GPS Time and Frequency Transfer Activities at NIST · 2014. 9. 18. · 54nd CGSIC Meeting in Tampa,...
Transcript of GPS Time and Frequency Transfer Activities at NIST · 2014. 9. 18. · 54nd CGSIC Meeting in Tampa,...
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54nd CGSIC Meeting in Tampa, Florida, September 2014 1
GPS Time and Frequency Transfer
Activities at NIST
Victor Zhang
National Institute of Standards and Technology
Time and Frequency Division
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Code-Based Common-View
• Backup link for contributing NIST time scale to the
computation of TAI and UTC
• Time and frequency comparison network in the Inter-
American Metrology System (SIM)
• Synchronization of clocks in radio stations
WWV/WWVB, and WWVH to UTC(NIST)
• Time Measurement and Analysis Service (TMAS)
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Time Measurement and Analysis Service
For details of the TMAS, contact Michael Lombardi: [email protected]
• Monitor the customer's local time standard by
continuously comparing it to the national time
standard using GPS common-view
• Comparison result is available in every 10 minutes
• Time transfer Uncertainty < 15 ns, and frequency
uncertainty < 5 x 10-14 after 1 day of averaging (k = 2)
• Steer a remote clock to UTC(NIST) with the
TMAS system
• The remote clock can be a NIST provided Rb
clock or a customer’s Cs clock
• Steering based on common-view difference every
10 minutes
• Averaged time offset < 1 ns, and time uncertainty
< 15 ns after 1 day of averaging (k = 2)
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Code-Based One-Way
• Frequency Measurement and Analysis Service
(FMAS)
• GPS Disciplined Oscillator and GPS One-Way
Receiver Calibration Service
• NIST GPS Data Archive
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Carrier-Phase (1)
• Contribute NIST time scale to the computation of TAI
and UTC, and compare remote clocks with the BIPM
TAIPPP results
• Participate in the IGS tracking network
• Compare remote clock with the IGS clock products
• Analyze carrier-phase data for studies of receiver
performance and remote clock comparison
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Carrier-Phase (2)
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The RINEX-Shift algorithms for minimizing data boundary discontinuity
“An Improvement of RINEX-Shift Algorithm for Continuous GPS Carrier-Phase Time Transfer” to be
presented during ION GNSS+ 2014 by Jian Yao and Judah Levine, Contact: [email protected]
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NIST TAI-1 GPS Time Transfer Receiver
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• Low cost, suitable for
timing labs with limited
resource
• Used for common-view/all-
in-view time and frequency
transfer
• Able to survey antenna
coordinates
• Data in the CGGTTS
format, ready for the BIPM
TAI/UTC computation
• Time transfer uncertainty <
15ns (k = 2)
For details about the receiver, Contact Michael Lombardi: [email protected]
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Solar Flare and GPS Time Transfer
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The modeled ionosphere delay correction is effective in
dark (nighttime), but inadequate to handle the ionosphere
delay change due to the daytime solar activity.
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Primary Receiver Performance
-5
-4
-3
-2
-1
0
1
2
3
56539 56569 56599 56629 56659 56689 56719 56749 56779 56809 56839 56869
Dif
fere
nce
(n
s)
MJD (days)
Double Differences for UTC(NIST) - UTC(PTB)
CirT-CV (mean = -1.0ns, std = 1.1ns)
CirT-PPP (mean = -2.7, std = 0.7ns)
CirT-TW (mean = 0ns, std = 0.1ns)
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Primary Receiver Performance
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Time and Frequency Comparison Network in the Inter-American Metrology System
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NIST GPS Time and Frequency Transfer Service
• Frequency Measurement and Analysis Service (FMAS) (Service ID#76100S)
• Time Measurement and Analysis Service (TMAS) (Service ID#76101S)
• Global Time Service (Service ID#76110S)
• Characterization of Global Positioning System (GPS) Satellite Receivers (Service ID#76120S)
http://ts.nist.gov/ts/htdocs/230/233/calibrations/time_freq/broadcast.htm
GPS Data Archive [GPS - UTC(NIST) all-in-view]
http://tf.nist.gov/service/gpstrace.htm