A Measurement of the Sky Brightness Temperature at 408 MHz

Abstract

The absolute value of the background brightness temperature has been measured at a radiofrequency of 408 MHz. Observations were made with a large pyramidal "standard gain" horn aerial and the aerial temperatures were compared direct with the temperature observed with the receiver input connected to a matched resistive load of known temperature. For the region within 240 of the south celestial pole an average brightness temperature of 23· 9°K was obtained. Observations of northern regions indicate that values from previous determinations at northern latitudes are 4-5 degK too high.