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Thursday, May 15, 2014

GPS 2F-6: Anticipated Satellite Launch Timeline

As reported by SpaceFlight Now: GPS services have permeated daily lives for countless millions of people, and now the latest Global Positioning System satellite is awaiting blastoff Thursday (May 15) to bolster the navigation network.  

Liftoff of the GPS 2F-6 spacecraft aboard a United Launch Alliance Delta 4 rocket from Cape Canaveral is planned for 8:08 p.m. EDT at the opening of an 18-minute window.  

GPS IIF-6 will be the United Launch Alliance’s fifth launch of 2014 and 82nd overall. It also will mark the 26th flight of the Delta IV launch vehicle since its inaugural flight in November 2002.  

ULA will provide a live webcast of the launch, beginning at 7:48 p.m. EDT. Also, those interested can hear updates to the launch countdown via phone, by dialing the ULA launch hotline at 1-877-852-4321, or join the conversation at and, hashtag #GPSIIF6.

The satellite, built by Boeing, is one of the next-generation GPS satellites, incorporating  improvements to provide greater accuracy, increased signals, and enhanced performance for users. According to Boeing, each GPS IIF satellite has:
  • greater navigational accuracy through improvements in atomic clock technology.
  • a new civilian L5 signal to aid commercial aviation and search and rescue operations.
  • improved military signal and variable power for better resistance to jamming in hostile environments.
  • a 12-year design life providing long-term service and reduced operating costs.
  • an on-orbit, reprogrammable processor that can receive software uploads for improved system operation.

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T-0:00:05.0 Engine start
The RS-68 main engine begins to ignite as the liquid hydrogen fuel valve is opened, creating a large fireball at the base of the rocket. The engine powers up to full throttle for a computer-controlled checkout before liftoff.
T-0:00:00.0 Liftoff
The rocket's two strap-on solid rocket motors are lit, the four hold-down bolts are released and the Delta 4 lifts off from Cape Canaveral's pad 37B. The pad's three swing arms retract at T-0 seconds.
T+0:01:00.7 Max-Q
The vehicle experiences the region of maximum dynamic pressure. Both solid motors and the RS-68 liquid hydrogen/liquid oxygen engine continue to fire as the vehicle heads downrange, arcing over the Atlantic along a 45-degree flight azimuth.
T+0:01:40.0 Jettison solid motors
Having used up all their solid-propellant and experienced burnout six seconds ago, the two strap-on boosters are jettisoned from the Delta's first stage. The spent casings fall into the ocean.
T+0:04:07.2 Main engine cutoff
The hydrogen-fueled RS-68 rocket engine completes its firing and shuts down to finish the first stage burn.
T+0:04:14.5 Stage separation
The Common Booster Core first stage and the attached interstage are separated in one piece from the Delta 4's upper stage. The upper stage engine's extendible nozzle drops into position as the first stage separates.
T+0:04:29.0 Second stage ignition
The upper stage begins its job to place the GPS 2F-6 satellite into space with the first of two firings by the RL10B-2 liquid hydrogen/liquid oxygen engine.
T+0:04:39.5 Jettison payload fairing
The four-meter diameter composite payload fairing that protected the GPS 2F-6 cargo atop the Delta 4 during the atmospheric ascent is no longer needed, allowing it to be jettisoned in two halves.
T+0:15:31.5 Upper stage shutdown
The RL10 upper stage engine shuts down to complete its first firing of the launch. The rocket and attached satellite reach an intermediate transfer orbit where it coasts for the next three hours.
T+3:03:25.0 Restart upper stage
The upper stage reaches the proper point in space and reignites the the RL10 engine to circularize the orbit.
T+3:05:08.2 Upper stage shutdown
The powered phase of the Delta 4's mission to reach the GPS constellation concludes. The targeted circular orbit is 11,047 nautical miles with an inclination of 55 degrees.
T+3:15:49.5 Separate spacecraft
The GPS 2F-6 satellite is released into space from the Delta 4 rocket to upgrade the orbiting navigation network.