Proximity Switch

Introduction and brief history of satellites

A satellite is an object that orbits another object (known as its primary). All the masses that part of the solar system, including Earth, are satellites of either sun or satellites of those objects as the moon. It is not always easy to decide what is "satellite" in a pair of organs. Because all objects exert gravity, the motion of the primary object is influenced also by satellite. If twoufficiently objects are similar in mass, are generally described as a binary system, rather than the main and satellite. The general criterion of an object to be a satellite, is the center of mass of two objects is inside the primary object. The popular use of the term "satellite" usually refers to an artificial satellite (a man-made object on Earth, or another circuit of the body).

In May 1946, the preliminary design of an experimental World-Circling Spaceshipsaid, "Can a vehicle with appropriate equipment satellite should be one of the most powerful science of the twentieth century. The acquisition of a satellite craft would produce effects comparable to the detonation of the atomic bomb …"

The space age began in 1946 when researchers began to use the included German V-2 rockets to make measurements in the atmosphere. Before that time, the scientists used balloons that went on for 30 km, and radio waves to studyionosphere. From 1946 to 1952, was the upper atmosphere research conducted using V-2s and Aerobee rockets. This allowed for the measurement of atmospheric pressure, density and temperatures up to 200 km. The United States was considering launching orbital satellites since 1945 under the chairmanship of Aeronautics of the U.S. Navy. Air Force's Project RAND eventually released the report mentioned above, but had not believed that the satellite, as potential military weapon was not, but as a toolscience, politics and propaganda. Under pressure from the American Rocket Society, the National Science Foundation and the International Geophysical Year, the military interest beginning in 1955, was the Air Force and Navy, working on project Orbiter, which involved using Jupiter C rocket of a small satellite called Explorer 1 31 January 1958.

On 29 July 1955, informed the White House that the U.S. intended to launch satellites in the spring 1958 itwas known as Project Vanguard. On July 31 the Soviets announced that they are intended for a satellite in autumn 1957 and October 4, 1957 Sputnik I launched into orbit, triggering the space race between the two nations.

The largest artificial satellite currently in orbit around the Earth is the International Space Station, which sometimes can be seen with the naked eye can see.

Types of satellites

· Astronomical satellites: These satellites are used forobservation of distant planets, galaxies and other objects in space.

· Communications satellites: they are artificial satellites stationed in space for telecommunications using radio at microwave frequencies. Most communications satellites use geostationary lanes, or nearly geostationary lanes, although some newer systems use low Earth orbit satellites.

• Earth observation satellites are satellites specifically designed to observe Earth from space, resemblesreconnaissance satellites but intended for non-military applications such as environmental monitoring, meteorology, map making etc. (See especially Earth Observing System).

· Navigation satellites are satellites which use radio signals to mobile receivers time on the ground so that their exact position to decide. The relatively clear line of sight between the satellites and receivers on the ground, combined with a continuing improvement in the electronics, satellite systems can bePositioning accuracy measurement after a few meters in real time.

· Reconnaissance satellites are Earth observation satellite or communications satellite used for military or intelligence. Less knowledge of the power of these satellites, as governments that operate them usually keep the information on their classified reconnaissance satellites.

· Solar power satellites are proposed satellites built in high Earth orbit that uses microwavetransmission power of the beam of solar energy for large antenna on Earth where you can replace conventional energy sources can be used.

· Space stations are man-made structures designed for human beings to live in space. A space station is different from other manned spacecraft by its lack of major propulsion or landing facilities – instead, other vehicles such as transport, use, and the station. Space stations are designed for mid-life term in a job forPeriods of weeks, months or even years.

• Weather satellites are satellites used primarily to monitor weather conditions and / or the Earth's climate.

Miniaturized satellites are satellites · unusually low weights and small sizes. New format used for the structuring of these satellites: mini-satellite (500-200 kg), micro (less than 200 kg), nano-satellite (under 10 kg).

Course types

Many times the satellites are characterized by their jobs. Although asatellite that can monitor almost any height, the satellites are usually classified by their height:

Low Earth Orbit (LEO: 200 to 1200 km above the Earth's surface)

· Medium Earth Orbit (ICO or MEO: 1200-35286 km)

· Geostationary orbit (GEO: 35786 km above the Earth) and geostationary orbit (zero inclination geostationary orbit). These pathways are of particular interest to communications satellites and discuss in detail later.

High Earth Orbit(Heo: more than 35786 km)

The following special lanes, alleys, which are also used to categorize satellites

· Molniya orbit: There is a class from a highly elliptical orbit. A satellite placed in orbit, who spends most of his time on a certain area of land, a phenomenon that higher living, is well known. Molniya orbits are named in a series of Soviet / Russian Molniya communications satellites that were of this class of paths has been used since the mid-1960s.

Helio · synchronous orSun-synchronous orbit, a sun synchronous orbit, or more generally, a sun-geostationary orbit is an orbit in which an object is always passed for a given point on Earth at the same local solar time. This is a useful characteristic for satellites that image the Earth's surface at visible or infrared wavelengths (eg weather, spy satellites and remote sensing).

· Polar orbit: a satellite in polar orbit that passes above or nearly above both poles of the earth (or other celestial bodiesbody) on each revolution.

· Hohmann transfer orbit: for this particular type of circuit, is more common to identify the satellite as a spacecraft. In space and aerospace engineering, Hohmann transfer orbit is an orbit maneuver a spaceship that moves from one orbit to another.

· Job or Supersynchronous driver circuit: a path of GEO. Satellites will operate westbound.

· Job or Subsynchronous driver circuit: orbit close to but below GEO. Usedsatellites during the change station heading east.

Communications satellites

A communication satellite (sometimes abbreviated to comsat) is an artificial satellite stationed in space for telecommunications. Use modern communication satellites in geostationary orbit, Molniya-lane or low earth orbits.

For fixed services, communications satellites provide a technology complementary to that of fiber-optic submarine communications. For mobileprograms such as communications with vessels and aircraft, satellite communicationis the only possible means of communication, such as implementation of other new technologies, such as cable, are impractical or impossible.

Top Mission: The origin of satellite communications, after an article by Arthur C. Clarke wrote in 1945, could be identified. He suggested that a radio relay satellite in an equatorial location, with a period of 24 hours of rest will remain in the earth's surface, and canused for long distance communication, as it will be about the limits of the earth is bending. Sputnik 1, the first artificial world (not communications) satellite was launched October 4, 1957 The first satellite to relay communications was Project SCORE in 1958, used a tape recorder to store and send voice messages. E 'was used to send a Christmas greeting to the world of President Eisenhower. NASA begins with an Echo satellite in 1960. This 100-foot aluminized Mylarflask served as a passive reflector for radio communications. Courier 1B, (built by Philco) also launched in 1960, was the first active repeater satellite. Below is given information on milestones in the history of satellite communications: —

· Herman Potocnik – describes a space station in geostationary orbit – 1928

• Arthur C. Clarke – put a station in geostationary orbit to relay communications and television broadcasting – 1945

Project SCORE – firstSatellite communications – 1958

· Echo – the first satellite reflector passive – August 1960

· Courier 1B – first active repeater satellite – October 1960

· Telstar – the first satellite-active, designed to transmit television and communication of data at high speeds. Telstar was in orbit was elliptical (completed once every 2 hours and 37 minutes), a rotation angle of 45 ° above the equator. July 1962

· Syncom – first communications satellitegeostationary orbit. Syncom 2 revolved around the Earth once a day at a steady speed, but because the north-south was still moving special equipment is needed to detect it. 1963

• Oscar-III – the first satellite for radio amateurs – March 1965

· Molniya – first Soviet communication satellite, a highly elliptical orbit – October 1965

· Early Bird – first Intelsat satellite into commercial service – April 1965

· Recent changes – the first national television network, which is based onSatellite Television – November 1967

· Anik 1 – the first national satellite system, Canada – 1973

· Vigan 1, use the first geosynchronous communications satellite – April 1974

· Ekran – the first series of direct-to-home television satellite in 1976

· PALAPA A1 – Indonesia first communication satellite – July 8, 1976

· TDRSS – the first satellite designed to provide communications transfer to other spacecraft. – 1983

• Mars GlobalMeter – the first communications satellites in orbit around another planet (Mars) – 1997

· Relay Cassini to Earth images of the Huygens probe as the land on Saturn's moon Titan, is the longest relay race so far. – January 14, 2005

Depending on the needs of communications satellites could be placed in different orbits. We discuss some common types: —

(a) satellites into geostationary orbit a satellite in geostationary orbit appears to be in a fixed position for aEarth-based observer. A geostationary satellite orbits the Earth at a constant speed once a day for the equator. The geostationary orbit is useful for communications applications, because the ground antenna, the direction of the satellite is correct, can not function effectively without the need for expensive equipment to track the motion of the satellite. In particular for applications requiring a high number of antennas on the ground (such as direct TV distribution), you save the earthequipment could not be more than offset the additional costs and complexity of lifting on board a satellite in geostationary orbit relatively high.

The concept of a geostationary satellite for the first time proposed by Arthur C. Clarke, based on work by Konstantin Tsiolkovsky and on the 1929 work by Herman Potočnik (writing Herman Noordung) Das Problem des Weltraums us Befahrung – we Raketen highway. In October 1945 Clarke published an article titled "Extra-TerrestrialRelays "in the British magazine Wireless World. The article describes the principles underlying the use of artificial satellites in geostationary orbit lanes in order to communicate radio signals. Arthur C. Clarke is often quoted as the inventor of satellite communications.

The first geostationary communications satellite, Anik 1 was a Canadian satellite launched in 1972. The United States launched its geostationary satellites for communications and then, withWestern Union began Vigan 1 satellite in 1974, and RCA Americom (later GE Americom, now SES Americom) has launched Satcom 1 in 1975.
E 'was Satcom 1 that was instrumental to help cable television, as anticipated WTBS (now TBS Super Station), HBO, CBN (now ABC Family), and The Weather Channel has been a success, because these channels distributed their All local television programming at the head end of the cable via satellite. Furthermore, it was the first satellite used by broadcastnetwork in the United States as ABC, NBC, CBS and distribute their programs for all their local affiliate stations. The reason is that Satcom 1 was so widespread that it had twice as many communication skills Maldives 1 (24 transponders, unlike Vigan 1's 12), which led to lower costs transponder used.

In 2000, Hughes Space and Communications (now Boeing Satellite Systems) has produced nearly 40 percent of satellites in use around the world. Other major satellitesmanufacturers include Space Systems / Loral, Lockheed Martin (formerly owned by RCA Astro Electronics / GE Astro Space Affairs), Northrop Grumman, Alcatel Space and EADS Astrium.

(b) low-earth orbit satellites in low earth orbit is typically a circular orbit about 150 kilometers above the Earth's surface, and then a period (the time to rotate around the Earth) in about 90 minutes. Because of their low altitude of these satellites are visible only within a radius of about 1000km sub-satellite point. Moreover, satellites in low orbit changed their position on the position on the ground quickly. Thus, even for local programs, a large number of satellites are needed if the mission requires uninterrupted connectivity.

Earth orbiting satellites are cheaper position in the space of geostationary satellites, and because of their approach closer to the ground, require lower signal strength. There is a trade-offbetween the number of satellites and their cost. There are important differences in the board and ground equipment to support two types of tasks.

A group of satellites working in concert, this is known as a satellite constellation. Two constellations as for the determination of the transaction were maintained telephony, particularly in remote areas, were the Iridium and Globalstar. Iridium system has 66 satellites. Another constellation of LEO satellites, with the supportMicrosoft entrepreneur Paul Allen, was to have up to 720 satellites. E 'can also stop offering coverage of a satellite in low Earth orbit is able to store the data received, while you have more than one part of the land and submitted at a later time, while the other half used. Will be the case with the current system of satellite communications in Canada Cassiope.

(c) Molniya satellites: As mentioned, geostationary satellites are required to work overtimeEquator. As a result, are not always suitable for the provision of services at high latitudes: at high latitudes for a geostationary satellite may appear low in the company (or even below) the horizon, and that's causing multipathing (interference caused by signals reflected from land to land the antenna). The first satellite of Molniya series was 23 April 1965 and began transmitting experimental television uplink signals from Moscow, which is used to downlink stationsLocated in the Russian Far East, Khabarovsk, Magadan and Vladivostok. In November 1967 the Soviet engineers have a unique system of a national television network of satellite television, called the recent changes on the basis of Molniya satellites.

Molniya orbits can be substituted in these cases. Molniya orbit is highly tilted in order to ensure good elevation over selected points in the northern part of the circuit. (Height above sea level, the magnitude of the position of the satellite is overhorizon. So a satellite on the horizon is zero elevation and a satellite directly overhead has elevation of 90 degrees). Furthermore, the Molniya orbit is designed so that the satellite, the vast majority of his time northern latitudes, where its footprint on the ground moves only slightly used. Its period is half a day, so that the satellite is available for operation in the targeted region for eight hours every second revolution. In this way, a constellation of threeMolniya satellites (plus in-orbit spare) capable of providing continuous coverage.

Molniya satellites are typically used for telephony and television services in Russia. Another use is to use for mobile telephone systems (even at lower latitudes) as vehicles traveling through the city have access to satellites that have a high water to ensure good connectivity, for example in the presence of tall buildings.

Satellite applications

(a) Application: One of the largestusing a communication satellite is in the provision of long distance telephone services. The connection uses Frequency Division Multiple Access (FDMA) or Time Division Multiple Access (TDMA), respectively. Telephone subscribers through a network of professionals in satellite earth stations for satellite uplink traffic for further processing of new connections online.

(b) Television and radio: There are two types of satellites used for televisionand radio:

(i) Direct Broadcast Satellite (DBS): a direct broadcast satellite, a communication satellite that transmits to small DBS satellite dishes (usually 18 "to 24" in diameter). Direct broadcast satellites generally operate in Ku-band high. DBS technology is used for DTH-oriented (Direct-to-Home) satellite television services like DirecTV and Dish Network in the United States, Expressvu in Canada, and Sky Digital in the UK.

(ii) a fixed-satellite service(FSS): Use C-band and the lower parts of the Ku-band. They are normally used to transmit feeds to and from television networks and local affiliate stations (such as program feeds for network and distributed programming, film, and backhaul), as it is used for training distance in schools and universities, business TV (BTV), video conferencing, and general telecommunications. FSS satellites are also used to distribute national cable channels to cablehead ends. FSS satellites differ from DBS satellites in that they have a lower RF power to the latter requires a much larger scale for the reception (3 to 8 meters in diameter for the Ku band and 12 meters to up to C-band) . FSS satellite technology was also originally used for DTH satellite television from 1970 until the end of 1990 beginning in the United States in the form of Tvro (TV Receive Only) receivers and dishes (also known as the large bowl or more derogatory call great satellite antenna systems ugly). Was alsoused in the Ku-band to form the now defunct first satellite TV service Star.

(c) the technology mobile satellite initially available for transmission to stationary TV receivers in 2004 popular mobile applications for direct transmission to their appearance, with the arrival of two satellite radio systems in the United States: Sirius and XM Satellite Radio Holdings. Some manufacturers also have a special antenna for mobile reception of DBS television. Using GPS technology as aof reference, these antennas automatically re-target the satellite, regardless of where or how the vehicle (where the antenna is mounted on) is located. These mobile satellite antennas are very popular with some owners of recreational vehicles. Such mobile DBS antennas are also used by JetBlue Airways for DirecTV (supplied by a LIVETV, a subsidiary of JetBlue), which could see the passengers on board on LCD screens mounted in the seats.

(d) Amateur: amateur radio operators have access to an Oscarsatellites that were designed specifically for the transportation of traffic of ham radio. Most satellites operate as a repeater to organize space and are generally accessible by amateurs equipped with UHF or VHF equipment and highly directional antennas like yagi antennas or satellite dishes. Due to limitations of soil amateur equipment, most amateur satellite was launched into earth orbit low enough, and is designed to handle a limited number of short contacts in a given time. A bit 'ofsatellites, data transmission service based on X.25 or similar protocols provided.

Broadband services via satellite: In recent years the technology of satellite communications as a means to access the Internet via broadband connections. It 'very useful for users of proof, which is in a very isolated areas, and have access to a provider of fixed telephony and dial-up is not.

Countries with a capacity to launch satellites

This list includes counties with aindependent capacity of satellites in orbit, including the production of the necessary launch vehicle. Many other countries have built satellites, together with the help of others, has launched. The ability of French and British are now integrated into the European Union under the ESA.

First launch of the country

Country Year of first launch first satellite

Russia 1957 "Sputnik 1"

United States in 1958 "Explorer1 "

France 1965 "Marius"

Japan 1970 "Osumi"

China 1970 "Dong Fang Hong I"

United Kingdom 1971 Prospero X-3 "

The European Union 1979 "Ariane-1"

India 1980 "Rohini"

Israel 1988 "Ofea 1"

Iran 2005 "Sina 1"

In 1998, he argued that North Korea, that a lota satellite, but has never been confirmed, and many believe is a cover for trying to launch Taepodong-1 missile over Japan (see Kwangmyongsong).

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