The last of eight GPS IIR-M satellites, modernised for the US Air Force by Lockheed Martin, is all set for lift-off on 17 August 2009 from Cape Canaveral Air Force Station in Florida.

The spacecraft, designated GPS IIR-21(M), will complete the IR and IIR-M series of satellites for the global positioning systems wing of the Space and Missile Systems Centre.

The modernised satellite will deliver increased signal power to receivers on the ground and two new military signals to improve accuracy, improved encryption and anti-jamming capabilities.

The satellite will also supply a second civil signal that will provide users with an open access signal on a different frequency.

US Air Force GPS wing commander Col. Dave Madden said the GPS IIR 21 has completed its launch readiness review and is ready for flight.

The GPS II constellation of 21 satellites where originally built by Lockheed Martin.

The satellite will be followed by its next generation system, the GPS IIIA that will ready for launch in 2014.