The Imaging Science Subsystem consists of two cameras, a Wide Angle Camera (ISS-WAC) and a Narrow Angle Camera (ISS-NAC). Both cameras produce images 1024 by 1024 pixels in size. Each camera is equipped with a pair of filter wheels that give the cameras excellent color vision: 23 different filters for the Narrow Angle and 17 for the Wide Angle Camera, spanning wavelengths of light from the ultraviolet to the near-infrared. Because the filters are on two overlapping filter wheels, filters can be combined to yield a great many more effective filter combinations (about 100 for the NAC and about 50 for the WAC).
The Wide Angle Camera will provide context images for all of the other optical remote sensing instruments. The Narrow Angle Camera will be used for high-resolution studies.
The ISS cameras are affixed to Cassini's Remote Sensing Pallet. The Remote Sensing Pallet also contains the CIRS, VIMS, and UVIS instruments. In order for ISS to capture images, the Cassini spacecraft must rotate to point the Remote Sensing Pallet to a target. Consequently, whenever ISS captures an image of a target, the other three Optical Remote Sensing instruments are also pointed in the same direction and can study the same target. This is both a strength and a weakness: a strength, because there is no question that the whole instrument suite is focused on exactly the same spot, and a weakness, because the four instruments cannot operate independently. The four instrument teams cooperate in planning their science observations.
The resolution of the cameras depends upon their distance from the target. When Cassini is 1000 km from her target, the Narrow Angle Camera will achieve a resolution of 6 meters per pixel.
