Harris Corp. [HRS] said Aug. 9 that it expects to deliver the fourth of 10 navigation payloads for the U.S. Air Force’s Global Positioning System (GPS) III satellites this fall.

The first two payloads have already been integrated into the first two GPS III satellites, and the third payload is undergoing that process now.

The second GPS III satellite has been assembled. (Photo courtesy of Lockheed Martin)
The second GPS III satellite has been assembled. (Photo courtesy of Lockheed Martin)

Lockheed Martin [LMT] is the prime contractor for the initial 10 GPS III satellites, the first of which is in storage awaiting its expected launch in 2018. The second is undergoing environmental testing. The Air Force, which is holding a competition for satellites 11 and beyond, issued a draft request for proposals (RFP) in July and plans to release a final RFP this fall (Defense Daily, July 21).

The navigation payload’s mission data unit (MDU), which generates the navigation signals, is currently 70 percent digital. For satellites 11+, Harris is developing an all-digital version of the MDU and plans to conduct a spaceflight-like demonstration with it late this fall at a Lockheed Martin facility.

GPS III satellites are designed to replenish the GPS constellation and provide more accurate signals, be more resistant to jamming and last longer than existing spacecraft.