IAS Mantra Series : Satellite Communication -3


Q.1. Why satellite communication is particularly useful in our country?
Ans.: Satellite communication offers a very cost-effective mode of communication in our country. For thin route remote area communication in the plains as well as hilly terrains like India’s North-East region, Himachal Pradesh, Ladakh, Sikkim etc. satellite communication is very useful. It is particularly useful for communication between the mainland and islands such as Andaman and Nicobar Islands.

Q.2 What is the advantage of satellite communication over fiber optic communications?
Ans.: Both of them are suitable for broadband communication. But the quality of transmitted signal and the locations of stations sending and receiving information are independent of distance in the case of satellite communication unlike fiber optic communications. Thus so long as two stations fall within the geographic coverage area of the satellite antenna pattern, those two stations maintain the same quality of information transfer whether they are 50 Kms or 2500 Kms apart.

Q3. : How does a communication satellite differ from a communication relay?

Ans.:1. The range of communication satellite is much higher than that of a communication relay. A communication satellite can cover a range of several thousands Kms.

2. A communication satellite uses different up-link and down-link frequencies unlike a communication relay, which uses same frequency.

Q4. What are the advantages of Microwave and Millimeter waves in satellite communication?

Ans.: The main advantages are (i) High receptivity (ii) Improved bandwidth. availability (iii) Leas fading effect and more reliability and (iv) transparency property.
Microwave and millimeter waves are highly directive and receptivity increases with frequency. Since the carrier frequency in this range is high it offers large bandwidth of modulating signals. At these frequencies the fading effect is less and hence communication is more reliable, Moreover, these frequencies can freely propagate though free space, through atmosphere and the ionosphere.
Q5. Why digital signal transmission is preferred in satellite communication?
Ans.: As in many other communication systems, digital signal transmission is preferred in satellite communication due to the following reasons.
1. Digital system offer the ease and efficiency of multiplexing multiple signals. It can handle digital messages in ‘packets’for convenient switching.
2. Digital circuits are relatively insensitive to re-transmission noise.
3. Digital signal transmission offers extremely low error rate and highly fidelity by using error detection and correction techniques.
4. There is flexibility of digital hardware implementation as it permits the use of microprocessors, digital switching, digital, signal processors (DSP) and very large scale integration (VLSI) devices.
5. Digital modulation and multiple access techniques can accommodate a large number of earth stations with a small loss in transponder capacity. Further increase in efficiency can be easily obtained with demand assignment and digital speech interpolation.
6. INSDN systems enhance the importance of digital communication networking with satellites.
7. Digital signal transmission offers communication privacy.
Q6. What do you mean of 6/4 GHz system in satellite communication?
Ans.: 6/4 GHz frequency band in satellite communications means the uplink frequency is in 6 GHz band and the down-link frequency is in 4GHz band.

Q7. Why 6/4 GHz band is most popular in satellite communication?
Ans.: 6/4 GHz band is most popular in satellite communication. The reasons are:
1. Rain attenuation is much less in this band as compared to other frequency bands, namely, Ku-band and Ka-band.
2. Sky noise is relatively low at down-link frequency of 4 GHz.
3. RF components and equipment are readily available and their costs are less in this band.
Q8. What is Van-Allen Radiation belt? How is it important in satellite communication?
Ans.: There is extremely large radiation in the space lying between altitudes of 200 Km and 10,000 Km. This region of space is known as Van-Allen Radiation belt.
In satellite communication, consideration of this belt is important because the satellite cannot be kept in this region. Otherwise, the satellite will be damaged if placed in this region. The satellite to be above or below this belt.

Q9. Mention some of the applications of satellites.
Ans.: There are many applications of satellite. Some of them are:
1. It is extensively used for providing long distance communication such as in television, telephony, data communications, e-mail, Internet etc. Direct-to-home (DTH) television and cable TV use satellite.
2. It has meteorological applications such as in weather forecasting, weather survey and study of different layers of the atmosphere and other scientific studies of the atmosphere.
3. It is widely used in remote sensing and earth observation such as in cartography (i.e., the technique of making maps), oceanography and monitoring agriculture and forestry.
4. It has military applications including surveillance, spying, providing strategic communication links navigational aids for ship and aircraft . Satellites are used for reconnaissance and intelligence gathering functions, nuclear detection and early warning purposes against a missile attack.
5. Satellite are being used for global positioning system (GPS), monitoring of oil pollution and air pollution, snow melts and oil and mineral exploration.

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