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Basic Principles of Satellite Basic Principles of Satellite HEO MEO GEO LEO Dr. Md. Mostafizur Rahman Professor Department of Electronics and Communication Engineering (ECE) Khulna University of Engineering & Technology (KUET) Contents of Presentation Section I What is Satellite Earth Station Basic Principles Operating Frequency Types of Satellite Orbits and its Types How is it Orbit Applications of Satellite Section II Bangobandhu Satellite 1 Prof. Dr. Md. Mostafizur Rahman, ECE, 2 KUET . A Satellite is a moon, planet or machine that orbits a planet or star. For example, Earth is a satellite because it orbits the sun. Likewise, the moon is a satellite because it orbits Earth. Usually, the word "satellite" refers to a machine that is launched into space and moves around Earth or another body in space. Satellite is an artificial object which is makes to rotate around the earth in order to collect the information and for communication. The satellite serves as a relay station between earth stations at different locations. Prof. Dr. Md. Mostafizur Rahman, ECE, 3 KUET . A satellite doesn't necessarily have to be a tin can spinning through space. The word "satellite" is more general than that: it means a smaller, space- based object moving in a loop (an orbit) around a larger object. The Moon is a natural satellite of Earth, for example, because gravity locks it in orbit around our planet. The tin cans we think of as satellites are actually artificial (human-built) satellites that move in precisely calculated paths, circular or elliptical (oval), at various distances from Earth, usually well outside its atmosphere. 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 Earth's Moon. Prof. Dr. Md. Mostafizur Rahman, ECE, 4 KUET . 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 Earth's Moon. Satellites are specifically made for telecommunication purpose. They are used for mobile applications such as communication to ships, vehicles, planes, hand -held terminals and for TV and radio broadcasting. They are responsible for providing these services to an assigned region (area) on the earth. The power and bandwidth of these satellites depend upon the preferred size of the footprint, complexity of the traffic control protocol schemes and the cost of ground stations. A satellite works most efficiently when the transmissions are focused with a desired area. Satellites antenna patterns play an important role and must be designed to best cover the designated geographical area (which is generally irregular in shape). Satellites should be designed by keeping in mind its usability for short and long term effects throughout its life time. Prof. Dr. Md. Mostafizur Rahman, ECE, 5 KUET Earth Station Earth Station (an Earth-based satellite dish) is a collection of equipment installed on the earth surfaces that enable communication work one or more Satellite. The earth station should be in a position to control the satellite if it drifts from its orbit it is subjected to any kind of drag from the external forces. Earth Station consists of 5 subsystem. (i) Antenna Subsystem (ii) Transmit Subsystem (iii) Receive Subsystem (iv) GCE Subsystem (v) Power Subsystem. Transmit Antenna Subsystem GCE (Transmit) Subsystem Subsystem Multiplexer Duplexer Receive GCE (Receive) Subsystem Subsystem De-Multiplexer GCE – Ground Control equipment DC Power to all Subsystem Power Subsystem AC Power Prof. Dr. Md. Mostafizur Rahman, ECE, 6 KUET Fundamental Principles 12 to 15 Transponder 22300 miles 22300 Earth station Earth station Terrestrial Link Terrestrial Link User User Prof. Dr. Md. Mostafizur Rahman, ECE, 7 KUET Operating Frequency Uplink and Downlink Frequency: For GEO satellite uplink frequency is 5.9 to 6.4 GHz. These frequencies are used for the earth transmitter to the satellite. The downlink frequencies are 3.7 to 4.2 GHz. These frequencies are used for the satellite transmitter to the earth station receiver. These are called (6 GHz/ 4GHz) There are satellites that operate at other frequency band such as; 14 GHz/11 GHz , 17 GHz/12 GHz and 30 GHz/21 GHz. The uplink transmitter power is nearly 25-110 W, while the downlink transmitter is nearly 5-8.5 W. The dc power requirements are supplied by solar cells. The operating band of the satellites are [C band (4-8 GHZ), X band (8-12.4 GHZ), Ku band (12.4 – 18 GHz) and Ka band (26.5 – 40 GHz)] Prof. Dr. Md. Mostafizur Rahman, ECE, 8 KUET Transponder The satellite has 12 to 15 transponders for separate channels having bandwidth of 36 MHz each. The whole satellite has a bandwidth of 500 MHz. As a relay station the satellite picks up the signal from an earth station at one location and sends it back to earth, where it can be received at location about halfway around the world. Transponder: A transponder is a combined receiver and transmitter. Uplink signals are received to be converted to downlink frequencies and then transmitted to the earth station receivers. The stage between the reception of the uplink signal and the transmission of downlink signal is called a transponder L. O Low noise down Duplexer Band Pass Low noise amplifier converter Filter at 6 GHz at Uplink signal Uplink Band Pass Duplexer TWTA Filter at 4 GHz at Downlink signal Downlink Fig. x Block diagram of a Transponder Prof. Dr. Md. Mostafizur Rahman, ECE, 9 KUET Types of Satellite In respect of nature there are two types Satellite : Natural : Moon, Earth Artificial or Man-made : Sputnik 1 (Russia, 1957), Explorer 1 (USA 1958), Asterix (France 1965), Ohsumi (Japan 1970), Dong Fang Hong (China 1970), Prospero (UK 1971), Rohini D1 (India 1980), Ofeg 1 (Israel 1988) Classified by Altitude : • Low Earth Orbit (LEO) Satellite [500 – 2000 km] • Medium Earth Orbit (MEO) Satellite [5000 – 15000 Km] • Geostationary (GEO) Satellite [35786 Km] • Highly Elliptric Orbit (HEO) Satellite Prof. Dr. Md. Mostafizur Rahman, ECE, 10 KUET Classified by Centric : • Geocentric Orbit : An orbit around the planet earth. Such as Moon, Artificial satellite • Heliocentric Orbit : An orbit around the sun. Such as : solar system, All planets, Comets, Asteroids • Areocentric Orbit : An orbit around the planet Mars. Such as : moon, Artificial satellite Scientific and Research Satellites : • Astronomical Satellite 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 • Earth observation satellites are satellites intended for non-military uses such as environmental monitoring, meteorology, map making etc. • Navigational satellites are satellites which use radio time signals transmitted to enable mobile receivers on the ground to determine their exact location Prof. Dr. Md. Mostafizur Rahman, ECE, 11 KUET • Killer Satellites are satellites that are designed to destroy enemy warheads, satellites, and other space assets. • Crewed spacecraft (spaceships) are large satellites able to put humans into (and beyond) an orbit, and return them to Earth. • Miniaturized satellites are satellites of unusually low masses and small sizes.[18] New classifications are used to categorize these satellites: minisatellite (500–100 kg), microsatellite (below 100 kg), nanosatellite (below 10 kg) • Reconnaissance satellites are Earth observation satellite or communications satellite deployed for military or intelligence applications. • Recovery satellites are satellites that provide a recovery of reconnaissance, biological, space-production and other payloads from orbit to Earth. • Space stations are artificial orbital structures that are designed for human beings to live on in outer space. A space station is distinguished from other crewed 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. • 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. Eccentricity Classifications of Satellites : • Circular Orbit , Elliptic Orbit (Geosynchronous transfer orbit, Geostationary transfer Orbit, Molniya Orbit), Tundra Orbit (Highly elliptic orbit) Prof. Dr. Md. Mostafizur Rahman, ECE, 12 KUET Orbits and its Type of Satellite The path in which satellite rotates around the earth is called orbit. Depending on the types of rotation the orbits are classified as ; • Equatorial Orbit • Polar Orbit Depending upon their height above the Earth, Orbits are classified as ; • Low earth Orbit (LEO) : 500 to 2000 Km, The period of rotation is 90-120 minutes, Polar Orbit, 90 degree with horizontal axis, Little LEO Below 1GHz, Big LEO-1-3 GHz, Broadband LEO-Broadband Internet access, Footprint-8000 Km diameter, Speed – 20000 to 25000 Km/h. Ex- Space Shuttle, Hubble Space Shuttle • Medium earth Orbit (MEO) : 5000-15000 Km (Position between two Van Allen Belts, Altitide:10000 Km, The period of rotation is 6 Hours. HEO MEO GEO LEO 35786 Km 5000-15000 Km Prof. Dr. Md. Mostafizur Rahman, ECE, 13 KUET Orbits and its Type of Satellite • Geostationary Orbit (GEO): 35786 Km, Radius : 42000 Km, Period : 24 hours, Equatorial Orbit. The period of rotation is 24 hours. 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). • Highly Elliptical Orbit (HEO) : HEO MEO GEO LEO Prof. Dr. Md. Mostafizur Rahman, ECE, 14 KUET Prof. Dr. Md. Mostafizur Rahman, ECE, 15 KUET How is Satellite Orbit . Most satellites are launched into space on rockets.
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