J. Mauricio Lopez R. a, Michael A. Lombardi b, Andrew N. Novick b, Jean-Simon Boulanger c, Raymond Pelletier c, Carlos Donado M. d, and Ricardo Carvalho e a Centro Nacional de Metrología (CENAM), Querétaro, Mexico, mauricio.lopez@cenam.mx b National Institute of Standards and Technology, Boulder, Colorado, United States, lombardi@nist.gov c National Research Council (NRC), Ottawa, Canada, jean-simon.boulanger@nrc-cnrc.gc.ca d Centro Nacional de Metrología de Panamá (CENAMEP), Panama City, Panama e Observatorio Nacional, Rio de Janeiro, Brazil
Outline 1. 1. Motivations 2. 2. The TheGPS system 3. 3. SIM SIM time time and and frequency network 4. 4. SIM SIM and andbipm comparisons 5. 5. Conclusions and andnear nearfuture work
Country BIPM/ CGPM Member? Maintains Time and Freq. Lab? Submits to BIPM? Argentina Member Yes Yes Brazil Member Yes Yes Canada Member Yes Yes Chile Member Yes Yes Colombia No Yes No Costa Rica Associate Yes No Dominican Rep. Member Unknown No Ecuador Associate Yes No El Salvador No Interested No Guatemala No Yes No Jamaica Associate Yes No Mexico Member Yes Yes Panama Associate Yes Yes Paraguay No Interested No Peru No Interested No Trinidad / Tobago No Interested No United States Member Yes Yes Uruguay Member Interested No Venezuela Member Yes No
-GPS stands for Global Positioning System - -Space-based radio positioning system -Provides users with highly accurate position, velocity, and time data
24 satelites with atomic clocks on board semi-synchronous orbit height of 4.2 earth radii (~20,200 km) 6 orbital planes, 55 degrees inclination to equatorial plane
Operates on two L-band frequencies 1.57542 GHz and 1.2276 GHz At least four satellites always in view
GPS satellite with an atomic clock on board Slave oscillator on earth
Velocity of propagation is not constant along the path Ionosphere Troposphere GPS Receiver
15 hours
nanoseconds 300 200 100 0-100 -200-300 -400-500 -600 7954.007 7963.504 7979.935 7989.824 7998.822 8009.182 Modified Julian Day - 40000 (Thousands) March 25 th,1990
Oscillator in common view Propagation media Oscillator 1 Oscillator 2
Variation on the velocity of propagation introduces a uncertainty which is usually a few nanoseconds Ionosphere Troposphere L >> 10 km L < 10 km
Técnica de COMMON-VIEW TIME AND FREQUENCY METROLOGY WORKING GROUP Clock B Clock A
Técnica de COMMON-VIEW GPS-B receiver GPS-A receiver Common agenda to view GPS satellites
Técnica de COMMON-VIEW t B = t B t GPS ±ε B t A = t A t GPS ±ε A t BA = t B - t A =(t B -t GPS + ε B ) (t A t GPS + ε A ) = t B -t A ± (ε B + ε A )
NRC NRC NIST NIST CENAM CENAM ICE ICE CENAMEP CENAMEP SIC SIC ONRJ ONRJ INTI INTI
SIM GPS system - Multichannel (8) GPS receiver - SIM receiver sends data automatically to the SIM server every 10 minutes - includes SIM s own software (developed by NIST) - Includes a PC. It is able to show common view results in near real time among participating laboratories
SIM GPS antenna Novatel antenna Rejects multiple reflections of the GPS signal
SIM Network server tf.nist.gov/sim/
SIM Time and Frequency comparison network: a democratic system
Comparison between NIST and CENAM
Comparison between NIST and CENAM
Comparison between NRC and ONRJ
Comparison between NRC and ONRJ
-4450-4500 SIM Network Circular-T -4450-4500 SIM Network Circular-T -4550-4550 Nanoseconds -4600-4650 -4700-4750 -4800-4850 -4900 60 days 53790 53800 53810 53820 53830 53840 53850 53860 Modified Julian Dates UTC(CNM) UTC(CNMP). 350 ns Nanoseconds -4600-4650 -4700-4750 -4800-4850 -4900 60 days -4950 53790 53800 53810 53820 53830 53840 53850 53860 Modified Julian Dates UTC(NIST) UTC(CNMP). 400 ns -4500 SIM Network 40 SIM Network -4550 Circular-T Circular-T 30-4600 Nanoseconds 20 10 0 50 ns Nanoseconds -4650-4700 -4750-4800 350 ns -10-20 -30 60 days 53790 53800 53810 53820 53830 53840 53850 53860 Modified Julian Dates UTC(NIST) UTC(CNM). 40 SIM Network Circular-T 30 SIM BIPM -4850-4900 -4950 60 days 53790 53800 53810 53820 53830 53840 53850 53860 Modified Julian Dates UTC(NRC) UTC(CNMP). 60 SIM Network Circular-T 50 40 Nanoseconds 20 10 0-10 -20-30 60 days 53790 53800 53810 53820 53830 53840 53850 53860 Modified Julian Dates UTC(CNM) UTC(NRC). 50 ns Nanoseconds 30 20 10 0-10 60 days -20 53790 53800 53810 53820 53830 53840 53850 53860 Modified Julian Dates UTC(NIST) UTC(NRC). 60 ns
Summary of uncertainties (in nanoseconds) for all six comparisons (March-April 2006) CNM CNMP NIST CNM CNM NRC NIST CNMP NRC CNMP NIST NRC Baseline (km) 2544.0 2198.9 3520.7 4194.9 3989.0 2471.3 Mean Freq. Offset 6.7 10-14 2.8 10-15 4.8 10-15 7.0 10-14 6.3 10-14 7.7 10-15 Mean Time Offset 4690.4 +10.3 +11.0 4680.7 4702.8 +21.2 U A, σ x (τ) 1.8 1.2 1.4 1.5 1.5 1 U B, Calibration 4 4 4 4 4 4 U B, Coordinates 3 3 3 3 3 3 U B, Environment 3 3 3 3 3 3 U B, Multipath 2 2 2 2 2 2 U B, Ionosphere 2 1.5 2.5 3 3 1.5 U B, Ref. delay 0.5 0.5 0.5 0.5 0.5 0.5 U B, Resolution 0.05 0.05 0.05 0.05 0.05 0.05 U C, k = 2 13.5 13.1 13.5 14.0 14.0 12.9
Conclusions TIME AND FREQUENCY METROLOGY WORKING GROUP 1. The SIM time and frequency network began operation in June 2005. Currently 7 NMIs are in participation. 2. The network is expected to enhance time and frequency Metrology capabilities on the SIM region by providing NMIs with a convenient way to compare their standards and to establish traceability to the SI. 3. Due to the SIM T&F Network some labs are in the process of acquiring Cs clocks. 4. The SIM network produces results that agree closely with results published in the BIPM s Circular-T, but have the distinct advantage of being available in near real time. 5. New labs will be joining the network during the next weeks or months (Argentina, Guatemala and )
Conclusions TIME AND FREQUENCY METROLOGY WORKING GROUP 1. The SIM time and frequency network began operation in June 2005. Currently 7 NMIs are in participation. 2. The network is expected to enhance time and frequency Metrology capabilities on the SIM region by providing NMIs with a convenient way to compare their standards and to establish traceability to the SI. 3. Due to the SIM T&F Network some labs are in the process of acquiring Cs clocks. 4. The SIM network produces results that agree closely with results published in the BIPM s Circular-T, but have the distinct advantage of being available in near real time. 5. New labs will be joining the network during the next weeks or months (Argentina, Guatemala and )
Conclusions TIME AND FREQUENCY METROLOGY WORKING GROUP 1. The SIM time and frequency network began operation in June 2005. Currently 7 NMIs are in participation. 2. The network is expected to enhance time and frequency Metrology capabilities on the SIM region by providing NMIs with a convenient way to compare their standards and to establish traceability to the SI. 3. Due to the SIM T&F Network some labs are in the process of acquiring Cs clocks. 4. The SIM network produces results that agree closely with results published in the BIPM s Circular-T, but have the distinct advantage of being available in near real time. 5. New labs will be joining the network during the next weeks or months (Argentina, Guatemala and )
Conclusions TIME AND FREQUENCY METROLOGY WORKING GROUP 1. The SIM time and frequency network began operation in June 2005. Currently 7 NMIs are in participation. 2. The network is expected to enhance time and frequency Metrology capabilities on the SIM region by providing NMIs with a convenient way to compare their standards and to establish traceability to the SI. 3. Due to the SIM T&F Network some labs are in the process of acquiring Cs clocks. 4. The SIM network produces results that agree closely with results published in the BIPM s Circular-T, but have the distinct advantage of being available in near real time. 5. New labs will be joining the network during the next weeks or months (Argentina, Guatemala and )
Conclusions TIME AND FREQUENCY METROLOGY WORKING GROUP 1. The SIM time and frequency network began operation in June 2005. Currently 7 NMIs are in participation. 2. The network is expected to enhance time and frequency Metrology capabilities on the SIM region by providing NMIs with a convenient way to compare their standards and to establish traceability to the SI. 3. Due to the SIM T&F Network some labs are in the process of acquiring Cs clocks. 4. The SIM network produces results that agree closely with results published in the BIPM s Circular-T, but have the distinct advantage of being available in near real time. 5. New labs will be joining the network during the next weeks or months (Argentina, Guatemala and )
Conclusions TIME AND FREQUENCY METROLOGY WORKING GROUP 6. Measurement results produced by the SIM T&F network will be used in the near future to generate a virtual time scale called SIM-time. SIMtime will be a time scale with very high metrological characteristics (accuracy and stability) accessible in real time. CENAM is developing an algorithm to generate the SIM-time scale starting on the second part of 2008. 7. Improvement of time and frequency capabilities can be observed at SIM as result of the SIM T&F network. However, it is necessary to continue supporting Time and Frequency activities in the SIM region not only providing more SIM type GPS receivers but also with training courses to those countries interested on improving their T&F laboratories or establishing their own one. 8. Enhanced time and frequency capabilities on SIM laboratories along with the SIM-time scale will help to pave the way to improve Metrology and provide a better support to industry in the Americas.
Conclusions TIME AND FREQUENCY METROLOGY WORKING GROUP 6. Measurement results produced by the SIM T&F network will be used in the near future to generate a virtual time scale called SIM-time. SIM-time will be a time scale with very high metrological characteristics (accuracy and stability) accessible in real time. CENAM is developing an algorithm to generate the SIMtime scale starting on the second part of 2008. 7. Improvement of time and frequency capabilities can be observed at SIM as result of the SIM T&F network. However, it is necessary to continue supporting Time and Frequency activities in the SIM region not only providing more SIM type GPS receivers but also with training courses to those countries interested on improving their T&F laboratories or establishing their own one. 8. Enhanced time and frequency capabilities on SIM laboratories along with the SIM-time scale will help to pave the way to improve Metrology and provide a better support to industry in the Americas.
Conclusions TIME AND FREQUENCY METROLOGY WORKING GROUP 6. Measurement results produced by the SIM T&F network will be used in the near future to generate a virtual time scale called SIM-time. SIM-time will be a time scale with very high metrological characteristics (accuracy and stability) accessible in real time. CENAM is developing an algorithm to generate the SIMtime scale starting on the second part of 2008. 7. Improvement of time and frequency capabilities can be observed at SIM as result of the SIM T&F network. However, it is necessary to continue supporting Time and Frequency activities in the SIM region not only providing more SIM type GPS receivers but also with training courses to those countries interested on improving their T&F laboratories or establishing their own one. 8. Enhanced time and frequency capabilities on SIM laboratories along with the SIM-time scale will help to pave the way to improve Metrology and provide a better support to industry in the Americas.
Thank Thank you you for for your your attention attention J. Mauricio Lopez R. a, Michael A. Lombardi b, Andrew N. Novick b, Jean-Simon Boulanger c, Raymond Pelletier c, Carlos Donado M. d, and Ricardo Carvalho e a Centro Nacional de Metrología (CENAM), Querétaro, Mexico, mauricio.lopez@cenam.mx b National Institute of Standards and Technology, Boulder, Colorado, United States, lombardi@nist.gov c National Research Council (NRC), Ottawa, Canada, jean-simon.boulanger@nrc-cnrc.gc.ca d Centro Nacional de Metrología de Panamá (CENAMEP), Panama City, Panama e Observatorio Nacional, Rio de Janeiro, Brazil