Cosmic microwave background dipole spectrum measured by the COBE FIRAS instrument

Abstract

The FIRAS instrument on the COBE has determined the dipole spectrum of the cosmic microwave background radiation (CMBR) from 2 to 20 cm^-1^, For each frequency the signal is decomposed by fitting to a monopole, a dipole, and a Galactic template for ~60% of the sky. The overall dipole spectrum fits the derivative of a Planck function with an amplitude of 3.343 +/- 0.016 mK (95% confidence level), a temperature of 2.714 +/- 0.022 K (95% confidence level), and an rms deviation of 6 x 10^-9^ ergs cm^-2^ s^-1^ sr^-1^ cm limited by detector and cosmic-ray noise. The monopole temperature is consistent with that determined by direct measurement in the accompanying article by Mather et al.