Telecommunications Satellite Communications 2 — Questions and Answers
Question 1: What is a VSAT (Very Small Aperture Terminal)?
- A satellite in low Earth orbit used for broadband
- A small ground-based antenna system for two-way satellite communications (Correct answer)
- A military frequency band allocation for satellite links
- A satellite modulation technique for high-throughput links
Correct answer: A small ground-based antenna system for two-way satellite communications
VSAT is a compact ground-based satellite terminal using dish antennas typically under 3 meters in diameter, enabling two-way satellite data, voice, and video communications.
Question 2: Which multiple access technique allocates satellite bandwidth dynamically based on actual user demand rather than fixed pre-assigned slots?
- FDMA (Frequency Division Multiple Access)
- TDMA (Time Division Multiple Access)
- DAMA (Demand Assigned Multiple Access) (Correct answer)
- CDMA (Code Division Multiple Access)
Correct answer: DAMA (Demand Assigned Multiple Access)
DAMA assigns satellite capacity on demand in real time, improving efficiency by only allocating bandwidth when users actually need it rather than reserving fixed portions.
Question 3: SpaceX's Starlink broadband internet service uses which type of satellite constellation?
- GEO (Geostationary Earth Orbit)
- MEO (Medium Earth Orbit)
- LEO (Low Earth Orbit) (Correct answer)
- HEO (Highly Elliptical Orbit)
Correct answer: LEO (Low Earth Orbit)
Starlink operates a LEO constellation at approximately 550 km altitude, enabling low-latency broadband internet coverage with thousands of satellites.
Question 4: What is 'rain fade' in satellite communications?
- Signal loss caused by solar flare interference
- Attenuation of satellite signals by precipitation in the atmosphere (Correct answer)
- Antenna misalignment caused by wind during rainstorms
- Increased noise from moisture absorption in ground equipment
Correct answer: Attenuation of satellite signals by precipitation in the atmosphere
Rain fade is the attenuation of satellite signals by rain, snow, or ice in the atmosphere, where water droplets absorb and scatter microwave energy, and it is most severe at Ku and Ka bands.
Question 5: The 'footprint' of a communications satellite refers to:
- The physical dimensions of the satellite body in orbit
- The geographic area on Earth that the satellite's signal can cover (Correct answer)
- The total frequency bandwidth the satellite's transponders use
- The satellite's ground track as it moves through its orbit
Correct answer: The geographic area on Earth that the satellite's signal can cover
A satellite's footprint is the geographic region on Earth's surface within range of the satellite's antenna beams where ground stations can send and receive signals.
Question 6: GPS (Global Positioning System) satellites orbit Earth in which orbit type?
- LEO (Low Earth Orbit) at ~550 km
- MEO (Medium Earth Orbit) at ~20,200 km (Correct answer)
- GEO (Geostationary Orbit) at ~35,786 km
- HEO (Highly Elliptical Orbit) at variable altitudes
Correct answer: MEO (Medium Earth Orbit) at ~20,200 km
GPS satellites operate in MEO at approximately 20,200 km altitude with a 12-hour orbital period, providing global coverage while remaining in range of ground receivers.
Question 7: What is the primary purpose of the beacon signal continuously transmitted by a communications satellite?
- To carry commercial customer data traffic
- To allow earth stations to locate, track, and align their antennas (Correct answer)
- To broadcast meteorological and weather data to subscribers
- To relay telemetry data between satellite control centers
Correct answer: To allow earth stations to locate, track, and align their antennas
A satellite beacon is a continuous carrier signal used by earth stations as a reference to find the satellite in the sky and maintain accurate antenna pointing alignment.
Telecommunications Satellite Communications 2
What is a VSAT (Very Small Aperture Terminal)?