ULA - Delta IV / GPS IIF-5 launch poster.
February 22, 2014
United Launch Alliance (ULA) Delta IV rocket on the launch-pad
The US Air Force’s fifth GPS Block IIF navigation satellite was launched on Thursday night. Liftoff, from Cape Canaveral Air Force Station in Florida, via the United Launch Alliance (ULA) Delta IV rocket, came at the end of a nineteen-minute window, resulting in a T-0 of 8:59 pm Eastern (01:59 UTC on Friday 21 February 2014). The delay in the window was caused by high solar activity.
United Launch Alliance (ULA) Delta IV rocket liftoff
Built by Boeing, GPS IIF-5 is the fifth of twelve Block IIF satellites intended to replace older satellites in the Global Positioning System and introduce new capabilities ahead of the Block III series scheduled to begin launching in the next few years. Each satellite has a mass of 1,630 kilograms (3,534 lb) and is designed for twelve years’ service life.
Launch of GPS IIF-5 Satellite on Delta IV Medium Rocket
GPS satellites operate in semi-synchronous orbits with periods of twelve hours, making two revolutions per day. The constellation consists of six planes, designated A to F. In theory each plane should have four primary satellites in slots one to four, with a spare in slot five, however some planes have more than one backup; some of these satellites are kept operational in “slot six”, while others are in standby status.
Destined for slot 3 of plane A of the GPS constellation, GPS IIF-5 is scheduled to replace the USA-135 satellite, also known as GPS IIA-28, which was launched in November 1997. The nineteenth and final Block IIA satellite to fly, USA-135 will likely be moved to slot 5, which is typically occupied by an older, backup satellite.
Artist's view of the GPS IIF-5 satellite
The rocket that launched GPS IIF-5, United Launch Alliance’s Delta IV, conducted its twenty-fifth flight. Flying in the Medium+(4,2) configuration – its most-used variant – the rocket consists of a Common Booster Core (CBC) augmented by a pair of GEM-60 solid rocket motors, with a four-meter Delta Cryogenic Second Stage (DCSS) mounted atop the CBC.
The Common Booster Core is powered by a single RS-68 engine, while the DCSS makes use of an RL10B. Both core stages make use of cryogenic propellents, burning liquid hydrogen in a liquid oxygen oxidiser.
Delta IV rocket description
Originally developed by the US Air Force for military applications, President Ronald Reagan ordered that the Global Positioning System be made available to civilian users after a Korean Air Lines Boeing 747 was shot down after going off course and entering restricted Soviet airspace. The satellites broadcast freely-available civilian signals, and military ones with greater precision.
For more information about United Launch Alliance (ULA), visit: http://www.ulalaunch.com/site/default.shtml
For more information about GPS satellites, visit: http://en.wikipedia.org/wiki/Global_Positioning_System
Images, Video, Text, Credits: United Launch Alliance (ULA) / Orbiter.ch Aerospace.