Named for the Arecibo Observatory in Puerto Rico, site of the largest filled-aperture telescope in the world. Arecibo is the principal research facility of the National Astronomy and Ionosphere Center and is used for radio astronomy, planetary radar astronomy and ionospheric investigations. Radar echoes obtained at Arecibo have provided valuable information about the physical and dynamical properties of about fifty minor planets, five comets, the terrestrial planets, the Galilean satellites and Saturn’s rings. (M 16445) _ _.