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  • 1
    Publication Date: 2011-08-17
    Description: The intercontinental clock synchronization capabilities of Very Long Baseline Interferometry (VLBI) and the Navigation Technology Satellite (NTS) were compared in May 1978 by using both methods to synchronize the cesium clocks at the NASA Deep Space Net complexes at Madrid, Spain, and Goldstone, California. The VLBI experiments used the Wideband VLBI Data Acquisition System. The Navigation Technology Satellites were used with NTS Timing Receivers developed by the Goddard Space Flight Center. The two methods agreed at about the one-half microsecond level. The VLBI system also obtained long-term stability information on the HP5061A004 cesium standards by measuring delta T/T over four 3- to 4-day intervals, obtaining stability estimates of (1 + or - 1)x10 to the -13th power for the combined timing systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 64-69
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  • 2
    Publication Date: 2016-06-07
    Description: The OMEGA transmissions from North Dakota on 13.10 and 12.85 kHz were monitored at several sites using a recently developed OMEGA timing receiver specifically designed for this purpose. The experiments were conducted at Goddard Space Flight Center, Greenbelt, Maryland; U.S. Naval Observatory, Washington, D.C.; and at the NASA tracking station, Rosman, North Carolina. Results show that cycle identification of the two carrier frequencies was made at each test site, thus, coarse time (76 microseconds) from the OMEGA transmitted signals to within the ambiguity period of each OMEGA frequency was extracted. The fine time determination, which was extracted from the phase difference between the received OMEGA signals and locally generated signals, was about + or - 2 microseconds for daytime reception and about + or - 5 microseconds for nighttime reception.
    Keywords: AIRCRAFT COMMUNICATIONS AND NAVIGATION
    Type: Proc. of the 5th Ann. NASA and DOD Precise Time and Time Interval Planning Meeting; p 369-395
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  • 3
    Publication Date: 2017-10-02
    Description: Global Positioning System (GPS) Time Transfer receivers were developed by the Naval Research Laboratory (NRL) to provide synchronization for the NASA Global Laser Tracking Network (GLTN). The capabilities of the receiver are being expanded mainly through software modification to: Demonstrate the position location capabilities of a single channel receiver unsign the GPS C/A code; and Demonstrate the time/navigation capability of the receiver onboard a moving platform, by sequential tracking of GPS satellites.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NRL Proc. of the 15th Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 211-235
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  • 4
    Publication Date: 2017-10-02
    Description: The overall experiment was designed to test the positioning and navigation capabilities of the GPS timing receivers developed by the Naval Research Laboratory (NRL) for the NASA Goddard Laser Tracking Network (GITN). To perform this experiment, a reliable and redundant time scale was set up onboard the ship, and a back-up on shore. This situation provided the opportunity to perform simultaneously a timing experiment ideally divided into two parts, the main objectives of the experimentation being: (1) To test GPS timing receiver synchronization capabilities on a moving platform, and to perform an intercontinental synchronization via GPS between participating international timing laboratories in Europe and in the United States. (2) To evaluate the performance of cesium portable clocks in the field.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NRL Proc. of the 15th Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 283-330
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  • 5
    Publication Date: 2018-06-08
    Description: (view graphs).
    Keywords: Geophysics
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  • 6
    Publication Date: 2016-06-07
    Description: The results are presented of clock synchronization experiments using OMEGA transmissions from North Dakota on 13.10 kHz and 12.85 kHz. The OMEGA transmissions were monitored during April 1974 from NASA tracking sites located at Madrid, Spain; Canary Island; and Winkfield, England. The sites are located at distances between 6600 kilometers (22,100 microseconds) to 7300 kilometers (24,400 microseconds) from North Dakota. The data shows that cycle identification of the received signals was accomplished. There are, however, discrepancies between the measured and calculated propagation delay values which have not been explained, but seem to increase with distance between the receiver and the transmitter. The data also indicates that three strategically located OMEGA transmitting stations may be adequate to provide worldwide coverage for clock synchronization to within plus or minus two (2) microseconds.
    Keywords: AIRCRAFT COMMUNICATIONS AND NAVIGATION
    Type: Proc. of the Sixth Ann. Precise Time and Time Interval (PTTI) Planning Meeting; p 187-197
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  • 7
    Publication Date: 2016-06-07
    Description: An interim demonstration was performed of the time transfer capability of the NAVSTAR GPS system using a single NTS satellite. Measurements of time difference (pseudo-range) are made from the NTS tracking network and at the participating observatories. The NTS network measurements are used to compute the NTS orbit trajectory. The central NTS tracking station has a time link to the Naval Observatory UTC (USNO,MC1) master clock. Measurements are used with the NTS receiver at the remote observatory, the time transfer value UTC (USNO,MC1)-UTC (REMOTE, VIA NTS) is calculated. Intercomparisons were computed using predicted values of satellite clock offset and ephemeus.
    Keywords: PHYSICS (GENERAL)
    Type: Proc. of the 10th Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 601-627
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  • 8
    Publication Date: 2017-10-02
    Description: In response to a NASA Goddard Space Flight Center Work Assignment, Bendix Field Engineering Corporation evaluated the performance of the Oscilloquartz EPOS-2 hydrogen maser along with that of NASA NX-3 and NP-2 hydrogen masers in early 1983. This paper presents the results of that evaluation.
    Keywords: LASERS AND MASERS
    Type: NRL Proc. of the 15th Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 653-676
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  • 9
    Publication Date: 2016-06-07
    Description: Current and future Precise Time and Time Interval (PTTI) programs at the Goddard Space Flight Center (GSFC) and the evolution of frequency and time requirements over past years within the various NASA satellite tracking networks are described. A brief history of the network development is also given.
    Keywords: LASERS AND MASERS
    Type: Proc. of the 12th Ann. Precise Time and Time Interval Appl. and Planning Meeting; p 151-198
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  • 10
    Publication Date: 2019-01-25
    Keywords: LASERS AND MASERS
    Type: Proc. of the 9th Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 319-342
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