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In the context of
spaceflight Spaceflight (or space flight) is an application of astronautics to fly spacecraft into or through outer space, either with or without humans on board. Yuri Gagarin of the Soviet Union was the first human to conduct a spaceflight. Examples of hum ...
, a satellite is an object that has been intentionally placed into
orbit In physics, an orbit is the gravitationally curved trajectory of an object, such as the trajectory of a planet around a star or a natural satellite around a planet. Normally, orbit refers to a regularly repeating trajectory, although it may als ...
. These objects are called artificial satellites to distinguish them from
natural satellite A natural satellite, or moon, is, in the most common usage, an astronomical body that orbits a planet or minor planet (or sometimes another small Solar System body). In the Solar System, there are six planetary satellite systems containing 20 ...
s such as Earth's
Moon The Moon is Earth's only proper natural satellite. At one-quarter the diameter of Earth (comparable to the width of Australia), it is the largest natural satellite in the Solar System relative to the size of its planet, and the fifth largest ...

Moon
. On 4 October 1957 the
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a federal socialist state in Northern Eurasia that existed from 1922 to 1991. Nominally a union of multiple national Soviet republics, in practice its governmen ...
launched the world's first artificial satellite,
Sputnik 1 Sputnik 1 (; "Satellite-1", or "PS-1", Простейший Спутник-1 or ''Prosteyshiy Sputnik-1'', "Elementary Satellite 1") was the first artificial Earth satellite. The Soviet Union launched it into an elliptical low Earth orbit on 4 ...

Sputnik 1
. Since then, about 8,900 satellites from more than 40 countries have been launched. According to a 2018 estimate, some 5,000 remain in orbit. Of those, about 1,900 were operational, while the rest have exceeded their useful lives and become
space debris Space debris (also known as space junk, space pollution, space waste, space trash, or space garbage) is defunct human-made objects in space—principally in Earth orbit—which no longer serve a useful function. These include derelict spacecraft ...
. Approximately 63% of operational satellites are in
low Earth orbit#REDIRECT Low Earth orbit#REDIRECT Low Earth orbit {{R from other capitalisation ...
{{R from other capitalisation ...
, 6% are in
medium-Earth orbit#REDIRECT Medium Earth orbit {{Redirect category shell, 1= {{R from other capitalisation ...
(at 20,000 km), 29% are in
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 geosynchronous orbit above Earth' ...
(at 36,000 km) and the remaining 2% are in various
elliptical orbits In astrodynamics or celestial mechanics, an elliptic orbit or elliptical orbit is a Kepler orbit with an eccentricity of less than 1; this includes the special case of a circular orbit, with eccentricity equal to 0. In a stricter sense, it is a ...
. In terms of countries with the most satellites, the
USA The United States of America (USA), commonly known as the United States (U.S. or US), or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major self-governing territories, 326 India ...
has the most with 1,897 satellites,
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population of around 1.4 billion. Covering approximately 9.6 million square kilometers (3.7 million m ...
is second with 412, and
Russia Russia (russian: link=no, Россия, , ), or the Russian Federation, is a country spanning Eastern Europe and Northern Asia. It is the largest country in the world, covering and encompassing more than one-eighth of the Earth's inhabited l ...
third with 176. A few large
space stations A space station, also known as an orbital station or an orbital space station, is a spacecraft capable of supporting a human crew in orbit for an extended period of time, and is therefore a type of space habitat. It lacks major propulsion or land ...
, including the
International Space Station The International Space Station (ISS) is a modular space station (habitable artificial satellite) in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russi ...

International Space Station
, have been launched in parts and assembled in orbit. Over a dozen
space probe A space probe or a spaceprobe is a robotic spacecraft that doesn't orbit the Earth, but instead explores farther into outer space. A space probe may approach the Moon; travel through interplanetary space; flyby, orbit, or land or fly on other p ...
s have been placed into orbit around other bodies and become artificial satellites of the
Moon The Moon is Earth's only proper natural satellite. At one-quarter the diameter of Earth (comparable to the width of Australia), it is the largest natural satellite in the Solar System relative to the size of its planet, and the fifth largest ...

Moon
,
Mercury Mercury usually refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol 'Hg' * Mercury (mythology), a Roman god Mercury may also refer to: Companies * Mercury (toy manufacture ...
,
Venus Venus is the second planet from the Sun. It is named after the Roman goddess of love and beauty. As the brightest natural object in Earth's night sky after the Moon, Venus can cast shadows and can be, on rare occasion, visible to the naked ey ...
,
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, being larger than only Mercury. In English, Mars carries the name of the Roman god of war and is often referred to as the "Red Planet". The latter refe ...

Mars
,
Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass one-thousandth that of the Sun, but two and a half times that of all the other planets in the Solar System combined. Jupiter is the th ...

Jupiter
,
Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It only has one-eighth the average density of Earth; how ...

Saturn
, a few
asteroid An asteroid is a minor planet of the inner Solar System. Historically, these terms have been applied to any astronomical object orbiting the Sun that did not resolve into a disc in a telescope and was not observed to have characteristics of an ...
s, a
comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena are d ...
and the
Sun The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy mainly as visible light and infrared radiation. It is b ...

Sun
. Satellites are used for many purposes. Among several other applications, they can be used to make star maps and maps of
planetary surface OSIRIS-REx collecting a surface sample from asteroid Full-sized image)''">:File:OSIRIS-REX SamCam TAGSAM Event 2020-10-20.gif">Full-sized image)'' A planetary surface is where the solid (or liquid) material of the outer crust on certain types of a ...
s, and also take pictures of planets they are launched into. Common types include military and civilian
Earth observation satellite#REDIRECT Earth observation satellite#REDIRECT Earth observation satellite {{R from other capitalisation ...
{{R from other capitalisation ...
s,
communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Com ...
s,
navigation satellite A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows small electronic receivers to determine their location (longitude, latitude, and altitude/elevation) to high precis ...
s,
weather satellite , a United States weather satellite of the meteorological-satellite service A weather satellite is a type of satellite that is primarily used to monitor the weather and climate of the Earth. Satellites can be polar orbiting (covering the entire ...

weather satellite
s, and
space telescope A space telescope or space observatory is a telescope located in outer space to observe distant planets, galaxies and other astronomical objects. Space telescopes avoid the filtering of ultraviolet frequencies, X-rays and gamma rays; the distort ...
s.
Space station A space station, also known as an orbital station or an orbital space station, is a spacecraft capable of supporting a human crew in orbit for an extended period of time, and is therefore a type of space habitat. It lacks major propulsion or land ...
s and human
spacecraft 275px, The US Space Shuttle flew 135 times from 1981 to 2011, supporting Spacelab, ''Mir'', the maiden_launch,_which_had_a_white_external_tank,_shown).html" style="text-decoration: none;"class="mw-redirect" title="Hubble Space Telescope, and the ...
in orbit are also satellites. Satellites can operate by themselves or as part of a larger system, a satellite formation or
satellite constellation A satellite constellation is a group of artificial satellites working together as a system. Unlike a single satellite, a constellation can provide permanent global or near-global coverage, such that at any time everywhere on Earth at least one sat ...
. Satellite orbits vary greatly, depending on the purpose of the satellite, and are classified in a number of ways. Well-known (overlapping) classes include low Earth orbit,
polar orbit A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It has an inclination of about 6 ...
, and
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 geosynchronous orbit above Earth' ...
. A
launch vehicle Russian Soyuz TMA-5 lifts off from the Baikonur Cosmodrome in Kazakhstan heading for the International_Space_Station">Soyuz_TMA-5_lifts_off_from_the_Baikonur_Cosmodrome_in_Kazakhstan_heading_for_the_International_Space_Station_ A_launch_veh ...
is a
rocket A rocket (from it, rocchetto, , bobbin/spool) is a projectile that spacecraft, aircraft or other vehicle use to obtain thrust from a rocket engine. Rocket engine exhaust is formed entirely from propellant carried within the rocket. Rocket engines ...
that places a satellite into orbit. Usually, it lifts off from a
launch pad A launch pad is an above-ground facility from which a rocket-powered missile or space vehicle is vertically launched. The term ''launch pad'' can be used to describe just the central launch platform (mobile launcher platform), or the entire co ...
on land. Some are launched at sea from a
submarine upright=1.35, Russian ''Akula''-class submarine of the Northern Fleet A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. It is also someti ...
or a mobile maritime platform, or aboard a plane (see
air launch to orbit Air launch to orbit is the method of launching rockets at altitude from a conventional horizontal-takeoff aircraft, to carry satellites to low Earth orbit. It is a follow-on development of air launches of experimental aircraft that began in the l ...
). Satellites are usually semi-independent computer-controlled systems. Satellite subsystems attend many tasks, such as power generation,
thermal control Example of a thermal column between the ground and a cumulus A thermal column (or thermal) is a column of rising air in the lower altitudes of Earth's atmosphere, a form of atmospheric updraft. Thermals are created by the uneven heating of Earth ...
, telemetry,
attitude control Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle at ...
, scientific instrumentation,
communication Communication (from Latin ''communicare'', meaning "to share") is the act of developing meaning among entities or groups through the use of sufficiently mutually understood signs, symbols, and semiotic conventions. The main elements inherent to ...
, etc.


History

The first published mathematical study of the possibility of an artificial satellite was
Newton's cannonball 240px Newton's cannonball was a thought experiment Isaac Newton used to hypothesize that the force of gravity was universal, and it was the key force for planetary motion. It appeared in his 1687 work ''Philosophiæ Naturalis Principia Mathematica'' ...
, a thought experiment by
Isaac Newton Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, physicist, astronomer, theologian, and author (described in his time as a "natural philosopher") who is widely recognised as one of the greatest math ...

Isaac Newton
to explain the motion of
natural satellite A natural satellite, or moon, is, in the most common usage, an astronomical body that orbits a planet or minor planet (or sometimes another small Solar System body). In the Solar System, there are six planetary satellite systems containing 20 ...
s, in his ''
Philosophiæ Naturalis Principia Mathematica ''Philosophiæ Naturalis Principia Mathematica'' (''Mathematical Principles of Natural Philosophy'') by Isaac Newton, often referred to as simply the ''Principia'' (), is a work in three books written in Latin, first published 5 July 1687. After ...
'' (1687). The first fictional depiction of a satellite being launched into orbit was a
short story A short story is a piece of prose fiction that typically can be read in one sitting and focuses on a self-contained incident or series of linked incidents, with the intent of evoking a single effect or mood. The short story is one of the oldest ty ...
by
Edward Everett Hale Edward Everett Hale (April 3, 1822 – June 10, 1909) was an American author, historian, and Unitarian minister, best known for his writings such as "The Man Without a Country", published in ''Atlantic Monthly'', in support of the Union during ...
, "
The Brick Moon "The Brick Moon" is a novella by American writer Edward Everett Hale, published serially in ''The Atlantic Monthly'' starting in 1869. It is a work of speculative fiction containing the first known depiction of the launch of an artificial satellit ...
" (1869). The idea surfaced again in
Jules Verne Jules Gabriel Verne (;''Longman Pronunciation Dictionary''. ; 8 February 1828 – 24 March 1905) was a French novelist, poet, and playwright. His collaboration with the publisher Pierre-Jules Hetzel led to the creation of the ''Voyages extraord ...

Jules Verne
's ''
The Begum's Fortune ''The Begum's Fortune'' (french: Les Cinq cents millions de la Bégum, literally "the 500 millions of the begum"), also published as ''The Begum's Millions'', is an 1879 novel by Jules Verne, with some utopian elements and other elements that seem c ...
'' (1879). In 1903,
Konstantin Tsiolkovsky Konstantin Eduardovich Tsiolkovsky (russian: Константин Эдуардович Циолковский , , p=kənstɐnʲˈtʲin ɪdʊˈardəvʲɪtɕ tsɨɐlˈkofskʲɪj , a=Ru-Konstantin Tsiolkovsky.oga; – 19 September 1935), was a Russ ...
(1857–1935) published ''Exploring Space Using Jet Propulsion Devices'', which is the first academic treatise on the use of rocketry to launch spacecraft. He calculated the
orbital speed In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter or, if one object is much more more m ...
required for a minimal orbit, and that a
multi-stage rocket multistage sounding rocket Image:minuteman 3 stage2.jpg">The second stage of a engines_and_Rocket_propellant.html" style="text-decoration: none;"class="mw-redirect" title="launch vehicle that uses two or more Minuteman III_rocket A_multi ...
fueled by liquid
propellant A propellant or propellent is a chemical substance used in the production of energy or pressurized gas that is subsequently used to create movement of a fluid or to generate propulsion of a vehicle, projectile, or other object. Common propellants ar ...
s could achieve this. In 1928,
Herman Potočnik Herman Potočnik (pseudonym Hermann Noordung; 22 December 1892 – 27 August 1929) was a Slovene rocket engineer and pioneer of astronautics. He is chiefly remembered for his work addressing the long-term human habitation of space. Early life Pot ...
(1892–1929) published his sole book, ''The Problem of Space Travel – The Rocket Motor''. He described the use of orbiting spacecraft for observation of the ground and described how the special conditions of space could be useful for scientific experiments. In a 1945 ''
Wireless World ''Electronics World'' (''Wireless World'', founded in 1913, and in September 1984 renamed ''Electronics & Wireless World'') is a technical magazine in electronics and RF engineering aimed at professional design engineers. It is produced monthly in ...
'' article, the English science fiction writer Arthur C. Clarke described in detail the possible use of
communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Com ...
s for mass communications. He suggested that three geostationary satellites would provide coverage over the entire planet. In May 1946, the
United States Air Force The United States Air Force (USAF) is the air service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services. Initially formed as a part of the United States Army on 1 August 1907, the USAF was established as ...
's
Project RAND RAND Corporation ("research and development") is an American nonprofit global policy think tank created in 1948 by Douglas Aircraft Company to offer research and analysis to the United States Armed Forces. It is financed by the U.S. government ...
released the Preliminary Design of an Experimental World-Circling Spaceship, which stated that "A satellite vehicle with appropriate instrumentation can be expected to be one of the most potent scientific tools of the Twentieth Century." The United States had been considering launching orbital satellites since 1945 under the
Bureau of AeronauticsThe Bureau of Aeronautics (BuAer) was the U.S. Navy's material-support organization for naval aviation from 1921 to 1959. The bureau had "cognizance" (''i.e.'', responsibility) for the design, procurement, and support of naval aircraft and related s ...
of the
United States Navy ), (unofficial)."''Non sibi sed patriae''" ( en, "Not for self but for country") (unofficial). , colors = Blue and gold  , colors_label = Colors , march = "Anchors Aweigh" , m ...
. Project RAND eventually released the report, but considered the satellite to be a tool for science, politics, and propaganda, rather than a potential military weapon. In 1946, American theoretical astrophysicist
Lyman Spitzer Lyman Spitzer Jr. (June 26, 1914 – March 31, 1997) was an American theoretical physicist, astronomer and mountaineer. As a scientist, he carried out research into star formation, plasma physics, and in 1946, conceived the idea of telescopes ...

Lyman Spitzer
proposed an orbiting
space telescope A space telescope or space observatory is a telescope located in outer space to observe distant planets, galaxies and other astronomical objects. Space telescopes avoid the filtering of ultraviolet frequencies, X-rays and gamma rays; the distort ...
. In February 1954 Project RAND released "Scientific Uses for a Satellite Vehicle", written by R.R. Carhart. This expanded on potential scientific uses for satellite vehicles and was followed in June 1955 with "The Scientific Use of an Artificial Satellite", by H.K. Kallmann and W.W. Kellogg. In the context of activities planned for the
International Geophysical Year The International Geophysical Year (IGY; french: Année géophysique internationale) was an international scientific project that lasted from 1 July 1957 to 31 December 1958. It marked the end of a long period during the Cold War when scientific int ...
(1957–58), the
White House The White House is the official residence and workplace of the president of the United States. It is located at 1600 Pennsylvania Avenue NW in Washington, D.C., and has been the residence of every US president since John Adams in 1800. Th ...
announced on 29 July 1955 that the U.S. intended to launch satellites by the spring of 1958. This became known as
Project Vanguard Project Vanguard was a program managed by the United States Naval Research Laboratory (NRL), which intended to launch the first artificial satellite into Earth orbit using a Vanguard rocket as the launch vehicle from Cape Canaveral Missile Annex, ...
. On 31 July, the Soviets announced that they intended to launch a satellite by the fall of 1957. The first artificial satellite was
Sputnik 1 Sputnik 1 (; "Satellite-1", or "PS-1", Простейший Спутник-1 or ''Prosteyshiy Sputnik-1'', "Elementary Satellite 1") was the first artificial Earth satellite. The Soviet Union launched it into an elliptical low Earth orbit on 4 ...

Sputnik 1
, launched by the
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a federal socialist state in Northern Eurasia that existed from 1922 to 1991. Nominally a union of multiple national Soviet republics, in practice its governmen ...
on 4 October 1957 under the
Sputnik program Sputnik (Спутник, Russian for "satellite"NOTE: The Russian word "sputnik" can have many meanings: "satellite", "travelling companion", "fellow traveller", etc. However, in astronomy it only means "satellite".) is a spacecraft launched und ...
, with
Sergei Korolev Sergei Pavlovich Korolev ( rus, Сергей Павлович Королёв, p =sʲɪrˈgʲej ˈpavɫəvʲɪtɕ kərɐˈlʲɵf, a=Ru-Sergei Pavlovich Korolev.ogg, also transliterated as Sergey Pavlovich Korolyov; uk, link=no, Сергій Павл ...
as chief designer. Sputnik 1 helped to identify the density of high atmospheric layers through measurement of its orbital change and provided data on radio-signal distribution in the
ionosphere The ionosphere () is the ionized part of Earth's upper atmosphere, from about to altitude, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an important role ...
. The unanticipated announcement of Sputnik 1's success precipitated the
Sputnik crisis The Sputnik crisis was a period of public fear and anxiety in Western nations about the perceived technological gap between the United States and Soviet Union caused by the Soviets' launch of ''Sputnik 1'', the world's first artificial satellite. ...
in the United States and ignited the so-called Space Race within the
Cold War The Cold War was a period of geopolitical tension between the Soviet Union and the United States and their respective allies, the Eastern Bloc and the Western Bloc, after World War II. Historians do not fully agree on the dates, but the per ...
.
Sputnik 2 Sputnik 2 (, russian: Спутник-2, ''Satellite 2''), or Prosteyshiy Sputnik 2 (PS-2, russian: Простейший Спутник 2, italic=yes, ''Simplest Satellite 2'') was the second spacecraft launched into Earth orbit, on 3 November 1957, ...
was launched on 3 November 1957 and carried the first living passenger into orbit, a dog named
Laika Laika (russian: Лайка; c. 1954 – 3 November 1957) was a Soviet space dog which became one of the first animals in space, and the first animal to orbit the Earth. Laika, a stray mongrel from the streets of Moscow, was selected to be the ...
. In early 1955, following pressure by the
American Rocket Society The American Rocket Society (ARS) began its existence on April 4, 1930, under the name of the American Interplanetary Society. It was founded by science fiction writers G. Edward Pendray, David Lasser, Laurence Manning, and others. Pendray correspo ...
, the
National Science Foundation The National Science Foundation (NSF) is an independent agency of the United States government that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National Inst ...
, and the International Geophysical Year, the Army and Navy were working on
Project Orbiter Project Orbiter was a proposed United States spacecraft, an early competitor to Project Vanguard. It was jointly run by the United States Army and United States Navy. It was ultimately rejected by the Ad Hoc Committee on Special Capabilities, whic ...
with two competing programs. The army used the Jupiter C rocket, while the civilian/Navy program used the
Vanguard rocket The Vanguard rocket was intended to be the first launch vehicle the United States would use to place a satellite into orbit. Instead, the Sputnik crisis caused by the surprise launch of Sputnik 1 led the U.S., after the failure of Vanguard TV-3, t ...
to launch a satellite.
Explorer 1 Explorer 1 was the first satellite launched by the United States and was part of the U.S. participation in the International Geophysical Year (IGY). The mission followed the first two satellites the previous year; the Soviet Union's Sputnik 1 ...
became the United States' first artificial satellite on 31 January 1958. In June 1961, three-and-a-half years after the launch of Sputnik 1, the
United States Space Surveillance Network The United States Space Surveillance Network detects, tracks, catalogs and identifies artificial objects orbiting Earth, e.g. active/inactive satellites, spent rocket bodies, or fragmentation debris. The system is the responsibility of United State ...
cataloged 115 Earth-orbiting satellites. Early satellites were constructed to unique designs. With advancements in technology, multiple satellites began to be built on single model platforms called
satellite bus A satellite bus or spacecraft bus is a general model on which multiple-production satellite spacecraft are often based. The bus is the infrastructure of the spacecraft, usually providing locations for the payload (typically space experiments or ins ...
es. The first standardized satellite bus design was the HS-333
geosynchronous 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 ...

geosynchronous
(GEO)
communication satellite Communication (from Latin ''communicare'', meaning "to share") is the act of developing meaning among entities or groups through the use of sufficiently mutually understood signs, symbols, and semiotic conventions. The main elements inherent to ...
launched in 1972. Currently the largest artificial satellite ever is the
International Space Station The International Space Station (ISS) is a modular space station (habitable artificial satellite) in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russi ...

International Space Station
.


Tracking

Satellites can be tracked from Earth stations and also from other satellites.


Space Surveillance Network

The
United States Space Surveillance Network The United States Space Surveillance Network detects, tracks, catalogs and identifies artificial objects orbiting Earth, e.g. active/inactive satellites, spent rocket bodies, or fragmentation debris. The system is the responsibility of United State ...
(SSN), a division of the
United States Strategic Command United States Strategic Command (USSTRATCOM) is one of the eleven unified combatant commands in the United States Department of Defense. Headquartered at Offutt Air Force Base, Nebraska, USSTRATCOM is responsible for strategic deterrence, globa ...
, has been tracking objects in Earth's orbit since 1957 when the
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a federal socialist state in Northern Eurasia that existed from 1922 to 1991. Nominally a union of multiple national Soviet republics, in practice its governmen ...
opened the
Space Age lifts off on a crewed mission to space. The Space Age is a period encompassing the activities related to the Space Race, space exploration, space technology, and the cultural developments influenced by these events. The Space Age is generally co ...
with the launch of
Sputnik I Sputnik 1 (; "Satellite-1", or "PS-1", Простейший Спутник-1 or ''Prosteyshiy Sputnik-1'', "Elementary Satellite 1") was the first artificial Earth satellite. The Soviet Union launched it into an elliptical low Earth orbit on 4 ...
. Since then, the SSN has tracked more than 26,000 objects. The SSN currently tracks more than 8,000-artificial orbiting objects. The rest have re-entered Earth's atmosphere and disintegrated, or survived re-entry and impacted the Earth. The SSN tracks objects that are 10 centimeters in diameter or larger; those now orbiting Earth range from satellites weighing several tons to pieces of spent rocket bodies weighing only 10 pounds. About seven percent are operational satellites (i.e. ~560 satellites), the rest are
space debris Space debris (also known as space junk, space pollution, space waste, space trash, or space garbage) is defunct human-made objects in space—principally in Earth orbit—which no longer serve a useful function. These include derelict spacecraft ...
. The United States Strategic Command is primarily interested in the active satellites, but also tracks space debris which upon reentry might otherwise be mistaken for incoming missiles.


Services

There are three basic categories of (non-military) satellite services:


Fixed satellite services

Fixed satellite services Fixed-satellite service (short: FSS | also: fixed-satellite radiocommunication service) is – according to ''article 1.21'' of the International Telecommunication Union's (ITU) Radio Regulations (RR) – defined as ''A radiocommunication serv ...
handle hundreds of billions of voice, data, and video transmission tasks across all countries and continents between certain points on the Earth's surface.


Mobile satellite systems

Mobile satellite systems help connect remote regions, vehicles, ships, people and aircraft to other parts of the world and/or other mobile or stationary communications units, in addition to serving as navigation systems.


Scientific research satellites (commercial and noncommercial)

Scientific research satellites provide meteorological information, land survey data (e.g. remote sensing), Amateur (HAM) Radio, and other different scientific research applications such as earth science, marine science, and atmospheric research.


Types

*
Astronomical satellite A space telescope or space observatory is a telescope located in outer space to observe distant planets, galaxies and other astronomical objects. Space telescopes avoid the filtering of ultraviolet frequencies, X-rays and gamma rays; the distort ...
s are satellites used for observation of distant planets, galaxies, and other outer space objects. *
Biosatellite A biosatellite is an artificial satellite designed to carry plants or animals in outer space. They are used to research the effects of space (cosmic radiation, weightlessness, etc.) on biological matter while in orbit around a celestial body. The ...
s are satellites designed to carry living organisms, generally for scientific experimentation. *
Communication satellite Communication (from Latin ''communicare'', meaning "to share") is the act of developing meaning among entities or groups through the use of sufficiently mutually understood signs, symbols, and semiotic conventions. The main elements inherent to ...
s are satellites stationed in space for the purpose of
telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, optical or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that feasi ...
. Modern communications satellites typically use
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 ...

geosynchronous orbit
s,
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 an incl ...
s or
Low Earth orbit#REDIRECT Low Earth orbit#REDIRECT Low Earth orbit {{R from other capitalisation ...
{{R from other capitalisation ...
s. *
Earth observation satellite#REDIRECT Earth observation satellite#REDIRECT Earth observation satellite {{R from other capitalisation ...
{{R from other capitalisation ...
s are satellites intended for non-military uses such as
environmental A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale fr ...
monitoring,
meteorology Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorolo ...
,
map making Cartography (; from Greek χάρτης ''chartēs'', "papyrus, sheet of paper, map"; and γράφειν ''graphein'', "write") is the study and practice of making and using maps. Combining science, aesthetics, and technique, cartography builds ...
etc. (See especially
Earth Observing System The Earth Observing System (EOS) is a program of NASA comprising a series of artificial satellite missions and scientific instruments in Earth orbit designed for long-term global observations of the land surface, biosphere, atmosphere, and oceans. ...
.) * Navigational satellites are satellites that use radio time signals transmitted to enable mobile receivers on the ground to determine their exact location. The relatively clear line of sight between the satellites and receivers on the ground, combined with ever-improving electronics, allows satellite navigation systems to measure location to accuracies on the order of a few meters in real time. * Killer satellites are satellites that are designed to destroy enemy warheads, satellites, and other space assets. * Crewed
spacecraft 275px, The US Space Shuttle flew 135 times from 1981 to 2011, supporting Spacelab, ''Mir'', the maiden_launch,_which_had_a_white_external_tank,_shown).html" style="text-decoration: none;"class="mw-redirect" title="Hubble Space Telescope, and the ...
(spaceships) are large satellites able to put humans into (and beyond) an orbit, and return them to Earth. (The Lunar Module of the U.S. Apollo program was an exception, in that it did not have the capability of returning human occupants to Earth.) Spacecraft including spaceplanes of reusable launch system, reusable systems have major Spacecraft propulsion, propulsion or landing facilities. They can be used as transport to and from the orbital stations. * Miniaturized satellites are satellites of unusually low masses and small sizes. New classifications are used to categorize these satellites: minisatellite (500–1000 kg), Microsatellite (spaceflight), microsatellite (below 100 kg), nanosatellite (below 10 kg). * Reconnaissance satellites are
Earth observation satellite#REDIRECT Earth observation satellite#REDIRECT Earth observation satellite {{R from other capitalisation ...
{{R from other capitalisation ...
or
communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Com ...
deployed for military or espionage, intelligence applications. Very little is known about the full power of these satellites, as governments who operate them usually keep information pertaining to their reconnaissance satellites classified. * Recovery satellites are satellites that provide a recovery of reconnaissance, biological, space-production and other payloads from orbit to Earth. * Space-based solar power satellites are proposed satellites that would collect energy from sunlight and transmit it for use on Earth or other places. *
Space station A space station, also known as an orbital station or an orbital space station, is a spacecraft capable of supporting a human crew in orbit for an extended period of time, and is therefore a type of space habitat. It lacks major propulsion or land ...
s are artificial orbital structures that are designed for human, human beings to live on in outer space. A space station is distinguished from other crewed spacecraft by its lack of major propulsion or landing facilities. Space stations are designed for medium-term living in orbit, for periods of weeks, months, or even years. * Tether satellites are satellites that are connected to another satellite by a thin cable called a tether. * Weather satellites are primarily used to monitor Earth's weather and climate.


Orbits

The first satellite,
Sputnik 1 Sputnik 1 (; "Satellite-1", or "PS-1", Простейший Спутник-1 or ''Prosteyshiy Sputnik-1'', "Elementary Satellite 1") was the first artificial Earth satellite. The Soviet Union launched it into an elliptical low Earth orbit on 4 ...

Sputnik 1
, was put into orbit around Earth and was therefore in geocentric orbit. This is the most common type of orbit by far, with approximately 2,787 active artificial satellites orbiting the Earth. Geocentric orbits may be further classified by their altitude, inclination and Orbital eccentricity, eccentricity. The commonly used altitude classifications of geocentric orbit are
Low Earth orbit#REDIRECT Low Earth orbit#REDIRECT Low Earth orbit {{R from other capitalisation ...
{{R from other capitalisation ...
(LEO), Medium Earth orbit (MEO) and High Earth orbit (HEO). Low Earth orbit is any orbit below 2,000 km. Medium Earth orbit is any orbit between 2,000 and 35,786 km. High Earth orbit is any orbit higher than 35,786 km.


Centric classifications

*galactic centre, Galactocentric orbit: An orbit around the centre of a galaxy. The
Sun The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy mainly as visible light and infrared radiation. It is b ...

Sun
follows this type of orbit about the galactic centre of the Milky Way. * Geocentric orbit: An orbit around the planet Earth, such as the Moon or artificial satellites. Currently there are over 2,787 active artificial satellites orbiting the Earth. * Heliocentric orbit: An orbit around the Sun. In our Solar System, all planets, comets, and
asteroid An asteroid is a minor planet of the inner Solar System. Historically, these terms have been applied to any astronomical object orbiting the Sun that did not resolve into a disc in a telescope and was not observed to have characteristics of an ...
s are in such orbits, as are many artificial satellites and pieces of
space debris Space debris (also known as space junk, space pollution, space waste, space trash, or space garbage) is defunct human-made objects in space—principally in Earth orbit—which no longer serve a useful function. These include derelict spacecraft ...
. Natural satellite#Natural satellites of the Solar System, Moons by contrast are not in a heliocentric orbit but rather orbit their parent planet. * Areocentric orbit: An orbit around the planet
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, being larger than only Mercury. In English, Mars carries the name of the Roman god of war and is often referred to as the "Red Planet". The latter refe ...

Mars
, such as by Moons of Mars, moons or artificial satellites.


Altitude classifications

*
Low Earth orbit#REDIRECT Low Earth orbit#REDIRECT Low Earth orbit {{R from other capitalisation ...
{{R from other capitalisation ...
(LEO): Geocentric orbits ranging in altitude from 180 km – * Medium Earth orbit (MEO): Geocentric orbits ranging in altitude from – . Also known as an intermediate circular orbit. * Geosynchronous orbit (GEO): Geocentric circular orbit with an altitude of . The period of the orbit equals one sidereal day, coinciding with the rotation period of the Earth. The speed is approximately . * High Earth orbit (HEO): Geocentric orbits above the altitude of
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 ...

geosynchronous orbit
.


Inclination classifications

* Inclined orbit: An orbit whose inclination in reference to the equatorial plane is not zero degrees. ** Polar orbit: An orbit that passes above or nearly above both poles of the planet on each revolution. Therefore, it has an inclination of (or very close to) 90 degree (angle), degrees. ** Polar sun synchronous orbit: A nearly polar orbit that takes advantage of nodal precession such that a satellite in such an orbit passes the equator at the same local time on every pass. Useful for image taking satellites because shadows will be nearly the same on every pass, and for Solar observation#Satellites, solar observation satellites because they can have a continuous view of the Sun throughout the year.


Eccentricity classifications

* Circular orbit: An orbit that has an Orbital eccentricity, eccentricity of 0 and whose path traces a circle. ** Hohmann transfer orbit: An orbit that moves a spacecraft from one approximately circular orbit, usually the orbit of a planet, to another, using two engine Impulse (physics), impulses. The perihelion of the transfer orbit is at the same distance from the Sun as the radius of one planet's orbit, and the aphelion is at the other. The two rocket burns change the spacecraft's path from one circular orbit to the transfer orbit, and later to the other circular orbit. This maneuver was named after Walter Hohmann. * Elliptic orbit: An orbit with an eccentricity greater than 0 and less than 1 whose orbit traces the path of an ellipse. ** Geosynchronous transfer orbit: An elliptic orbit where the perigee is at the altitude of a
Low Earth orbit#REDIRECT Low Earth orbit#REDIRECT Low Earth orbit {{R from other capitalisation ...
{{R from other capitalisation ...
(LEO) and the apogee at the altitude of a geosynchronous orbit. Satellites use this orbit to transfer to 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 geosynchronous orbit above Earth' ...
. ** Geostationary transfer orbit: A geosynchronous transfer orbit that is used to transfer to a geostationary 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 an incl ...
: A highly eccentric orbit with inclination of 63.4° and orbital period of half of a sidereal day (roughly 12 hours). Such a satellite spends most of its time over two designated areas of the planet (usually Russia and the United States). ** Tundra orbit: A highly eccentric orbit with inclination of 63.4° and orbital period of one sidereal day (roughly 24 hours). Such a satellite spends most of its time over a single designated area of the planet.


Synchronous classifications

* Synchronous orbit: An orbit where the satellite has an orbital period equal to the average rotational period (earth's is: 23 hours, 56 minutes, 4.091 seconds) of the body being orbited and in the same direction of rotation as that body. To a ground observer such a satellite would trace an analemma (figure 8) in the sky. * Semi-synchronous orbit (SSO): An orbit with an altitude of approximately and an orbital period equal to one-half of the average rotational period (Earth's is approximately 12 hours) of the body being orbited * Geosynchronous orbit (GSO): Orbits with an altitude of approximately . Such a satellite would trace an analemma (figure 8) in the sky. **Geostationary orbit (GEO): A geosynchronous orbit with an inclination of zero. To an observer on the ground this satellite would appear as a fixed point in the sky. *** Clarke orbit: Another name for a geostationary orbit. Named after scientist and writer Arthur C. Clarke. ** Supersynchronous orbit: A disposal / storage orbit above GSO/GEO. Satellites will drift west. Also a synonym for Disposal orbit. ** Subsynchronous orbit: A drift orbit close to but below GSO/GEO. Satellites will drift east. ** Graveyard orbit: An orbit a few hundred kilometers above geosynchronous that satellites are moved into at the end of their operation. ***Disposal orbit: A synonym for graveyard orbit. *** Junk orbit: A synonym for graveyard orbit. * Areosynchronous orbit: A synchronous orbit around the planet
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, being larger than only Mercury. In English, Mars carries the name of the Roman god of war and is often referred to as the "Red Planet". The latter refe ...

Mars
with an orbital period equal in length to Mars' sidereal day, 24.6229 hours. * Areostationary orbit (ASO): A circular areosynchronous orbit on the equatorial plane and about 17000 km (10557 miles) above the surface. To an observer on the ground this satellite would appear as a fixed point in the sky. * Heliosynchronous orbit: A heliocentric orbit about the Sun where the satellite's orbital period matches the Sun's period of rotation. These orbits occur at a radius of 24,360 gigametre, Gm (0.1628 Astronomical unit, AU) around the Sun, a little less than half of the orbital radius of
Mercury Mercury usually refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol 'Hg' * Mercury (mythology), a Roman god Mercury may also refer to: Companies * Mercury (toy manufacture ...
.


Special classifications

* Sun-synchronous orbit: An orbit which combines altitude and inclination in such a way that the satellite passes over any given point of the planets' surface at the same local solar time. Such an orbit can place a satellite in constant sunlight and is useful for Satellite imagery, imaging, spy satellite, spy, and
weather satellite , a United States weather satellite of the meteorological-satellite service A weather satellite is a type of satellite that is primarily used to monitor the weather and climate of the Earth. Satellites can be polar orbiting (covering the entire ...

weather satellite
s. * Moon orbit: The Orbital parameters, orbital characteristics of Earth's Moon. Average altitude of , elliptical orbit, elliptical–inclined orbit.


Pseudo-orbit classifications

* Horseshoe orbit: An orbit that appears to a ground observer to be orbiting a certain planet but is actually in Co-orbital satellite, co-orbit with the planet. See asteroids 3753 Cruithne, 3753 (Cruithne) and 2002 AA29, 2002 AA29. * Suborbital spaceflight: A maneuver where a spacecraft approaches the height of orbit but lacks the velocity to sustain it. * Lunar transfer orbit (LTO) * Prograde orbit: An orbit with an inclination of less than 90°. Or rather, an orbit that is in the same direction as the rotation of the primary. * Retrograde orbit: An orbit with an inclination of more than 90°. Or rather, an orbit counter to the direction of rotation of the planet. Apart from those in sun-synchronous orbit, few satellites are launched into retrograde orbit because the quantity of fuel required to launch them is much greater than for a prograde orbit. This is because when the rocket starts out on the ground, it already has an eastward component of velocity equal to the rotational velocity of the planet at its launch latitude. * Halo orbit and Lissajous orbit: Orbits "around" Lagrangian points.


Subsystems

The satellite's functional versatility is embedded within its technical components and its operations characteristics. Looking at the "anatomy" of a typical satellite, one discovers two modules. Note that some novel architectural concepts such as Fractionated spacecraft somewhat upset this taxonomy.


Spacecraft bus or service module

The Spacecraft bus, bus module consists of the following subsystems:


Structure

The structural subsystem provides the mechanical base structure with adequate stiffness to withstand stress and vibrations experienced during launch, maintain structural integrity and stability while on station in orbit, and shields the satellite from extreme temperature changes and micro-meteorite damage.


Telemetry

The telemetry subsystem (aka Command and Data Handling, C&DH) monitors the on-board equipment operations, transmits equipment operation data to the earth control station, and receives the earth control station's commands to perform equipment operation adjustments.


Power

The power subsystem may consist of solar panels to convert solar energy into electrical power, regulation and distribution functions, and batteries that store power and supply the satellite when it passes into the Earth's shadow. Nuclear power sources (Radioisotope thermoelectric generator) have also been used in several successful satellite programs including the Nimbus program (1964–1978).


Thermal control

The thermal control subsystem helps protect electronic equipment from extreme temperatures due to intense sunlight or the lack of sun exposure on different sides of the satellite's body (e.g. optical solar reflector)


Attitude and orbit control

The attitude and orbit control subsystem consists of sensors to measure vehicle orientation, control laws embedded in the flight software, and actuators (reaction wheels, Spacecraft propulsion, thrusters). These apply the torques and forces needed to re-orient the vehicle to the desired attitude, keep the satellite in the correct orbital position, and keep antennas pointed in the right directions.


Communications

The second major module is the communication payload, which is made up of transponders. A transponder is capable of : * Receiving uplinked radio signals from earth satellite transmission stations (antennas). * Amplifying received radio signals * Sorting the input signals and directing the output signals through input/output signal multiplexers to the proper downlink antennas for retransmission to earth satellite receiving stations (antennas).


End of life

When satellites reach the end of their mission (this normally occurs within 3 or 4 years after launch), satellite operators have the option of de-orbiting the satellite, leaving the satellite in its current orbit or moving the satellite to a graveyard orbit. Historically, due to budgetary constraints at the beginning of satellite missions, satellites were rarely designed to be de-orbited. One example of this practice is the satellite Vanguard 1. Launched in 1958, Vanguard 1, the 4th artificial satellite to be put in Geocentric orbit, was still in orbit , as well as the upper stage of its launch rocket. Instead of being de-orbited, most satellites are either left in their current orbit or moved to a graveyard orbit. As of 2002, the FCC requires all geostationary satellites to commit to moving to a graveyard orbit at the end of their operational life prior to launch. In cases of uncontrolled de-orbiting, the major variable is the solar flux, and the minor variables the components and form factors of the satellite itself, and the gravitational perturbations generated by the Sun and the Moon (as well as those exercised by large mountain ranges, whether above or below sea level). The nominal breakup altitude due to aerodynamic forces and temperatures is 78 km, with a range between 72 and 84 km. Solar panels, however, are destroyed before any other component at altitudes between 90 and 95 km.


Launch-capable countries

This list includes countries with an independent capability to place satellites in orbit, including production of the necessary launch vehicle. Note: many more countries have the capability to design and build satellites but are unable to launch them, instead relying on foreign launch services. This list does not consider those numerous countries, but only lists those capable of launching satellites indigenously, and the date this capability was first demonstrated. The list does not include the European Space Agency, a multi-national state organization, nor private consortiums.


Attempted first launches

* The United States tried in 1957 to launch the first satellite using its own launcher before successfully completing a launch in 1958. * Japan tried four times in 1966–1969 to launch a satellite with its own launcher before successfully completing a launch in 1970. *
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population of around 1.4 billion. Covering approximately 9.6 million square kilometers (3.7 million m ...
tried in 1969 to launch the first satellite using its own launcher before successfully completing a launch in 1970. * India, after launching its first national satellite using a foreign launcher in 1975, tried in 1979 to launch the first satellite using its own launcher before succeeding in 1980. * Iraq have claimed an orbital launch of a warhead in 1989, but this claim was later disproved. * Brazil, after launching its first national satellite using a foreign launcher in 1985, tried to launch a satellite using its own VLS 1 launcher three times in 1997, 1999, and 2003, but all attempts were unsuccessful. * North Korea claimed a launch of Kwangmyŏngsŏng-1 and Kwangmyŏngsŏng-2 satellites in 1998 and 2009, but U.S., Russian and other officials and weapons experts later reported that the rockets failed to send a satellite into orbit, if that was the goal. The United States, Japan and South Korea believe this was actually a ballistic missile test, which was a claim also made after North Korea's 1998 satellite launch, and later rejected. The first (April 2012) launch of Kwangmyŏngsŏng-3 was unsuccessful, a fact publicly recognized by the DPRK. However, the December 2012 launch of the "second version" of Kwangmyŏngsŏng-3 was successful, putting the DPRK's first confirmed satellite into orbit. * South Korea (Korea Aerospace Research Institute), after launching their first national satellite by foreign launcher in 1992, unsuccessfully tried to launch its own launcher, the Korea Space Launch Vehicle, KSLV (Naro)-1, (created with the assistance of Russia) in 2009 and 2010 until success was achieved in 2013 by Naro-3. * The First European multi-national state organization European Launcher Development Organisation, ELDO tried to make the orbital launches at Europa (rocket), Europa I and Europa II rockets in 1968–1970 and 1971 but stopped operation after failures.


Other notes

*
Russia Russia (russian: link=no, Россия, , ), or the Russian Federation, is a country spanning Eastern Europe and Northern Asia. It is the largest country in the world, covering and encompassing more than one-eighth of the Earth's inhabited l ...
and Ukraine were parts of the Soviet Union and thus inherited their launch capability without the need to develop it indigenously. Through the Soviet Union they are also on the number one position in this list of accomplishments. * France, the United Kingdom, and Ukraine launched their first satellites by own launchers from foreign spaceports. * Some countries such as South Africa, Spain, Italy, Germany, Canada, Australia, Argentina, Egypt and private companies such as OTRAG, have developed their own launchers, but have not had a successful launch. * Only twelve, countries from the list below (USSR, USA, France, Japan, China, UK, India, Russia, Ukraine, Israel, Iran and North Korea) and one regional organization (the European Space Agency, ESA) have independently launched satellites on their own indigenously developed launch vehicles. * Several other countries, including Brazil, Argentina, Pakistan, Romania, Taiwan, Indonesia, Australia, Malaysia, Turkey and Switzerland are at various stages of development of their own small-scale launcher capabilities.


Launch capable private entities

Orbital Sciences Corporation launched a satellite into orbit on the Pegasus (rocket), Pegasus in 1990. SpaceX launched a satellite into orbit on the Falcon 1 in 2008. Rocket Lab launched three cubesats into orbit on the Electron (rocket), Electron in 2018.


First satellites of countries

While Canada was the third country to build a satellite which was launched into space, it was launched aboard an United States, American rocket from an American spaceport. The same goes for Australia, who launched first satellite involved a donated U.S. PGM-11 Redstone, Redstone rocket and American support staff as well as a joint launch facility with the United Kingdom of Great Britain and Northern Ireland, United Kingdom. The first Italian satellite San Marco 1 launched on 15 December 1964 on a U.S. Scout rocket from Wallops Island (Virginia, United States) with an Italian launch team trained by NASA. By similar occasions, almost all further first national satellites was launched by foreign rockets.


Attempted first satellites

* United States tried unsuccessfully to launch its first satellite in 1957; they were successful in 1958. *
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population of around 1.4 billion. Covering approximately 9.6 million square kilometers (3.7 million m ...
tried unsuccessfully to launch its first satellite in 1969; they were successful in 1970. * Chile tried unsuccessfully in 1995 to launch its first satellite FASat-Alfa by foreign rocket; in 1998 they were successful.† * North Korea has tried in 1998, 2009, 2012 to launch satellites, first successful launch on 12 December 2012. * Libya since 1996 developed its own national Libsat satellite project with the goal of providing telecommunication and remote sensing services that was postponed after the fall of Gaddafi. * Belarus tried unsuccessfully in 2006 to launch its first satellite BelKA by foreign rocket.† †-note: Both Chile and Belarus used Russian companies as principal contractors to build their satellites, they used Russian-Ukrainian manufactured rockets and launched either from Russia or Kazakhstan.


Planned first satellites

* Armenia founded ArmCosmos in 2012 and announced an intention to create and launch the countries first telecommunication satellite, named ArmSat. The investment estimate is $250 million and potential contractors for building the satellite includes Russia, China and Canada. * Cambodia's Royal Group plans to purchase for $250–350 million and launch in the beginning of 2013 the telecommunication satellite. * Cayman Islands's Global IP Cayman private company plans to launch GiSAT-1 geostationary communications satellite in 2018. * Democratic Republic of Congo ordered at November 2012 in China (China Academy of Space Technology, Academy of Space Technology (CAST) and Great Wall Industry Corporation, Great Wall Industry Corporation (CGWIC)) the first telecommunication satellite CongoSat-1 which will be built on DFH-4
satellite bus A satellite bus or spacecraft bus is a general model on which multiple-production satellite spacecraft are often based. The bus is the infrastructure of the spacecraft, usually providing locations for the payload (typically space experiments or ins ...
platform and will be launched in China till the end of 2015. * Croatia has a goal to construct a satellite by 2013–2014. Launch into Earth orbit would be done by a foreign provider. * Ireland's team of Dublin Institute of Technology intends to launch the first Irish satellite within European University program CubeSat QB50. * Republic of Moldova's first remote sensing satellite plans to start in 2013 by Space centre at national Technical University. * Myanmar plans to purchase for $200 million their own telecommunication satellite. * Nicaragua ordered for $254 million at November 2013 in China the first telecommunication satellite Nicasat-1 (to be built at DFH-4 satellite bus platform by CAST and CGWIC), that planning to launch in China at 2016. * Paraguay under new Agencia Espacial del Paraguay –- AEP airspace agency plans first Eart observation satellite. * Serbia's first satellite Tesla-1 was designed, developed and assembled by nongovernmental organisations in 2009 but still remains unlaunched. * Sri Lanka has a goal to construct two satellites beside of rent the national SupremeSAT payload in Chinese satellites. Sri Lankan Telecommunications Regulatory Commission has signed an agreement with Surrey Satellite Technology Ltd to get relevant help and resources. Launch into Earth orbit would be done by a foreign provider. * Syrian Space Research Center developing CubeSat-like small first national satellite since 2008. * Tunisia is developing its first satellite, ERPSat01. Consisting of a CubeSat of 1 kg mass, it will be developed by the University of Sfax, Sfax School of Engineering. ERPSat satellite is planned to be launched into orbit in 2013. * Uzbekistan's State Space Research Agency (UzbekCosmos) announced in 2001 about intention of launch in 2002 first remote sensing satellite. Later in 2004 was stated that two satellites (remote sensing and telecommunication) will be built by Russia for $60–70 million each * Bangladesh Bangladesh launched Bangabandhu-1 at 12 May 2018. SpaceX helped with the launching.


Attacks on satellites

Since the mid-2000s, satellites have been hacked by militant organizations to broadcast propaganda and to pilfer classified information from military communication networks. For testing purposes, satellites in low earth orbit have been destroyed by ballistic missiles launched from earth.
Russia Russia (russian: link=no, Россия, , ), or the Russian Federation, is a country spanning Eastern Europe and Northern Asia. It is the largest country in the world, covering and encompassing more than one-eighth of the Earth's inhabited l ...
, United States,
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population of around 1.4 billion. Covering approximately 9.6 million square kilometers (3.7 million m ...
and India have demonstrated the ability to eliminate satellites. In 2007 the China, Chinese military shot down an aging weather satellite, followed by the US Navy shooting down a NRO L-21, defunct spy satellite in February 2008. On 27 March 2019 India shot down a live test satellite at 300 km altitude in 3 minutes. India became the fourth country to have the capability to destroy live satellites.


Jamming

Due to the low received signal strength of satellite transmissions, they are prone to Radio jamming, jamming by land-based transmitters. Such jamming is limited to the geographical area within the transmitter's range. GPS satellites are potential targets for jamming, but satellite phone and television signals have also been subjected to jamming. Also, it is very easy to transmit a carrier radio signal to a geostationary satellite and thus interfere with the legitimate uses of the satellite's transponder. It is common for Earth stations to transmit at the wrong time or on the wrong frequency in commercial satellite space, and dual-illuminate the transponder, rendering the frequency unusable. Satellite operators now have sophisticated monitoring that enables them to pinpoint the source of any carrier and manage the transponder space effectively.


Earth observation

During the last five decades, space agencies have sent thousands of space crafts, space capsules, or satellites to the universe. In fact, weather forecasters make predictions on the weather and natural calamities based on observations from these satellites. The National Aeronautics and Space Administration (NASA) requested the National Academies to publish a report entitled, Earth Observations from Space; The First 50 Years of Scientific Achievements in 2008. It described how the capability to view the whole globe simultaneously from satellite observations revolutionized studies about the planet Earth. This development brought about a new age of combined Earth sciences. The National Academies report concluded that continuing Earth observations from the galaxy are necessary to resolve scientific and social challenges in the future.


NASA

The NASA introduced an Earth Observing System (EOS) composed of several satellites, science component, and data system described as the Earth Observing System Data and Information System (EOSDIS). It disseminates numerous science data products as well as services designed for interdisciplinary education. EOSDIS data can be accessed online and accessed through File Transfer Protocol (FTP) and Hyper Text Transfer Protocol Secure (HTTPS). Scientists and researchers perform EOSDIS science operations within a distributed platform of multiple interconnected nodes or Science Investigator-led Processing Systems (SIPS) and discipline-specific Distributed Active Archive Centers (DACCs).


ESA

The European Space Agency have been operating Earth Observation satellites since the launch of Meteosat 1 in November 1977. ESA currently has plans to launch a satellite equipped with an artificial intelligence (AI) processor that will allow the spacecraft to make decisions on images to capture and data to transmit to the Earth. BrainSat will use the Intel Myriad X vision processing unit (VPU). The launching will be scheduled in 2019. ESA director for Earth Observation Programs Josef Aschbacher made the announcement during the PhiWeek in November 2018. This is the five-day meet that focused on the future of Earth observation. The conference was held at the ESA Center for Earth Observation in Frascati, Italy. ESA also launched the PhiLab, referring to the future-focused team that works to harness the potentials of AI and other disruptive innovations. Meanwhile, the ESA also announced that it expects to commence the qualification flight of the Space Rider space plane in 2021. This will come after several demonstration missions. Space Rider is the sequel of the Agency's Intermediate Experimental vehicle (IXV) which was launched in 2015. It has the capacity payload of 800 kilograms for orbital missions that will last a maximum of two months.


Pollution and regulation

Generally liability has been covered by the Liability Convention. Issues like
space debris Space debris (also known as space junk, space pollution, space waste, space trash, or space garbage) is defunct human-made objects in space—principally in Earth orbit—which no longer serve a useful function. These include derelict spacecraft ...
, radio and light pollution are increasing in magnitude and at the same time lack progress in national or international regulation. With future increase in numbers of
satellite constellation A satellite constellation is a group of artificial satellites working together as a system. Unlike a single satellite, a constellation can provide permanent global or near-global coverage, such that at any time everywhere on Earth at least one sat ...
s, like SpaceX Starlink, it is feared especially by the astronomical community, such as the International Astronomical Union, IAU, that orbital pollution will increase significantly. A report from the SATCON1 workshop in 2020 concluded that the effects of large satellite constellations can severely affect some astronomical research efforts and lists six ways to mitigate harm to astronomy. Some notable satellite failures that polluted and dispersed radioactive materials are Kosmos 954, Kosmos 1402 and the List of nuclear power systems in space, Transit 5-BN-3. Using wood as an alternative material has been posited in order to reduce pollution and debris from satellites that reenter the atmosphere.


Open source satellites

Several open source satellites both in terms of open source hardware and open source software were flown or are in development. The satellites have usually form of a CubeSat or PocketQube. In 2013 an amateur radio satellite OSSI-1 was launched and remained in orbit for about 2 months. In 2017 UPSat created by the Greek University of Patras and Libre Space Foundation remained in orbit for 18 months. In 2019 FossaSat-1 was launched. As of February 2021 the Portland State Aerospace Society is developing two open source satellites called OreSat and the Libre Space Foundation also has ongoing satellite projects.


Satellite services

* Satellite crop monitoring * Satellite Internet access * Satellite navigation * Satellite phone * Satellite radio * Satellite television


See also

* 2009 satellite collision * Artificial moon * Artificial satellites in retrograde orbit * Atmospheric satellite *Crowdfunded satellites * Cubesat * Fractionated spacecraft * Ground track * Imagery intelligence * International Designator * List of communications satellite firsts * List of Earth observation satellites * List of passive satellites * Rocket engine test facility * Satellite Catalog Number * Satellite formation flying * Satellite geolocation * Satellite watching * Space exploration * * *
Space station A space station, also known as an orbital station or an orbital space station, is a spacecraft capable of supporting a human crew in orbit for an extended period of time, and is therefore a type of space habitat. It lacks major propulsion or land ...
* Space probe * Spaceport (including list of spaceports) * U.S. space exploration history on U.S. stamps, Satellites on stamps * USA-193 (2008 American anti-satellite missile test)


References


Further reading

* Ann Finkbeiner, "Orbital Aggression: How do we prevent war in space?", ''Scientific American'', vol. 323, no. 5 (November 2020), pp. 50–57.


External links

*
''Eyes in the Sky'' Free video by the Vega Science Trust and the BBC/OU
Satellites and their implications over the last 50 years. {{Authority control Satellites, Articles containing video clips Spacecraft Russian inventions