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Satellite

Specialty Definition: Satellite

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Specialty Definition: British Sky Broadcasting

(From Wikipedia, the free Encyclopedia)

British Sky Broadcasting (BSkyB - formerly Sky Television) is a direct broadcast satellite (DBS) service operating in the United Kingdom and Ireland. It was launched in February 1989 and was one of the first DBS services in the world to become operational. Sky TV originated as a four-channel service on the Astra satellite at 19.2° east.

The Astra satellite was owned by a Luxembourg-based consortium and controlled from there, but Sky's broadcasts originated in the UK and were subject to British regulation, originally by the Cable Authority and later by the Independent Television Commission.

The failure of rival company British Satellite Broadcasting (BSB) in November 1990 led to a merger, although some of Sky's detractors saw it as a takeover. The new company was called British Sky Broadcasting (BSkyB). The merger may have saved Sky financially. Despite its popularity, Sky had very few major advertisers to begin with, and was also beginning to suffer from embarrassing breakdowns. Acquiring BSB's advertising contracts and equipment solved these problems at a stroke.

With the launch of more Astra satellites from 1991 onward BSkyB was able to begin expanding its services (the Astra satellites were all orbitally co-located so that they could be received using the same dish), and the launch of the first Astra 2 series satellite at a new orbital position, 28.2° east, in 1997, enabled the company to launch a new all-digital service, Sky Digital, with the potential to carry hundreds of television and radio channels. Once again Sky faced competition, this time from ONdigital (later renamed ITV Digital), and once more saw off its rivals partly thanks to aggressive marketing and partly because of its rivals' technical and financial failures.

Rupert Murdoch's News Corporation, which was originally the sole owner of Sky Television, currently has a 38% stake in the company.

Channels

• Sky Movies
• Sky News
• Sky One
• Sky Sports
• Sky Travel

External Link

• Sky TV homepage

  Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "British Sky Broadcasting."

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Communications satellite

(From Wikipedia, the free Encyclopedia)

A communications satellite (sometimes abbreviated to comsat) is an artificial satellite stationed in space for the purposes of telecommunications using radio at microwave frequencies. Most communications satellites use geosynchronous orbits or near-geostationary orbits, although some recent systems use low Earth-orbiting satellitess.

Communications satellites provide a technology that is complementary to that of fiber optic submarine communication cables.

The concept of the communications satellite was first proposed by Arthur C. Clarke, based on Herman Potočnik's previous work from 1929. In 1945 Clarke published an article titled "Extra-terrestrial Relays" in the magazine Wireless World. The article described the fundamentals behind the deployment artificial satellites in geostationary orbits for the purpose of relaying radio signals. Thus Arthur C. Clarke is often quoted as the inventor of the communcations satellite.

Telstar was the first active communications satellite. Belonging to AT&T as part of a a multi-national agreements between AT&T, Bell Telephone Laboratories, NASA, the British Post Office, and the French National PTT (Post Office.) to develop satellite communication. It was launched by NASA from Cape Canaveral on July 10, 1962, the first privately sponsored space launch. Telstar was placed in an elliptical orbit (completed once every 2 hours and 37 minutes), rotating at a 45 degree angle above the equator.

The first geosynchronous communications satellite was Syncom 2, launched on July 26 1963. However, Syncom 2 was positioned in an inclined orbit so special tracking equipment was needed to see it. The first geosynchronous communications satellite that could be seen from a fixed satellite antenna (over North America) was Anik 1, a Canadian satellite launched in 1973.

A low Earth orbiting satellite is a satellite with a low orbit with an orbital period much shorter than a day. As these satellites can only be seen from any given part of the Earth for a short time as it passes over, large numbers of these satellites are needed to ensure coverage. A group of satellites working in concert is known as a satellite constellation.

A direct broadcast satellite is a special high-powered communications satellite that transmits to small DBS satellite dishes. Direct broadcast satellites always operate in the upper portion of the Ku-Band.

Examples of satellite constellations are the GPS and the Iridium and Globalstar satellite telephony services.

See also: Satmodem, DVB, Free-space optical communications, ICO, Intelsat, Iridium, NASA, Satellite television, Space communications, Spy satellite, Syncom, Teledesic, Telstar

External Links

• Communications satellites short history by David J. Whalen
• NASA experimental communications satellites
• Syncom 2 satellite description
• Lloyd's Satellite Constellations

  Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Communications satellite."

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Direct broadcast satellite

(From Wikipedia, the free Encyclopedia)

Direct broadcast satellite, or DBS, is a relatively recent development in the world of television distribution. "Direct broadcast satellite" can either refer to the communications satellites themselves that deliver DBS service or the actual television service. DBS systems are commonly referred to as "minidish" systems.

The first commercial DBS service, Sky Television, was launched in 1989. Sky TV originated as a four-channel service on the Astra satellite. Sky TV is a European DBS service and is now owned by News Corporation.

Hughes's DirecTV, the first high-powered DBS system, went online in 1994 and was the first North American DBS service. DirecTV's main competition was the now-defunct PrimeStar service, a DBS service that used larger 3 foot (91 cm) satellite dishes to receive medium-power Ku-Band satellite signals. DirecTV's introduction was the most successful consumer electronics debut in American history. In 1996, Echostar's DISH Network went online in the United States and went on to similar success as DirecTV's primary competitor. Echostar attempted to buy DirecTV but this was rejected by the U.S. Department of Justice based upon monopoly concerns. Hughes Eelectronic, owner of DirecTV, is due to be bought by News Corporation, controlled by Rupert Murdoch, which also owns Fox TV.

In addition there are dozens of satellite television stations that broadcast to specialized ethnic communities.

DBS uses special high powered Ku-Band satellites that send digitally compressed television and audio signals to 18- to 24-inch (45 to 60 cm) fixed satellite dishes. DBS systems transmit signals to Earth in what is called the Broadcast Satellite Service (BSS) portion of the Ku-Band between 12.2 and 12.7 GHz. Thanks to digital compression technologies, DBS systems can deliver hundreds of cable TV-style programming channels, as well as local network television affiliates.

Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Direct broadcast satellite."

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DVB

(From Wikipedia, the free Encyclopedia)

Digital Video Broadcasting (DVB) is an internationally accepted standard for digital television, including HDTV, satellite TV, and data ( one-way, named DVB-IP, and double-way, named DVB-RCS, data connections via satellite to Internet).

DVB is often used in signal compression and encoding of digital satellite communications. DVB is an open standard, used primarily outside of North America, but is also used frequently in North American satellite communications as well. Unlike Motorola's DigiCipher 2 standard, the DVB standard has a wider adoption in terms of the number of manufacturers of DVB-capable satellite receiver boxes.

In the United States, terrestrial HDTV broadcasts use 8VSB digital encoding instead of DVB-T, the HDTV variant of the DVB standard.

See also satmodem, ATSC

External links

• DVB

  Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "DVB."

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Earth observation satellite

(From Wikipedia, the free Encyclopedia)

Earth observation satellites are satellites specifically designed to observe Earth from orbit, similar to spy satellites but intended for non-military uses such as environmental monitoring, meteorology, map making etc.

Satellites or satellite series include:

• Landsat
• ERS
• SPOT
• EOS, Terra
• Envisat
• RADARSAT-1
• CBERS

See also weather satellite

Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Earth observation satellite."

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Natural satellite

(From Wikipedia, the free Encyclopedia)

The term moon (never capitalized) is used to mean any natural satellite of the other planets. There are, at least, 102 moons within Earth's solar system, and presumably many others orbiting the planets of other stars. Typically the larger gas giants have extensive systems of moons. Mercury and Venus have no moons at all, Earth has one large moon, Mars has two tiny moons, and Pluto a large companion called Charon (sometimes considered to be a double planet).

Most moons are assumed to have been formed out of the same collapsing region of protoplanetary disk that gave rise to its primary. However, there are many exceptions and variations to this standard model of moon formation that are known or theorized. Several moons are thought to be captured foreign objects, fragments of larger moons shattered by large impacts, or (in the case of Earth's moon) a portion of the planet itself blasted into orbit by a large impact. As most moons are known only through a few distant observations through probes or telescopes, most theories about them are still uncertain.

Most moons in the solar system are tidally locked to their primaries; an exception is Saturn's moon Hyperion, which rotates chaotically due to a variety of external influences. No moons have moons of their own; the tidal effects of their primaries make orbits around them unstable. However, several moons have companions in their Lagrangian points (eg, Saturn's moons Tethys and Dione).

The recent discovery of Ida's moon Dactyl confirms that some asteroids also have moons.

The largest moons in the solar system (those bigger than about 3000 km across) are Earth's Moon, Jupiter's Galilean moons Io, Europa, Ganymede, and Callisto, Saturn's moon Titan, and Neptune's captured moon Triton. For smaller moons see the appropriate planets.

A comparative table classifying the moons of the solar system by diameter, also including a column for some notable asteroids:

Diameter(km)	Earth	Mars	Asteroids	Jupiter	Saturn	Uranus	Neptune	Pluto
5000+				Ganymede	Titan
4000-5000				Callisto
3000-4000	Luna			Europa Io
2000-3000							Triton
1000-2000			1 Ceres		Iapetus Rhea Dione Tethys	Ariel Umbriel Titania Oberon		Charon
500-1000			4 Vesta 2 Pallas
100-500			(Too many to list)	Amalthea	Phoebe Hyperion Enceladus Mimas Janus Epimetheus	Sycorax Miranda Puck Portia	Proteus Nereid Larissa Galatea Despina
50-100			(Too many to list)	Himalia Thebe	Pandora Prometheus	Setebos Prospero Stephano Caliban 1986U10 Belinda Rosalind Juliet Desdemona Cressida Bianca Cordelia Ophelia	Thalassa Naiad
10-50		Phobos Deimos	(Too many to list)	Sinope Pasiphae Carme Ananke Elara Lysithea Leda Adrastea Metis	Helene Calypso Telesto Atlas Pan	Trinculo
less than 10	Cruithne¹			S/2000 J11 S/2000 J1 Iocaste Praxidike Harpalyke Isonoe Erinome Taygete Chaldene S/2002 J1 Kalyke Megaclite Callirrhoe Euporie Kale Orthosie Thyone Euanthe Hermippe Pasithee Eurydome Aitne Sponde Autonoe S/2001 J11 S/2003 J2 S/2003 J3 S/2003 J4 S/2003 J5 S/2003 J6 S/2003 J7 S/2003 J8 S/2003 J9 S/2003 J10 S/2003 J11 S/2003 J12 S/2003 J13 S/2003 J14 S/2003 J15 S/2003 J16 S/2003 J17 S/2003 J18 S/2003 J19 S/2003 J20 S/2003 J21
unknown				Themisto	Ymir Paaliaq Siarnaq Tarvos Kiviuq Ijiraq Thrym Skadi Mundilfari Erriapo Albiorix Suttung S/2003 S1	S/2002 N1 S/2002 N2 S/2002 N3

¹ It is debatable whether Cruithne counts as a real moon; it is mainly placed here for comparison's sake.

External links

Jupiter's moons

• Data on Jupiter's satellites
• Jupiter's new moons (discovered in 2000)
• Jupiter's new moons (discovered in 2002)
• Jupiter's new moons (discovered in 2003)

Saturn's moons

• Saturn's new moons (discovered in 2000)
• Saturn's new moon (discovered in 2003)

Neptune's moons

• Neptune's new moons (discovered in 2003)

Solar system:
Sun - Mercury - Venus - Earth - Mars - Asteroids - Jupiter - Saturn - Uranus - Neptune - Pluto - Comets

Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Natural satellite."

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Satellite

(From Wikipedia, the free Encyclopedia)

A satellite is an object that orbits another object. With sufficient tangential velocity, the object does not collide with the primary object it orbits, but maintains a distance from that object as the rate at which it falls towards that object is similar to the rate that it travels away, thus the object orbits the primary object and becomes a satellite. In other words: gravitational force serves as the centripetal force needed to make the object circle the primary object. The motion of the satellite around its primary gravitational source is known as freefall.

Because all objects exert gravity, the motion of the primary object is also affected by the satellite. (This observation allows for the discovery of extrasolar planets) If two objects are sufficiently close in mass, they are generally referred to as a binary system rather than a primary object and satellite. The general criterion for an object to be a satellite is that the center of mass of the two objects is inside one of the objects.

All masses that are part of the solar system, including the Earth, are satellites of the Sun, or satellites of those objects, such as the Moon.

In common usage, the term is usually used to describe an artificial satellite.

History of Artificial Satellites

In May, 1946, the Preliminary Design of an Experimental World-Circling Spaceship stated, "A satellite vehicle with appropriate instrumentation can be expected to be one of the most potent scientific tools of the Twentieth Century. The achievement of a satellite craft would produce repercussions comparable to the explosion of the atomic bomb..." (see: Project RAND)

The space age began in 1946¹, as scientists began using captured German V-2 rockets to make measurements in the upper atmosphere. Before this period, scientists could use balloons up to 30 km and radio waves to study the ionosphere, rockets changed that. From 1946 to 1952, upper-atmosphere research was conducted using V-2s and Aerobee rockets. This allowed measurements of atmospheric pressure, density, and temperature up to 200 km. (see also: magnetosphere, Van Allen radiation belt)

The US had been considering launching orbital satellites since 1945 under the Bureau of Aeronautics of the United States Navy. The 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."

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 small satellite called Explorer 1 on January 31st 1958.

On July 29, 1955, the White House announced that the US 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 and on October 4, 1957 Sputnik I was launched into orbit.

See also

• Astronomical satellite
• Communications satellite
• Earth observation satellite
• Navigation satellite
• Satellite television
• Space station
• Spy satellite
• Timeline of artificial satellites and space probes
• Weather satellite

Reference

• 1 -- The Radiation Belt and Magnetosphere

External Link

• Lloyd's satellite constellations

  Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Satellite."

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Satellite television

(From Wikipedia, the free Encyclopedia)

Satellite television is television delivered by way of orbiting communications satellites located 37,000 km (22,300 miles) above the earth's surface. The first satellite television signal was relayed from Europe to the Telstar satellite over North America in 1962. The first domestic North American satellite to carry television was Canada's Anik 1, which was launched in 1973.

Satellite television, like other communications relayed by satellite, starts with a transmitting antenna located at an uplink facility. Uplink satellite dishes are directed toward the satellite that its signals will be transmitted to, and are very large, as much as 9 to 12 meters (30 to 40 feet) in diameter. The increased diameter results in more accurate positioning and improved signal reception at the satellite. The signal is transmitted to devices located on-board the satellite called transponders, which retransmit the satellite signal back towards the Earth at a different frequency.

The satellite signal, quite weak after travelling through space, is collected by a parabolic receiving dish, which reflects the weak signal to the dish's focal point and is received, down-converted to a lower frequency band and amplified by a device called a low-noise block downconverter, or LNB (Direct broadcast satellite dishes use an LNBF, which integrates the feedhorn with the LNB).

The signal, now amplified, travels to a satellite receiver box through coaxial cable (RG-6 or RG-10; cannot be standard RG-59) and is converted by a local oscillator to the L-Band range of frequencies (approximately). Special on-board electronics in the receiver box help tune the signal and then convert it to a frequency that a standard television can use.

There are two primary types of satellite television distribution: direct broadcast satellite (DBS) and television receive-only (TVRO).

Direct broadcast satellite

Direct broadcast satellite, or DBS, is a relatively recent development in the world of television distribution. "Direct broadcast satellite" can either refer to the communications satellites themselves that deliver DBS service or the actual television service. DBS systems are commonly referred to as "minidish" systems. DBS uses the upper portion of Ku-Band.

DBS systems rely upon proprietary reception equipment, most often in the form of a television set-top signal descrambling box. This measure assures satellite television providers that only authorised, paying subscribers have access to the content.

History of satellite television

The first commercial DBS service, Sky Television, was launched in 1989 and served customers in the United Kingdom. Hughes's DirecTV, the first high-powered DBS system, went online in 1994 and was the first North American DBS service. In 1996, Echostar's DISH Network went online in the United States and has gone on to similar success as DirecTV's primary competitor. Commercial DBS services are the primary competition to cable television service.

In Canada, the two DBS services available are Bell Canada's ExpressVu and StarChoice.

Satellite television in Australia has proven to be a far more feasible option than Cable television, due to the vast distances between population centres. The first service to come online in Australia was Galaxy Television, which was later taken over by Cable Television giant Foxtel, which now operates both Cable and Satellite services to all State capital cities and the Southwest. Its main metropolitan rival is Optus Television, while rural areas of the Eastern States are served by Austar.

Television receive-only

Television receive-only, or TVRO, refers to satellite television reception equipment that is based primarily on open standards equipment. This contrasts sharply with direct broadcast satellite, which is a completely closed system that uses proprietary reception equipment. TVRO is often referred to as "big dish" satellite television.

TVRO systems are designed to receive analog satellite signals from both C-Band and Ku-Band satellite television or audio signals. TVRO systems tend to use larger rather than smaller satellite dish antennas, since it is more likely that the owner of a TVRO system would have a C-Band only setup rather than a Ku-Band only setup. Additional receiver boxes allow for different types of digital satellite signal reception, such as DVB/MPEG-2 and 4DTV.

Direct broadcasting satellites which can be received by what are known in Chinese as little ears have had a major role in breaking the government monopoly of information on Mainland China. Although met with frequent and generally unsuccessful efforts to regulate them, satellite dishes are fairly common in urban Chinese cities. Satellite television has also played an important role in broadcasting to expatriate communities such as Arabs, and overseas Chinese.

See also: satellite dish, microwave antenna

External Links

• DirecTV homepage (USA)
• DISH Network homepage (USA)
• Bell ExpressVu homepage (Canada)
• StarChoice homepage (Canada)
• Sky Television homepage (U.K.)
• Lyngemark Satellite Charts
• TVRO/C-Band FAQ List
• Satellite TV (USA)

  Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Satellite television."

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Abbreviations & Acronyms: Satellite

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Synonyms within Context: Satellite

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Modern Usage: Satellite

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Commercial Usage: Satellite

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Image Slideshow: Satellite

Photos: Satellite More pictures...

Illustrations: Satellite More pictures...

Computer Images: Satellite More pictures...

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Photo Album: Satellite

Thumbnail	Description & Credit	Thumbnail	Description & Credit
	Shown is EPN (Executive Plaza North), one of NIH's satellite office buildings located in Rockville, Maryland. Credit: Bill Branson (photographer).		Shown are EPN and EPS, (Executive Plaza North and Executive Plaza South), two of NIH's satellite office buildings located in Rockville, Maryland. Credit: Bill Branson (photographer).
	A CDC epidemiologist in Kikwit, Zaire, communicates with colleagues in Atlanta via satellite telephone. Credit: CDC.		ER-2 with Satellite Uplink Pod. Credit: NASA.
	TRMM Satellite Provides Five Year of Rainfall Data. Credit: NASA.		NASA Satellite Data Used Operationally to Help Combat Fires in the West. Credit: NASA.
	Echo Satellite. Credit: NASA.		Tikhonravov's Satellite Team. Credit: NASA.
	NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite has given astronomers their ... Credit: NASA.		Close-up image of Jupiter's satellite, Callisto. Credit: NASA.
Source: pictures compiled by the editor from various references; see picture credits.

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Digital Photo Gallery: Satellite
 

"Old Satellite Dish" by Matthew Maaskant Commentary: "An old satellite dish sits in a back yard. Visit: http://www.qr5.com ."	"Satellite dish" by Jana Werner Commentary: "Enjoy!!!."
Source: photographs selected by the editor, with permission from the photographers.

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Sounds Captioned with "Satellite".

Play	Caption	Play	Caption
	Cellular; cell phone; mobile phone; satellite; communication; communicate; dialing; connection; connecting.		Telephone; cellular; wireless; mobile; satellite; power; turn on.
Source: compiled by the editor from various references; see credits.

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Non-Fiction Usage: Satellite

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Speeches: Satellite

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Usage Frequency: Satellite

Source: compiled by the editor from several corpora; see credits.

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Usage in Company Names: Satellite

Source: compiled by the editor from Icon Group International, Inc.

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Expressions: Satellite

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Frequency of Internet Keywords: Satellite

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Modern Translation: Satellite