SIRMOS: NIR spectroscopy of 131,000,000 galaxies over 1 < z < 4 and R~1300

SIRMOS (Satellite for Infrared Multi-Object Spectroscopy) is a SMEX mission concept to map the universe in 3D over a cosmic volume of ~ 500 cubic gigaparsecs using 131 million H-alpha and [OIII] emission line galaxies (optimal for tracing cosmic large-scale structure) at 1 < z < 4. SIRMOS will probe the cosmic origin by placing unprecedented constraints on primordial non-Gaussianity, advance fundamental physics by precisely measuring the sum of neutrino masses, and definitively differentiate dark energy and modification of general relativity as the cause for the observed low-redshift cosmic acceleration. SIRMOS will measure galaxy evolution before and during the peak era of cosmic star formation over three orders of magnitude in environmental density, from cluster cores to cosmic filaments. SIRMOS has a 50 cm aperture telescope with 1.6 square degree FoV, and more than 4.4 million micromirrors on 2 digital micro-mirror devices (DMDs) to provide a programmable reflective slit mask allowing multi-slit spectroscopy at R~1300 over the wavelength range of 1.25 to 2.5 microns and a total survey area of 15,000 square degrees. The telescope is a modified Cassegrain followed by a prism mirror that splits the field toward 2 identical arms. Fore-optics reimage each subfield onto a DMD. The micro-mirrors in ON positions send the light to a spectrograph while those in OFF positions send the light to an imager which permits very precise measurements of the telescope pointing and everything not selected for spectroscopy.