Creating Color Images of Eros
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Creating Color Images of Eros

October 23, 2009
NEAR Shoemaker's electronic multispectral imager, MSI, takes color pictures in a fundamentally different way than does a conventional camera that uses color film. MSI's counterpart to film is a sensor called a charge couple device, or CCD, which is mounted at the focus of a refractive telescope. The CCD responds simultaneously to all visible wavelengths of light and to some near-infrared wavelengths, and converts the intensity of light in each pixel of an image to a digital number that is transmitted to the ground. To make a color picture, MSI actually takes three images through red, green, and blue filters mounted in a wheel. On the ground, the images are carefully overlaid (or "registered") and displayed in red, green, and blue colors. Those steps were used to render this color image of Eros, taken February 25, 2000, from a range of 349 kilometers (217 miles).

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