  ATLAS (Astrophysics Telescope for Large Area Spectroscopy) Probe is a concept
for a NASA probe-class space mission. It is the follow-up space mission to
WFIRST, boosting its scientific return by obtaining deep IR slit spectroscopy
for 70% of all galaxies imaged by a 2000 sq deg WFIRST High Latitude Survey at
z>0.5. ATLAS will measure accurate and precise redshifts for 200M galaxies out
to z < 7, and deliver spectra that enable a wide range of diagnostic studies of
the physical properties of galaxies over most of cosmic history. ATLAS Probe
science spans four broad categories: (1) Revolutionizing galaxy evolution
studies by tracing the relation between galaxies and dark matter from galaxy
groups to cosmic voids and filaments, from the epoch of reionization through
the peak era of galaxy assembly; (2) Opening a new window into the dark
Universe by weighing the dark matter filaments using 3D weak lensing with
spectroscopic redshifts, and obtaining definitive measurements of dark energy
and modification of General Relativity using galaxy clustering; (3) Probing the
Milky Way's dust-enshrouded regions, reaching the far side of our Galaxy; and
(4) Exploring the formation history of the outer Solar System by characterizing
Kuiper Belt Objects. ATLAS Probe is a 1.5m telescope with a field of view of
0.4 sq deg, and uses Digital Micro-mirror Devices (DMDs) as slit selectors. It
has a spectroscopic resolution of R = 1000 over 1-4 microns, and a
spectroscopic multiplex factor >5,000. ATLAS is designed to fit within the NASA
probe-class space mission cost envelope; it has a single instrument, a
telescope aperture that allows for a lighter launch vehicle, and mature
technology. ATLAS Probe will lead to transformative science over the entire
range of astrophysics: from galaxy evolution to the dark Universe, from Solar
System objects to the dusty regions of the Milky Way.
