satellite communication

Satellite Communication: 

Satellite Communication

Group Members :: 

Group Members : Nikhil Bhavsar Yogesh Pawar Chetan Shewale

What are Communication Satellites?: 

What are Communication Satellites? A satellite is an object that orbits another large object like planet. A communication satellite is a station in space that is used for telecommunication, radio and television signals. The first satellite with radio transmitter was in 1957 .

Why Use Satellite?: 

Why Use Satellite? Satellite communication is just one example of wireless communication systems. Familiar examples of wireless systems are all around us, such as radio and television broadcasting and mobile and cordless telephones. These systems rely on a network of ground-based transmitters and receivers and for this reason they are often referred to as "terrestrial" systems. One major use of satellites familiar to everyone is satellite television broadcasting. Other applications of satellite communications include high speed internet, telephony and corporate networks for multinational businesses.

INTRODUCTION: 

INTRODUCTION Satellite is a microwave repeater in the space. There are about 750 satellite in the space, most of them are used for communication. They are: Wide area coverage of the earth’s surface. Transmission delay is about 0.3 sec. Transmission cost is independent of distance.

HOW DO SATELLITES WORK: 

HOW DO SATELLITES WORK Two Stations on Earth want to communicate through radio broadcast but are too far away to use conventional means. The two stations can use a satellite as a relay station for their communication One Earth Station sends a transmission to the satellite. This is called a Uplink . The satellite Transponder converts the signal and sends it down to the second earth station. This is called a Downlink .

ADVANTAGES OF SATELLITE: 

ADVANTAGES OF SATELLITE The advantages of satellite communication over terrestrial communication are: The coverage area of a satellite greatly exceeds that of a terrestrial system. Transmission cost of a satellite is independent of the distance from the center of the coverage area i.e., cheaper over long distances. Satellite to Satellite communication is very effective.

DISADVANTAGES OF SATELLITE: 

DISADVANTAGES OF SATELLITE The disadvantages of satellite communication: Launching satellites into orbit is costly. Satellite bandwidth is gradually becoming used up. There is a larger propagation delay in satellite communication than in terrestrial communication

HOW SATELLITES ARE USED: 

HOW SATELLITES ARE USED Service Types Fixed Service Satellites (FSS) Example: Point to Point Communication Broadcast Service Satellites (BSS) Example: Satellite Television/Radio Also called Direct Broadcast Service (DBS). Mobile Service Satellites (MSS) Example: Satellite Phones

Types of Satellites : 

Types of Satellites Astronomical satellites are satellites used for observation of distant planets, galaxies, and other outer space objects. Communications satellites are artificial satellites 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 satellites.

Slide 11: 

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

Slide 12: 

Reconnaissance satellites are Earth observation satellite or communications satellite deployed for military or intelligence applications. Space stations are man-made 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 - instead, other vehicles are used as transport to and from the station. Space stations are designed for medium-term living in orbit, for periods of weeks, months, or even years.

Slide 13: 

Weather satellites are satellites that primarily are used to monitor the weather and/or climate of the Earth. Drag-free satellites are satellites that offers an environment that is as isolated as possible from the forces of nature. A properly designed drag-free-satellite proof mass is uncoupled from the rest of the Universe to a remarkable degree. Miniaturized Satellites are satellites of unusually low weights and small sizes. New classifications are used to categorize these satellites: minisatellite (500-200kg), microsatellite (below 100kg), nanosatellite (below 10kg).

SATELLIE ORBITS: 

SATELLIE ORBITS Satellite Orbits GEO LEO MEO MOLNIYA HAP

Geostationary Earth Orbit (GEO): 

Geostationary Earth Orbit (GEO) These satellites are in orbit 35,863 km above the earth’s surface along the equator. Objects in Geostationary orbit revolve around the earth at the same speed as the earth rotates. This means GEO satellites remain in the same position relative to the surface of earth.

GEO (cont.): 

GEO (cont.) Advantages A GEO satellite’s distance from earth gives it a large coverage area, almost a fourth of the earth’s surface. GEO satellites have a 24 hour view of a particular area. These factors make it ideal for satellite broadcast and other multipoint applications.

GEO (cont.): 

GEO (cont.) Disadvantages A GEO satellite’s distance also cause it to have both a comparatively weak signal and a time delay in the signal, which is bad for point to point communication. GEO satellites, centered above the equator, have difficulty broadcasting signals to near polar regions

Low Earth Orbit (LEO): 

Low Earth Orbit (LEO) LEO satellites are much closer to the earth than GEO satellites, ranging from 500 to 1,500 km above the surface. LEO satellites don’t stay in fixed position relative to the surface, and are only visible for 15 to 20 minutes each pass. A network of LEO satellites is necessary for LEO satellites to be useful

LEO (cont.): 

LEO (cont.) Advantages A LEO satellite’s proximity to earth compared to a GEO satellite gives it a better signal strength and less of a time delay, which makes it better for point to point communication. A LEO satellite’s smaller area of coverage is less of a waste of bandwidth.

LEO (cont.): 

LEO (cont.) Disadvantages A network of LEO satellites is needed, which can be costly LEO satellites have to compensate for Doppler shifts cause by their relative movement. Atmospheric drag effects LEO satellites, causing gradual orbital deterioration.

Medium Earth Orbit (MEO): 

Medium Earth Orbit (MEO) A MEO satellite is in orbit somewhere between 8,000 km and 18,000 km above the earth’s surface. MEO satellites are similar to LEO satellites in functionality. MEO satellites are visible for much longer periods of time than LEO satellites, usually between 2 to 8 hours. MEO satellites have a larger coverage area than LEO satellites.

MEO (cont.): 

MEO (cont.) Advantage A MEO satellite’s longer duration of visibility and wider footprint means fewer satellites are needed in a MEO network than a LEO network. Disadvantage A MEO satellite’s distance gives it a longer time delay and weaker signal than a LEO satellite, though not as bad as a GEO satellite.

Other Orbits: 

Other Orbits Molniya Orbit Satellites Used by Russia for decades. Molniya Orbit is an elliptical orbit. The satellite remains in a nearly fixed position relative to earth for eight hours. A series of three Molniya satellites can act like a GEO satellite. Useful in near polar regions.

Other Orbits (cont.): 

Other Orbits (cont.) High Altitude Platform (HAP) One of the newest ideas in satellite communication. A blimp or plane around 20 km above the earth’s surface is used as a satellite. HAPs would have very small coverage area, but would have a comparatively strong signal. Cheaper to put in position, but would require a lot of them in a network.

Applications: 

Applications Telephony - Fixed points < earth station> Satellite> earth station> fixed points. Televesion & Radio - e.g. Direct broadcast satellite (DBS) & Fixed service satellite (FFS). Mobile satellite technology - Special antenna called mobile satellite antenna. - No matter where or how this antenna is mounted on.

Applications: 

Applications Amateur radio - Access to OSCAR satellite . - Low earth orbits. Internet - High Speed. - Useful for far away places. Military - Uses geostationary satellites. - Example: The Defense Satellite Communications System (DSCS).

First Launching Of Satellites By Country :: 

First Launching Of Satellites By Country :

In Conclusion: 

In Conclusion Satellites remain the best utilization used for communications due to their speed and other advantages mentioned in this presentation.

Slide 30: 

Thank You…..!!!!!