MILLIMETER-WAVELENGTH OBSERVATIONS OF MINOR PLANETS

Bolometer observations at 250 GHz of fifteen minor planets have shown that the emissivity of these objects is close to unity. This results i n an independent method to determine the absolute calibration scale of radio observations at mm wavelengths: Applying our results to Mars, t he prime calibrator at this wavelength, gives a mean absolute disk tem perature at mean solar distance of almost-equal-to 210 K. Further, the diameters of circularly symmetric asteroids can be determined or the surface area of asteroids can be estimated assuming some geometric con straints on their shape.