Scientists know little about Charon because no spacecraft has ever flown close to it and it is so far from Earth. How scientists study satellites Scientists use several techniques to gather information about satellites. The most useful means of studying satellites are telescopes and spacecraft. Most telescopes used to study satellites are based on Earth's surface. The remainder are mounted in Earth-orbiting artificial satellites, such as the Hubble Space Telescope, and in spacecraft.
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.