Unlike the geosynchronous satellites, which hover about the equator at an altitude of 35, 900kilometers ( 22,300 miles), the Iridium constellation of 66 satellites are in polar orbitalorbital an altitude of only 780 kilometers (485 miles). The LEO orbital configuration provides the following benefits over systems based on other orbital configurations: no significant transmission delays, small, handheld pagers and phones, (versus laptop-size terminals), lower transmit power resulting in longer battery life and complete global coverage . This includes all oceans and all land areas including the Poles.
The Iridium system is predicated upon line-of-sight access to the satellite. In-building coverage for handsets is generally not available. The Iridium pager provides a better means of receiving messages in urban locations and can be used inside buildings. Callers who are unable to reach the subscriber on an Iridium handset for any reason will have the option of leaving a message. The message will be delivered the next time the handset has line-of-site access to the satellite constellation.
The Iridium system provides true global communications coverage including oceans, and all land areas including the Poles. The Iridium system blankets the Earth, connecting global satellite coverage with local ground-based wireless services.