
A geosynchronous satellite is a
satellite
A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...
in
geosynchronous orbit
A geosynchronous orbit (sometimes abbreviated GSO) is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds (one sidereal day). The synchronization of rotation and orbital ...
, with an
orbital period
The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...
the same as the
Earth's rotation
Earth's rotation or Earth's spin is the rotation of planet Earth around its own Rotation around a fixed axis, axis, as well as changes in the orientation (geometry), orientation of the rotation axis in space. Earth rotates eastward, in progra ...
period. Such a satellite returns to the same position in the sky after each
sidereal day
Sidereal time ("sidereal" pronounced ) is a system of timekeeping used especially by astronomers. Using sidereal time and the celestial coordinate system, it is easy to locate the positions of celestial objects in the night sky. Sidereal t ...
, and over the course of a day traces out a path in the sky that is typically some form of
analemma
In astronomy, an analemma (; ) is a diagram showing the position of the Sun in the sky as seen from a fixed location on Earth at the same Solar time#Mean solar time, mean solar time over the course of a year. The change of position is a result ...
. A special case of geosynchronous satellite is the
geostationary satellite, which has a
geostationary orbit
A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular orbit, circular geosynchronous or ...
– a circular geosynchronous orbit directly above the Earth's
equator
The equator is the circle of latitude that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern Hemispheres of Earth, hemispheres. It is an imaginary line located at 0 degrees latitude, about in circumferen ...
. Another type of geosynchronous orbit used by satellites is the
Tundra elliptical orbit.
Geostationary satellites have the unique property of remaining permanently fixed in exactly the
same position in the sky as viewed from any fixed location on Earth, meaning that ground-based antennas do not need to track them but can remain fixed in one direction. Such satellites are often used for
communication purposes; a geosynchronous network is a
communication network
A telecommunications network is a group of nodes interconnected by telecommunications links that are used to exchange messages between the nodes. The links may use a variety of technologies based on the methodologies of circuit switching, messa ...
based on communication with or through geosynchronous satellites.
Definition
The term ''geosynchronous'' refers to the satellite's orbital period which enables it to be matched, with the rotation of the Earth ("geo-"). Along with this orbital period requirement, to be ''
geostationary
A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitud ...
'' as well, the satellite must be placed in an orbit that puts it in the vicinity over the equator. These two requirements make the satellite appear in an unchanging area of visibility when viewed from the Earth's surface, enabling continuous operation from one point on the ground. The special case of a geostationary orbit is the most common type of orbit for communications satellites.
If a geosynchronous satellite's orbit is not exactly aligned with the Earth's
equator
The equator is the circle of latitude that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern Hemispheres of Earth, hemispheres. It is an imaginary line located at 0 degrees latitude, about in circumferen ...
, the orbit is known as an
inclined orbit. It will appear (when viewed by someone on the ground) to oscillate daily around a fixed point. As the angle between the orbit and the equator decreases, the magnitude of this oscillation becomes smaller; when the orbit lies entirely over the equator in a circular orbit, the satellite remains stationary relative to the Earth's surface – it is said to be ''geostationary''.
Application
, there are approximately 446 active geosynchronous satellites, some of which are not operational.

Geostationary satellites appear to be fixed over one spot above the equator. Receiving and transmitting
antennas on the earth do not need to track such a satellite. These antennas can be fixed in place and are much less expensive than tracking antennas. These satellites have revolutionized global
communication
Communication is commonly defined as the transmission of information. Its precise definition is disputed and there are disagreements about whether Intention, unintentional or failed transmissions are included and whether communication not onl ...
s,
television broadcasting
A television broadcaster or television network is a telecommunications network for the distribution of television content, where a central operation provides programming to many television stations, pay television providers or, in the United ...
and
weather forecasting
Weather forecasting or weather prediction is the application of science and technology forecasting, to predict the conditions of the Earth's atmosphere, atmosphere for a given location and time. People have attempted to predict the weather info ...
, and have a number of important
defense
Defense or defence may refer to:
Tactical, martial, and political acts or groups
* Defense (military), forces primarily intended for warfare
* Civil defense, the organizing of civilians to deal with emergencies or enemy attacks
* Defense industr ...
and
intelligence
Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, critical thinking, and problem-solving. It can be described as t ...
applications.
One disadvantage of geostationary satellites is a result of their high altitude:
radio
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connec ...
signals take approximately 0.25 of a second to reach and return from the satellite, resulting in a small but significant signal
delay. This delay increases the difficulty of
telephone
A telephone, colloquially referred to as a phone, is a telecommunications device that enables two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most ...
conversation and reduces the performance of common
network protocol
A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any variation of a physical quantity. The protocol defines the rules, syntax, semantics, and synchronization of ...
s such as
TCP/IP
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are ...
, but does not present a problem with non-interactive systems such as
satellite television
Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location.ITU Radio Regulations, Section IV. Radio Stations and Systems ...
broadcasts. There are a number of proprietary satellite data protocols that are designed to proxy TCP/IP connections over long-delay satellite links—these are marketed as being a partial solution to the poor performance of native TCP over satellite links. TCP presumes that all loss is due to congestion, not errors, and probes link capacity with its "
slow start"
algorithm
In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algo ...
, which only sends
packets once it is known that earlier packets have been received. Slow start is very slow over a path using a geostationary satellite. RFC 2488, written in 1999, gives several suggestions on this issue.
There are some advantages of geo-stationary satellites:
*Get high temporal resolution data.
*Tracking of the satellite by its earth stations is simplified.
*Satellite always in same position.
A disadvantage of geostationary satellites is the incomplete geographical coverage, since ground stations at higher than roughly 60 degrees latitude have difficulty reliably receiving signals at low elevations.
Satellite dish
A satellite dish is a dish-shaped type of parabolic antenna designed to receive or transmit information by radio waves to or from a communication satellite. The term most commonly means a dish which receives direct-broadcast satellite televisio ...
es at such high latitudes would need to be pointed almost directly towards the horizon. The signals would have to pass through the largest amount of atmosphere, and could even be blocked by land topography, vegetation or buildings. In the
USSR
The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
, a practical solution was developed for this problem with the creation of special
Molniya /
Orbita inclined path
satellite networks with
elliptical orbits. Similar elliptical orbits are used for the
Sirius Radio satellites.
History
The concept was first proposed by
Herman Potočnik
Herman Potočnik (pseudonym Hermann Noordung; 22 December 1892 – 27 August 1929) was an Austro-Hungarian Army officer, electrical engineer and astronautics theorist. He is regarded as an early theorist of modern space flight and is remembered m ...
in 1928 and popularised by the
science fiction author Arthur C. Clarke in a paper in ''
Wireless World
''Electronics World'' (''Wireless World'', founded in 1913, and in October 1983 renamed ''Electronics & Wireless World'') is a technical magazine published by Datateam Business Media Ltd that covers electronics and RF engineering and is aimed at ...
'' in 1945. Working prior to the advent of solid-state electronics, Clarke envisioned a trio of large, crewed space stations arranged in a triangle around the planet. Modern satellites are numerous, uncrewed, and often no larger than an automobile.
Widely known as the "father of the geosynchronous satellite",
Harold Rosen, an engineer at Hughes Aircraft Company, invented the first operational geosynchronous satellite,
Syncom 2
Syncom (for "synchronous communication satellite") started as a 1961 NASA program for active geosynchronous communication satellites, all of which were developed and manufactured by the Space and Communications division of Hughes Aircraft Compa ...
.
It was launched on a
Delta rocket
The Delta rocket family was a versatile range of American rocket-powered expendable launch systems that provided space launch capability in the United States from 1960 to 2024. Japan also launched license-built derivatives (N-I (rocket), N-I, N ...
B booster from
Cape Canaveral
Cape Canaveral () is a cape (geography), cape in Brevard County, Florida, in the United States, near the center of the state's Atlantic Ocean, Atlantic coast. Officially Cape Kennedy from 1963 to 1973, it lies east of Merritt Island, separated ...
July 26, 1963.
The first
geostationary
A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitud ...
communication satellite was
Syncom 3
Syncom (for "synchronous communication satellite") started as a 1961 NASA program for active geosynchronous communication satellites, all of which were developed and manufactured by the Space and Communications division of Hughes Aircraft Compa ...
, launched on August 19, 1964, with a Delta D launch vehicle from Cape Canaveral. The satellite, in orbit approximately above the
International Date Line
The International Date Line (IDL) is the line extending between the South and North Poles that is the boundary between one calendar day and the next. It passes through the Pacific Ocean, roughly following the 180.0° line of longitude and de ...
, was used to telecast the
1964 Summer Olympics
The , officially the and commonly known as Tokyo 1964 (), were an international multi-sport event held from 10 to 24 October 1964 in Tokyo, Japan. Tokyo had been awarded the organization of the 1940 Summer Olympics, but this honor was subseq ...
in Tokyo to the United States.
Westar 1
Westar 1 was America's first domestic and commercially launched geostationary communications satellite, launched by Western Union (WU) and NASA on April 13, 1974. It was built by Hughes for Western Union, using the HS-333 platform of spin-st ...
was America's first domestic and commercially launched geostationary communications satellite, launched by
Western Union
The Western Union Company is an American multinational financial services corporation headquartered in Denver, Denver, Colorado.
Founded in 1851 as the New York and Mississippi Valley Printing Telegraph Company in Rochester, New York, the co ...
and
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
on April 13, 1974.
See also
*
Geosynchronous orbit
A geosynchronous orbit (sometimes abbreviated GSO) is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds (one sidereal day). The synchronization of rotation and orbital ...
*
Geostationary orbit
A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular orbit, circular geosynchronous or ...
*
Geostationary balloon satellite
*
Graveyard orbit
A graveyard orbit, also called a junk orbit or disposal orbit, is an Orbit (physics), orbit that lies away from common operational orbits. One significant graveyard orbit is a supersynchronous orbit well beyond geosynchronous orbit. Some satellit ...
*
List of orbits
This is a list of types of gravitational orbit classified by various characteristics.
Common abbreviations
List of abbreviations of common Earth orbits
List of abbreviations of other orbits
Classifications
The following is a list of t ...
*
List of satellites in geosynchronous orbit
*
Molniya orbit
A Molniya orbit ( rus, Молния, p=ˈmolnʲɪjə, a=Ru-молния.ogg, "Lightning") is a type of satellite orbit designed to provide communications and remote sensing coverage over high latitudes. It is a highly elliptical orbit with ...
*
Tundra orbit
*
Polar mount - Mount useful for aiming a satellite dish at geosynchronous satellites
*
Satellite television
Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer's location.ITU Radio Regulations, Section IV. Radio Stations and Systems ...
References
External links
Lyngsat list of communications satellites in geostationary orbit*For an interactive list of active inactive satellites geosynchronous and orbital a
NORAD Celestrack
{{DEFAULTSORT:Geosynchronous Satellite
Satellites by orbit
Satellite broadcasting
Telecommunications-related introductions in 1963