Asatellite system employs many satellites that are spaced so that, from any point on the earth at any time, at least one satellite is on a line of sight, each in an orbit at an altitude of less than 1,000 miles.

Lower earth orbit

Explanation:

A low Earth orbit (LEO ) is an Earth-centered orbit with an altitude of 2,000 km (1,200 mi) or less (approximately one-third of the radius of Earth), or with at least 11.25 periods per day (an orbital period of 128 minutes or less) and an

eccentricity less than 0.25. Most of the manmade objects in outer space are in LEO. The altitude of an object in an elliptic orbit can vary significantly along the orbit. Even for

circular orbits , the altitude above ground can vary by as much as 30 km (19 mi) (especially for polar orbits ) due to the oblateness of Earth's spheroid figure and local topography. While definitions based on altitude are inherently ambiguous, most of them fall within the range specified by an orbit period of 128 minutes because, according to Kepler's third law , this corresponds to a semi-major axis of 8,413 km (5,228 mi). For circular orbits, this in turn corresponds to an altitude of 2,042 km (1,269 mi) above the mean radius of Earth, which is consistent with some of the upper altitude limits in some LEO definitions.