An animation depicting the orbits of GPS satellites in medium Earth orbit.

A full-size model of the Earth observation satellite ERS 2

In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon.

The world's first artificial satellite, the Sputnik 1, was launched by the Soviet Union in 1957. Since then, thousands of satellites have been launched into orbit around the Earth; also some satellites, notably space stations, have been launched in parts and assembled in orbit. Artificial satellites originate from more than 50 countries and have used the satellite launching capabilities of ten nations. A few hundred satellites are currently operational, whereas thousands of unused satellites and satellite fragments orbit the Earth as space debris. A few space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Mercury, Venus, Mars, Jupiter, Saturn, and the Sun.

Satellites are used for a large number of purposes. Common types include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites. 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, and geostationary orbit.

Satellites are usually semi-independent computer-controlled systems. Satellite subsystems attend many tasks, such as power generation, thermal control, telemetry, attitude control and orbit control.

History[link]

Early conceptions[link]

"Newton's cannonball", presented as a "thought experiment" in A Treatise of the System of the World, was the first published mathematical study of the possibility of an artificial satellite.

The first fictional depiction of a satellite being launched into orbit is a short story by Edward Everett Hale, The Brick Moon. The story is serialized in The Atlantic Monthly, starting in 1869.^[1][2] The idea surfaces again in Jules Verne's The Begum's Fortune (1879).

In 1903, Konstantin Tsiolkovsky (1857–1935) published Means of Reaction Devices (in Russian: Исследование мировых пространств реактивными приборами), which is the first academic treatise on the use of rocketry to launch spacecraft. He calculated the orbital speed required for a minimal orbit around the Earth at 8 km/s, and that a multi-stage rocket fueled by liquid propellants could be used to achieve this. He proposed the use of liquid hydrogen and liquid oxygen, though other combinations can be used.

In 1928 Slovenian Herman Potočnik (1892–1929) published his sole book, The Problem of Space Travel — The Rocket Motor (German: Das Problem der Befahrung des Weltraums — der Raketen-Motor), a plan for a breakthrough into space and a permanent human presence there. He conceived of a space station in detail and calculated its geostationary orbit. He described the use of orbiting spacecraft for detailed peaceful and military observation of the ground and described how the special conditions of space could be useful for scientific experiments. The book described geostationary satellites (first put forward by Tsiolkovsky) and discussed communication between them and the ground using radio, but fell short of the idea of using satellites for mass broadcasting and as telecommunications relays.

In a 1945 Wireless World article the English science fiction writer Arthur C. Clarke (1917–2008) described in detail the possible use of communications satellites for mass communications.^[3] Clarke examined the logistics of satellite launch, possible orbits and other aspects of the creation of a network of world-circling satellites, pointing to the benefits of high-speed global communications. He also suggested that three geostationary satellites would provide coverage over the entire planet.

The US military studied the idea of what was referred to as the earth satellite vehicle when Secretary of Defense, James Forrestal, made a public announcement on December 29, 1948 that his office was coordinating that project between the various services.^[4]

History of artificial satellites[link]

Sputnik 1: The first artificial satellite to orbit Earth.

The first artificial satellite was Sputnik 1, launched by the Soviet Union on October 4, 1957, and initiating the Soviet Sputnik program, with Sergei Korolev as chief designer (there is a crater on the lunar far side which bears his name). This in turn triggered the Space Race between the Soviet Union and the United States.

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 unanticipated announcement of Sputnik 1's success precipitated the Sputnik crisis in the United States and ignited the so-called Space Race within the Cold War.

Sputnik 2 was launched on November 3, 1957 and carried the first living passenger into orbit, a dog named Laika.^[5]

In May, 1946, Project RAND had released the Preliminary Design of an Experimental World-Circling Spaceship, which stated, "A satellite vehicle with appropriate instrumentation can be expected to be one of the most potent scientific tools of the Twentieth Century.^[6] The United States had been considering launching orbital satellites since 1945 under the Bureau of Aeronautics of the United States Navy. The United States Air Force's Project RAND eventually released the above report, but did not believe that the satellite was a potential military weapon; rather, they considered it to be a tool for science, politics, and propaganda. In 1954, the Secretary of Defense stated, "I know of no American satellite program."^[7]

On July 29, 1955, the White House announced that the U.S. intended to launch satellites by the spring of 1958. This became known as Project Vanguard. On July 31, the Soviets announced that they intended to launch a satellite by the fall of 1957.

Following pressure by the American Rocket Society, the National Science Foundation, and the International Geophysical Year, military interest picked up and in early 1955 the Army and Navy were working on Project Orbiter, two competing programs, the army's which involved using a Jupiter C rocket, and the civilian/Navy Vanguard Rocket, to launch a satellite. At first, they failed: initial preference was given to the Vanguard program whose launch vehicle had a strange and uncanny way of exploding on national television. But finally, three months after Sputnik 2, the project succeeded; Explorer 1 thus became the United States' first artificial satellite on January 31, 1958.^[8]

In June 1961, three-and-a-half years after the launch of Sputnik 1, the Air Force used resources of the United States Space Surveillance Network to catalog 115 Earth-orbiting satellites.^[9]

The largest artificial satellite currently orbiting the Earth is the International Space Station.

Space Surveillance Network[link]

The United States Space Surveillance Network (SSN), a division of The United States Strategic Command, has been tracking objects in Earth's orbit since 1957 when the Soviets opened the space age with the launch of Sputnik I. Since then, the SSN has tracked more than 26,000 objects. The SSN currently tracks more than 8,000 man-made 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.^[10] 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.

A search of the NSSDC Master Catalog at the end of October 2010 listed 6,578 satellites launched into orbit since 1957, the latest being Chang'e 2, on 1 October 2010.^[11]

Non-military satellite services[link]

There are three basic categories of non-military satellite services:^[12]

Fixed satellite services[link]

Fixed satellite services 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[link]

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)[link]

Scientific research satellites provide us with 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[link]

MILSTAR: A communication satellite

• Anti-Satellite weapons/"Killer Satellites" are satellites that are designed to destroy enemy warheads, satellites, other space assets.
• Astronomical satellites are satellites used for observation of distant planets, galaxies, and other outer space objects.
• Biosatellites are satellites designed to carry living organisms, generally for scientific experimentation.
• Communications satellites are satellites stationed in space for the purpose of telecommunications. Modern communications satellites typically use geosynchronous orbits, Molniya orbits or Low Earth orbits.
• Miniaturized satellites are satellites of unusually low weights and small sizes.^[13] New classifications are used to categorize these satellites: minisatellite (500–100 kg), microsatellite (below 100 kg), nanosatellite (below 10 kg).
• Navigational satellites are satellites which 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.
• Reconnaissance satellites are Earth observation satellite or communications satellite deployed for military or 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.
• Earth observation satellites are satellites intended for non-military uses such as environmental monitoring, meteorology, map making etc. (See especially Earth Observing System.)
• Tether satellites are satellites which are connected to another satellite by a thin cable called a tether.
• Weather satellites are primarily used to monitor Earth's weather and climate.^[14]
• Recovery satellites are satellites that provides a recovery of reconnaissance, biological, space-production and other payloads from orbit to Earth.
• Manned spacecraft (spaceships) are large satellites able for put human into (and beyond) an orbit, being on it and recovery back to Earth. Spacecrafts, and orbital parts-spaceplanes of reusable systems also, has a major propulsion or landing facilities, and often uses as transport to and from the orbital stations.
• Space stations are man-made orbital structures that are designed for human beings to live on in outer space. A space station is distinguished from other manned 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.

Orbit types[link]

Various earth orbits to scale; cyan represents low earth orbit, yellow represents medium earth orbit, the black dashed line represents geosynchronous orbit, the green dash-dot line the orbit of Global Positioning System (GPS) satellites, and the red dotted line the orbit of the International Space Station (ISS).

The first satellite, Sputnik 1, was put into orbit around Earth and was therefore in geocentric orbit. By far this is the most common type of orbit with approximately 2456 artificial satellites orbiting the Earth. Geocentric orbits may be further classified by their altitude, inclination and eccentricity.

The commonly used altitude classifications are Low Earth orbit (LEO), Medium Earth orbit (MEO) and High Earth orbit (HEO). Low Earth orbit is any orbit below 2000 km, and Medium Earth orbit is any orbit higher than that but still below the altitude for geosynchronous orbit at 35786 km. High Earth orbit is any orbit higher than the altitude for geosynchronous orbit.

Centric classifications[link]

• Geocentric orbit: An orbit around the planet Earth, such as the Moon or artificial satellites. Currently there are approximately 2465 artificial satellites orbiting the Earth.
• Heliocentric orbit: An orbit around the Sun. In our Solar System, all planets, comets, and asteroids are in such orbits, as are many artificial satellites and pieces of space debris. Moons by contrast are not in a heliocentric orbit but rather orbit their parent planet.
• Areocentric orbit: An orbit around the planet Mars, such as by moons or artificial satellites.

The general structure of a satellite is that it is connected to the earth stations that are present on the ground and connected through terrestrial links.

Altitude classifications[link]

• Low Earth orbit (LEO): Geocentric orbits ranging in altitude from 0–2000 km (0–1240 miles)
• Medium Earth orbit (MEO): Geocentric orbits ranging in altitude from 2,000 km (1,200 mi) to just below geosynchronous orbit at 35,786 km (22,236 mi). Also known as an intermediate circular orbit.
• High Earth orbit (HEO): Geocentric orbits above the altitude of geosynchronous orbit 35,786 km (22,236 mi).

Orbital Altitudes of several significant satellites of earth.

Inclination classifications[link]

• 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 degrees.
  • Polar sun synchronous orbit: A nearly polar orbit that 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.

Eccentricity classifications[link]

• Circular orbit: An orbit that has an eccentricity of 0 and whose path traces a circle.
  • Hohmann transfer orbit: An orbital maneuver that moves a spacecraft from one circular orbit to another using two engine impulses. 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 (LEO) and the apogee at the altitude of a geosynchronous orbit.
  • Geostationary transfer orbit: An elliptic orbit where the perigee is at the altitude of a Low Earth orbit (LEO) and the apogee at the altitude of a geostationary orbit.
  • Molniya orbit: A highly elliptic 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 (specifically Russia and the United States).
  • Tundra orbit: A highly elliptic 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[link]

• 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 20,200 km (12,600 mi) 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 35,786 km (22,236 mi). 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.^[15]
    • 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 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 Gm (0.1628 AU) around the Sun, a little less than half of the orbital radius of Mercury.

Special classifications[link]

• 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's surface at the same local solar time. Such an orbit can place a satellite in constant sunlight and is useful for imaging, spy, and weather satellites.
• Moon orbit: The orbital characteristics of Earth's Moon. Average altitude of 384,403 kilometres (238,857 mi), elliptical–inclined orbit.

Pseudo-orbit classifications[link]

• Horseshoe orbit: An orbit that appears to a ground observer to be orbiting a certain planet but is actually in co-orbit with the planet. See asteroids 3753 (Cruithne) and 2002 AA₂₉.
• Exo-orbit: A maneuver where a spacecraft approaches the height of orbit but lacks the velocity to sustain it.
  • Suborbital spaceflight: A synonym for exo-orbit.
• 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.

Satellite subsystems[link]

The satellite's functional versatility is imbedded within its technical components and its operations characteristics. Looking at the "anatomy" of a typical satellite, one discovers two modules.^[12] Note that some novel architectural concepts such as Fractionated Spacecraft somewhat upset this taxonomy.

Spacecraft bus or service module[link]

This bus module consist of the following subsystems:

• The Structural Subsystems

The structural subsystem provides the mechanical base structure, shields the satellite from extreme temperature changes and micro-meteorite damage, and controls the satellite's spin functions.

• The Telemetry Subsystems (aka Command and Data Handling, C&DH)

The telemetry subsystem 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.

• The Power Subsystems

The power subsystem consists of solar panels and backup batteries that generate power when the satellite passes into the Earth's shadow. Nuclear power sources (Radioisotope thermoelectric generators) have been used in several successful satellite programs including the Nimbus program (1964–1978).^[16]

• The Thermal Control Subsystems

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)

• The Attitude and Orbit Control Subsystems

The attitude and orbit control subsystem consists of small rocket thrusters that keep the satellite in the correct orbital position and keep antennas positioning in the right directions.

Communication payload[link]

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[link]

When satellites reach the end of their mission, 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 manmade satellite put in Geocentric orbit, was still in orbit as of August 2009.^[17]

Instead of being de-orbited, most satellites are either left in their current orbit or moved to a graveyard orbit.^[18] As of 2002, the FCC now requires all geostationary satellites to commit to moving to a graveyard orbit at the end of their operational life prior to launch.^[19]

Launch-capable countries[link]

Launch of the first British Skynet military satellite.

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. Does not include consortium satellites or multi-national satellites.

'First launch by country

Order	Country	Year of first launch	Rocket	Satellite
1	Soviet Union	1957	Sputnik-PS	Sputnik 1
2	United States	1958	Juno I	Explorer 1
3	France	1965	Diamant	Astérix
4	Japan	1970	Lambda-4S	Ōsumi
5	China	1970	Long March 1	Dong Fang Hong I
6	United Kingdom	1971	Black Arrow	Prospero X-3
7	India	1980	SLV	Rohini
8	Israel	1988	Shavit	Ofeq 1
_	Russia[1]	1992	Soyuz-U	Kosmos 2175
_	Ukraine[1]	1992	Tsyklon-3	Strela
11	Iran	2009	Safir-2	Omid

Attempted first launches[link]

This section requires expansion.

• United States tried in 1957 to launch the first satellite by own launcher before successfully completing a launch in 1958.
• China tried in 1969 to launch the first satellite by own launcher before successfully completing a launch in 1970.
• India, after launching the first national satellite by foreign launcher in 1975, tried in 1979 to launch the first satellite by own launcher before succeeding in 1980.
• Iraq have claimed orbital launch of warhead in 1989, but this claim is unconfirmed.
• Brazil, after launch of first national satellite by foreign launcher in 1985, tried to launched the satellites by own VLS 1 launcher three times in 1997, 1999, 2003 but all 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 satellites into orbit, if that was the goal. The United States, Japan and South Korea believe this was actually a ballistic missile test, which is a claim also made after North Korea's 1998 satellite launch, and later rejected. The launch of Kwangmyŏngsŏng-3 was unsuccessful, a fact publicly recognized by the DPRK.
• South Korea (Korea Aerospace Research Institute), after launching their first national satellite by foreign launcher in 1992, tried to launch a first KSLV own launcher (created with assistance of Russia) in 2009 and 2011, but all were unsuccessful.

Other notes[link]

• Russia and Ukraine were parts of the Soviet Union and thus inherited their launch capability without the need to develop it indigenously. Through Soviet Union they also are on the number one position in this list of accomplishments.
• France, United Kingdom, 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 eight countries from the list above (Russia and Ukraine instead of USSR, also USA, Japan, China, India, Israel and Iran) and one regional organization (the European Space Agency, ESA) have independently launched satellites on their own indigenously developed launch vehicles. (The launch capabilities of the United Kingdom and France now fall under the ESA.)
• Several other countries, including South Korea, Brazil, Pakistan, Romania, Kazakhstan, Taiwan, Indonesia, Australia, New Zealand, Malaysia^{[citation needed]} and Turkey, are at various stages of development of their own small-scale launcher capabilities.

Launch capable private entities[link]

• Orbital Sciences Corporation is conducting launches using its Taurus I rocket.
• On September 28, 2008, the private aerospace firm SpaceX successfully launched its Falcon 1 rocket in to orbit. This marked the first time that a privately built liquid-fueled booster was able to reach orbit.^[20] The rocket carried a prism shaped 1.5 m (5 ft) long payload mass simulator that was set into orbit. The dummy satellite, known as Ratsat, will remain in orbit for between five and ten years before burning up in the atmosphere.^[20]

A few other private companies are capable of sub-orbital launches.

First satellites of countries[link]

First satellites of countries including launched indigenously or by help of other^[21]

Country	Year of first launch	First satellite	Payloads in orbit in 2010-2011[22]
Soviet Union ( Russia)	1957 (1992)	Sputnik 1 (Cosmos 2175)	1437
United States	1958	Explorer 1	1099
United Kingdom	1962	Ariel 1	0029
Canada	1962	Alouette 1	0032
Italy	1964	San Marco 1	0017
France	1965	Astérix	0049
Australia	1967	WRESAT	0011
Germany	1969	Azur	0042
Japan	1970	Ōsumi	0127
China	1970	Dong Fang Hong I	0120
Poland	1973	Intercosmos Copernicus 500	00001
Netherlands	1974	ANS	0005
Spain	1974	Intasat	0009
India	1975	Aryabhata	0045
Indonesia	1976	Palapa A1	0010
Czechoslovakia	1978	Magion 1	0005
Bulgaria	1981	Intercosmos Bulgaria 1300	0001
Brazil	1985	Brasilsat A1	0011
Mexico	1985	Morelos 1	0007
Sweden	1986	Viking	0011
Israel	1988	Ofeq 1	00010
Luxembourg	1988	Astra 1A	0015
Argentina	1990	Lusat	0010
Pakistan	1990	Badr-1	0005
South Korea	1992	Kitsat A	0012
Portugal	1993	PoSAT-1	0001
Thailand	1993	Thaicom 1	0006
Turkey	1994	Turksat 1B	0005
Ukraine	1995	Sich-1	0006
Malaysia	1996	MEASAT	0004
Norway	1997	Thor 2	0003
Philippines	1997	Mabuhay 1	0002
Egypt	1998	Nilesat 101	0003
Chile	1998	FASat-Bravo	0002
Singapore	1998	ST-1	0003
Taiwan	1999	ROCSAT-1	0009
Denmark	1999	Ørsted	0004
South Africa	1999	SUNSAT	0002
Saudi Arabia	2000	Saudisat 1A	0012
United Arab Emirates	2000	Thuraya 1	0003
Morocco	2001	Maroc-Tubsat	0001
Algeria	2002	Alsat 1	0001
Greece	2003	Hellas Sat 2	0002
Cyprus	2003	Hellas Sat 2	0002
Nigeria	2003	Nigeriasat 1	0004
Iran	2005	Sina-1	0004
Kazakhstan	2006	KazSat 1	0002
Colombia	2007	Libertad 1	0001
Mauritius	2007	Rascom-QAF 1	0002
Vietnam	2008	Vinasat-1	0002
Venezuela	2008	Venesat-1	0001
Switzerland	2009	SwissCube-1[23]	0001
Hungary	2012	MaSat-1 [24]	0005[citation needed]
Poland	2012	PW-Sat [25]	0001
Romania	2012	Goliat [26]	0001

While Canada was the third country to build a satellite which was launched into space,^[27] it was launched aboard a U.S. rocket from a U.S. spaceport. The same goes for Australia, who launched on-board a donated Redstone rocket. The first Italian-launched was San Marco 1, launched on 15 December 1964 on a U.S. Scout rocket from Wallops Island (VA,USA) with an Italian Launch Team trained by NASA.^[28] Australia's launch project (WRESAT) involved a donated U.S. missile and U. S. support staff as well as a joint launch facility with the United Kingdom.^[29] The first satellite built by Singapore, X-SAT, was launched aboard a PSLV rocket on April 20, 2011.^[30]

Attempted first satellite[link]

This section requires expansion.

•  USA tried in 1957 to launch the first satellite by own launcher before this was successfully happened later in 1958
•  China tried in 1969 to launch the first satellite by own launcher before this was successfully happened later in 1970
•  Chile tried in 1995 to launch the first satellite FASat-Alfa by foreign launcher before this was successfully happened later in 1998
•  North Korea tried in 1998, 2009, 2012 to launch the first satellites by own launcher (see above)
•  Belarus tried in 2006 to launch the first satellite BelKA by foreign launcher

Planned first satellites[link]

This section requires expansion.

•  Afghanistan announced in April 2012 that it is planning to launch its first communications satellite to the orbital slot it has been award. The satellite is expected to be launched by a commercial company.^[31]
•  Austria The micro-satellite BRITE-AUSTRIA (TUG-SAT-1) plans to start in early 2012.^[32]
•  Azerbaijan is developing its space satellite Azerspace. According to the approved plan, the Azerspace satellite will be launched into orbit in 2012.^[33]
•  Bangladesh announced in 2009 that it intends to launch its first satellite into space by 2011.^[34]
•  Belgium Its nano-satellite OUFTI-1 within European University program CubeSat for test radio protocol in space are under construction in University of Liege.^[35]
•  Bolivia New Bolivian Space Agency plans a first satellite to 2012 by Chinese help ^[36]
•  Cambodia Royal Group plans to purchase for 250-350 billion $ and launch in the beginning of 2013 the telecommunication satellite [4]
•  Croatia has a goal to construct a satellite by 2013–2014. Launch into Earth orbit would be done by a foreign provider.^[37]
•  Ecuador presented its first satellite in April 4, 2011, the NEE-01 Pegasus designed and built by the Ecuadorian Space Agency. The pico-satellite will be launched into orbit by 2012, and will have an expected 1-year lifespan. it has 16 missions and 3 payloads, it is the first known CubeSat to be able to send real-time video from orbit, both visible and infrared. It also carries a thermal and radiation shield.
•  Estonia The nano-satellite ESTCube-1 plans by University of Tartu within student CubeSat projects [5]
•  Finland Aalto-1 with solar panels is a funded by EU student nano-satellite project of Aalto University, Finland and Finnish Meteorological Institute [6]. When launched (plan to 2013), it would be the first Finnish satellite.
•  Laos First satellite will be telecommunication and will be built and launched in 2013 for $250 million by China Asia-Pacific Mobile Communications Company (China-APMT) [7] [8]
•  Latvia The 5 kg nano-satellite Venta-1 is built in Latvia in cooperation with the German engineers. The data received from satellite will be received and processed in Irbene radioastronomical centre (Latvia); satellite will have software defined radio capabilities. "Venta-1" will serve mainly as a means for education in Ventspils University College with additional functions, including an automatic system of identification of the ships of a sailing charter developed by OHB-System AG. The launch of the satellite was planned for the end of 2009 using the Indian carrier rocket. Due to the financial crisis the launch has been postponed until late 2011.^[38] Started preparations to produce the next satellite "Venta-2".
•  Lithuania New national Space Science and Technology Institute ^[39] plans nano-satellite with space capsules by Russian help ^[40]
•  Moldova The remote sensing satellite plans to start in 2013 by Space centre at national Technical University.^[41]
•  Myanmar plans to purchase for $200 million the own telecommunication satellite [9]
•  New Zealand Private New Zealand Satellite Opportunities company since 2005 plans to launch in 2010 or later a commercial satellite NZLSAT for $200 million. [10] [11] Radio enthusiasts federation at Massey University [12] since 2003 hopes for $400,000 to launch a nano-satellite KiwiSAT to relay a voice and data signals [13] Also another RocketLab company works under suborbital space launcher and may use a further version of one to launch into low polar orbit a nano-satellite [14] [15]
•  North Korea will launch several more satellites according to national space program of Korean Committee of Space Technology ^[42][43]
•  Peru developed its space satellite with the National Engineering University, called Chasqui 1. The nano-satellite planning to launch into orbit in 2012 with an expected 60-day lifespan. Payload includes two small VGA cameras with NIR filter(s).
•  Serbia Nongovermental organisations designed, developed and assembled the first Serbian satellite Tesla-1 in 2009 but it still remains unlaunched.
•  Sri Lanka has a goal to construct two 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.^[44][45]
•  Tunisia is developing its first satellite, ERPSat01. Consisting of a CubeSat of 1 kg weight, it will be developed by the Sfax School of Engineering. ERPSat satellite is planned to be launched into orbit in 2013.^[46]
•  Turkmenistan New National Space Agency plans a first satellite by help of SpaceX to 2014 ^[47]
•  Uzbekistan Uzbek State Space Research Agency (UzbekCosmos) announced in 2001 about intention of launch in 2002 first remote sensing satellite [16] Later in 2004 was stated that two satellites (remote sensing and telecommunication) will be build by Russia for 60-70 billion $ each [17]

Attacks on satellites[link]

In recent times satellites have been hacked by militant organizations to broadcast propaganda and to pilfer classified information from military communication networks.^[48][49]

For testing purposes, satellites in low earth orbit have been destroyed by ballistic missiles launched from earth. Russia, the United States and China have demonstrated the ability to eliminate satellites.^[50] In 2007 the Chinese military shot down an aging weather satellite,^[50] followed by the US Navy shooting down a defunct spy satellite in February 2008.^[51]

Jamming[link]

Due to the low received signal strength of satellite transmissions, they are prone to 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,^[52][53] but satellite phone and television signals have also been subjected to jamming.^[54][55]

Also, it is trivial 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.^{[citation needed]}

Satellite services[link]

• Satellite Internet access
• Satellite phone
• Satellite radio
• Satellite television
• Satellite navigation

See also[link]

Spaceflight portal

• 2009 satellite collision
• Footprint (satellite)
• Fractionated Spacecraft
• International Designator
• IMINT
• Space exploration
• List of Earth observation satellites
• List of communications satellite firsts
• Satellite Catalog Number
• Satellite formation flying
• USA 193 (2008 American anti-satellite missile test)
• Spaceport (including list of spaceports with achieved satellite launches)
• Echo 1
• Pioneer 10
• Mariner 10
• Viking I
• Viking II
• Satellites on stamps
• List of passive satellites

References[link]

External links[link]

• Satellite at the Open Directory Project
• Satellite Ground Tracks Real time satellite tracks (Full catalog of satellite orbit). (English) (German) (Spanish) (French) (Italian) (Portuguese) (Chinese)
• Real Time Satellite Tracking provides real-time tracks for about 17000 satellites, as well as 5-day predicitions of visibility
• Heavens Above provides 10-day predictions of satellite visibility
• 'Eyes in the Sky' Free video by the Vega Science Trust and the BBC/OU Satellites and their implications over the last 50 years.
• UCS Satellite Database Lists operational satellites currently in orbit around the Earth. Updated quarterly.
• Current and Historical Launch Calendar
• Satellite launch schedule

Wikimedia Commons has media related to: Satellite

Rainbow Bridge in Tokyo at night

Night or nighttime is the period of time between the sunset and the sunrise when the Sun is below the horizon. This occurs after dusk. The opposite of night is day (or "daytime" to distinguish it from "day" as used for a 24-hour period). The start and end points of time of a night vary based on factors such as season, latitude, longitude and timezone.

At any given time, one side of the planet Earth is bathed in light from the Sun (the daytime) and the other side of the Earth is in the shadow caused by the Earth blocking the light of the sun. This shadow is what we call the darkness of night. Natural illumination is still provided by a combination of moonlight, planetary light, starlight, diffuse zodiacal light, gegenschein, and airglow. In some circumstances, bioluminescence, aurorae and lightning can provide some illumination. The glow provided by artificial illumination is sometimes referred to as light pollution because it can interfere with observational astronomy and ecosystems.