Optical Calibration Target
The target plate is a flat rectangle of known color and brightness, fixed to the spacecraft so the instruments on the movable scan platform (cameras, infrared instrument, etc.) can point to a predictable target for calibration purposes.
Photopolarimeter Subsystem (PPS)
The Photopolarimeter Subsystem uses a 0.2 m telescope fitted with filters and polarization analyzers. It covers eight wavelengths in the region between 235 nm and 750 nm. The experiment is designed to determine the physical properties of particulate matter in the atmospheres of Jupiter, Saturn, and the Rings of Saturn by measuring the intensity and linear polarization of scattered sunlight at eight wavelengths in the 2350-7500A region of the spectrum. The experiment will also provide information on the texture and probable composition of the surfaces of the satellites of Jupiter and Saturn and the properties of the sodium cloud around Io. During the planetary encounters a search for optical evidence of electrical discharges (lighting) and auroral activity will also be conducted.