TAG: GPS satellite

Innovation: Position estimation using non-line-of-sight GPS signals

March 15, 2017By and
FIGURE 9.  Normalized overall correlation with contributions from all satellites, including the satellite mirror-image of PRN 5.

Reflected Blessings.
A technique developed by researchers at the University of Illinois at Urbana-Champaign distinguishes a reflected non-line-of-sight (NLOS) signal of a particular satellite from the LOS signal and characterizes the NLOS signal as coming from a virtual mirror-image satellite in the direction of the signal reflection point. By using information on the position and orientation of the reflector, the NLOS signal can be treated as an additional LOS signal. read more

New book explains GPS for the rest of us

February 24, 2017By
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GPS terms, its history and uses are all described in the new book GPS for Everyone: You Are Here by Pratap Misra. read more

Last Block IIF to replace oldest GPS satellite

January 22, 2016By
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On Feb. 3, the Air Force plans to launch the 12th, and last, satellite in the Block IIF series of modernized GPS spacecraft. The Air Force has produced 12 IIF satellites, featuring new clocks, new civil and military signals, and other upgrades for enhanced accuracy and robustness. Currently, 31 GPS satellites are in operational service, including 11 Block IIF satellites and 20 spacecraft from... read more

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GPS IIF-11 Launch Delayed until Saturday

October 30, 2015By
Major General David Thompson announces a 24-hour delay for the launch of the eleventh GPS-IIF satellite.

Major General David Thompson, Vice Commander, U.S. Air Force Space Command, announced this morning that the GPS IIF launch scheduled for today will be delayed for 24 hours due to a water deluge suppression system at the launch site. Launch should only be delayed for 24 hours. The water deluge suppression system is a launch site safety issue. Officials made the call... read more

GPS Glitch Two Years Older than First Stated

April 15, 2015By

On Wednesday, the GPS Directorate said further data analysis shows that a technical error affecting some Boeing GPS IIF satellites first appeared in 2011, two years earlier than originally stated, according to a Reuters report. The error first appeared one year after the GPS IIF satellites became operational. The error affects the way the ground control system builds and uploads messages transmitted by the satellites, but... read more

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Air Force Working on Glitch for GPS IIF Satellites

March 23, 2015By

The U.S. Air Force is working to resolve a technical error that affected some Boeing GPS satellites, according to a report by Reuters. The error does not affect the accuracy of GPS signals. It involves the ground-based software used to index some messages transmitted by GPS IIF satellites built by Boeing, Air Force Space Command said according to Reuters. Still, officials are investigating other possible causes.... read more

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The System: Three’s the Challenge

August 1, 2010By

A small variance in the L5 signal, which remains well within signal specifications and will not affect pseudorange measurements, may show some impact on triple-frequency combinations of the signal’s carrier phase in high-precision applications. Observations suggest a temperature-dependent line bias in one or more carriers as a likely cause of the observed variation in the tri-carrier combination of L1, L2, and L5. read more

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Expert Advice: Cause Identified for Pseudorange Error from New GPS Satellite SVN-49

July 15, 2009By and

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. read more