Overview
Non-geostationary satellite orbit systems, or non-GSO systems, use satellites that move relative to the Earth's surface. They include systems in low Earth orbit (LEO) and medium Earth orbit (MEO), often operating as constellations of multiple satellites to provide continuous coverage.
These systems can complement terrestrial networks by extending broadband and other communication services to rural and remote communities, users in motion, and locations where distance, terrain, infrastructure costs or disruption make conventional network deployment difficult. They can also support connectivity for aircraft and vessels beyond the reach of terrestrial networks.
Operating at lower altitudes than geostationary satellites can reduce signal delay. Advances in satellite design, manufacturing, launch services, antennas and user terminals have expanded the range of communications applications that non-GSO systems can support, including high-capacity broadband and Internet of Things services.
These opportunities depend on access to radio-frequency spectrum, along with effective coordination among satellite systems and other radiocommunication services through the International Telecommunication Union (ITU). The ITU Radio Regulations provide the international framework for using spectrum and associated satellite-orbit resources efficiently and for preventing harmful interference.
ITU Member States update this framework through the World Radiocommunication Conference (WRC), held every four years to address evolving technologies, spectrum requirements and regulatory issues. WRC-23 (Dubai, 2023) revised provisions affecting non-GSO systems, including rules on orbital tolerances, constellation deployment milestones, aggregate interference, earth stations in motion and inter-satellite links.
Studies ahead of WRC-27 (Shanghai, 2027) continue addressing space satellite-related issues associated with expanding non-GSO deployments, evolving mobile connectivity requirements and increasing global demand for spectrum and orbit resources.
Opportunities
Satellite systems can extend coverage across large geographical areas without being constrained by difficult terrain. They may offer an alternative or complement to terrestrial networks in sparsely populated areas where infrastructure investment can yield a lower return than in urban areas.
Non-GSO systems can support communications for:
- rural and remote communities;
- aircraft and ships travelling beyond terrestrial network coverage;
- high-capacity broadband services;
- Internet of Things applications; and
- services supporting intelligent transport, e-government, tele-education, digital health, logistics, energy and agriculture.
Lower orbital altitudes can reduce the distance travelled by radio signals. Constellations can therefore be designed to provide wide-area coverage while processing high volumes of data with lower delay than systems operating at geostationary altitude.
Advances in satellite manufacturing, launch services, antennas and terminal technologies have also supported the development of fixed-satellite service systems using frequencies above 30 GHz, including the 40/50 GHz frequency range.
Technical and operational considerations
Geostationary-satellite orbit (GSO) satellites operate at an altitude of approximately 36,000 kilometres and appear fixed relative to a point on the ground.
Non-geostationary satellite orbit (non-GSO) systems operate at lower altitudes than geostationary satellites. They include low Earth orbit (LEO) systems, which typically operate a few hundred to around 2,000 kilometres above Earth, and medium Earth orbit (MEO) systems, which operate at higher altitudes below geostationary orbit.
Because non-GSO satellites move relative to Earth, operators typically deploy multiple satellites, known as constellations, to provide continuous coverage. Advances in satellite manufacturing, launch services, antennas and user terminals have enabled increasingly large constellations capable of supporting high-capacity communications services worldwide.
The operation of large constellations can increase the complexity of spectrum sharing and interference management. Coordination must take account of interactions among multiple non-GSO systems, geostationary networks and other radiocommunication services.
Challenges
The rapid growth of non-GSO satellite systems presents regulatory, technical and operational challenges.
These include:
- Managing increasingly large satellite constellations and ensuring that regulatory records reflect actual deployment.
- Preventing harmful interference between non-GSO systems, geostationary-satellite orbit (GSO) networks and other radiocommunication services.
- Ensuring efficient and equitable use of radio-frequency spectrum and associated satellite-orbit resources.
- Balancing regulatory certainty with the operational flexibility needed to deploy, maintain and modify large constellations.
- Supporting the long-term sustainable use of spectrum and associated satellite-orbit resources as the number of satellite systems continues to grow.
Recent regulatory developments have sought to address some of these challenges through updated provisions on deployment milestones, orbital-tolerance transparency and aggregate interference management.
Policy and regulatory considerations
Radio-frequency spectrum is shared among satellite systems and many terrestrial and scientific services. The Radio Regulations include provisions intended to enable geostationary and non-geostationary systems to operate without causing harmful interference to one another.
Regulatory mechanisms must also balance:
- efficient use of spectrum and associated orbital resources;
- prevention of spectrum warehousing;
- effective coordination, notification and recording;
- operational flexibility for satellite systems;
- protection of existing services; and
- equitable access to spectrum and orbital resources.
Filings for non-GSO systems confirm rapid growth both in satellite numbers and system sizes, with some constellations now comprising tens of thousands of satellites.
The growth of constellations also raises wider questions about the long-term sustainability of space-based spectrum use and the associated usage of satellite orbits. ITU's radiocommunication mandate focuses on spectrum coordination and the prevention of harmful interference.
ITU's contribution
International regulations and spectrum coordination
The Radio Regulations establish the international framework governing the use of radio-frequency spectrum, including by satellite systems. Their provisions support the introduction of new radiocommunication applications while seeking to ensure efficient spectrum use and the protection of existing services.
Through advance publication, coordination, notification and recording procedures, administrations provide information on planned satellite networks and work to resolve potential interference with other systems. Relevant frequency assignments and their regulatory status are recorded in the Master International Frequency Register.
Constellation deployment milestones
WRC-19 adopted a milestone-based approach for the deployment of non-GSO systems in specified frequency bands and services. The mechanism requires systems subject to the relevant provisions to deploy 10 per cent of their constellation within two years after the end of the regulatory period for bringing the frequency assignments into use, 50 per cent within five years, and the full constellation within seven years.
The approach is intended to help ensure that the Master International Frequency Register reasonably reflects actual deployment. It also seeks to balance the prevention of spectrum warehousing, the functioning of coordination mechanisms and the operational requirements of non-GSO systems.
WRC-23 revised Resolution 35 and introduced post-milestone provisions addressing changes in deployment after a system has completed the milestone process.
Orbital tolerances and deployment information
WRC-23 adopted Resolution 8 on tolerances for specified orbital characteristics of non-GSO space stations in the fixed-satellite, broadcasting-satellite and mobile-satellite services. The resolution addresses differences between notified or recorded orbital characteristics and observed deployment parameters.
The framework requires administrations to provide deployment information in specified circumstances and establishes procedures where observed orbital parameters differ from previously declared parameters. The measures are intended to improve transparency and help the regulatory record reflect actual deployment.
Interference management
WRC-23 revised Resolution 76, which addresses the protection of geostationary fixed-satellite and broadcasting-satellite service networks from aggregate equivalent power flux-density produced by multiple non-GSO fixed-satellite service systems.
The Radio Regulations and associated resolutions also contain provisions for coordination, sharing and compatibility between non-GSO systems and other radiocommunication services.
Earth stations in motion and inter-satellite links
WRC-23 adopted provisions for aeronautical and maritime earth stations in motion communicating with non-GSO space stations in specified fixed-satellite service frequency bands.
The Conference also adopted provisions for inter-satellite service use in specified frequency bands, enabling links between satellites under the applicable regulatory and technical conditions.
Studies and international cooperation
ITU-R study groups carry out technical studies on spectrum sharing, compatibility and interference management. The results can support revisions to the Radio Regulations and the development of ITU-R Recommendations, Reports and Handbooks.
WRC-23 established or continued studies relevant to non-GSO systems, including:
- unauthorized operation of non-GSO earth stations;
- gateway earth stations transmitting to non-GSO systems;
- equitable access to specified fixed-satellite service frequency bands;
- low-data-rate non-GSO mobile-satellite systems;
- direct connectivity between mobile-satellite service space stations and IMT user equipment;
- aggregate interference affecting radio astronomy; and
- compatibility involving inter-satellite links.
Last update:
Oct 2026
