Artificial satellites are used for many purposes, including communications, navigation, gathering weather information, creating maps and even spying. Artificial satellites come in several forms, including telescopes and probes. They enter orbit around the Earth's atmosphere or travel to other planets after launching through rockets, and remain in the atmosphere for a specific period of time before returning to Earth.
Satellites vary in size and complexity, and have different features making them suitable for various functions. Space telescopes rank among the largest and most innovative objects in space. These telescopes enjoy a complex internal layout, with capabilities for retrieving and storing information. Space telescopes gather information on objects in outer space, such as the stars and other planets. They include several well-known craft, such as the Hubble Space Telescope. These telescopes provide valuable information to scientists and astronomers. However, they typically rank high on the list of expensive telescopes. Some require frequent maintenance, which necessitates visits from astronauts. Space probes, in contrast to space telescopes, do not orbit the Earth. Instead, they fly to distant planets and even other solar systems, gathering information and bringing back scientific data. In addition to collecting scientific information, satellites help make maps, provide navigation services and see use in the military, acting as a spy and reconnaissance vessel.