Satellite Orbits

Satellite orbits are chosen based on the mission objectives, required coverage, revisit times, and the operational environment. Certain orbits may require more frequent station-keeping or orbital adjustments, impacting overall mission costs and lifespan. Each orbit type is tailored to balance performance with practical constraints such as fuel efficiency, launch vehicle capability, and mission-specific needs. By understanding these factors, one can appreciate why satellites are deployed into particular orbits to best serve their intended applications.

Here are some common types of satellite orbits and their applications:

Low Earth Orbit (LEO)

  • Altitude ~160-2000 km
  • Applications: Earth observation, remote sensing, scientific experiments, and certain communications.
  • LEO satellites benefit from lower launch costs and shorter communication delays. They provide high-resolution imagery and fast revisit rates, ideal for monitoring weather, environmental changes, and disaster response.

Medium Earth Orbit (MEO)

  • Altitude ~2000-35786 km
  • Applications: Navigation systems (e.g., GPS, Galileo), telecommunications, and some scientific research.
  • MEO offers a compromise between orbital altitude and coverage. Navigation satellites in these orbits provide global positioning with improved accuracy and reduced signal delays compared to higher orbits.

Geostationary Orbit (GEO)

  • Altitude ~35786 km
  • Applications: Weather forecasting, broadcasting, and continuous communications.
  • A satellite in GEO remains fixed relative to a point on Earth, allowing constant coverage of the same area. This is critical for uninterrupted television signals, meteorological monitoring, and strategic communication services.

Highly Elliptical Orbit (HEO)

  • Altitude perigee ~< 600 km and apogee ~30,000 - 40,000 km
  • Applications: Coverage in high latitude regions (e.g., Molniya orbit), scientific studies of the Earth’s magnetosphere, and certain reconnaissance missions.
  • The elliptical nature of these orbits allows satellites to spend extended periods over specific regions (especially at apogee) where ground coverage is needed most, such as the polar areas.

Sun-Synchronous Orbit (SSO)

  • Altitude ~600-800 km
  • Applications: Earth observation and remote sensing, particularly for imaging applications.
  • Sun-synchronous orbits allow satellites to pass over the same part of the Earth at roughly the same local solar time, ensuring consistent lighting conditions. This uniformity is crucial for environmental monitoring, agricultural analysis, and mapping.