1 Centro Nacional de Metrología (CENAM), Querétaro, Mexico

J. Mauricio Lopez R.1, Michael A. Lombardi2, N. Diaz-Muñoz1 and Eduardo de Carlos Lopez1 1Centro Nacional de Metrología (CENAM), Querétaro, Mexico

2National Institute of Standards and Technology (NIST), Boulder, Colorado, United States,

A NEW ALGORITHM FOR CLOCK WEIGHTSFOR THE SIM TIME SCALE

OUTLINE

1. Motivations

2. The SIM Time Network (SIMTN)

3. The SIM time scale (SIMT)

4. New weights algorithm

5. Conclusions and future work


J. Mauricio Lopez R., Michael A. Lombardi, N. Diaz-Muñoz and Eduardo de Carlos Lopez

OUTLINE

1. Motivations 2. The SIM Time Network (SIMTN)






TIMEThe most measured physical quantity

TWO FACES OF TIME

The current SITime is the most accurate measurement

Scientific and fundamental research Technological and practical applications

OUTLINE

1. Motivations







TIME AND FREQUENCY METROLOGY WORKING GROUPWorking to support time and frequency metrology throughout the Americas

34 NMIs

3 NMIs

7 NMIs

5 NMIs

5 NMIs

14 NMIs


Current SIMTN members

18 1


SIMTN Area Coverage

18 1 SIM NMIs

Clock A

Clock B


Clock A

Clock B

GPS satellite

Mea

surin

g sy

stem

A

Mea

surin

g sy

stem

B


Clock A

Clock B

GPS satellite

Mea

surin

g sy

stem

A

Mea

surin

g sy

stem

B

Time of the day

GP

S –

Clo

ck A

Time of the day

GP

S –

clo

ck B


Clock A

Clock B

Mea

surin

g sy

stem

A

Mea

surin

g sy

stem

B

SIMTN servers

CENAM

NIST

NRC

ONRJ

Time of the day

GP

S –

Clo

ck A

Time of the day

GP

S –

clo

ck B


timeClo

ck A

– C

lock

B ±

u

(Clock A – S) – (Clock B – S) = (Clock A – Clock B) + (dSA – dSB)

Time of the day

GP

S –

clo

ck B

Time of the day

GP

S –

Clo

ck A


21

)1(...321 N

NNNC

NC number of bilateral comparisons

N number of laboratories in the network

For

N=18

there are

NC = 153

bilateral comparisons

LNM

ICE

SIC

CENAM

NIST

NRC

ONRJ

INDP

INTNUTE

INTI

BSJ

SLBS

CENAMEP

links in the SIMTN


LNM

ICE

SIC

CENAM

NIST

NRC

ONRJ

INDP

INTNUTE

INTI

BSJ

SLBS

CENAMEP

Shortest link

215.301 km baselineArgentina to Uruguay


links in the SIMTN

Longest link

8676.511 km baselineUSA to Argentina

http://www.tf.nist.gov/sim

CENAM Time – NIST time


OUTLINE

1. Motivations







30 Cesium beam clocks

9 Active Hydrogen Masers

1 Cs fountain clock (NIST)

2 Cs fountain clocks in progress(NRC and CENAM)

4 ensemble time scales(NRC, NIST, CENAM and ONRJ)


SIMT(k) (clock or time scale)

SIMTN Computer

8-channel GPS Receiver

New data every 10 minutes

Time Interval Counter

FTP Server (CENAM)(processes CVGPS and

AVGPS data)

1 pps

GPS satellites

1.57542 GHz (L1 carrier)

1 pps

FTP FTP Server (NIST)(processes CVGPS and

AVGPS data)

FTP Server (NRC)(processes CVGPS and

AVGPS data)k-th member of SIMTN

(18 members)

SIMTN Web Server (NIST)(publishes comparisons every 10 minutes)

(publishes SIMT every hour)

SIMTN Web Server (CENAM)(publishes comparisons every 10 minutes)

SIMTN Web Server (NRC)(publishes comparisons every 10 minutes)

FTP

FTP

SIMT Computer (CENAM)(reads SIMTN data feeds, runs SIMT

algorithms, generates SIMT every hour)SIMTN data feeds (HTTP)

FTP

(new data every hour)

10 MHz

GPS antenna


2)()()( k

kkk

DtYtXtX

Prediction of the time difference between clock k and SIMT at the future time t+

Time difference between clock k and SIMT at the time t (0th order aproximation)

Correction due to sistematic frequency difference between clock k and SIMT (1st order aproximation)

Correction due to non constant (linear) frequency difference between clock k and SIMT (2th order aproximation)

Taylor series expansion on the predicted time difference of clock k respect to SIMT


N

jjkjjk tXtXwtX

1

)()()(

Time difference between clock k and SIMT at the current time t+

Prediction of the time difference between clock j and SIMT made at the past time t

Time difference between clock j and clock k at the time t+

Averaging


OUTLINE

1. Motivations







)(

1

ii ,

1

)(

1

fi

i

N

jjkjjk tXtXwtX

1

)()()(

Since February, 2012


55750 55800 55850 55900 55950 56000 56050 56100 56150-30

-20

-10

0

10

20

30

MJD

SIM

T - S

IMT(

NIS

T) /

ns

)(

1

ii ,

1

)(

1

fi

i

February 9, 2012



5561055620556305564055650556605567055680556905570055710

5561055620556305564055650556605567055680556905570055710

-30

-20

-10

0

10

20

30

40

-30

-20

-10

0

10

20

30

40

from Feb 9, 2012 to May 9, 2012

From Feb 23, 2011, to May 23, 2011

MJD

SIM

T - S

IMT(

NIS

T) /

ns

MJD

SIM

T -

SIM

T(N

IST

) /

ns

1E+03 1E+04 1E+05 1E+06 1E+071E-16

1E-14

1E-12

Feb - May 2012Feb - May 2011

Averaging time / s

AVAR



55960 55980 56000 56020 56040 56060 56080 56100 56120 56140-20

-15

-10

-5

0

5

10

15

20

25

SIMT - SIMT(NIST)

MJD

Tim

e di

ffere

nce

/ ns


55960 55980 56000 56020 56040 56060 56080 56100 56120 56140-20

-15

-10

-5

0

5

10

15

20

25

UTC - UTC(NIST)SIMT - SIMT(NIST)

MJD

Tim

e di

ffere

nce

/ ns


55960 55980 56000 56020 56040 56060 56080 56100 56120 56140-20

-15

-10

-5

0

5

10

15

20

25

UTC - UTC(NIST)SIMT - SIMT(NIST)UTCr - UTC(NIST)

MJD

Tim

e di

ffere

nce

/ ns

55960 55980 56000 56020 56040 56060 56080 56100 56120 56140 561600

5

10

15

20

25

UTC - UTC(NIST)

MJD

Tim

e di

ffere

nce

/ ns


55960 55980 56000 56020 56040 56060 560800

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

SIMT(NIST) SIMT(CNM)SIMT(NRC)SIMT(CNMP)SIMT(ONRJ)SIMT(ICE)SIMT(SIC)SIMT(INTI)

MJD

SIM

T W

eigh

ts

,1

)(

1

fi

i


OUTLINE

1. Motivations







3 +1 SIMTN servers

CENAM

NIST

NRC

ONRJ


Computation of SIMT in 3 different locations

CENAM

NIST

NRC


Cs clock(s) will be included

SIMT(k) will be steered to SIMT


Bolivia

18 SIM NMIs

+


More room to improve the SIMT stability


Development of new SIM GPS systems with full compatibility with the BIPM algorithm to produce the UTC (in progress). More SIM NMIs contributing data to TAI.


J. Mauricio Lopez R.1, Michael A. Lombardi2, N. Diaz-Muñoz1 and Eduardo de Carlos Lopez1, 1Centro Nacional de Metrología (CENAM), Querétaro, Mexico

2National Institute of Standards and Technology (NIST), Boulder, Colorado, United States,

THANK YOU FOR YOUR ATTENTION!



1 Centro Nacional de Metrología (CENAM), Querétaro, Mexico

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