SSPI Satellite Network Design & Operations 4 — Questions and Answers
Question 1: What does the term 'figure of merit' (G/T) represent in satellite earth station performance?
- The ratio of antenna gain to system noise temperature, indicating receive sensitivity (Correct answer)
- The ratio of transmit power to antenna size
- The ratio of uplink frequency to downlink frequency
- The ratio of modulation efficiency to coding overhead
Correct answer: The ratio of antenna gain to system noise temperature, indicating receive sensitivity
G/T (dB/K) quantifies how effectively an earth station receives weak satellite signals, combining antenna gain and total noise temperature.
Question 2: Which orbital regime do most broadband LEO constellation satellites (e.g., Starlink, OneWeb) operate in?
- 200-400 km altitude
- 500-1,200 km altitude (Correct answer)
- 2,000-10,000 km altitude (MEO)
- 35,786 km altitude (GEO)
Correct answer: 500-1,200 km altitude
Modern LEO broadband constellations typically operate at 500-1,200 km to balance low latency, coverage, and atmospheric drag.
Question 3: What is the primary function of a satellite's attitude control system (ACS)?
- To maintain the satellite's antennas and solar panels in their correct orientations (Correct answer)
- To regulate transponder power output levels
- To manage propellant flow to station-keeping thrusters
- To encode and decode telemetry data streams
Correct answer: To maintain the satellite's antennas and solar panels in their correct orientations
The ACS keeps the satellite properly oriented so antennas point toward Earth and solar panels face the Sun for power generation.
Question 4: In satellite frequency coordination, what is a 'coordination arc'?
- The portion of the geostationary arc within which other operators must coordinate frequency use with a given satellite (Correct answer)
- The arc traced by a satellite during an eclipse period
- The angular range over which an earth station antenna can track satellites
- The frequency range allocated to a specific orbital slot
Correct answer: The portion of the geostationary arc within which other operators must coordinate frequency use with a given satellite
The coordination arc defines the range of GSO orbital positions whose satellites could cause harmful interference and therefore require ITU coordination.
Question 5: What is the key design challenge when implementing inter-satellite links (ISLs) in a LEO constellation?
- Pointing and tracking fast-moving neighbor satellites while maintaining sufficient link margin (Correct answer)
- Obtaining ITU frequency assignments for GEO interference coordination
- Managing rain fade attenuation on ISL paths
- Synchronizing multiple geostationary orbital slots
Correct answer: Pointing and tracking fast-moving neighbor satellites while maintaining sufficient link margin
LEO ISLs require precise, rapidly-updated pointing mechanisms because neighboring satellites move relative to each other at high angular rates.
Question 6: Which parameter describes the amount of satellite transponder power consumed per unit of bandwidth and is used in link budget calculations?
- Power Spectral Density (PSD) (Correct answer)
- Effective Isotropic Radiated Power (EIRP)
- Back-off level
- Noise Power Density (N0)
Correct answer: Power Spectral Density (PSD)
PSD (dBW/Hz) describes how the satellite's transmitted power is distributed across frequency, directly impacting interference and link budget calculations.
Question 7: What is the primary purpose of a satellite's omni-directional antenna used during early orbit operations?
- To provide wide-angle TT&C coverage regardless of satellite attitude before deployment of main reflectors (Correct answer)
- To serve broadband users during normal operations
- To provide frequency diversity for rain fade mitigation
- To receive GPS navigation signals for orbital determination
Correct answer: To provide wide-angle TT&C coverage regardless of satellite attitude before deployment of main reflectors
Omni-directional antennas ensure reliable TT&C contact during the critical early orbit phase when the satellite's attitude may not yet be fully controlled.
SSPI Satellite Network Design & Operations 4
What does the term 'figure of merit' (G/T) represent in satellite earth station performance?