Will retired satellites be revived to fill GPS gap?

By: John Sheridan

July 1, 2009
Avionics, ATC

Testifying before Congress in May, Stanford University professor Brad Parkinson–the chief architect of GPS and the original GPS program manager before his retirement from the USAF–echoed the concern of the Government Accountability Office (GAO) that there will be insufficient backup satellites to fill gaps in the constellation before the DOD’s forecast 2014 launches of its next-generation GPS III units. (see AIN, June, page one.)

But Parkinson was more specific than the GAO. Noting that the DOD expects to fill the gap with Boeing-built Block IIF satellites produced under a troubled and costly program that was three years late, he pointed out that those units are still untried, their design and parts are obsolete and they may have “further congenital defects,” since their ongoing production program “is still overrunning its budget.”

Parkinson proposed three approaches to backstopping the IIF satellites. First, reactivate five older satellites that were shut down but still occupy constellation “slots,” while limiting their remaining power capabilities to supporting navigation,
and turning off all military features. GPS satellites carry several exclusively DOD systems, including power-hungry Nudet sensors that detect and locate nuclear explosions anywhere on earth. Second, to speed early GPS III satellite launches, no military payloads should be installed, including Nudet and a new, high-power, steerable counter-jamming beam. Third, accelerate the whole GPS III program to actually achieve what the GAO described as the DOD’s “optimistic” forecast launch commencement in 2014. Parkinson summarily dismissed building more Boeing IIF units.

The DOD has not publicly commented on his proposals. The first would be a relatively low-cost solution, requiring no new launches, although the remaining longevity of the previously withdrawn satellites is unknown. But the DOD would be unhappy with both it and his second proposal since, in light of North Korea’s latest nuclear test, navigation-only satellites lacking Nudet capabilities could comprise almost a quarter of the constellation. And third, accelerating the whole program would be expensive.

Yet there’s a bizarre twist to all this. Should Boeing’s IIF satellites be affected by any of their “congenital defects” when in orbit, help could also come from an unlikely source–the SBAS/Waas satellites that Boeing essentially boycotts from its airplanes.    

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