This circular silicon wafer holds two charge coupled devices (CCD). Silicon is the substrate for all CCDs, and usually the silicon is "doped" (infused) to become photoreactive. These devices consist of two dimensional arrays of large numbers of tiny silicon diodes etched into the silicon. Those diodes convert light photons directly to electical signals which are then processed digitally to produce images. Each of the CCD's on surface of this wafer contains an array of 2048 by 4096 pixels for a total of over eight million elements. Because of their enhanced sensitivity CCD's have become favored as detectors for low light level astronomical applications.

This example was manufactured by Scientific Imaging Technologies Inc. and donated by them to NASM in 2000.