About this previous year paper
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
| Orbit | Altitude | Advantages | Disadvantages |
|---|---|---|---|
| LEO | 500–2000 km | Low delay | Many satellites needed |
| MEO | 5000–20000 km | GPS orbits | Moderate delay |
| GEO | 35786 km | Fixed position | High delay |