Galilean satellites - 1976 radar results

In addition to a report of radar observations concerning the Galilean satellites made in the fall of 1976, Doppler results are presented from 1975 and January 1976. The primary objectives of the investigation conducted in 1976 are related to a study of each satellite at widely separated orbital phases and a close examination of the polarization of its scattered energy. The investigation included an observation of Io, Europa, Ganymede, and Callisto with the upgraded Arecibo S-band radar system on 11 nights irregularly distributed from 26 October 1976 to 7 December 1976. Several peculiarities revealed by the radar observations of the three outer Galilean satellites are related to large and possibly time-varying albedos, and the unexpected result that the circular polarization transmitted exceeds unity by a substantial amount.