A United Launch Alliance Delta 4 rocket thundered away from Cape Canaveral Wednesday, boosting the ninth in a series of upgraded Global Positioning System navigation satellites into orbit.
The 206-foot-tall rocket's hydrogen-fueled main engine throttled up with a rush of fire at 2:36 p.m. EDT (GMT-4), followed a moment later by ignition of two solid-fuel strap-on boosters. Generating 1.1 million pounds of thrust, the Delta 4 quickly climbed away through low fog over the Cape Canaveral Air Force Station and arced away to the northeast over the Atlantic Ocean.
The climb out of the dense lower atmosphere went smoothly and 15 minutes after liftoff, the rocket's second stage engine shut down as planned to put the satellite payload into an initial parking orbit.
A second firing was planned about two hours and 45 minutes after launch to put the GPS 2F-9 satellite into the required 12,600-mile-high circular orbit. If all goes well with tests and checkout, the satellite, valued at around $170 million in recent-year dollars, will enter service in four to six weeks, eventually replacing a satellite launched in 1993.
The GPS program requires 24 satellites in six orbital planes to ensure at least four spacecraft are above the horizon as viewed from any point on or above the planet. Each satellite transmits ultra-precise location and atomic clock timing signals.
Combining the signals from four satellites, small terminals carried by hand or mounted aboard ships, aircraft, cars and other vehicles can calculate a user's location, altitude and velocity with extraordinary precision.
While two dozen satellites are required for global GPS coverage, the constellation currently includes 30 operational spacecraft, not counting GPS 2F-9.
The GPS 2F-9 satellite is the ninth of 12 Boeing-built navigation beacons that are replacing older spacecraft and increasing the constellation's precision with more powerful atomic clocks and additional features to improve accuracy and reliability for both civilian and military users.
"Today, we have 30 operational satellites on orbit providing precise global positioning navigation and timing services to users around the globe," said Brig. Gen. Bill Cooley, director of the Air Force Space and Missile Systems Center's Global Positioning System Directorate.
"A path forward is in work to modernize GPS, and the 2F capability plays a vital role updating the GPS constellation and maintaining the high level of accuracy required by the GPS system."
Modernization includes replacing older satellites with more capable versions, upgrading military terminals with "cyber-hardened equipment and software" and developing equipment to take advantage of additional signals transmitted by GPS 2F satellites to improve precision.
Cooley said the 2F satellites feature three atomic clocks per spacecraft, allowing users to determine their positions to within less than 20 inches.
"GPS is the global gold standard for providing accurate, reliable and continuous space-based PNT (positioning, navigation and timing) services to our nation and the world," Cooley said.
Two more GPS 2F satellites are scheduled for launch later this year with the 12th and final spacecraft in the series expected to take off in January. More powerful GPS 3A satellites, built by Lockheed Martin, are scheduled for launch starting in 2017.