SSPI Orbital Mechanics & Spacecraft Operations 2 — Questions and Answers
Question 1: What is station-keeping in satellite operations?
- Storing the satellite in a parking orbit before final deployment
- Performing periodic thruster burns to maintain the satellite's assigned orbital position (Correct answer)
- Turning off non-essential subsystems during eclipse periods
- Repositioning a satellite to a new orbital slot
Correct answer: Performing periodic thruster burns to maintain the satellite's assigned orbital position
Station-keeping involves regular thruster firings to counteract perturbations such as solar pressure and gravitational effects that cause drift from the assigned orbital slot.
Question 2: What is the approximate one-way signal latency from a ground station to a GEO satellite and back?
- 10–20 milliseconds
- 50–80 milliseconds
- 240–280 milliseconds (Correct answer)
- 500–600 milliseconds
Correct answer: 240–280 milliseconds
The round-trip distance to GEO (~71,572 km total) divided by the speed of light yields approximately 240–280 ms of propagation delay for a single hop.
Question 3: Which type of orbit is best suited for Earth observation satellites requiring consistent lighting conditions?
- Geostationary orbit
- Molniya orbit
- Sun-synchronous orbit (Correct answer)
- Highly elliptical orbit
Correct answer: Sun-synchronous orbit
Sun-synchronous orbits are designed so the satellite passes over any given point at the same local solar time each day, ensuring consistent illumination for imaging.
Question 4: What is the Molniya orbit primarily used for?
- Broadband internet coverage over the tropics
- High-latitude coverage where GEO satellites have low elevation angles (Correct answer)
- Real-time imaging of the entire Earth surface
- Deep space communications relay
Correct answer: High-latitude coverage where GEO satellites have low elevation angles
Molniya orbits have high inclinations (~63.4°) and high eccentricity, spending most of their ~12-hour period at high northern or southern latitudes, ideal for polar region coverage.
Question 5: What does the term 'apogee' refer to in orbital mechanics?
- The point in an orbit closest to Earth
- The point in an orbit farthest from Earth (Correct answer)
- The orbital altitude above the equator
- The satellite's ground track crossing point
Correct answer: The point in an orbit farthest from Earth
Apogee is the farthest point from Earth in a satellite's elliptical orbit; the satellite moves slowest at this point according to Kepler's second law.
Question 6: What is the graveyard orbit used for in satellite operations?
- A temporary parking orbit during launch vehicle separation
- A disposal orbit above GEO where end-of-life satellites are relocated (Correct answer)
- An orbit used for satellites awaiting regulatory approval
- A low-altitude orbit for satellite refueling operations
Correct answer: A disposal orbit above GEO where end-of-life satellites are relocated
The graveyard orbit is located a few hundred kilometers above the GEO belt and is used to dispose of satellites at end of life, freeing up GEO slots without re-entry risks.
Question 7: Which of the following best describes the Van Allen radiation belts and their significance for satellite operations?
- They are bands of concentrated solar wind that increase signal interference
- They are regions of trapped high-energy particles that can degrade satellite electronics (Correct answer)
- They are atmospheric layers that cause signal scintillation
- They are magnetic field anomalies that cause GPS errors
Correct answer: They are regions of trapped high-energy particles that can degrade satellite electronics
The Van Allen belts are toroidal zones of trapped energetic particles (electrons and protons) that pose radiation hazards to satellite components, particularly electronics and solar cells.
SSPI Orbital Mechanics & Spacecraft Operations 2
What is station-keeping in satellite operations?