The spectrum of Cosmic Microwave Background at low frequency

The spectrum of the cosmic microwave background at a frequency close or below 1 GHz is currently known with a large uncertainty. The difficulties arise both from the calibration technique and the presence of large foreground signals. In this spectral region large deviations from the Planck distribution are still permitted. In this paper the current status of our knowledge is described. Experiments involved and techniques employed are also discussed

The spectrum of Cosmic Microwave Background at frequency close or below 1 GHz is currently known with a large uncertainty. The difficulties arise both from the calibration technique and the presence of large foreground signals. In this spectral region large deviations from the Planck distribution are still permitted. In this paper the current status of our knowledge is described. Experiments involved and techniques employed are also discussed. © 1999 Elsevier Science B.V. All rights reserved.