Preliminary Observations of the Far-Infrared Night-Sky Background Radiation

We have carried out far-infrared rocket observations in the spectral range from 0.4 to 1.3 mm and have detected a flux of 5 × ${10}^{-9\mathrm{}}$ W${/\mathrm{c}\mathrm{m}}^{-2\mathrm{}}$ sr, with an uncertainty of a factor of 2. The flux is nearly two orders of magnitude greater than that to be expected from a 3°K black cosmic background in this spectral range; its equivalent blackbody temperature would correspond to 8.3°${\mathrm{K}}_{-1.3\mathrm{}}^{+2.2\mathrm{}}$°K.