Intermediate Circular Orbit (ICO)

In satellite communications, an intermediate circular orbit (ICO) is a circular Earth-centered orbit at altitudes typically between about 10,000 km and 15,000 km above the Earth’s surface. ICOs were originally proposed for global mobile satellite systems as a compromise between LEO and GEO, offering reduced propagation delay compared with GEO while requiring fewer satellites than LEO constellations. ICO concepts typically employed orbital periods of several hours, resulting in end-to-end delays intermediate between LEO and GEO systems.

The term ICO is closely associated with the proposed ICO Global Communications system and is sometimes used interchangeably with MEO, although MEO is a broader classification that encompasses a wider range of orbital altitudes and is not restricted to circular orbits. While no large-scale ICO constellation entered full commercial service, the concept influenced later MEO navigation and communications system designs.