The Boeing-built Global Positioning System 2F-5 satellite was expected to be released from the Delta 4 second stage three hours and 33 minutes into the mission.
The satellite is the first of three GPS navigation beacons scheduled for launch through July to replace older spacecraft in the constellation. The 2F-5 satellite is the fifth of 12 planned “block 2” spacecraft that make up the core of the current GPS fleet.
Equipped with ultra-accurate atomic clocks, Global Positioning System satellites circle the globe in six orbital planes. Using an active constellation of more than two dozen satellites, at least four GPS spacecraft are visible in the sky from any point on the Earth’s surface, transmitting location and timing signals that allow compact receivers to compute position, altitude and velocity.
An encrypted band gives military users position accuracy to within a few feet while an unencrypted public channel provides slightly less precise data to a wide variety of devices, from smart phones to automobile-mounted GPS mapping units.
The block 2F satellites are more accurate than earlier spacecraft and feature new channels to support commercial and civil aviation, more easily upgradeable flight computers and beefed up anti-jamming hardware.
The satellite being replaced by the GPS 2F-5 spacecraft was launched in 1997 and is well past its design life.
“The satellite we are replacing is over 16 years old and its design life was 7.5 years,” Col. William Cooley, Global Positioning Systems director, told reporters before launch.