Code: D-17                                 Subject: ELEMENTS OF SATELLITE COMMUNICATION

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 9 Questions in all.

· Question 1 is compulsory and carries 20 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.

· Any required data not explicitly given, may be suitably assumed and stated.

Q.1       Choose the correct or best alternative in the following:                                         (2x10)

a. The place where a line drawn from the centre of the earth to the satellite passing through earths surface is called as____________

(A)  subsatellite point.                          (B)  longitude point.

(C)   latitude point.                               (D)  All of the above.

b. The system which collects data from sensors of the space craft and sends to the controlling earth station is called _____________

(A) Tracking system                           (B)  AOCS system

(C)  Telemetry system                          (D)  Power system

             c.   The sun radiation falling on a spacecraft at geostationary altitude is __________

(A) .                             (B) .

(C) .                                 (D) .

             d.   Which multiple access technique is more suited to commercial satellite system.

                   (A)  TDMA.                                        (B)  CDMA.

(C)  FDMA.                                        (D) TDMA & FTDMA.

             e.   ___________ injects satellites from transfer orbit into Geostationary orbit.

(A) Apogee kick motor                      (B)  Perigee kick motor

(C)  STS                                             (D)  ELV

             f.    Most preferred modulation method in satellite communication is

(A) Frequency shift keying                  (B)  QAM

(C)  DPSK                                          (D)  BPSK

             g.   Figure of merit of Earth station is given by the ratio

(A) .                                          (B) .

(C) .                                       (D) .

             h.   Large earth station preferred antenna

(A) Front fed.                                     (B) Parabolic.

(C) Cassegrain.                                   (D) Spherical reflector.

             i.    The fartheist distance that a satellite orbit reaches from the earth surface is called

(A) Apogree.                                      (B) Perigee.

(C) Prograde.                                      (D) Retrograde.

             j.    The geographical presentation of a satellite antenna radiation pattern is called  

(A)  EIRP.                                           (B)  Foot print.

(C)  Look angle.                                  (D) SSP.

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Explain in detail about the ground segment of a satellite.                                    (10)

             b.   Write a note on Earth Station Antennas.                                                             (6)

Q.3           Write short notes on

(i) TDMA Technique.

(ii) QPSK Modulation and Demodulation Techniques.                   (16)

Q.4           How many subsystems are there in a spacecraft? Explain them in detail.            (16)

Q.5     a.   Explain in detail why 6/4 GHz communication is used in satellite communication systems?                (10)

b.   Explain the importance of G/T ratio in satellite link design.                                   (6)

  Q.6     a. Explain briefly Satellite stabilization & various techniques used for it.                    (7)

             b.   Write briefly on

(i) Various applications of satellites.

(ii) INMARSAT                                                               (6+3)

Q.7     a.   List the various advantages and disadvantages of satellite communications?          (8)

b.   Explain why for covering the entire globe continuously only 3 communications satellites are sufficient?                                                           (8)

Q.8     a.   What are the orbital parameters required to determine a satellite’s orbit? Name and explain them.                                                              (8)

             b.   What is the eclipse effects on the satellites?  Explain.                                           (8)

Q.9           Write short notes on

(i) Attitude control.

(ii) Frequency reuse.                                                                           

(iii) DAMA.

(iv) SCPC system.                                                                         (16)