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GPS satellite mounted atop booster for Feb. 20 launch

Posted: February 5, 2014

Beginning a slate of three launches in five months to fortify the Global Positioning System, the first craft was mounted atop its Delta 4 booster rocket Wednesday for liftoff Feb. 20.

File image of payload being attached to Delta 4. Credit: United Launch Alliance
The launch is precisely timed at 8:40 p.m. EST to replace a 16-year-old member of the navigation network -- the GPS 2A-28 satellite. The evening launch opportunity extends 19 minutes.

Built by Boeing, the new GPS 2F-5 satellite brings with it modernized features including greater accuracy, better anti-jamming and a civil signal for commercial aviation as the fifth Block 2F bird.

Crews transported the satellite to Complex 37 overnight and lifted it into the gantry. The initial stage of attachment of the craft onto the upper stage of the rocket was completed at....

The Air Force and partner United Launch Alliance plan to launch GPS 2F-6 in May on another Delta and GPS 2F-7 on an Atlas 5 in July.

The Feb. 20 launch is headed for Plane A, Slot 3 of the constellation where it will become a primary spacecraft to transmit navigation and timing to military and civilian users around the globe. The satellite currently in that slot will be moved into a backup role for remainder of its useful life.

It will be the 25th Delta 4 launch and the fourth with a GPS satellite. ULA intends to conduct four flights of the Delta 4 this year.

A GPS 2F satellite in the California factory. Credit: Boeing
The launch was delayed from October while engineers ran additional tests and analysis on the low-thrust condition experienced on the successful GPS 2F-3 flight.

"The delay of the GPS 2F-5 was not related to any new observation from the GPS 2F-3 launch. The Phase II investigation of the GPS 2F-3 flight telemetry continues the analysis from Phase I with the goal to thoroughly confirm there are no systematic issues with RL10B-2 engine," the Air Force says.

"Over the last several months, the team has continued testing and analysis which has increased our understanding and confidence in the conclusions of the GPS 2F-3 flight telemetry and the conclusions from Phase I."

Investigators believe a tiny fuel leak developed at the first ignition of the upper stage engine, resulting in lower-than-expected thrust and longer burn times. It is possible there were low-frequency dynamic responses that occurred on the engine system during ignition.

Additional inspections, in-flight helium purges to critical areas of the engine system and changes to how the engine is thermally conditioned during ascent to prepare for its initial ignition have been put in place to mitigate the risks.

An artist's concept of the GPS 2F constellation. Credit: Air Force
GPS is marking the 20th anniversary of its Initial Operational Capability, the point in which the constellation was populated sufficiently to go into service.

"GPS has grown to become a vital worldwide utility serving billions of users around the globe. GPS multi-use Precision Navigation and Timing services are integral to the United States global security, economy, and transportation safety, and are a critical part of our national infrastructure," the Air Force says.

"GPS contributes vital capabilities to our nation's military operations, emergency response, agriculture, aviation, maritime, roads and highways, surveying and mapping, and telecommunications industries, as well as recreational activities. It is not an overstatement to say GPS is fundamental to today's technical infrastructure and culture."