6.5 Special features of non-GSO (NGSO) satellite systems
6.5.1 Introduction
There are many non-GSO satellite systems which have been operational for over three decades,
performing special functions and services such as weather observations, remote earth exploration,
radionavigation, communications, surveillance, etc. One of the unique features of these satellites is
the ability to view the entire Earth's surface periodically from a single satellite. If simultaneous
viewing of the Earth is required, a number of satellites can be employed depending on their orbit
altitude. These systems include 1) low-Earth orbit (LEO) satellites such as several weather satellite
systems; 2) medium-Earth orbit (MEO) satellites; and 3) high-Earth orbit (HEO) satellites such as
the navigational satellites GPS and GLONASS. The MOLNIYA satellite system uses a highly
elliptical orbit to provide coverage in latitude of 60-70°. A description of the characteristics of a
range of non-GSO orbits is provided in section 6.1.
This section and Appendix 6.1 provide technical descriptions of some newly conceived and
developed non-GSO fixed-satellite service communication systems which have created a great deal
of interest in industry circles and the ITU Radiocommunication Sector.