The US Navy's FLTSATCOM (Fleet Satellite Communications System) is a constellation of five operational satellites used by both the Navy and Air Force as well as the presidential command network. The system, with a design life of five years, serves as a secure communications link between the three users. Each FLTSATCOM spacecraft has 23 communications channels in ultra-high and super-high frequency bands. Ten of the channels are used by the Navy for worldwide communications among its land, sea, and air forces. Twelve of the channels are used by the Air Force as part of the Air Force Satellite Communications System for command and control of nuclear-capable forces. A 500-kilohertz channel on the satellite is allotted to National Command Authority.