UPDATE Launch delayed to 2nd August at 3:23 GMT

Early morning Saturday sees the launch of the seventh GPS IIF satellite fro the Cape Canaveral Air Force Station. This will be lofted into orbit on top of an Atlas V rocket. The GPS IIF-7 satellite is part of the upgraded and modernised fleet of Block IIF navigation spacecraft designed to replace one of the ageing Block IIA satellites originally launched in the early 1990s.

The launch is scheduled for 3:23am GMT (4:23 BST) which is late evening on the 1st August in Florida. Launch complex 41 will be used for this launch, the most northerly active launch pad at Cape Canaveral. If you want to follow the launch the AmericaSpace Live Launch Tracker will have live commentary and video feed.

There are currently 4 types of Block II GPS satellites: Block IIA, Block IIR, Block IIR(M) and Block IIF. These different blocks represent:

IIA - Advanced, launched between 1990 and 1997 currently 6 are operational
IIR - Replacement, launched between 1997 and 2004 currently 12 are operational
IIR(M) - Modernised, launched between 2005 and 2009 7 are operational
IIF - Follow-on, launched since 2010 6 operational and a further 6 scheduled (including Friday’s satellite)

The GPS constellation requires 24 operational satellites to provide service so currently with 31 there is some spare capacity. The Block IIA satellites were designed with an expected lifespan of seven and a half years so are well past their operational lifetime. With one satellite to be launched on Friday and another in October the remaining 4 Block IIF satellites are manufactured and are expected to be launched in the next two years or so.

After the deployment of the final Block IIF GPS satellite the next development will be the GPS III satellites. Currently the GPS III is in production with two satellites on order and options to fill out the GPS III to a full compliment of 12 spacecraft. The GPS III will not only provide additional features to the ageing fleet, but will also include improved accuracy and anti-jamming capabilities.

Saturday’s launch will see second recent use of the United Launch Alliance Atlas V rocket booster to place a GPS into orbit. The vast majority of the constellation was launched on the Delta II and Delta IV rockets. The Atlas V is a workhorse of the USA space rockets with 46 previous launches, 34 of them for the USAF who manage the GPS Fleet. Including the Delta rockets ULA have launched 54 of the 66 GPS satellites.

The GPS IIF satellites are build by Boeing in El Segundo California. The Block IIF improvements offer: Better atomic clocks; Greater accuracy; New L5 signal for civilian use; enhanced military signal with variable power to assist against jamming; reprogrammable in orbit for system upgrades. The design life of the GPS IIF is 12 years.

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Comments Posted by MikeB on Thu Jul 31, 2014 10:13 am UPDATE The launch date has been changed to 2nd August at 3:23am GMT (4:23 BST). Mike Barrett   Posted by MikeB on Thu Jul 31, 2014 9:57 pm The Atlas V with GPS IIF-7 is on the launch pad. Mike Barrett