • United Kingdom,
  • The Netherlands,
  • Brazil,
  • Germany,

and six Associated Partners

  • Austria,
  • Finland,
  • Italy,
  • Portugal,
  • Spain,
  • Sweden


Who are we? Infos on the MOSAIC consortium.


Scientific goals and milestones: why MOSAIC?


How do we get there? All the technology behind MOSAIC.


What performance can we expect from MOSAIC?


How will MOSAIC fit in the instrumental landscape?