Imaging photopolarimeter on Pioneer Saturn
Results of Pioneer 11 imaging photopolarimeter observations of Saturn, its rings, and Titan are presented. The imaging photopolarimeter is a pointable telescope with an aperture of 2.5 cm and passbands of 390 to 500 to 720 nm which uses the spin of the spacecraft to scan across an object. Images of the Saturn system and of the rings are presented, and the absence of a D ring, structures in the C, B and A rings and the Cassini division and the discoveries of the F ring and the provisionally named Pioneer division separating it from the A ring are reported. A mean particle size less than 15 meters is estimated from estimates of total ring mass and the optical depth of the B ring. The discovery of the satellite 1979 S 1 at 2.53 Saturn radii is also noted. Models of the vertical aerosol structure of Saturn's atmosphere are compared with the polarization data, and it is indicated that the density of cloud particles decreases with altitude with a scale height about one fourth that of the gas, and that an optical depth of one is to be found at 750 mbar.