Far-Infrared Observations of the Night Sky

Abstract

We have flown a telescope cooled to liquid-helium temperatures and made far-infrared observations of the night sky. A gallium-doped germanium detector, sensitive from 5.2 to 130 micrometers, detected a minimum signal of 10^-9 watt per square centimeter per steradian referred to 100 micrometers. The origin of this signal can be instrumental, atmospheric, interplanetary, or interstellar. We can place a firm upper limit on the color temperature of a dilute cosmic background flux.