The ISS is a modified version of the slow scan vidicon camera designs that were used in the earlier Mariner flights. The ISS consists of two television-type cameras, each with 8 filters in a commandable Filter Wheel mounted in front of the vidicons. One has a low resolution 200 mm wide-angle lens with an aperture of f/3, while the other uses a higher resolution 1500 mm narrow-angle f/8.5 lens.

Unlike the other onboard instruments, operation of the cameras is not autonomous, but is controlled by an imaging parameter table residing in one of the spacecraft computers, the Flight Data Subsystem (FDS).

A sideways diagram of the narrow-angle camera. A sideways diagram of the narrow-angle camera
A sideways diagram of the wide-angle camera. A sideways diagram of the wide-angle camera

Imaging Science Subsystem Objective

  • Observe and characterize the circulation of the planetary atmosphere, provide limits on atmospheric composition, and determine the wind velocities in the regions observed.
  • Map the radial and azimuthal distribution of material in the ring plane; search for new rings.
  • Obtain global multi-spectral coverage of all satellites; establish rotation rates and spin axis orientations, study the surface morphology of Triton at spatial resolutions less than 2 km; search for undiscovered satellites.
  • Provide support images to assist other onboard investigations in their data reduction.