The microwave brightness temperature spectrum of the quiet sun

New measurements of the microwave brightness temperature spectrum of the center of the quiet sun, acquired at Owens Valley over several months during the 1986-1987 sunspot minimum, are reported. The resulting brightness temperature spectra are consistent with previous data, but exhibit much less frequency-to-frequency scatter. The corona is fitted well by an optically thin source at temperature of 10 to the 6th k, scale height H = 5 x 10 to the 9th, and density of 3.2 x 10 to the 8th/cu cm, and the chromosphere, an optically thick source at around 11,000 k.