Delta IV soars at sunset

Friday's sunset launch of a Global Positioning System satellite marked the halfway point in an upgrade of what Air Force officials call "the most widely recognized constellation in the world."

The sixth in a series of 12 new-generation GPS spacecraft blasted off from Cape Canaveral Air Force Station atop a United Launch Alliance Delta IV rocket at 8:03 p.m.

As the 206-foot rocket shot from Launch Complex 37, a pink-tinged trail of exhaust turned bright white as the rocket climbed high enough to catch the day's last light, casting a shadow on the horizon.

ULA reported the rocket performed well through the first of two burns by the upper stage then said the $245 million satellite was scheduled to separated from the rocket around 11:30 p.m. over the southern Indian Ocean, southwest of Australia, confirming a success.

Upon reaching orbit roughly 11,000 miles up, the new satellite was expected to undergo a month of tests before joining a constellation with 31 active satellites, including one launched from the Cape in February by a Delta IV.

The constellation needs at least 24 satellites, but many are getting older.

"We launched a whole bunch of these to get the constellation up and running in the early days," said Col. Steve Steiner, GPS Space Systems Division chief at the Air Force's Spaceand Missile Systems Center in Los Angeles. "And so you have large numbers of satellites that are all about the same age, that are all susceptible to old age, if you will, and there's always the possibility that you can have large numbers of failures in that aged group at one time."

The new satellite, built by Boeing, replaces one that is about to turn 21 and considered the worst performing of the group to be moved out of active service.

GPS satellites are essential to military operations, from moving troops to guiding missiles to precise targets, but are also deeply embedded in civilian life.

"Civilian users around the world use and depend on GPS for highly accurate time, location and velocity information," said Lt. Col. Dave Ashley, commander of the 45^th Space Wing's 5th Space Launch Squadron. "From the navigation systems on our vehicles to the timing of most electronic financial transactions, GPS has permeated into nearly every aspect of our lives."

Walter Lauderdale, the Air Force director for this mission, called GPS the world's most recognized satellite constellation.

Designed to last at least 12 years, the new-generation spacecraft, labeled IIF, provide more powerful signals, improved accuracy and better resistance to jamming.

The next two in the series are expected to launch this July and November on ULA's Atlas V rockets, and all 12 should be in orbit by 2016.

Friday's launch followed a first try Thursday that was scrubbed by poor weather. The launch was ULA's fifth successful mission this year and the 26^th by a Delta IV since it debuted in 2002.

Assuming all went well, ULA planned to turn around quickly for its next launch, planned next Thursday by an Atlas V rocket carrying a classified National Reconnaissance Office satellite.