What is a Non-Geostationary Orbit or NGSO?

What is a Non-Geostationary Orbit?

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Apr 24, 2023


Non-Geostationary Orbit (NGSO) refers to a type of orbit used by satellites in which the satellite is not stationary relative to the surface of the Earth. Instead, it orbits the Earth at a lower altitude than geostationary satellites and completes an orbit in a much shorter period of time.

Unlike geostationary satellites, which are located at a specific point in the sky relative to the Earth's surface, NGSO satellites are constantly moving across the sky. This can provide several advantages over geostationary satellites, such as the ability to provide better coverage for mobile satellite services, improve global connectivity, and offer more efficient use of the limited radio frequency spectrum.

There are several different types of NGSO orbits which include:

  • Low Earth Orbit (LEO): This is the closest NGSO orbit to the Earth's surface, with an altitude ranging from about 160 to 2000 kilometers. LEO satellites typically orbit the Earth once every 90 minutes or less and provide low-latency communications for applications such as broadband internet access, remote sensing, and Earth observation.
  • Medium Earth Orbit (MEO): MEO satellites have an altitude ranging from about 2000 to 36,000 kilometers and orbit the Earth once every few hours. MEO satellites are commonly used for navigation systems like GPS, GLONASS, and Galileo.
  • Highly Elliptical Orbit (HEO): HEO satellites have a highly elliptical orbit that takes them much further from the Earth's surface with an altitude of over 36000 km. HEO satellites are often used for applications such as weather monitoring, remote sensing, and communications.


Advantages of NGSO

Non-Geostationary Orbit (NGSO) satellites offer several advantages over geostationary orbit (GEO) satellites, including:

  • Improved coverage: NGSO satellites can provide better coverage for mobile satellite services and remote areas of the planet, whereas GEO satellites may not have a clear line of sight. With a constellation of NGSO satellites in orbit, coverage can be provided to any point on Earth without the need for expensive ground infrastructure.
  • Lower latency: NGSO satellites in low Earth orbit (LEO) orbit at a lower altitude than GEO satellites, which means that signals can travel a shorter distance to and from the satellite. This results in lower latency and faster communication speeds, which is particularly important for applications like video conferencing, online gaming, and other real-time applications.
  • Increased bandwidth: NGSO satellites can support higher bandwidth applications because they can use a broader range of radio frequencies. This is because the radio frequency spectrum is a limited resource and is often congested in GEO orbits due to the high number of satellites operating in this orbit.
  • Greater flexibility: NGSO satellites can be repositioned more easily than GEO satellites, which allows for greater flexibility in terms of coverage and service offerings. For example, NGSO satellites can be positioned to provide coverage for disaster areas, where terrestrial infrastructure may have been damaged or destroyed.
  • Reduced cost: NGSO constellations require fewer satellites than GEO systems to provide the same level of coverage and redundancy. This can lead to lower launch and operational costs, making NGSO systems more cost-effective in the long run.

Disadvantages of NGSO

While non-geostationary orbit (NGSO) satellites offer several advantages over geostationary orbit (GEO) satellites, they also come with some disadvantages, including:

  • Limited dwell time: NGSO satellites spend less time over any given area of the Earth's surface than GEO satellites, which can limit their usefulness for certain applications that require continuous monitoring or communication.
  • More complex tracking: Because NGSO satellites are constantly moving, they require more complex tracking and control systems to maintain their orbits. This can lead to higher development and operational costs.
  • Greater susceptibility to atmospheric drag: Satellites in LEO orbits are subject to atmospheric drag, which can cause their orbits to decay over time. This requires constant repositioning and reboosting of the satellites, which can be expensive and time-consuming.
  • More frequent handovers: As NGSO satellites move across the sky, they require more frequent handovers between ground stations, which can lead to interruptions in communication or data transmission.
  • Radio frequency interference: With a larger number of NGSO satellites orbiting the Earth, there is a greater risk of radio frequency interference between satellites and terrestrial communication networks. This can cause issues with signal quality and reliability.
  • Higher radiation exposure: NGSO satellites operate at lower altitudes than GEO satellites and are therefore exposed to more radiation from the Earth's Van Allen radiation belts. This can cause performance degradation or even failure over time.

Despite these challenges, NGSO satellites offer several key advantages over geostationary satellites in terms of coverage, bandwidth, and flexibility. As demand for high-speed internet access, navigation services, and other satellite-based applications continues to grow, NGSO satellites are likely to play an increasingly important role in the global communications infrastructure.