The instruments that provide the most data in today’s observatories with 8-10 metre class telescopes are multi-object spectrographs (MOS), capable of observing thousands of objects every night, enabling exhaustive follow-up of imaging data from ground- and space-based telescopes. With the advent of even deeper imaging surveys, for example with HST, VISTA, JWST and Euclid, many scientific cases require complementary spectroscopy with high sensitivity and good spatial resolution to identify objects in every wavelength range and measure their astrophysical parameters. Thanks to its 39-meter primary mirror, the ELT will provide light-gathering power and spatial resolution unmatched on Earth, which, combined with a MOS, will make it possible to obtain the large samples of cosmic objects needed to address some of the ELT project’s main scientific objectives, ranging from studies of stellar populations to the most distant galaxies at redshift.
The MOSAIC instrument has been designed to meet this objective. This multi-object, full-field spectrograph will exploit the large field of view offered by the ELT. The high-level requirements for the MOSAIC instrument are based on an exhaustive White Paper summarizing the very many scientific cases justifying a multi-object spectrograph on the ELT.
MOSAIC is designed as a versatile MOS, covering wavelengths from the visible to the near infrared (0.45 - 1.8 μm) with two modes: multi-object spectroscopy (MOS) and spatially resolved spectroscopy (mIFU).
In this ambitious project, UNIDIA is in charge of the mIFUs, whose role will be to collect light from celestial objects imaged in around 200 pixels. Multiplied by the number of mIFUs, this represents thousands of optical fibers to be manufactured to transfer the light from the telescope’s focal plane to the spectrograph.
