Unexpected Anomalies Put Future GPS Under Stress

 - June 25, 2009, 11:58 AM

One key benefit of the future GPS III satellites that the DOD plans to launch in 2014 is that they will transmit a second civil aviation signal, called L-5, that new receivers will compare with today’s L-1 civil signals to eliminate ionospheric interference, the last major cause of GPS errors. Unfortunately, while a pre-production L-5 test package launched earlier this year worked well on a current model satellite, it caused that satellite’s L-1 and several encrypted military GPS frequencies to wander unpredictably. This unexpected outcome has created another headache for the DOD, which has already been criticized by the Government Accountability Office for sloppy management of its space program. In addition, the GAO has rapped the DOD for relying on a batch of interim but unproven satellites–said by one expert to have “congenital defects”–to bridge the five-year gap caused by progressive failures of older satellites before the first launches of the advanced GPS III units still in development can begin.