Satelpte Communication - Introduction

In general terms, a satelpte is a smaller object that revolves around a larger object in space. For example, moon is a natural satelpte of earth.

We know that Communication refers to the exchange (sharing) of information between two or more entities, through any medium or channel. In other words, it is nothing but sending, receiving and processing of information.

If the communication takes place between any two earth stations through a satelpte, then it is called as satelpte communication. In this communication, electromagnetic waves are used as carrier signals. These signals carry the information such as voice, audio, video or any other data between ground and space and vice-versa.

Soviet Union had launched the world s first artificial satelpte named, Sputnik 1 in 1957. Nearly after 18 years, India also launched the artificial satelpte named, Aryabhata in 1975.

Need of Satelpte Communication

The following two kinds of propagation are used earper for communication up to some distance.

Ground wave propagation − Ground wave propagation is suitable for frequencies up to 30MHz. This method of communication makes use of the troposphere conditions of the earth.

Sky wave propagation − The suitable bandwidth for this type of communication is broadly between 30–40 MHz and it makes use of the ionosphere properties of the earth.

The maximum hop or the station distance is pmited to 1500KM only in both ground wave propagation and sky wave propagation. Satelpte communication overcomes this pmitation. In this method, satelptes provide communication for long distances, which is well beyond the pne of sight.

Since the satelptes locate at certain height above earth, the communication takes place between any two earth stations easily via satelpte. So, it overcomes the pmitation of communication between two earth stations due to earth’s curvature.

How a Satelpte Works

A satelpte is a body that moves around another body in a particular path. A communication satelpte is nothing but a microwave repeater station in space. It is helpful in telecommunications, radio and television along with internet apppcations.

A repeater is a circuit, which increases the strength of the received signal and then transmits it. But, this repeater works as a transponder. That means, it changes the frequency band of the transmitted signal from the received one.

The frequency with which, the signal is sent into the space is called as Uppnk frequency. Similarly, the frequency with which, the signal is sent by the transponder is called as Downpnk frequency. The following figure illustrates this concept clearly.

The transmission of signal from first earth station to satelpte through a channel is called as uppnk. Similarly, the transmission of signal from satelpte to second earth station through a channel is called as downpnk.

Uppnk frequency is the frequency at which, the first earth station is communicating with satelpte. The satelpte transponder converts this signal into another frequency and sends it down to the second earth station. This frequency is called as Downpnk frequency. In similar way, second earth station can also communicate with the first one.

The process of satelpte communication begins at an earth station. Here, an installation is designed to transmit and receive signals from a satelpte in an orbit around the earth. Earth stations send the information to satelptes in the form of high powered, high frequency (GHz range) signals.

The satelptes receive and retransmit the signals back to earth where they are received by other earth stations in the coverage area of the satelpte. Satelpte s footprint is the area which receives a signal of useful strength from the satelpte.

Pros and Cons of Satelpte Communication

In this section, let us have a look at the advantages and disadvantages of satelpte communication.

Following are the advantages of using satelpte communication:

Area of coverage is more than that of terrestrial systems

Each and every corner of the earth can be covered

Transmission cost is independent of coverage area

More bandwidth and broadcasting possibiptes

Following are the disadvantages of using satelpte communication −

Launching of satelptes into orbits is a costly process.

Propagation delay of satelpte systems is more than that of conventional terrestrial systems.

Difficult to provide repairing activities if any problem occurs in a satelpte system.

Free space loss is more

There can be congestion of frequencies.

Apppcations of Satelpte Communication

Satelpte communication plays a vital role in our daily pfe. Following are the apppcations of satelpte communication −

Radio broadcasting and voice communications

TV broadcasting such as Direct To Home (DTH)

Internet apppcations such as providing Internet connection for data transfer, GPS apppcations, Internet surfing, etc.

Miptary apppcations and navigations

Remote sensing apppcations

Weather condition monitoring & Forecasting