  The Diffuse Microwave Emission Survey (DIMES) has been selected for a mission
concept study for NASA's New Mission Concepts for Astrophysics program. DIMES
will measure the frequency spectrum of the cosmic microwave background and
diffuse Galactic foregrounds at centimeter wavelengths to 0.1% precision (0.1
mK), and will map the angular distribution to 20 muK per 6 degree field of
view. It consists of a set of narrow-band cryogenic radiometers, each of which
compares the signal from the sky to a full-aperture blackbody calibration
target. All frequency channels compare the sky to the same blackbody target,
with common offset and calibration, so that deviations from a blackbody
spectral shape may be determined with maximum precision. Measurements of the
CMB spectrum complement CMB anisotropy experiments and provide information on
the early universe unobtainable in any other way; even a null detection will
place important constraints on the matter content, structure, and evolution of
the universe. Centimeter-wavelength measurements of the diffuse Galactic
emission fill in a crucial wavelength range and test models of the heat
sources, energy balance, and composition of the interstellar medium.
