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[p][em]Satellites communicate by exchanging electromagnetic waves, either on the Earth’s surface or in space, hovering above a pole or orbiting us everyday. Communication doesn’t necessarily have to occur in the Radio spectrum. Your TV remote communicates with its set top box with infrared waves, while phones communicate with microwaves.[/em] [p]Satellites come in two types:[ol][li]Polar: These satellites hover over the poles and monitor the Earth while it rotates continuously beneath them, so that eventually the entire Earth is subject to their scrutiny, as they remain in the same place.[/li][li]Geosynchronous or Geostationary: These are attached to a particular location, as their rotation is synchronized with the Earth’s rotation. These are used to monitor or communicate with the receivers in a particular location.[/li][/ol][p]
[br][h2]Anatomy of a satellite[/h2][p]
[br][h3]Attitude control[/h3][ul][li]Satellites must take precise measurements from their place in orbit without wobbling. This is why they are regularly stabilized, which is called attitude control.[/li][li]Gyroscopic motion is utilized to stabilize the position of a satellite’s cameras and its orientation in space with respect to the object that it’s orbiting.[/li][/ul][h3]Body or Bus[/h3][p]The body of a satellite houses the necessary scientific equipment it possesses. It is designed specifically to carry them safely into space. Engineers must consider a number of different objectives while designing and developing the body.[ul][li]Anti-radiation materials that protect it from the Sun’s harmful UV radiation.[/li][li]The satellite must sustain a comfortable temperature for proper functioning and must conduct heat away from its equipment.[/li][/ul][h3]Communication[/h3][p]The circuits responsible for communication are known as the satellite’s transponders. A satellite communicates by either transmitting or receiving signals.[div][div][/div][/div][h4]Transmitter[/h4][p]The transmitter is a combination of many individual circuits.[p]
[br][ol][li]Power supply: To provide constant power to all the circuits in a transmitter for their functioning.[/li][li]Oscillator: The oscillator circuit generates a radio frequency signal, which is a sine wave of constant amplitude. This wave is known as the carrier, as it is later combined with the information to be transmitted and literally carries it on itself.[/li][li]Modulator: This circuit combines the carrier with the information to be transmitted by varying some parameter of the carrier, such as its amplitude or frequency.[/li][/ol][h4]Receiver[/h4][p]The receiver intercepts the transmitted EM wave and extracts the information inside it to be used. The receiver consists of circuits that mirror a transmitter’s individual circuits.[p]
[br][ol][li]Antenna: The antenna converges the radio waves through a reflector. The waves are further converged by foci, passing through twists and turns to finally reach the circuits where they are processed.[/li][li]Amplifier: As the signal travels through a medium, some of its energy is attenuated, which is why it’s amplified again at the receiver’s end.[/li][li]Tuner: The receiver receives multiple signals on a variety of frequencies from different transmitters. A tuner is used to listen to a particular signal that you want to hear.[/li][/ol][p]
[br][h3]Power source[/h3][p]A satellite needs to operate 365 days a year, 24/7, revolving and collecting data. The most readily available source for power is the Sun, but even the Sun is screened by the Earth during eclipses. This is why solar cells are accompanied by high-performance batteries.[h3]How does a satellite communicate?[br][/h3][p]Communication doesn’t necessarily have to occur in the Radio spectrum. Your TV remote communicates with its set top box with infrared waves, while phones communicate with microwaves. The selection of a particular portion of the electromagnetic spectrum depends on many factors, such as the size of antennae, distance between the two participating devices and the obstacles between them.[p]
[br][p]Waves undergo a phenomenon called diffraction, which makes them deviate and travel around an obstacle. Diffraction can only take place if a wave’s wavelength is comparable to the obstacle’s size. The large wavelengths of radio waves allow them to be easily diffracted around buildings and mountains. [br][h2]Bandwidth and Transmission[/h2][p]The radio spectrum comprises a range of frequencies on which information can travel. However, communication only occurs on specific frequencies set by The International Telecommunication Union based in Geneva, Switzerland. The frequencies are grouped together to form bandwidths. They can either be Narrow-band signals (kHz), which are used for limited services, such as paging and low-data communication, or Broadband signals (MHz), which are used for advanced communication, such as video transmission.[p]
[br][p]Satellites are extremely useful devices that help us comprehend the incomprehensible geography of our planet. Although satellites have lately gotten a bad reputation, as they allow nosy tech-giant advertising corporations and security organizations to keep us under constant surveillance and disrespect our privacy, they still connect us to people across the globe through our phone or computer screens, and help us reach those people by navigating us one turn at a time. [p][br][p]Source:- ScienceABC [br] |
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发表于 2019-04-24 20:27:05
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