Satellite Communications Technologies & Systems Flashcards

What is the primary function of a satellite transponder?

Answer: Processes and relays communication signals

A satellite transponder is a crucial component that receives incoming signals from Earth, amplifies them, and then retransmits them back to Earth at a different frequency. Its primary function is to process and relay communication signals, acting as a repeater in space. This enables long-distance communication, broadcasting, and data transmission across vast geographical areas.

What does GEO stand for in satellite communications?

Answer: Geostationary Earth Orbit

In satellite communications, GEO stands for Geostationary Earth Orbit. Satellites in this orbit revolve around the Earth at the same rate as the Earth's rotation, making them appear stationary from the ground. This characteristic allows ground antennas to remain fixed, providing continuous and reliable communication coverage to a specific region.

What is a key advantage of using LEO satellites?

Answer: Lower latency and faster data transmission

A key advantage of using Low Earth Orbit (LEO) satellites is their significantly lower latency and faster data transmission speeds compared to geostationary satellites. Because LEO satellites orbit much closer to Earth, the signal travel time is greatly reduced. This makes them ideal for applications requiring real-time communication, such as internet services and voice calls, where minimal delay is crucial.

What type of antenna is commonly used in satellite ground stations?

Answer: Parabolic dish

Parabolic dish antennas are commonly used in satellite ground stations due to their ability to efficiently focus radio waves into a narrow beam for transmission and to collect weak signals from distant satellites. Their curved shape concentrates incoming signals to a single focal point, maximizing signal strength and minimizing interference. This design is essential for reliable long-distance satellite communication.

Which frequency band is commonly used for satellite television broadcasts?

Answer: Ku-band

The Ku-band (K-under band) is a widely used frequency band for satellite television broadcasts and other communication services. Its higher frequency allows for smaller dish antennas on the ground, making it convenient for residential and commercial installations. While susceptible to rain fade, its broad bandwidth and availability make it a popular choice for direct-to-home TV and data links.

What is meant by 'uplink' in satellite communications?

Answer: Sending signals from Earth to the satellite

In satellite communications, 'uplink' specifically refers to the transmission of signals from a ground station on Earth up to a satellite in orbit. This is the initial leg of a two-way communication link, where data or commands are sent from the ground. It is distinct from the 'downlink,' which is the transmission from the satellite back to Earth.

Which component manages satellite orientation in space?

Answer: Attitude control system

The Attitude Control System (ACS) is a critical component responsible for maintaining a satellite's desired orientation and position in space. It uses sensors to detect the satellite's attitude and actuators (like thrusters or reaction wheels) to make precise adjustments. This ensures that antennas are pointed correctly for communication and scientific instruments are aimed accurately.

What challenge is associated with satellite latency?

Answer: Delays in transmission due to distance

Satellite latency is primarily caused by the immense distances signals must travel from Earth to the satellite and back, even at the speed of light. For geostationary satellites, this round trip can introduce a delay of over 500 milliseconds. This inherent delay in transmission due to distance can impact real-time applications like voice calls or online gaming.

Which orbit allows satellites to cover polar regions?

Answer: Polar orbit

A polar orbit is an orbit in which a satellite passes over or nearly over both the North and South Poles on each revolution. This unique trajectory allows satellites to provide comprehensive coverage of the Earth's polar regions, which are typically not covered by geostationary or equatorial orbits. It is crucial for applications like Earth observation and weather monitoring in high latitudes.