Abstract

The Comet Rendezvous/Asteroid Flyby (CRAF) mission to Comet Kopff and the Cassini mission to Saturn will be briefly outlined, with emphasis on the environmental considerations that constrain the design of the imaging science subsystem (ISS). The ISS employs both wide- and narrow-angle cameras, which share a common electronics module. The narrow-angle camera contains a 2000 mm focal-length, Ritchey–Chretien telescope operating at f/10.5 over a spectral range of 200–1100 nm. The wide-angle camera contains a 300 mm focal length refractor operating at f/2.5 over a spectral range of 380–1100 nm. Dust covers will protect the optics during the missions. A two wheel filter mechanism will be employed, which is similar to that flown on the wide-field planetary camera of the Hubble space telescope. The shutters will be of the two-blade focal plane design used on the Voyager and Galileo cameras. The detectors will be Ford 1024 × 1024 charge coupled devices (CCDs) with 12µm pixels, a full well of greater than 50,000 electrons/pixel, and read noise of less than 10 electrons/pixel rms. Dark current will be suppressed by cooling the devices to -110°C. Radiation damage will be controlled by using tantalum and quartz shielding around the CCD.

© 1990 Optical Society of America