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:''This this is about artificial satellites. For natural satellites, also known as moons, see [[Natural satellite]].''
:''This article is about artificial satellites. For natural satellites, also known as moons, see [[Natural satellite]].''
:''[[Satellites]] and [[Satalite]] redirect here. For the Canadian reggae band, see [[Sattalites]].''
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Revision as of 20:28, 23 November 2008

This article is about artificial satellites. For natural satellites, also known as moons, see Natural satellite.
Satellites and Satalite redirect here. For the Canadian reggae band, see Sattalites.
For other uses, see Satellite (disambiguation).
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 endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon.

History

Early conceptions

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

In 1903 Konstantin Tsiolkovsky (1857–1935) published Исследование мировых пространств реактивными приборами (The Exploration of Cosmic Space by Means of Reaction Devices), 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, Das Problem der Befahrung des Weltraums - der Raketen-Motor (The Problem of Space Travel — The Rocket 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.

History of artificial satellites

Further information: Timeline of artificial satellites and space probes
See also: Space Race

The first artificial satellite was Sputnik 1, launched by the Soviet Union on 4 October 1957, and that started the whole Soviet Sputnik program, with Sergei Korolev as chief designer and Kerim Kerimov as his assistant.[4] This 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. Because the satellite's body was filled with pressurized nitrogen, Sputnik 1 also provided the first opportunity for meteoroid detection, as a loss of internal pressure due to meteoroid penetration of the outer surface would have been evident in the temperature data sent back to Earth. 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 Air Force and Navy were working on Project Orbiter, which involved using a Jupiter C rocket to launch a satellite. The project succeeded, and Explorer 1 became the United States' first 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

The United States Space Surveillance Network (SSN) has been tracking space objects 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 space objects orbiting Earth. The SSN currently tracks more than 8,000 man-made orbiting objects. The rest have re-entered Earth's turbulent atmosphere and disintegrated, or survived re-entry and impacted the Earth. The space objects now orbiting Earth range from satellites weighing several tons to pieces of spent rocket bodies weighing only 10 pounds. About seven percent of the space objects are operational satellites (i.e. ~560 satellites), the rest are space debris.[10] USSTRATCOM is primarily interested in the active satellites, but also tracks space debris which upon reentry might otherwise be mistaken for incoming missiles. The SSN tracks space objects that are 10 centimeters in diameter (baseball size) or larger.

Non-Military Satellite Services

There are three basic categories of non-military satellite services:[11]

Fixed Satellite Service

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 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 Satellite (commercial and noncommercial)

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

Types

MILSTAR: A communication satellite

Orbit types

Main article: List of orbits
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

Altitude classifications

Orbital Altitudes of several significant satellites of earth.

Inclination classifications

Eccentricity classifications

Synchronous classifications

Special classifications

Pseudo-orbit classifications

Satellite Modules

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

Spacecraft bus or service module

This first module consist of five 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

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 generator's) have been used in several successful satellite programs including the Nimbus program (1964-1978).[15]

  • 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

  • The Attitude and Orbit Controlled Control Subsystems
Main article: Attitude control

The attitude and orbit controlled 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

The second major module is the communication payload, which is made up of transponders. A transponders 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).

Launch-capable countries

Main article: Timeline of first orbital launches by nationality
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 — which relatively speaking, does not require much economic, scientific and industrial capacity — 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
Country Year of first launch First satellite
 Soviet Union 1957 Sputnik 1
 United States 1958 Explorer 1
 France 1965 Astérix
 Japan 1970 Ōsumi
 China 1970 Dong Fang Hong I
 United Kingdom 1971 Prospero X-3
 India 1980 Rohini
 Israel 1988 Ofeq 1
 Iran[citation needed] 2008 Safir-1

Both North Korea (1998) and Iraq (1989) have claimed orbital launches (satellite and warhead accordingly), but these claims are unconfirmed.

In addition to the above, 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. On September 28th, 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.[16] 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.[16]

As of 2008, only seven countries from list above ( Russia and Ukraine instead of USSR, also USA, Japan, China, India, and Israel) 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, Iran, Brazil, Pakistan, Romania, Kazakhstan, Australia, Malaysia[citation needed] and Turkey, are at various stages of development of their own small-scale launcher capabilities.

It is scheduled that in early 2008 South Korea will launch a KSLV rocket (created with assistance of Russia). Iran already has successfully tested its own space launch vehicle (Kavoshgar 1) and is scheduled to put its first domestic satellite (Omid 1) into orbit within a year from February 4, 2008.[citation needed]

First launch by country including help of other parties[17]
Country Year of first launch First satellite Payloads in orbit in 2008[18]
 Soviet Union 1957 Sputnik 1 1398
 United States 1958 Explorer 1 1042
 Canada 1962 Alouette 1 25
 Italy 1964 San Marco 1 14
 France 1965 Astérix 44
 Australia 1967 WRESAT 11
 Germany 1969 Azur 27
 Japan 1970 Ōsumi 111
 China 1970 Dong Fang Hong I 64
 United Kingdom 1971 Prospero X-3 25
 Poland 1973 Intercosmos Kopernikus 500 ?
 Netherlands 1974 ANS 5
 Spain 1974 Intasat 9
 India 1975 Aryabhata 34
 Indonesia 1976 Palapa A1 10
 Czechoslovakia 1978 Magion 1 5
 Bulgaria 1981 Intercosmos 22
 Brazil 1985 Brasilsat A1 11
 Mexico 1985 Morelos 1 7
 Sweden 1986 Viking 11
 Israel 1988 Ofeq 1 7
 Luxembourg 1988 Astra 1A 15
 Argentina 1990 Lusat 10
 Pakistan 1990 Badr-1 5
 South Korea 1992 Kitsat A 10
 Portugal 1993 PoSAT-1 1
 Thailand 1993 Thaicom 1 6
 Turkey 1994 Turksat 1B 5
 Chile 1995 FASat-Alfa 1
 Malaysia 1996 MEASAT 4
 Norway 1997 Thor 2 3
 Philippines 1997 Mabuhay 1 2
 Egypt 1998 Nilesat 101 3
 Denmark 1999 Ørsted 3
 South Africa 1999 SUNSAT 1
 Saudi Arabia 2000 Saudisat 1A 12
 United Arab Emirates 2000 Thuraya 1 3
 Algeria 2002 Alsat 1 1
 Greece 2003 Hellas Sat 2 2
 Nigeria 2003 Nigeriasat 1 2
 Iran 2005 Sina-1 1
 Kazakhstan 2006 KazSat 1 1
 Colombia 2007 Libertad 1 1
 Vietnam 2008 VINASAT-1 1
 Venezuela 2008 Venesat-1 1

While Canada was the third country to build a satellite which was launched into space,[19] 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.[20] 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.[21]

Attacks on satellites

Further information: Anti-satellite weapon

In recent times satellites have been hacked by militant organisations to broadcast propaganda and to pilfer classified information from military communication networks.[22][23]

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.[24] In 2007 the Chinese military shot down an aging weather satellite,[24] followed by the US Navy shooting down a defunct spy satellite in February 2008.[25] Russia and the United States have also shot down satellites during the Cold war.

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,[26][27] but satellite phone and television signals have also been subjected to jamming.[28][29]

Satellite Services

See also

References

  1. ^ "Rockets in Science Fiction (Late 19th Century)". Marshall Space Flight Center. Retrieved 2008-11-21. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  2. ^ Everett Franklin Bleiler (1991). Science-fiction, the Early Years. Kent State University Press . p. 325. ISBN 978-0873384162. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ Richard Rhodes (2000). Visions of Technology. Simon & Schuster. p. 160. ISBN 978-0684863115.
  4. ^ "Kerim Kerimov", [[Encyclopædia Britannica]], retrieved 2008-10-12 {{citation}}: URL–wikilink conflict (help)
  5. ^ "A Brief History of Animals in Space". NASA. Retrieved 2007-08-08. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  6. ^ "Preliminary Design of an Experimental World-Circling Spaceship". RAND. Retrieved 2008-03-06. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  7. ^ Alfred Rosenthal (1968). Venture Into Space: Early Years of Goddard Space Flight Center. NASA. p. 15. {{cite book}}: Italic or bold markup not allowed in: |publisher= (help)
  8. ^ Alicia Chang. "50th anniversary of first U.S. satellite launch celebrated". Associated Press. Retrieved 2008-11-21. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  9. ^ David S. F. Portree (1999). "Orbital Debris: A Chronology" (PDF). Lyndon B. Johnson Space Center. p. 18. Retrieved 2008-11-21. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  10. ^ "Orbital Debris Education Package" (PDF). Lyndon B. Johnson Space Center. Retrieved 2008-03-06. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  11. ^ a b Grant, A. (2004). Communication Technology Update (ninth edition ed.). Focal Press. p. 284. ISBN 0240806409. {{cite book}}: |edition= has extra text (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  12. ^ "Workshop on the Use of Microsatellite Technologies" (PDF). United Nations. 2008. p. 6. Retrieved 2008-03-06.
  13. ^ "Earth Observations from Space" (PDF). National Academy of Science. 2007. Retrieved 2008-03-06. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  14. ^ James Oberg (1984). "Pearl Harbor In Space". Omni Magazine. pp. 42–44. Retrieved 2008-03-06. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help); Unknown parameter |month= ignored (help)
  15. ^ George Schmidt. "Radioisotope-based Nuclear Power Strategy for Exploration Systems Development" (PDF). Marshall Space Flight Center. Retrieved 2008-10-02. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  16. ^ a b Tariq Malik. "SpaceX Successfully Launches Falcon 1 Rocket Into Orbit". Space.com. Retrieved 2008-10-02. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  17. ^ "First time in History". The Satellite Encyclopedia. Retrieved 2008-03-06. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  18. ^ "SATCAT Boxscore". celestrak.com. Retrieved 2008-03-05.
  19. ^ Daphne Burleson (2005). Space Programs Outside the United States. McFarland & Company. p. 43. ISBN 978-0786418527.
  20. ^ Brian Harvey (2003). Europe's Space Programme. Springer Science+Business Media. p. 114. ISBN 978-1852337223.
  21. ^ "WRESAT_Australia's_First_Satellite". powerup.com.au. Retrieved 2008-03-05.
  22. ^ Dan Morrill. "Hack a Satellite while it is in orbit". ITtoolbox. Retrieved 2008-03-25. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  23. ^ "AsiaSat accuses Falungong of hacking satellite signals". Press Trust of India. Retrieved 2008-03-25.
  24. ^ a b "China Tests Anti-Satellite Weapon, Unnerving U.S." nytimes.com. Retrieved 2008-03-25.
  25. ^ "Navy Missile Successful as Spy Satellite Is Shot Down". popularmechanics.com. Retrieved 2008-03-25.
  26. ^ "U.S.-Led Forces Destroy GPS Jamming Systems in Iraq". space.com. Retrieved 2008-03-25.
  27. ^ "Homemade GPS jammers raise concerns". computerworld.com. Retrieved 2008-03-25.
  28. ^ "Iran government jamming exile satellite TV". iranfocus.com. Retrieved 2008-03-25.
  29. ^ "Libya Pinpointed as Source of Months-Long Satellite Jamming in 2006". space.com. Retrieved 2008-03-25.

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