Like your own personal digital camera, a spacecraft camera records images using a CCD--an array of tiny detectors whose combined measurements of light form a picture. This CCD is identical to the one used by the Mars Reconnaissance Orbiter's HiRISE (High Resolution Imaging Science Experiment) camera, flown at the beginning of the twenty-first century.
The Ball Aerospace and Technologies Corporation and the University of Arizona donated this artifact to the Museum in 2010.
Gift of Ball Aerospace Systems Division
Charge-coupled devices (CCD) have revolutionized many aspects of modern life, and have been central to planetary exploration since the 1970s. Invented in 1969 at AT&T Bell Labs by Willard Boyle and George E. Smith, this tiny device made possible digital imaging and is widely used in professional, medical, and scientific applications where high-quality image data is required. Originally conceived as a new type of computer memory circuit, it soon became apparent that the CCD had many other potential applications, including signal processing and imaging—the latter because of silicon's light sensitivity. CCDs work by capturing through a lens an image that is then projected onto a capacitor array. Each capacitor accumulates an electric charge reflective of the light intensity in that one location. With large amounts of capacitor input an image emerges that is then tranformed in its entirety into a semiconductor to a sequence of voltages that are then processed and fed out to other circuits for transmission, recording, or other processing. An image is acquired when incident light in the form of photons falls on the array of pixels. The energy associated with each photon is absorbed by the silicon and a reaction takes place that creates an electron-hole charge pair (for example, an electron). The number of electrons collected at each pixel is linearly dependent on light level and exposure time, nonlinearly dependent on wavelength. The result is a strong, high quality image.