Transponder and TT&C Functions

Question 1

Advantage/Disadvantage of Earth Coverage Beams

Answer 1

Advantage:
Large footprint. Covers 1/3 of the earth

Disadvantage:
Does not cover polar regions

Question 2

Advantage/Disadvantage of Multi-Beam Arrays

Answer 2

Advantage:
More resistant to jamming, as individual elements can be turned on and off

Disadvantage:
Smaller footprint = smaller number of users able to access the satellite

Question 3

Advantage/Disadvantage of Fixed-Spot Beams

Answer 3

Advantage:
More resistant to jamming since footprint is smaller and power is higher

Disadvantage
Cannot follow mobile forces

Question 4

Advantage/Disadvantage of Steerable Spot Beams

Answer 4

Advantage:
Can follow mobile forces

Disadvantage:
Smaller footprint = smaller number of users able to access the satellite

Question 5

Advantage/Disadvantage of Phased Array

Answer 5

Advantage:
Flexibility in beam configuration

Disadvantage:
Complex design and costly

Question 6

What are the functions of TT&C?

Answer 6

1. Telemetry
   State of health of bus and subsystems
2. Tracking
   Used by operators to precisely determine a satellite’s orbit
3. Command
   How the satellite can be reconfigured in response to RF signals from the ground

Question 7

What is the Downlink Footprint?

Answer 7

The transmission path from a satellite to Earth stations

Question 8

What is the Uplink Footprint?

Answer 8

The transmission path from an Earth station to a satellite

Question 9

What are the two channelizing techniques?

Answer 9

Fan-in and Fan-out

Question 10

What is a Transponder?

Answer 10

A series of interconnected units forming a single communication channel between the receiver and transmit antennas

Transponders are a communication path or “channel” rather than a specific piece of equipment