Iridium is a global wireless digital communication system based on a constellation of 66 Lockheed-built communications satellites (plus six on-orbit spares) in 780-kilometer-high orbits inclined at 86.6° to the equator. Begun in 1997, Iridium was the first commercial satellite system to operate from low Earth orbit. Named because the initial design involved 77 satellites (the number of electrons in an iridium atom), it provides voice, messaging, and data services to mobile subscribers using Motorola-built handheld user terminals. The satellites are arranged in six planes, each 60° out of phase with its neighbors, to provide global coverage. The current operator, Iridium Satellite LLC of Leesburg, Virginia, acquired the system after its previous owner became bankrupt and it appeared that the armada of satellites would be de-orbited.