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Time Transfer Research and Development at USNO

Time Transfer Research and Development at USNO. CGSIC March 2004 Presented by Jim Brad. R&D Time Transfer Outline. Improved GPS time transfer New GPS time transfer receiver evaluation Real Time GPS Carrier Phase Demonstration (JPL) Improved Standard Positioning Service (Civil)

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Time Transfer Research and Development at USNO

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  1. Time Transfer Research and Development at USNO CGSIC March 2004 Presented by Jim Brad

  2. R&D Time Transfer Outline • Improved GPS time transfer • New GPS time transfer receiver evaluation • Real Time GPS Carrier Phase Demonstration (JPL) • Improved Standard Positioning Service (Civil) • Improved Precise Positioning Service (Military) • WAAS Time Transfer • Improve Two-way satellite time transfer • Time Transfer to US Navy Ship • Thermal Stability Studies/Improvements

  3. GPS Hardware Time Transfer Stabilitycomparison of two high performance receivers

  4. Time Transfer Test BedUSNO to USNO AMC PPS CV TWSTT CP Realtime Post-processed SPS CV

  5. JPL and USNO Demonstration of Live Real Time Carrier Phase Time Transfer 1.5E-15 at one day See link at http://galia.gdgps.net/igdg/

  6. How WAAS timing works today • WAAS Network Time (WNT) is an average of WAAS reference station clocks steered to GPS time • GPS time is steered to UTC(USNO) and is specified to be maintained to within 1 microsecond of UTC(USNO) modulo one second • GPS broadcasts UTC corrections including leap second information in GPS navigation message • Today no UTC corrections are broadcast by WAAS • WAAS message type-12 is designated to contain UTC corrections. At present this message type-12 has not been implemented

  7. Joint USNO and WAAS program was initiated in 1999 to study WAAS timing • Investigate WAAS broadcast of UTC(USNO) corrections to support UTC time transfer • Investigate using WAAS geostationary satellite as an independent UTC timing source • Investigate use of the WAAS geostationary satellite signal as a method for improved common view time transfer • Investigate improvements to WNT to better support time transfer • Investigate use of the WAAS ionosphere correction grid data to improve time transfer

  8. Modulo 1 Second

  9. USNO Two-Way Satellite Time Transfer Earth Terminals

  10. TWSTT to SHIPS

  11. Temperature-stable Enclosures

  12. Thermal Control of TWSTT

  13. Correlation of Diurnal Time Variations with Outside Temperature Variations

  14. Correlation of Diurnal Time Variations Reduced with Better Thermal Control Temperature

  15. Future Work • Focus on Robust Operation Center • Improved Calibration of Time Transfer • New GPS Calibrator (February 2004) • Continue to Work on Time Transfer Hardware Stability • Continue Work on Real Time Carrier Phase Time Transfer (JPL, NRCan, IGS) • Demonstration of Two-way and GPS Time Transfer to Navy Ship at Sea

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