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TAG: GPS constellation

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GPS Constellation Management: Playing Not to Lose

October 22, 2009

In sports, there is a phenomenon that sometimes occurs when a team is leading towards the end of a game. It’s called “playing not to lose.” The reason you are seeing high HDOP warnings from the NAVCEN and GPS “brownouts” during the day when RTK (GPS-only) isn’t working is because the GPS satellite constellation is sub-optimal. The current design of the GPS constellation is not focused on “playing to win”, but rather “playing not to lose.”


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This article is tagged with , and posted in Opinions, Survey
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Expert Advice: Cause Identified for Pseudorange Error from New GPS Satellite SVN-49

July 15, 2009

The GPS Wing and its contractors have traced the cause of pseudorange errors on L1 and L2 broadcast by the newest GPS satellite, SVN-49, to the manner in which the L5 signal demonstration payload was added to the satellite. Signal leakage between the two input ports of the antenna coupler network for the satellite’s array of 12 helical antenna elements, reflected from the L5 filter and then transmitted, creates a second signal with a delay of approximately 30 nanoseconds, and the appearance of a multipath component. While testing an adjustment to the signal-in-space to minimize the effect of the problem on receiver navigation solutions on Earth, the GPS Wing is interested in hearing from manufacturers and the user community concerning the different impacts of SVN-49 signals on the wide range products and applications in operation, before reaching a final decision on what to do with the satellite prior to setting it healthy.


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Innovation: GPS L5 First Light

June 1, 2009

A Preliminary Analysis of SVN49’s Demonstration Signal
Great excitement surrounds the activation of a new transmitter from a satellite — an occasion dubbed first light. Research groups around the globe joined the GPS Wing in monitoring and analyzing the first L5 signals from space. We describe the equipment and procedures used to capture and analyze SVN49’s signals and give an assessment of their characteristics.


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This article is tagged with , , , , and posted in GNSS, Innovation
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Parkinson Prescribes Remedy for GAO Report Alarm

May 26, 2009

Brad Parkinson, the first GPS Program Office director, chief architect and advocate for GPS, submitted written testimony to Congress on mitigation options for possible GPS brownouts. His presentation comes in reference to the recent GAO report highlighting the risk that the GPS constellation may fall below the minimum level of 24 satellites required for full operational capability. In his opening, Parkinson states that GAO correctly points out the possibility that the GPS constellation will be reduced to less than the current number of 30 to 32 satellites. In fact, it is possible that the constellation will be at a level of less than 24 satellites. I would like to focus on the options that would help reduce this risk.”


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GPS at Risk: Doomsday 2010

May 12, 2009

The United States Government Accountability Office (GAO) issued on May 7 an alarming report on the future of GPS, characterizing ongoing modernization efforts as shaky. The agency appears to single out the 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.”


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headshot: John Lavrakas

Expert Advice: Managing the GPS Constellation for Today’s Needs

September 1, 2006

For many, GPS is at its best performance ever, with 29 satellites in orbit and user range errors at their lowest levels in years. Yet for others, GPS performance falls short of expectations.


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This article is tagged with , , and posted in GNSS, Opinions, Survey
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