Nowadays, if you want to communicate with your old friend who is present thousands of miles away. You just need to make a phone call. How good it is. In earlier days things were not easy as it seems now. Many inventors work to bring this technology to us. These innovations are not only limited to phone calls. As of now, we are using communication and tracking systems to connect the entire world. And it is being possible because of an object which is moving around the Earth, this is Satellite. The satellites are becoming a key that opens the door of communication to connect the worldwide people.
What is a Satellite?
The term satellite is more general than that means a smaller space-based object moving in a loop around a large object. A satellite does not necessarily have to be a mechanical object spinning through space. All of us know that the moon is a natural satellite of our planet and it is moving around the Earth due to gravitational forces. The mechanical objects, which are also moving into Earth orbit, are artificial or human-made satellites. We put satellites in space or Earth orbit to overcome the various geographical limitations of the Earth.
Types of Satellite:
We can categorize satellites based on their services like communication, climate change observation, and more. The three main uses of satellites are given below:
- Scientific surveying
- Navigation or tracking
The communication satellites provide communication links between several points on Earth. These satellites are using transponders to transmit and receive data from Earth. The communication satellite redirects data from one Earth station to another to cover the huge area. Typically, a communication satellite works when it receives data from terrestrial or Earth stations in the form of electromagnetic waves. The data is usually sent via huge size dish antennas. Most of the communication satellites are placed in geostationary Earth orbit. Based on the intended destination, communication satellites redirect the signal to the corresponding Earth stations. There are two vital components present in communication satellites Antenna and Transponder.
Communication satellite Antenna:
Satellite antennas are specifically engineered to concentrate the satellite’s transmitting power into a designed geographical location on Earth and also avoid interference from undesired signals transmitted from outside of the service area. Four main types of antennas are in use in most communication satellites, and these are Wire antennas, Horn antennas, Reflector antennas, and Array antennas.
Wire antennas were used on the initial operational satellites with having antenna gain about 4 dBi for signal reception and 9 dBi for signal transmission. These antennas can provide wide signal bandwidth so as of now they are mostly used in TTC (Telemetry, Tracking and Command) system.
Horn antennas have come under the category of simple directional antennas. Depending on their shape and size, there is a variety of horn antennas like pyramidal, sectoral, conical, multiflare, etc. The pyramidal and conical type horn antennas are easy to fabricate whereas they have some limitations. In those limitations, these antennas are not circularly symmetrical radiation patterns and this behavior reduces the efficiency of the antenna.
Reflector antenna is frequently used in communications satellites because of its simple structure and high gain. These antennas are having one or more reflective surfaces, which are paraboloid, hyperboloid, etc. Paraboloid reflector-based antenna consists of a single paraboloidal shaped reflector and a feed situated at the focus of the reflector. The feed may block some of the arriving waves and cause antenna gain to drop.
Communication satellite Transponder:
The transponder is a combination of signal transmitter and receiver. A satellite transponder is a transparent relay channel that connects the transmitting and receiving antennas for the purpose of communication. As we know, whenever there is a need to establish communication between two points it is required to send or receive signals. Communication satellite uses radio waves to cover a quite large area of Earth and it uses some specific frequency band ranges.
Satellite transponder performs below functions:
- Amplification of the received signal
- Frequency translation
Amplification of the received signal: Communication satellites are deployed far away from the Earth’s surface. So, whenever a radio signal is sent from the Earth station its strength got reduced due to atmospheric interference. The satellite receives this signal and boosts it at a significant level for further processing. Several electronic circuit boards are responsible for this boosting or amplification process.
Frequency translation: Communication satellite uses different frequency ranges for transmission and reception of radio signals. These satellites receive the signal from Earth stations at different frequency bands whereas transmits signal towards Earth stations at different frequency bands.
Today many developing countries are suffering from inadequate land information systems and it causes many obstacles to productivity and economic development. Satellites provide a technological breakthrough to offer some hope in reducing the analysis cost and improving the land information system. These technologies include remote sensing, satellite surveying by using satellite networks like GPS (Global Positioning System). Scientific surveying provides help to analyze the size and shape of different areas of the Earth with high accuracy. For example, by using satellite-based scientific surveys we can find the area and location of fertile land as well as terrain structure, and more.
Navigation or tracking:
Finally, today most of us are using GPS to enable several smart devices in our cars to get the correct driving direction. This becomes possible only because of the satellite navigation system. Satellite navigation is based on a global network of satellites that transmit radio signals from medium Earth orbit. The satellites in this orbit communicate with each other to provide the accurate positioning of any point on Earth.
Working of Satellite:
A satellite (human-made) is a self-contained communication system with the ability to receive signals from one Earth station and transmit those signals back to the other Earth stations. The reception and transmission of the signal are happening with the help of a transponder present at the satellite end. The communication system is the main component of a satellite which includes the antennas and transponder. Also, some other important components are the power system, which includes the solar panels that provide power, and the propulsion system, which contains a rocket to propel the satellite into the desired position of the Earth orbit.
A satellite, which has to operate continuously in the Earth’s orbit over its entire life span, needs internal power to the source to operate its entire electronic systems and communications payload. The main source of power is sunlight that is utilized by using solar panels. A satellite also contains backup batteries on board to provide power when the sunlight is blocked by other objects like Earth. These batteries are charged by the current generated by the solar panels when there is sunlight.
The entire circuitry and structure of a satellite are specially designed to operate in a wide temperature range — 150 °C (?238 °F) to 150 °C (300 °F). Also, these all are covered to prevent space radiation.
Satellites operate in three orbits:
Low Earth Orbit (LEO): These satellites are positioned at an altitude between 150 to 1500 Km (100 to 1000 miles) above Earth. To cover the entire Earth 20 or more than 20 LEO satellites are required.
Medium Earth Orbit (MEO): MEO satellites are positioned at 10,000 to 20,000 Km (6,300 to 12,500 mile) away from the Earth’s surface. 10 or more MEO satellites can cover the entire Earth.
Geostationary Earth Orbit (GEO): The GEO satellites are present at the highest altitude of the Earth’s orbit. These are present at 35,786 Km (22,236 miles) above the Earth’s surface where they complete their one rotation of the Earth in 24 hours. And because of this GEO satellites remain fixed over one spot with respect to Earth. Only Three GEO satellites can cover the entire Earth whereas we are using more than three satellites in GEO orbit to provide more precise and accurate data.
Satellite in earth orbit
Applications of Satellite:
The technology introduced various services that are being served by satellites today. Satellite provides various services to broadcasters, Internet service providers, Military intelligence, and other sectors. In the case of communication services, we will find that satellite is providing three types of communication – telecommunications, which includes telephone-related service, broadcasting, which includes radio and television services, and data communication that is transferring data from one point to another point.
Thanks for reading. See you soon with another exploration!
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