Giovanni De Amici

The Temperature of the Cosmic Microwave Background Radiation at 3.8 GHz; Results of a Measurement from the South Pole Site

As part of an international collaboration to measure the low-frequency spectrum of the cosmic microwave background (CMB) radiation, its temperature was measured at a frequency of 3.8 GHz (7.9 cm wavelength), during the austral spring of 1989, obtaining a brightness temperature of 2.64 ± 0.07 K (68% confidence level). The new result is in agreement with previous measurements at the same frequency obtained in 1986-88 from a very different site and has comparable error bars. Combining measurements from all years, a value of 2.64 ± 0.06 K is obtained for the brightness temperature

A measurement of the temperature of the cosmic microwave background at a frequency of 7.5 GHz

LBL-27451 Preprint Lawrence Berkeley Laboratory UNIVERSITY OF CALIFORNIA Physics Division For Reference R r- z \ v E D Not to be Submitted to Astrophysical Journal isk^al&afaeMm OCT 0 1909 U3KARY AND DOCUMENTS SECTION A Measurement of the Temperature of the Cosmic Microwave Background at a Frequency of 7.5 GHz A. Kogut, M . Bensadoun, G. De Amici, S. Levin, G.F. Smoot, and C. Witebsky June 1989 Prepared for the U.S. Department of Energy under Contract Number DE-AC03-76SF00098.

The temperature of the cosmic background radiation : results from the 1987 and 1988 measurements at 3.8 GHz

The low-frequency (Rayleigh-Jeans) spectrum of the cosmic background radiation (CBR) is expected to contain information relevant to the physical processes that occurred in the early universe. In this paper, the authors have measured the temperature of the cosmic background radiation (CBR) at a frequency of 3.8 GHz (7.9 cm wavelength), during two consecutive summers, obtaining a brightness temperature, T{sub CBR}, of 2.56 {plus minus} 0.08 K in 1987 and 2.71 {plus minus} 0.07 K in 1988 (68% confidence level). The new results are in agreement with their previous measurement at 3.7 GHz obtained in 1986 and have smaller error bars. Combining measurements from all 3 years, they obtain T{sub CBR} = 2.64 {plus minus} 0.07 K.

A Liquid-Helium-Cooled Absolute Reference Cold Load for Long-Wavelength Radiometric Calibration

We describe a large (78-cm) diameter liquid-helium-cooled black-body absolute reference cold load for the calibration of microwave radiometers. The load provides an absolute calibration near the liquid helium (LHe) boiling point, accurate to better than 30 mK for wavelengths from 2.5 to 25 cm (12-1.2 GHz). The emission (from non-LHe temperature parts of the cold load) and reflection are small and well determined. Total corrections to the LHe boiling point temperature are {le} 50 mK over the operating range. This cold load has been used at several wavelengths at the South Pole and at the White Mountain Research Station. In operation, the average LHe loss rate was {le} 4.4 l/hr. Design considerations, radiometric and thermal performance and operational aspects are discussed. A comparison with other LHe-cooled reference loads including the predecessor of this cold load is given.

Modeling galactic microwave emission from 0.4 to 50 GHz

We have developed a full‐sky model of galactic microwave radiation at frequencies from 0.4 GHz to ≳50 GHz, with a resolution of ∼2°. The primary components are free‐free emission from ionized hydrogen and synchrotron emission from cosmic rays. (Dust emission is negligible in this frequency range.) A variety of data are used to estimate free‐free emission from HII: the galactic plane and adjacent regions come from continuum surveys near 2.7 GHz; emission at higher galactic latitudes is approximated by a cosecant law. The synchrotron component is extrapolated from sky‐survey data at 408 MHz. Both components vary with frequency. This model has been used to derive corrections for galactic emission in our measurements of the low‐frequency CMBR spectrum.