SIMBAD references

During 6 days in April 1995 we have measured the intensity ratio of the planet Mars and the asteroid Ceres at a frequency of 250GHz with a wideband bolometer at the Heinrich-Hertz-Telescope. From 58 pairs of observations, the derived flux density ratio of Mars and Ceres is 268.5, corrected for the partial resolution of Mars on April 10, 1995. This corresponds to a flux density of 2.35Jy for Ceres at this date. The brightness variation with the rotation phase is smaller than ±2%. With the assumption of emissivity=1 we derive a diameter for Ceres of 963.0km. With this diameter and the computed equilibrium temperature, the absolute flux density of Ceres can be predicted to an accuracy better than 3%.