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Session 13 - Large Scale Structure & Cosmology.
Display session, Monday, January 13
The Diffuse Microwave Emission Survey (DIMES) is a mission concept selected by NASA in 1995 to answer fundamental questions about the content and history of the universe. DIMES will use a set of absolutely calibrated cryogenic radiometers from a space platform to measure the frequency spectrum of the cosmic microwave background (CMB) at wavelengths 15--0.3 cm (frequency 2--100 GHz) to precision 0.1 mK or better. Measurements at centimeter wavelengths probe different physical processes than the COBE-FIRAS spectra at shorter wavelengths, and complement the anisotropy measurements from DMR, balloon and ground-based instruments, and the planned MAP and COBRAS/SAMBA satellites. DIMES will observe the free-free signal from early photoionization to establish the precise epoch of structure formation, and will measure or limit energy release at redshift 10^4 < z < 10^7 by measuring the chemical potential distortion of the CMB spectrum. Both are likely under current cosmological theory and allowed by current measurement limits; even an upper limit at the expected sensitivity 10^-5 MJy/sr will place important constraints on the matter content, structure, and evolution of the universe. Detecting these distortions or showing that they do not exist constitutes the last frontier of CMB observations.
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