Satellite

In the context of spaceflight, a satellite is an artificial object which has been intentionally placed into orbit. 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. Some satellites, notably space stations, have been launched in parts and assembled in orbit. Artificial satellites originate from more than 40 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, Vesta, Eros, 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.

About 6,600 satellites have been launched. The latest estimates are that 3,600 remain in orbit. Of those, about 1,000 are operational; the rest have lived out their useful lives and are part of the space debris. Approximately 500 operational satellites are in low-Earth orbit, 50 are in medium-Earth orbit (at 20,000 km), the rest are in geostationary orbit (at 36,000 km).

Satellites are propelled by rockets to their orbits. Usually the launch vehicle itself is a rocket lifting off from a launch pad on land. In a minority of cases satellites are launched at sea (from a submarine or a mobile maritime platform) or aboard a plane (see air launch to 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

Early conceptions

"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. The idea surfaces again in Jules Verne's The Begum's Fortune (1879).

In 1903, Konstantin Tsiolkovsky (1857â€"1935) published Exploring Space Using Jet Propulsion 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 fuelled 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 (1892â€"1929) published his sole book, The Problem of Space Travel â€" The Rocket Motor (German: Das Problem der Befahrung des Weltraums â€" 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 (1917â€"2008) described in detail the possible use of communications satellites for mass communications. 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.

Artificial satellites

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.

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." 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." 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 (1957â€"58), the White House announced on July 29, 1955 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 first attempt at orbiting a satellite resulted in the explosion of the launch vehicle on national television. But finally, three months after Sputnik 2, the project succeeded; Explorer 1 became the United States' first artificial satellite on January 31, 1958.

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.

Early satellites were constructed as "one-off" designs. With growth in geosynchronous (GEO) satellite communication, multiple satellites began to be built on single model platforms called satellite buses. The first standardized satellite bus design was the HS-333 GEO commsat, launched in 1972.

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

Space Surveillance Network

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. 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.

Non-military satellite services

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

Fixed satellite services

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

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

• "Killer Satellites" are satellites that are designed to destroy enemy warheads, satellites, and 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 masses and small sizes. New classifications are used to categorize these satellites: minisatellite (500â€"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.
• Recovery satellites are satellites that provide a recovery of reconnaissance, biological, space-production and other payloads from orbit to Earth.
• Manned spacecraft (spaceships) are large satellites able to put humans into (and beyond) an orbit, and return them to Earth. Spacecraft including spaceplanes of reusable systems have major propulsion or landing facilities. They can be used 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

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 2,465 artificial satellites orbiting the Earth. Geocentric orbits may be further classified by their altitude, inclination and eccentricity.

The commonly used altitude classifications of geocentric orbit are Low Earth orbit (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 km-35,786 km. High Earth orbit is any orbit higher than 35,786 km.

Centric classifications

• Geocentric orbit: An orbit around the planet Earth, such as the Moon or artificial satellites. Currently there are approximately 2,465 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

• Low Earth orbit (LEO): Geocentric orbits ranging in altitude from 0â€"2000 km (0â€"1240 miles)
• Medium Earth orbit (MEO): Geocentric orbits ranging in altitude from 2,000 km (1,200 mi)-35,786 km (22,236 mi). Also known as an intermediate circular orbit.
• Geosynchronous Orbit (GEO): Geocentric circular orbit with an altitude of 35,786 kilometres (22,236 mi). The period of the orbit equals one sidereal day, coinciding with the rotation period of the Earth. The speed is approximately 3,000 metres per second (9,800 ft/s).
• High Earth orbit (HEO): Geocentric orbits above the altitude of geosynchronous orbit 35,786 km (22,236 mi).

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 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

• Circular orbit: An orbit that has an 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 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 (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

• 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.
    • 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

• 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 imaging, spy, and weather satellites.
• Moon orbit: The orbital characteristics of Earth's Moon. Average altitude of 384,403 kilometers (238,857 mi), ellipticalâ€"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-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

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. Note that some novel architectural concepts such as Fractionated Spacecraft somewhat upset this taxonomy.

Spacecraft bus or service module

The bus module consists of the following subsystems:

• The Structural Subsystem

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.

• The Telemetry Subsystem (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 Subsystem

The power subsystem consists 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 (1964â€"1978).

• The thermal control subsystem

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 Subsystem

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

Communication payload

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, 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.

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 of states 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 include multi-national state organization ESA but does not include private consortiums.

Attempted first launches

• 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 was later disproved.
• 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 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 a first KSLV(Naro)-1 own launcher (created with assistance of Russia) in 2009 and 2010 until success was achieved in 2013 by Naro-3.
• First European multi-national state organization ELDO tried to make the orbital launches at Europa I and Europa II rockets in 1968-1970 and 1971 but stopped operation after fails.

Other notes

• ^ 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 Brazil, Argentina, Pakistan, Romania, Taiwan, Indonesia, Australia, New Zealand, Malaysia, Turkey and Switzerland are at various stages of development of their own small-scale launcher capabilities.

Launch capable private entities

• Private firm Orbital Sciences Corporation, with launches since 1982, continues very successful launches of its Minotaur, Pegasus, Taurus and Antares rocket programs.
• On September 28, 2008, late comer and private aerospace firm SpaceX successfully launched its Falcon 1 rocket into orbit. This marked the first time that a privately built liquid-fueled booster was able to reach orbit. 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.

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

First satellites of countries

While Canada was the third country to build a satellite which was launched into space, it was launched aboard a U.S. rocket from a U.S. spaceport. The same goes for Australia, who launched first satellite involved a donated U.S. Redstone rocket and U.S. support staff as well as a joint launch facility with the United Kingdom. The first Italian satellite 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. By similar occasions, almost all further first national satellites was launched by foreign rockets.

Attempted first satellites

•  USA tried unsuccessfully to launch its first satellite in 1957; they were successful in 1958.
•  China tried unsuccessfully to launch its first satellite in 1969; they were successful in 1970.
•  Iraq under Saddam fulfilled in 1989 an unconfirmed launch of warhead on orbit by developed Iraqi vehicle that intended to put later the 75-kg first national satellite Al-Ta’ir, also developed.
•  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 the own national Libsat satellite project including telecommunication and remote sensing aims that was postponed after 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

•  Afghanistan announced in April 2012 that it is planning to launch its first communications satellite to the orbital slot it has been awarded. The satellite Afghansat 1 was expected to be obtained by a Eutelsat commercial company in 2014.
•  Angola will have the first telecommunication satellite AngoSat-1 that was ordered in Russia at 2009 for $400 millions, started to construction at the and of 2013 and planning for launch in November 2016.
•  Armenia in 2012 founded Armcosmos company and announced an intenton to have the first telecommunication satellite ArmSat. The investments estimates as $250 million and country selecting the contractor for building within 4 years the satellite amongst Russia, China and Canada
•  Bangladesh announced in 2009 that it intends to launch its first satellite into space by 2011.
•  Belgium's first nano-satellite OUFTI-1 within European University program CubeSat QB50 for test radio protocol in space is under construction in University of Liege.
•  Cambodia's Royal Group plans to purchase for $250â€"350 million and launch in the beginning of 2013 the telecommunication satellite.
•  Democratic Republic of the Congo ordered at November 2012 in China (Academy of Space Technology (CAST) and Great Wall Industry Corporation (CGWIC)) the first telecommunication satellite CongoSat-1 which will be built on DFH-4 satellite bus platform and will be launched in China till the end of 2015.
•  Croatia has a goal to construct a satellite by 2013â€"2014. Launch into Earth orbit would be done by a foreign provider.
•  Ethiopian Space Science Society planning the QB50-family research CubeSat ET-SAT by help of Belgian Von Karman Institute till 2015 and the small (20â€"25 kg) Earth observation and remote sensing satellite Ethosat 1 by help of Finnish Space Technology and Science Group till 2019.
•  Finland's Aalto-1 Cusesat-satellite (3U) with solar panels is a funded by student nano-satellite project of Aalto University and Finnish Meteorological Institute [3]. When launched (plan was to 2013), it would be the first Finnish satellite. Launch has been procured for the summer 2015.
•  Ghana plans to order in UK and Italy and launch within 2020 the first Earth observation satellite Ghanasat-1.
•  Ireland's team of Dublin Institute of Technology intends to launch the first Irish satellite within European University program CubeSat QB50.
•  Jordan's first satellite to be the private amateur pocketqube SunewnewSat.
•  Kenyan University of Nairobi has plans to create the microsatellite KenyaSat by help of UK's University of Surrey.
•  Laos announced that its 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).
•  Latvia's 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. Started preparations to produce the next satellite "Venta-2".
•  Moldova's first remote sensing satellite plans to start in 2013 by Space centre at national Technical University.
•  Mongolia's National Remote Sensing Center of Mongolia plans to order the communication satellite in Japan, Mongolian Academy of Sciences schedules to launch the first national experimental satellite Mongolsat by US launcher in the first quarter of 2013.
•  Myanmar plans to purchase for $200 million the own telecommunication satellite.
•    Nepal stated that planning to launch of own telecommunication satellite before 2015 by help of India or China.
•  New Zealand's private Satellite Opportunities company since 2005 plans to launch in 2010 or later a commercial satellite NZLSAT for $200 million. Radio enthusiasts federation at Massey University [4] since 2003 hopes for $400,000 to launch a nano-satellite KiwiSAT to relay a voice and data signals 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.
•  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 Aaepa airspace agency plans first Eart observation satellite.
•  Serbia's first satellite Tesla-1 was designed, developed and assembled by nongovermental organisations in 2009 but still remains unlaunched.
•  Slovenia's Earth observation microsatellite for the Slovenian Centre of Excellence for Space Sciences and Technologies (Space-SI) now under development for $2 million since 2010 by University of Toronto Institute for Aerospace Studies â€" Space Flight Laboratory (UTIAS â€" SFL) and planned to launch in 2015-2016.
•  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 Sfax School of Engineering. ERPSat satellite is planned to be launched into orbit in 2013.
•  Turkmenistan's new National Space Agency plans to launch in 2015 by SpaceX rocket its first telecommunication satellite Turkmensat 1 built by Italian Thales Alenia Space.
•  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 $60â€"70 million each

Attacks on satellites

In recent times, 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, the United States and China have demonstrated the ability to eliminate satellites. In 2007 the Chinese military shot down an aging weather satellite, followed by the US Navy shooting down a defunct spy satellite in February 2008.

Jamming

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, but satellite phone and television signals have also been subjected to jamming.

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.

Satellite services

See also

References

External links

• Satellite at DMOZ
• 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 predictions of visibility
• Heavens Above provides 10-day predictions of satellite visibility
• Satflare tracks in real time all the satellites orbiting the Earth
• 'Eyes in the Sky' Free video by the Vega Science Trust and the BBC/OU Satellites and their implications over the last 50 years.
• Daily animation of the Earth, made by 'Electro L' satellite photos Satellite shoots 48 images of the planet every day.
• Satellite Technologies
• Daily animation of the Earth, made by 'Electro L' satellite photos Satellite shoots 48 images of the planet every day.