The Iridium satellite constellation is a system of 66 active communication satellites with spares in orbit and on the ground. It allows worldwide voice and data communications using handheld satellite phones. The Iridium network is unique in that it covers the whole earth, including poles, oceans and airways.
The company, based in Bethesda, Maryland, US, derives its name from the chemical element iridium; the number of satellites projected in the early stages of planning was 77, the atomic number of iridium.
The satellites are frequently visible in the night sky as satellite flares – a phenomenon typically observed as short-lived bright flashes of light.