Scientists use light gathered by telescopes in two ways. In imaging, they create pictures, which they then analyze. In spectroscopy, they analyze the light itself. Most telescopes are equipped with cameras that record images showing the relative brightness of a satellite's surface areas. A change in brightness in an area may indicate geologic activity, such as volcanic eruptions.
Scientists photograph most satellites in black and white through a special light filter.
To create a color picture, they combine several images taken with different colored filters. Spectroscopy breaks up the sunlight reflected from a satellite into the light's individual colors. The colors form a rainbowlike band called a spectrum. Every chemical element absorbs and reflects certain wavelengths of light, producing an individual spectral pattern. By studying a satellite's spectral patterns, scientists can identify its chemical elements and determine whether the elements are solids, liquids, or gases.