This is a star tracker, a component from the Voyager 2 spacecraft program. This and related items are flight-qualified spare hardware, which were used in laboratory simulations to resolve in-flight problems encountered by the Voyager spacecraft. In flight, the device found and locked on to the star Canopus, providing a reference for guidance and navigation.
Voyager 2 was an unmanned space probe which, in 1986, passed close to the planet Uranus to transmit images of its surface.
NASA's Jet Propulsion Laboratory transferred this object to the Smithsonian in 1999.
Transfer from the Jet Propulsion Laboratory, California Institute of technology.