Measured properties of the cosmic background radiation

The existence of detectable and physically meaningful distortions in the 3K background is discussed. Data are sought in the form of frequency spectrum distortions, anisotropies in the spatial distribution and the degree of polarization. Thermodynamic narrowband measurements are cited and compared with blackbody distributions. Multifrequency data are considered in terms of the error ranges of the deviations and radiotelescope data are examined for the anisotropic and atmospheric effects. No features of cosmological significance are as yet detected. Measurements will continue and will be expanded with space-based instrumentation. 25 references