GPS World, June 2009

Policy and system news and developments GPS Galileo GLONASS SYSTEM THE GPS Health in Question T he U S Government Accountability Office GAO issued on May 7 an alarming report on GPS characterizing ongoing modernization efforts as shaky The agency appears to single out the Block IIF program as the weak link between current stability and ensured future capability calling into doubt whether the Air Force will be able to acquire new satellites in time to maintain current GPS service without interruption It asserts the very real possibility that in 2010 as old satellites begin to fail the overall GPS constellation will fall below the number of satellites required to provide the level of GPS service that the U S government commits to The GAO report concludes that some military operations and some civilian users could be adversely affected Military users will experience a delay in utilizing new GPS capabilities including improved resistance to jamming of GPS signals because of poor synchronization of the acquisition and development of the satellites with the ground control and user equipment Finally there are challenges in ensuring civilian requirements for GPS can be met and that GPS is compatible with other new potentially competing global space based positioning navigation and timing systems The report recommends that the Secretary of Defense appoint a single authority to oversee the development of GPS including space ground control and user equipment assets to ensure these assets are synchronized and well executed and potential disruptions are minimized The full report can be downloaded at http gao gov products GAO 09 670T and Congressional testimony from GPS providers industry and users can be found at http nationalsecurity oversight house gov story asp ID 2422 Gloomy Outcomes Based on the most recent satellite reliability and launch schedule data from March of this year the estimated long term probability of maintaining a constellation of at least 24 operational satellites falls below 95 percent during fiscal year 2010 and remains below 95 percent until the end of fiscal year 2014 at times falling to about 80 percent The results of fewer than 24 operational satellites could include the following Intercontinental commercial air carriers may have to delay cancel or reroute flights Enhanced 911 response to emergency calls could lose accuracy Accuracy of precision guided munitions could decrease forcing the military to use larger munitions or use more munitions on the same target Both standard and precise positioning service could suffer affecting civil users both professional for example surveyors and casual users of locationbased services via cell phones IIF at the Crux Cristina T Chaplain of the GAO presented the report to Congress stating In recent years the Air Force has struggled to successfully build GPS satellites within cost and schedule goals it encountered significant technical problems that still threaten its delivery schedule and it struggled with a different contractor As a result the current IIF satellite program has overrun its original cost estimate by about 870 million and the launch of its first satellite has been delayed to November 2009 almost three years late The Air Force is structuring the new GPS IIIA program to prevent mistakes made on the IIF program The GAO report cites specific problems with the IIF satellites contracted to Boeing During the first phase of thermal vacuum testing in 2008 one of the test payloads transmitters failed consequently the program suspended testing in August 2008 to identify the causes and take corrective action Other hang ups include maintaining the proper propellant fuel line temperature delaying final integration testing and re design of the satellites reaction wheels used for pointing accuracy because of on orbit failures on similar reaction wheels on other satellite programs 10 million in additional costs have accrued to the program according to the GAO While the Air Force is structuring the new GPS IIIA program to prevent mistakes made on the IIF program the Air Force is aiming to deploy the next generation of GPS satellites three years faster than the IIF satellites GAOs analysis found that this schedule is optimistic given the programs late start past trends in space acquisitions and challenges facing the new contractor GPS World June 2009 www gpsworld com 6