An Absolute Measurement of the Cosmic Microwave Background Radiation   Temperature at 10.7 GHz
  A balloon-borne experiment has measured the absolute temperature of the cosmic microwave background radiation (CMBR) at 10.7 GHz to be Tcmbr = 2.730 +- .014 K. The error is the quadratic sum of several systematic errors, with statistical error of less than 0.1 mK. The instrument comprises a cooled corrugated horn antenna coupled to a total-power radiometer. A cryogenic mechanical waveguide switch alternately connects the radiometer to the horn and to an internal reference load. The small measured temperature difference (<= 20 mK) between the sky signal and the reference load in conjunction with the use of a cold front end keeps systematic instrumental corrections small. Atmospheric and window emission are minimized by flying the instrument at 24 km altitude. A large outer ground screen and smaller inner screen shield the instrument from stray radiation from the ground and the balloon. In-flight tests constrain the magnitude of ground radiation contamination, and low level interference is monitored through observations in several narrow frequency bands. 
S. T. Staggs (1), N. C. Jarosik (2), S. S. Meyer (1), D. T. Wilkinson   (2) ((1) University of Chicago, (2) Princeton Univer...