Each Viking Lander was equipped with two identical cameras that, unlike conventional cameras, did not use film. Instead, a moveable mirror scanned a vertical segment of the martian scene, and photodetectors recorded the amount of light reflected into the camera. A complete picture, or "image" of the surface was made by completing a vertical scan, and then rotating the camera slightly for the next scan.
This back-up camera was transferred from NASA's Jet Propulsion Laboratory to the Museum in 1981.
This object is on display in Kenneth C. Griffin Exploring the Planets Gallery at the National Air and Space Museum in Washington, DC.