Session 67 - Cosmic Microwave Background.
Oral session, Tuesday, January 16
Salon del Rey North, Hilton

## [67.02] A Measurement of the Temperature of the Cosmic Microwave Background Radiation at 600 MHz

W. C. Smith, D. Wilkinson (Princeton U.)

A measurement of the cosmic microwave background radiation (CMBR) was made at 600 MHz. The instrument used was the 20' aperture horn antenna in Holmdel, NJ, used to discover the CMBR. Instrument emission was reduced by cooling the coupling between the antenna and the first RF amplifier. The amplifiers were kept at 11K to be approximately in equilibrium with the temperature of the sky signal. The gain was measured every 4 minutes. Instrument emission was measured with a sliding short, and checked by measurements with the waveguide both cooled and at room temperature. The ground emission was calculated by convolving the measured beam pattern with the ground signal. The atmospheric emission was calculated using a model for the emissivity together with radiosonde data. The sum of CMBR+galactic temperature is 6.98 \pm 0.32 K at \alpha=8^h 26^m. The galactic emission can be estimated by scaling measurements by Pauliny-Toth and Shakeshaft at 404 MHz to 600 MHz, yielding an expected galactic emission of 5.8 K. This implies a low temperature for the CMBR.