Absolute calibration of solar radio flux density at 35GHz

The absolute measurement of solar radio flux density at 35 GHz was carried out using a standard gain-horn and two precise standard noise sources. A pyramid-shaped microwave blackbody was made of foam polyurethane; its reflection coefficient in the direction of perpendicular incidence was -50 dB at 8.6 mm wavelength. Soaked in liquid nitrogen, this blackbody may be a precise and stable cryogenic standard noise source. During February 11-20, 1980, absolute measurements were made repeatedly with calibration at the aperture plane of the horn. The mean flux density of solar radio emission was found to be 2548 sfu, with a four percent systematic error and an eleven percent random error.