Measurement of the Spectrum of the Submillimeter Cosmic Background

Abstract

The spectrum of the night sky has been measured in the frequency range from 3 to 40 ${\mathrm{cm}}^{-1\mathrm{}}$ using a fully calibrated liquid-helium-cooled balloon-borne spectrophotometer at an elevation of 39 km. A model based on the known molecular parameters was used to subtract the atmospheric emission. In the frequency range from 4 to 17 ${\mathrm{cm}}^{-1\mathrm{}}$, the spectrum of the background radiation is that of a blackbody with a temperature of ${2.99}_{-0.14\mathrm{}}^{+0.07\mathrm{}}$ K.