A spacecraft instrument that uses optics such as lenses or mirrors to project an image onto a detector. The image is then converted into digital data and transmitted to ground stations. Science imagers include photometers which measure the intensity of light from a source, spectrometers which measure the intensities of wavelengths, polarimeters which measure the polarization of light reflected from a celestial target, and infrared radiometers which measure the intensity of infrared energy radiated by objects in space. Earlier spacecraft, such as the Mariner and Voyager probes, carried image detectors that used a vacuum tube called a vidicon. Since the late 1980s spacecraft have employed a charge-coupled device that is an integrated circuit.
Subjects: Astronomy and Astrophysics.