Iridium provides global mobile telecommunications services using a constellation of 66 low-earth orbit satellites in an 86.4° inclined orbit. Although 77 satellites were originally envisioned for the system and spawned the name based on the 77th element in the periodic table, the system has been scaled back. Motorola's Satellite Communications Group designed and manufactured the Iridium satellites with Lockheed Martin providing the LM-700A spacecraft buses.

Unlike other mobile satellite systems, Iridium employs Inter-Satellite Links to route signals from satellite to satellite using onboard signal processing. Each satellite is connected to its four neighboring satellites providing flexibility in where the ground network gateways are located. These gateways connect the Iridium network to the public switched telephone network.