Generation and Dissemination of Japan Standard Time (T Ido

Generation and dissemination of Japan Standard Time including the launch of Kobe substation

F. Nakagawa, T. Ido and Y. Hanado

National Institute of Information and Communications Technology (NICT), Japan

1 Outline of our laboratory

NICT Headquarters @Tokyo National institute of Information and Communications 135 deg. Technology

Tokyo  Space-Time Standard Laboratory  Atomic Freq. Standards  T&F transfer JST = UTC(NICT) + 9 hours  Japan Standard Time (JST)

Optical JST system Satellite Cs PFS clock T&F transfer VLBI LF station 2 Contents

 Generation process of Japan Standard Time

 Dissemination services

 Launch of JST sub-station at Kobe

3 Contents

 Generation process of Japan Standard Time

 Dissemination services

 Launch of JST sub-station at Kobe

4 Activity of Japan Standard Time (JST)

JST system (2006~) H-maser TWSTFT, GPS

Cs NICT-CsF1 5071A

LF stations Telephone NTP NTA for Calibration Time Service service Time stamp service 60kHz 23kW 40kHz TA 13kW TSA Analog line remote Digital line Internet Time stamp UTC 12:10:35 direct

NICT （1, 5, 10MHz） Monthly access daily access > 140,000. > 300 million. 5 Activity of Japan Standard Time (JST)

JST system (2006~) H-maser TWSTFT, GPS

Cs NICT-CsF1 5071A

LF stations Telephone NTP NTA for Calibration Time Service service Time stamp service 60kHz 23kW 40kHz TA 13kW TSA remote Internet Time stamp UTC 12:10:35 direct

NICT （1, 5, 10MHz） Monthly access daily access > 140,000. > 300 million. 6 Flow of making Japan Standard Time

Steering to H-Maser AOG ( Signal source ) ( microphase-stepper ) trace UTC Actual signals for UTC(NICT) JST ( 5MHz,1pps )

Various Steering services to trace NET

NICT Cs Ensemble Time scale (NET) 18 Cs-clocks 24ch-DMTD system & TI-counter ( for NET ) ( NET exists only in ( measure the time differences a computer) of all HM, Cs clocks, AOGs ) * DMTD: Dual Mixer Time Difference 7 Feature-1 : Combination of 5MHz + 1pps data

5MHz 100 smpl. average / 1sec  5MHz measurement by DMTD ○ high precision DMTD-C Clk1 - Clk2 △ risk of cycle slip

Time Clk1 DMTD-B Clk1 - Clk2 Diff. ？ Cycle slip may ？ occur after a long-term lack of data. DMTD-A Clk1 - Clk2 1 period Clk2 200ns time

TI counter Clk1 - Clk2 1PPS  1pps measurement by TIC One shot data / 1h △ precision is not so high ○ reliability of phase data

Initial phase Frequency 1pps measurement by reliable + by precise x t is less precise, 1pps data 5MHz data but more reliable in phase = “Clk1-Clk2” measurement data determination. 8 Feature-2 : Automatic data selection procedure

5MHz 4 devices measure the same data, but Only 100 smpl. average / 1sec one data is used for a NET calculation. DMTD-C

 Program for measured data processing Clk1 DMTD-B • Simultaneous data comparison • Anomaly detection / data selection DMTD-A Clk2

(ex.) If only data (B) is largely different, TI counter it is due to the anomaly of device (B). 1PPS If all three data are strange, One shot data / 1h it is due to the anomaly of clock itself. If at least one device works well, Bad data is judged and removed measurement data is by using Majority Rule. automatically obtained. 9 Stability of Cs 5071As and NET

-13

) t ( Cs clocks (5071A) y s

log log

-14

NET Allan deviation Allan

-15 104 105 106 107 108 Average time t (s) 10 Behavior of UTC(NICT)

Allan deviation (log scale) Manual Freq. Correct. Manual Time Correct. (10ns) -12 40 4

‘13 ‘14 ‘15 ‘16 ‘17 ‘18 Freq. Correction Freq. (1e 20 2 -13 UTC(NICT)- (=HM4+AOG)HM3 HM3- 0 0 -14 HM4

UTC(NICT) UTC(NICT) ] / ns NET

- -

-20 -2 15) [ UTC [ -15 HM4 -40 -4 56500 57500 58500 MJD -16100 101 102 103 104 105 106 107 108 Averaging time (sec)

NET-UTC,UTC(NICT)-UTC: 2011~2015 HM : 2015.Jn~Mar 11 Contents

 Generation process of Japan Standard Time

 Dissemination services

 Launch of JST sub-station at Kobe

12 Activity of Japan Standard Time (JST)

JST system (2006~) H-maser TWSTFT, GPS

Cs NICT-CsF1 5071A

LF stations Telephone NTP NTA for Calibration Time Service service Time stamp service 60kHz 23kW 40kHz TA 13kW TSA remote Internet Time stamp UTC 12:10:35 direct

NICT （1, 5, 10MHz） Monthly access daily access > 140,000. > 300 million. 13 LF stations

○Specification：  Time code on long wave carrier ・frequency accuracy < 1x10-12 ・time precisin < 1 us Hagane-yama (60 kHz) Antenna hieght 200m Ohtakadoya-yama (40 kHz) antenna height: 250m

2001 Oct.1 ～

～ • Signal source : local Cs clocks (5071A) 1999 Jun.10 • Time and frequency steered to JST by ＊short-wave service monitoring difference using Two-way satellite link terminated in 2001年 14 Telephone JJY

 Dissemination using analog • Usable in a closed environment telephone line (Telephone Utilize identical delay in two way JJY) • Delay estimated from the “back and forth” signal transmission time

# of access ＞ 150 K

/mon #ofaccess (/mon)

Telephone JJY using digital (photonic) line is currently in preliminary service 15 NTP (Network Time Protocol)

 Dissemination using ○Leased line： public and private company network ○Public line ： server open to Internet 5 billion access/day （Nov. 2018）ＮＴＰ (hardware)server NTP repeater (for radio clocks) • Originally developed using an ＦＰＧＡ・High capacity ana high speed due to hard ware • The time information obtained from process NTP is transmitted for distance of 10 ・Religient from soft-ware based attacking (no m or so as a fake LF signal software in the sytem) • Precision ＜ 10ms capacity ＞ 1 million request / s internet

10 m area NICT NTP server

ＮＴＰ repeater 16 Time business service

 Time traceable to JST is disseminated to time assessment authority (TAA) • Standardization to a system to disseminate and assess the time • An electronic document is certified to be genuine by the electric signature traceable to a standard time and time-stamping technology • Accepted by ITU-R as a recommendation • ISO/IEC18014-4 , JIS X 5094 (2015)

National Time Time Assessment Time Stamp user authority（NTA） GPS authority（TTA） authority (TSA） Time comparison Source at TAA （precision:±30 ms） Time Stamp （precision：±1s）・GPS common view data ・Time signal （LF、TellJJY、NTP） audit by TAA

17 Calibration of frequency standard

 Dissemination of frequency standards： Evaluation of the fractional frequency deviation with respect to frequency standards

 ４ services：１） calibration based on Radio=wave law ２） calibration on jcss ３） calibration on CIPM-MRA （ASNITE) ４） Others

uncertainty（CMC#）： carry-in： 5x10-14 （time interval counter） -12 2.5x10 （frequency counter） GPS Common-View remote： 5x10-13  Remote calibration： data Based on GPS Common-View Alternative method using LF is under development NICT client Remote calibration 18 Contents

 Generation process of Japan Standard Time

 Dissemination services

 Launch of JST sub-station at Kobe

19 Concept

• Current JST is generated from only the clocks at NICT-HQ (Tokyo).

Distributed system for Japan Standard Time generation

Sub-station NICT-Kobe Cs Cs Cs Cs Cs Cs

Cs Cs Cs JST Cs Cs Cs Master station NICT-HQ

20 Concept

• JST has been generated from only  Features the clocks at NICT-HQ (Tokyo). • NET from all distributed clocks linked via satellites • Multiple generation of NET by Distributed system for common database at remote sites Japan Standard Time generation  Merits • Robustness : Distribution of clocks and multiplex NETs decrease a risk of stopping a timescale. Sub-station NICT-Kobe Cs Cs Cs Cs Cs Cs • Scalability : Cs Cs Each station can generate UTC(NICT) Cs JST Cs equivalent via any local clock at the Cs Cs Master station station by using any NET by common NICT-HQ database. 21 Procedure

 Process

1. Remote stations share all data of local and remote clocks.

Sub-station NICT-Kobe Cs Cs Cs Cs Cs Cs

Cs Cs Cs JST Cs Cs Cs Master station NICT-HQ

22 Procedure

 Process NET(A),(B),, should be 1. Remote stations share all data • almost same, because of local and remote clocks. they use the same clock ensemble, • but different a little, because 2. Each station independently clocks include different link errors. calculates NET from all clocks.  Clock ensemble for each NET is common, but weight of each clock may be different D at each site. NET(D) B NET(B) Cs Cs  For a check, NETs should be Cs Cs compared with each other. Cs Cs

3. NET at the Master station is Cs Cs the origin of JST, in principle. Cs Cs Labo. Remote Cs Clocks Clocks Cs C NET(C) A NET(A) 23 JST sub-station at Kobe

 Construction of sub-station at Kobe has started since 2013. * CS-5071A (5) + H-maser (2) * GNSS receiver (1) + TWSTFT system (1) * NTP + new Tel-JJY (via optical telephone line)  Regular operation has started in June 2018. * Almost remote operation (with only one monitoring staff). * Independent atomic time scale is regularly generated. * Disseminations are in a stand-by state for emergency of HQ.

B A

24 Outline

5 Cs clocks

2 HM

25 Outline

Antenna for two-way satellite link

System for time scale generation 26 Timescale generation scheme

Kogane Realization process of Japan Standard Time Japan Micro-phase i H-Maser 5MHz 5MHz Standard stepper 1pps Time Cs Ensembl e atomic time When Koganei HQ is under normal operation, adjustment via satellite is one method for synchronizing Kobe time scale with JST Time difference

Time scale H-Maser Micro-phase 5MHz stepper 5MHz at 1pps Kobe Cs Cs Ensemble atomic LF station time When Koganei HQ stops functioning, ensemble atomic time at Kobe is used for frequency adjusting Kob e 27 Check 1: Steering of Kobe time scale

Kogane Realization process of Japan Standard Time Japan Micro-phase i H-Maser 5MHz 5MHz Standard stepper 1pps Time Cs Ensembl e atomic time

Time Can we sufficiently difference synchronize the Kobe Time scale H-Maser Micro-phase timescale with JST? 5MHz stepper 5MHz at 1pps Kobe

Steering check of a microphase stepper at Kobe. Kob e 28 Check 1: Steering of Kobe time scale

• Steering the micro-phase stepper at Kobe to synchronize with JST. • Precision : ~ 2.0ns (LO=H-maser), ~7ns (LO=Cs5071A).

(2017.3/3 ~ 2017.10/29）

LO = H-maser LO = Cs5071A HQ and Kobe (ns) HQ andKobe

STD = 2.0ns STD = 6.7ns Time difference between between Time difference

Day 29 Check 2: Ensemble atomic time scale

Kogane i Is the ensemble atomic

Cs Ensembl time scale at Kobe stably e atomic generated? time

Comparing the Kobe ensemble time scale with HQ. Cs Cs Ensemble atomic LF station time

Kob e 30 Check 2: Ensemble atomic time scale

• Ensemble atomic time scale can be stably generated by only distributed clocks. (2017.8/10 ~ 2017.9/8）

Kobe + LF station 5071A: 15 All 5071A :33 HQ

5071A: 18 Hadamard variance Hadamard

Averaging time (sec) 31 Current operation style

Kogane Japan Micro-phase i H-Maser 5MHz 5MHz Standard stepper 1pps Time Cs Ensembl e atomic time

monitoring time difference

Micro-phase Time scale H-Maser Micro-phase 5MHz stepperstepper 5MHz at 1pps Kobe Cs Cs Ensemble atomic Buck up for LF station time emergency of HQ

Kob e 32 Current operation

• Officially in-service since 10 June 2018. | HQ – KOBE | < 5 ns after June 10th. Stability ~ 2E-15 @ 10-30d

TIME DIFFERENCE between HQ and KOBE 202.00E-08

1.50E-08 Measured by TWSTFT

101.00E-08 KOBE / ns / KOBE

– 6/10 5.00E-09

00.00E+00

TIME of HQ HQ of TIME -5.00E-09

-10-1.00E-08 1/01/2018 2/03/2018 1/05/2018 30/06/2018 29/08/2018 28/10/2018 27/12/2018 1/1 3/2 5/1 6/30 8/29 10/28 12/27 DATE(UTC) in 2018 33 Summary

 Japan Standard Time system has been working at NICT Koganei HQ in Tokyo since 2006. • H-maser + 18 Cs ensemble atomic timescale • Phase measurement system of 5MHz &1PPS combination • Automatic measurement data selection program • Various dissemination service; 2 LF stations, Tel-JJY, NTP, Time business, Frequency calibration

 Sub-station of JST at Kobe has launched in June 2018. • Reduced system compared with HQ (master station of JST). • Independent atomic time scale generated regularly at Kobe. • All clocks at HQ, Kobe and LF stations are linked with satellites, and can be used to generate “crowd” JST in future.