Satellite

While the word satellite simply means some object or person that is attendant to another more important object or person, in astronomy it has taken on a much more specific meaning. Here the term refers to any object that is orbiting another larger more massive object under the influence of their mutual gravitational force. Thus, any planetary moon is most properly called a satellite of that planet. For example, Earth’s only natural satellite is called the moon.

Since the word is used to describe a single object, it is not used to designate rings of material orbiting a planet even though such rings might be described as being made up of millions of satellites. In those rare instances where the mass of the satellite approaches that of the object around which it orbits, the system is sometimes referred to as a binary. This is the reason that some people refer to the dwarf planet Pluto and its moon Charon as a binary dwarf planet system. This description is even more appropriate for some recently discovered asteroids that are composed of two similar sized objects orbiting each other.

In the late twentieth century, humans began launching objects from the Earth that orbit Earth and other planets. A tradition has developed to refer to these objects as artificially made satellites to distinguish them from the naturally occurring kind, such as Earth’s moon. Surveillance satellites orbiting Earth have been used to measure everything from aspects of the planet’s weather to movements of ships. Communications satellites revolve about Earth in geostationary orbits 25,000 mi (40,225 km) above the surface and a recent generation of navigation satellites enables one’s location on the surface of Earth to be determined with errors measured in centimeters. Such a system is called the global positioning system (GPS).

Different types of satellitesbuiltbyhumans include: astronomical satellites (used to observe celestial bodies); communications satellites (used for telecommunications); Earth observation satellites (used to observe Earth from a civilian standpoint); navigation satellites (such as GPS); reconnaissance satellites (used to observe Earth from a military standpoint); space station satellites (designed to house humans for extended periods of time); and weather satellites (used to observe and predict the weather of Earth).

Astronomical satellites have been placed in orbit about the sun, moon, Mars, Venus, Jupiter, Saturn, and Uranus to provide detailed maps of their surfaces and measure properties of their surrounding environment. This series of satellites is being extended by the United States to the dwarf planet Pluto when the Pluto-Kuiper Belt Mission, or New Horizons mission, was launched by NASA on January 19, 2006 from

Cape Canaveral, Florida. It was sent directly into an Earth- and solar-escape trajectory on its way to Pluto, Charon, and the Kuiper Belt (a large region of icy, rocky bodies located past the orbit of Neptune and continuing past Pluto’s orbit). The New Horizons mission will be the first reconnaissance of Pluto and Charon. After leaving the two prime celestial bodies, the probe will go on to explore objects in the Kuiper Belt. As of September 2006, the Pluto-Kuiper Belt mission should encounter Pluto and Charon in the summer of 2015, with a target date (as of June 2006) of July 14. Observations of Kuiper Belt Objects past Pluto should occur approximately between 2016 and 2020. Other countries are also sending astronomical satellites to planets and other bodies within the solar system. Some of these countries include: China, Australia, Israel, India, Japan, Russia, and the countries of the European Space Agency (such as France and England).

Spacecraft missions to other planets in the solar system have revealed the existence of numerous previously unknown natural satellites. In addition, the nature of many of the planetary satellites has become far clearer because of these voyages. It is said thatmore information concerning the four major Galilean Satellites of Jupiter was gained from the first flyby by Pioneer 10 than had been gained since the time of Italian astronomer and physicist Galileo Galilei (1564–1642). The knowledge gained from the satellites in the solar system have revealed considerable insights into their formation and evolution. As scientists continue to probe the solar system, there can be little doubt that the scientific knowledge of the satellites of the planets will continue to broaden human understanding of planetary moons and the nature of the solar system as a whole.

See also Gravity and gravitation; Space probe.

Satellite

While the word "satellite" simply means some object or person that is attendant to another more important object or person, in astronomy it has taken on a much more specific meaning. Here the term refers to any object that is orbiting another larger more massive object under the influence of their mutual gravitational force . Thus any planetary moon is most properly called a satellite of that planet . Since the word is used to describe a single object, it is not used to designate rings of material orbiting a planet even though such rings might be described as being made up of millions of satellites. In those rare instances where the mass of the satellite approaches that of

the object around which it orbits, the system is sometimes referred to as a binary. This is the reason that some people refer to Pluto and its moon Charon as a binary planet. This description is even more appropriate for some recently discovered asteroids which are composed of two similar sized objects orbiting each other.

In this century we have launched from the Earth objects that orbit the Earth and other planets. A tradition has developed to refer to these objects as man-made satellites to distinguish them from the naturally occurring kind. Surveillance satellites orbiting the Earth have been used to measure everything from aspects of the planet's weather to movements of ships. Communications satellites revolve about the earth in geostationary orbits 25,000 mi (40,225 km) above the surface and a recent generation of navigation satellites enables one's location on the surface of the earth to be determined with errors measured in centimeters.

Surveillance satellites have been placed in orbit about the Moon, Mars , and Venus to provide detailed maps of their surfaces and measure properties of their surrounding environment. This program will soon be extended to Jupiter and Saturn .

Spacecraft missions to other planets in the solar system have revealed the existence of numerous previously unknown natural satellites. In addition, the nature of many of the planetary satellites has become far clearer as a result of these voyages. It is said that more information concerning the four major Galilean Satellites of Jupiter was gained from the first flyby by Pioneer 10 then had been gained since the time of Galileo. The knowledge gained from the satellites in our solar system have revealed considerable insights into their formation and evolution . As we continue to probe the solar system, there can be little doubt that our knowledge of the satellites of the planets will continue to broaden our understanding of planetary moons and the nature of the solar system as a whole.

See also Gravity and gravitation; Space probe.

Satellite

In astronomy , a satellite refers to any object that is orbiting another larger, more massive object under the influence of their mutual gravitational force.

Thus, any planetary moon (e.g., the Moon revolving about Earth) is properly described as a satellite of that planet. Because the word is used to describe a single object, it is not used to designate rings of material orbiting a planet, even though such rings might be described as being made up of millions of satellites. In those rare instances where the mass of the satellite approaches that of the object around which it orbits, the system is sometimes referred to as a binary system. This is the reason that some people refer to Pluto and its moon Charon as a binary planet. This description is even more appropriate for some recently discovered asteroids which are composed of two similar sized objects orbiting each other.

In this century, scientific probes and commercial devices have been launched into Earth orbit or into orbits about the Sun or another planet. A tradition has developed to refer to these objects as man-made satellites to distinguish them from naturally occurring satellites. Surveillance satellites orbiting Earth have been used to measure everything from aspects of the planet's weather to movements of ships. Communications satellites revolve about Earth in geostationary orbits 25,000 mi (40,225 km) above the surface and a recent generation of navigation satellites and global positioning satellites (GPS ) enables receiving stations on the surface of Earth to be determined with errors measured within a few meters.

Surveillance satellites have been placed in orbit about the Moon, Mars, and Venus to provide detailed maps of their surfaces and measure properties of their surrounding environment. A number of probes have at least temporarily entered the orbits of Jupiter, Saturn, or moons of these Jovian worlds.

Spacecraft missions to other planets in the solar system have revealed the existence of numerous previously unknown natural satellites and data from the Hubble Space telescope continue to reveal satellite objects that explain discrepancies in orbital paths and rotation rates of celestial bodies.

See also History of manned space exploration; Terra satellite and Earth Observing Systems (EOS); Weather forecasting methods

sat·el·lite / ˈsatlˌīt/ • n. 1. (also ar·ti·fi·cial sat·el·lite) an artificial body placed in orbit around the earth or moon or another planet in order to collect information or for communication. ∎  [as adj.] transmitted by satellite; using or relating to satellite technology: satellite broadcasting. ∎  satellite television: a news service on satellite.2. Astron. a celestial body orbiting the earth or another planet.3. [usu. as adj.] something that is separated from or on the periphery of something else but is nevertheless dependent on or controlled by it: satellite offices in London and New York. ∎  a small country or state politically or economically dependent on another.4. Biol. a portion of the DNA of a genome with repeating base sequences and of different density from the main sequence.

satellite A minor body orbiting a planet in the solar system. About 60 are known, divided into three general classes. (a) Regular satellites form miniature solar systems and include all the classical major satellites, e.g. the Galilean satellites. (b) Collisional shards are tiny, craggy chunks, probably remnants of larger satellites, e.g. Amalthea, which is embedded in Jupiter's planetary ring system. (c) Irregular satellites have elongate, highly inclined orbits, mostly far from the planet, suggestive of capture, e.g. the outer satellites of Jupiter. Three bodies, the Earth's Moon, Triton (orbiting Neptune), and Charon (orbiting Pluto) do not fit into any of the above classes, and each has to be regarded as a unique case.