Filters for Color Imaging and for Science
The color cameras on NASA's Mars rover Curiosity, including the pair that make up the rover's Mast Camera (Mastcam) instrument, use the same type of Bayer pattern RGB filter as found in typical commercial color cameras. Bayer filtering means that the charge-coupled device (CCD) that detects each pixel of the image is covered with a grid of green, red and blue filters so that the camera gets the three color components of the entire scene in a single exposure. Electronics inside the camera can then merge the separate sets of color pixels into a single full-color image.
Besides the affixed red-green-blue filter grid, the Mastcam cameras also each have an eight-position filter wheel with specialized science filters between the camera optics and the CCD. The wheel can be rotated to choose one of these narrow-waveband filters, in the visible-light or infrared parts of the spectrum, or no filter at all. Each camera's filter wheel holds six science filters that, between both cameras, can yield images in nine unique wavelengths from the deep blue (445 nanometers) to the short-wave near-infrared (1012 nanometers). One additional science filter in each wheel is specially designed to enable direct imaging of the sun.
Image credit: NASA/JPL-Caltech/MSSS/ASU