Imaging and polarimetry with the Pioneer Venus Orbiter Cloud Photopolarimeter

The objective of the Orbiter Cloud Photopolarimeter (OCPP) on board the Pioneer Venus Orbiter spacecraft is twofold: (1) to determine the physical properties, vertical and horizontal distribution and the temporal variability of the haze and cloud aerosols on Venus; and (2) to record in images made in the near ultraviolet the varying cloud morphology and the short- and long-term character of the apparent cloud motions. Early images exhibit numerous cloud features and apparent circulation patterns similar to those observed by Mariner 10 in 1974. Features of the polar regions are identified. Polarimetry measurements indicate that the main visible cloud layer of 1-micron-radius sulfuric acid droplets is covered at least in the morning terminator region with a thin haze layer consisting of submicron-size particles. The OCPP performance appears to be excellent.