(SEM VI) THEORY EXAMINATION 2024-25 SATELLITE COMMUNICATION

BEC061 – SATELLITE COMMUNICATION

Time: 3 Hours | Max Marks: 70

SECTION A – Short Answer Questions

(2 × 7 = 14 marks | Attempt ALL)
Write definition + formula/diagram where applicable

a. Sun Synchronous Orbit

A sun synchronous orbit is a near-polar orbit in which the satellite passes over any given latitude at the same local solar time every day.
Used for remote sensing and weather satellites.

b. Kepler’s Second Law

The line joining a satellite and the earth sweeps equal areas in equal intervals of time.
 Satellite moves faster near perigee and slower near apogee.

c. Sun Transit Outage

Sun transit outage occurs when the sun aligns with the satellite and earth station antenna, causing severe interference and signal loss.                     Happens twice a year for GEO satellites.
(Draw neat alignment diagram)

d. Earth Station Parameters Affecting C/N Ratio            Antenna gain

System noise temperature                                             Receiver noise figure

Atmospheric losses

e. Noise Figure = 4 dB, Find Equivalent Noise Temperature

F=10(4/10)=2.51F = 10^{(4/10)} = 2.51F=10(4/10)=2.51 Te=(F−1)×T0=(2.51−1)×290=437.9 KT_e = (F - 1) \times T_0 = (2.51 - 1) \times 290 = \mathbf{437.9\ K}Te​=(F−1)×T0​=(2.51−1)×290=437.9 K 

f. GPS Block Diagram                                             Main blocks:

Space segment (satellites)                                     Control segment

User segment (receiver)                                        (Block diagram compulsory)

g. Space X Launch System

SpaceX uses reusable launch vehicles like Falcon 9 and Falcon Heavy, reducing launch cost and improving mission efficiency.

SECTION B – Medium Answer Questions

(7 × 3 = 21 marks | Attempt ANY THREE)

a. Space Qualification & Space Debris

Space Qualification: Testing components for vibration, vacuum, radiation, and thermal extremes

Space Debris: Non-functional satellites and fragments posing collision risks

b. Argument of Perigee, Mean Anomaly & True Anomaly

Argument of Perigee (ω): Angle from ascending node to perigee

Mean Anomaly (M): Time-based angular position

True Anomaly (ν): Actual angular position of satellite

c. TT & C System

TT (Telemetry & Tracking): Collects satellite health data

C (Command): Sends control commands to satellite
Essential for satellite operation and control.

d. VSAT & Distinguishing Features

VSAT (Very Small Aperture Terminal) is a small earth station used for data communication.

Features:                                                                   Small antenna size

Low power                                                                 Star/mesh topology

Used in banking, education, remote areas

e. Satellite Launch Sequence                                     Lift-off

Stage separation                                                       Parking orbit

Transfer orbit                                                            Final orbit insertion

SECTION C – Attempt ANY ONE

(7 marks)

a. Elements of Satellite Communication System         Information source

Transmitter                                                                  Earth station uplink

Satellite transponder                                                  Downlink

Receiver                                                                      (Draw complete block diagram)

b. LEO, MEO & GEO Orbits