  MSE is an 11.25m aperture observatory with a 1.5 square degree field of view
that will be fully dedicated to multi-object spectroscopy. More than 3200
fibres will feed spectrographs operating at low (R ~ 2000 - 3500) and moderate
(R ~ 6000) spectral resolution, and approximately 1000 fibers will feed
spectrographs operating at high (R ~ 40000) resolution. MSE is designed to
enable transformational science in areas as diverse as tomographic mapping of
the interstellar and intergalactic media; the in-situ chemical tagging of thick
disk and halo stars; connecting galaxies to their large scale structure;
measuring the mass functions of cold dark matter sub-halos in galaxy and
cluster-scale hosts; reverberation mapping of supermassive black holes in
quasars; next generation cosmological surveys using redshift space distortions
and peculiar velocities. MSE is an essential follow-up facility to current and
next generations of multi-wavelength imaging surveys, including LSST, Gaia,
Euclid, WFIRST, PLATO, and the SKA, and is designed to complement and go beyond
the science goals of other planned and current spectroscopic capabilities like
VISTA/4MOST, WHT/WEAVE, AAT/HERMES and Subaru/PFS. It is an ideal feeder
facility for E-ELT, TMT and GMT, and provides the missing link between wide
field imaging and small field precision astronomy. MSE is optimized for high
throughput, high signal-to-noise observations of the faintest sources in the
Universe with high quality calibration and stability being ensured through the
dedicated operational mode of the observatory. (abridged)
