Space-Time Standards Laboratory Japan Standard Time 6HUYLFHGroup
National Institute of Information and Communications Technology
-DSDQ6WDQGDUG7LPH6HUYLFH*URXSʊ*HQHUDWLRQ&RPSDULVRQDQG 'LVVHPLQDWLRQRI-DSDQ6WDQGDUG7LPHDQG)UHTXHQF\6WDQGDUGV
National Institute of Information and Communications Technology 7KH1DWLRQDO,QVWLWXWHRI,QIRUPDWLRQDQG&RPPXQLFDWLRQV7HFKQRORJ\ 1,&7 LVUHVSRQVLEOHIRUWKHLPSRUWDQW WDVNV RI *HQHUDWLRQ &RPSDULVRQ DQG 'LVVHPLQDWLRQ RI -DSDQ 6WDQGDUG 7LPH DQG )UHTXHQF\ 6WDQGDUGV ZKLFKKDYHDGLUHFWLPSDFWRQSHRSOH¶VOLYHV,QWKLVEURFKXUHZHILUVWH[SODLQKRZ,QWHUQDWLRQDO$WRPLF7LPH DQG &RRUGLQDWHG 8QLYHUVDO 7LPH DUH FDOFXODWHG :H WKHQ ORRN DW KRZ WKH VWDQGDUG WLPH DOO RYHU WKH ZRUOG LQFOXGLQJ -DSDQ 6WDQGDUG 7LPH LV JHQHUDWHG EDVHG RQ WKHP )LQDOO\ ZH LQWURGXFH WKUHH PDMRU IXQFWLRQV RI WKH-DSDQ6WDQGDUG7LPH6HUYLFH*URXS*HQHUDWLRQ&RPSDULVRQDQG'LVVHPLQDWLRQRI-DSDQ6WDQGDUG7LPH
6OJWFSTBM 5JNF 65 BU PO +BOVBSZ BOE UIF UXP IBWF TJODF ESJGUFE BQBSU 5"* JT EFDJEFE CZ DBMDVMBUJOH B XFJHIUFEBWFSBHFUJNFPGBUPNJDDMPDLTBSPVOEUIFXPSME
PPSEJOBUFE6OJWFSTBM5JNFBOE-FBQ4FDPOE$ڦ "EKVTUNFOU 8IBUJTUIF5JNF 0VSEBJMZMJWFTBSFHPWFSOFECZUIFBQQBSFOUNPUJPOPGUIF4VO 4JODF UIF UJNF TDBMF VTFE JO NFBTVSJOH UJNF JT BUPNJD UJNF UIFSFJTBOFFEGPSBOBUPNJDUJNFUIBUJTDMPTFUP6OJWFSTBM5JNF 65 5IJTBUPNJDUJNFJTDBMMFE$PPSEJOBUFE6OJWFSTBM5JNF 65$
"T UIF BOHVMBS WFMPDJUZ PG UIF &BSUI JT BGGFDUFE CZ OBUVSBM QIFOPNFOBTVDIBTUJEBMGSJDUJPO UIFNBOUMF BOEUIFBUNPT B UJNF EJGGFSFODF CFUXFFO 65 BOE 65$ JT GMVDUVBUFE FGJOJUJPOPGB4FDPOE QIFSF% ڦ 5IFSFGPSF UP LFFQ UIF UJNF EJGGFSFODF CFUXFFO 65$ BOE 65 %FGJOJUJPOPGBTFDPOE5IFEVSBUJPOPGUIFVOJUiTFDPOEwXBT XJUIJO TFDPOET iPOF TFDPOEw JT FJUIFS JOTFSUFE JOUP PS GJSTUEFGJOFEBDDPSEJOHUPFQIFNFSJTUJNF XIJDIJTUJFEUPUIF EFMFUFEGSPN65$ SPUBUJPOBOEPSCJUBMNPUJPOPGUIF&BSUI4JODF IPXFWFS 5IJTPOFTFDPOEJTSFGFSSFEUPBTBiMFBQTFDPOEw UIF TFDPOE IBT CFFO EFGJOFE JO UFSNT PG UIF GSFRVFODZ PG -FBQTFDPOE BEKVTUNFOU XBT JOUSPEVDFE BGUFS B TQFDJBM BUPNJDSBEJBUJPOVOEFSUIF*OUFSOBUJPOBM4ZTUFNPG6OJUT 4* BEKVTUNFOUXBTDBSSJFEPVUJO-FBQTFDPOEBEKVTUNFOUT 5IFTFDPOEJTEFGJOFEJOUIF4*BTiUIFEVSBUJPOPG IBWFCFFOQFSGPSNFEUJNFTGSPNUP+BOVBSZ"MM QFSJPET PG UIF SBEJBUJPO DPSSFTQPOEJOH UP UIF USBOTJUJPO BEKVTUNFOUTTPGBSIBWFJOWPMWFEJOTFSUJOHPOFTFDPOEUP65$ CFUXFFO UXP IZQFSGJOF MFWFMT PG UIF HSPVOE TUBUF PG UIF BOE65$JTOPXTFDPOETCFIJOE5"* DFTJVNBUPNw ڦ +45 +BQBO4UBOEBSE5JNF 5"* OUFSOBUJPOBM"UPNJD5JNF*ڦ 5IFUJNFTDBMFDSFBUFECZBUPNJDDMPDLTJTSFGFSSFEUPBTBUPNJD +BQBO4UBOEBSE5JNF +45 JTEFGJOFEUPTFUIPVSTGPSXBSEPG UJNF 65$ /*$5 UIFNFSJEJBOMJOFPG+BQBOJTBUEFHSFFTFBTUFSO 5IF *OUFSOBUJPOBM "UPNJD 5JNF 5"* XBT TZODISPOJ[FE XJUI MPOHJUVEF
Generation of JST
Atomic Clock ڦ JST is obtained using a maximum of 18 cesium atomic clocks and four hydrogen masers in accordance with the definition of the unit of the second as mentioned above. (Left) Hydrogen maser clock (Right) Cesium atomic clock Cesium atomic clocks are good for long-term (longer than 5 days) stability and hydrogen masers are good for short-term Generation of JST ڦ .shorter than 5 days) stability) The frequency (i.e., the number of oscillations per second) of Mutual time differences of cesium atomic clocks and hydrogen each atomic clock is easily affected by environmental masers mounted in four Clock Rooms are regularly measured conditions such as temperature, humidity, and the geo- every second by a specific measurement system. UTC (NICT) is magnetic UTC generated by the National Institute of Information and To stabilize the frequency, atomic clocks are mounted in Communications Technology (NICT) from averaging and temperature-and humidity-controlled “Clock Rooms” with synthesizing data obtained from atomic clocks once an hour. electromagnetic shielding. Furthermore, each atomic clock is This series of procedures for generating JST is fully and connected to an uninterruptible power supply unit in case automatically performed by computers. Three redundant units there is a power outage. (the main unit and backups) work in parallel, ensuring the continual generation of JST in the event of equipment failure. Flow of Time Generation Atomic Clocks Establishment of Distributed Structure ڦ Measurement system Measurement of Until recently the generation of JST was carried out only at the NICT headquarters in Koganei City, Tokyo. However, at the time of emergency, such as a serious natural disaster, in Tokyo, the operation of JST in headquarters might be Synthesis Average stopped due to infrastructure damage. Computer To increase reliability, therefore, we are promoting research Set the time forward by +9hours to UTC (NICT) and development for decentralization of the JST facilities. As
+9hours Hyogo on June 10, 2018. Japan Standard Time (JST) The equipment for JST sub-station, including cesium atomic clocks and high precision satellite time and frequency transfer TAI (International Atomic Time) systems, were installed there. The two accurate time scales determined by the International Bureau of Weights generated in Tokyo and Kobe are always compared. At the and Measures (BIPM) emergency of Tokyo, Kobe Sub-station can function as the UTC (Coordinated Universal Time) main JST station instead of the NICT headquarters. determined by the BIPM Development of technology to consolidate multiple time UTC (NICT) scaleswill further bring more accuracy of JST by using atomic determined by the NICT clocks ofdistant stations, including the LF standard time and frequencytransmission stations. JST (Japan Standard Time) set 9 hours forward to UTC (NICT)
2 *- ÕV>Ì Ã>ÌiÌi Ã>ÌiÌi $PNQBSJTPOT XJUI+45
$PNQBSJTPO PNQBSJTPOPG65$BOE+45 "UPNJDDMPDL "UPNJDDMPDL$ڦ 5IF/*$5NBOBHFT65$ /*$5 UPBQQSPYJNBUF65$BOEEFDSFBTF 5JNFDPNQBSJTPOVTJOH(/44 UIF UJNF EJGGFSFODF CFUXFFO 65$ BOE 65$ /*$5 XJUIJO *UJTQPTTJCMFUPPCUBJOUIFEJGGFSFODFCFUXFFOUJNFJOGPSNBUJPO OBOPTFDPOET OBOPTFDPOE TFDPOET 5P USBOTNJUUFE CZ OBWJHBUJPO TBUFMMJUFT TVDI BT (14 BOE 65$ NBLF UIJT BEKVTUNFOU IJHIMZ QSFDJTF JOUFSOBUJPOBM UJNF HFOFSBUFECZFBDIJOTUJUVUFIBWJOHBUPNJDDMPDLT DPNQBSJTPO NFUIPET VTJOH (MPCBM /BWJHBUJPO 4BUFMMJUF 65$ /*$5 BOE65$PCUBJOFECZFBDIJOTUJUVUFBSFDPNQBSFE 4ZTUFNT (/44 TVDI BT (MPCBM 1PTJUJPOJOH 4ZTUFN (14 BOE VTJOHUJNFJOGPSNBUJPOPGTBUFMMJUFTBTBOJOUFSNFEJBSZJOUIF DPNNVOJDBUJPOTBUFMMJUFTBSFJNQMFNFOUFE DBMDVMBUJPOT5IFUJNFTSFQPSUFECZUXPTUBOEBSETUBUJPOTBSF 4UBOEBSETJOTUJUVUFTBSPVOEUIFXPSMENBOBHFUIFJSTUBOEBSE DPNQBSFEXJUIQSFDJTJPOPGBCPVUPOFIVOESFENJMMJPOUITPGB UJNFT BOE FBDI JOTUJUVUF SFQPSUT UJNF JOGPSNBUJPO GPS FBDI TFDPOEUPFWFOUFOCJMMJPOUITPGBTFDPOE BUPNJD DMPDL JO UFSNT PG UJNF EJGGFSFODFT UP #VSFBV *OUFS OBUJPOBMEFT1PETFU.FTVSFT *OUFSOBUJPOBM#VSFBVPG8FJHIUT 5JNFDPNQBSJTPOVTJOHDPNNVOJDBUJPOTBUFMMJUFT BOE .FBTVSFT <#*1.> #*1. EFDJEFT UIF 5"* BOE 65$ PO UIF 5XP TUBUJPOT TJNVMUBOFPVTMZ USBOTNJU UJNF JOGPSNBUJPO VTJOH CBTJTPGUIFEBUBDPMMFDUFEGSPNFBDIDPVOUSZ DPNNVOJDBUJPOTBUFMMJUFT BOEUIFUJNFEJGGFSFODFJTDBMDVMBUFE 5IFQSFDJTJPOPGUIJTUJNFDPNQBSJTPOJTBCPVUPOFCJMMJPOUIPGB TFDPOEUPUFOCJMMJPOUITPGBTFDPOE OUFSOBUJPOBM$PNQBSJTPO*ڦ 5IF/*$5BEPQUTUXPNFUIPETJONBLJOHQSFDJTFJOUFSOBUJPOBM /PXBEBZT NBOZIJHIMZQSFDJTFUJNFDPNQBSJTPOTBSFNBEF UJNFDPNQBSJTPOT VTJOHUIFUXPNFUIPET
(FPHSBQIJDBMEJTUSJCVUJPOPGUIFMBCPSBUPSJFTUIBUDPOUSJCVUFUP5"*BOEUJNFUSBOTGFSFRVJQNFOU
%JTTFNJOBUJPO UJNF DPEF HJWJOH UIF NJOVUF IPVS EBZ PG ZFBS DPVOUFE GSPN +BOVBSZ ZFBS MBTUUXPEJHJUTPGUIFEPNJOJDBMZFBS BOEEBZPG PG+45 XFFL5IJTUJNFDPEFJTVTFEGPSSFDFQUJPOEFWJDFTTVDIBTSBEJP DPOUSPMMFEDMPDLTXJUIBVUPNBUJDUJNFDPSSFDUJPOGVODUJPOT 5IFUJNFDPEFTJHOBMJTFYQFDUFEUPCFVTFEJOBXJEFSBOHFPG BQQMJDBUJPOT TVDI BT DMPDLT JO IPNF FMFDUSPOJD BQQMJBODFT DBNFSBT BOEBVUPNPCJMFT BOEUIFCVJMUJODMPDLTPGNFBTVSJOH JOTUSVNFOUT BOE TFJTNPNFUFST 5IF TUBOEBSE GSFRVFODZ TVQQMJFE CZ UIF -' TUBOEBSE UJNF BOE GSFRVFODZ USBOTNJTTJPO PX'SFRVFODZ4UBOEBSE5JNFBOE TJHOBMJTBMTPFYQFDUFEUPTFSWFBTBQSFDJTFGSFRVFODZTUBOEBSE-ڦ 'SFRVFODZ5SBOTNJTTJPO4UBUJPOT GPS B WBSJFUZ PG BQQMJDBUJPOT TVDI BT NFBTVSJOH JOTUSVNFOUT 5IF TUBOEBSE UJNF BOE GSFRVFODZ USBOTNJTTJPO ++: JT B SBEJP DPNNVOJDBUJPO EFWJDFT NBTUFS TUBOEBSE EFWJDFT PG FMFDUSPOJD XBWF VTFE UP TVQQMZ TUBOEBSE GSFRVFODJFT BOE +45 UISPVHIPVU NBOVGBDUVSFST BOE TUBOEBSE PTDJMMBUPST VTFE JO HSPVOECBTFE +BQBO3BEJPDPOUSPMMFEXBUDIFTBOEDMPDLTBSFOPXXJEFMZVTFE EJHJUBMCSPBEDBTUJOH CZUIFHFOFSBMQVCMJDBOEUIFZTZODISPOJ[FXJUI+45CZSFDFJWJOH "MUIPVHI UIF -' TUBOEBSE UJNF BOE GSFRVFODZ USBOTNJTTJPO UIJTTUBOEBSESBEJPXBWF TJHOBMIBTPSEJOBSJMZCFFOUSBOTNJUUFEGPSIPVSTBEBZ JUNBZ 5IFGJSTUPQFSBUJPOBMTUBUJPO OBNFMZUIF0IUBLBEPZBZBNB-PX UFNQPSBSJMZCFTVTQFOEFECFDBVTFPGNBJOUFOBODFDIFDLVQTPG GSFRVFODZ -' 4UBOEBSE 5JNF BOE 'SFRVFODZ 5SBOTNJTTJPO EFWJDFTBOEBOUFOOBT PSJOUIFFWFOUPGQPTTJCMFMJHIUOJOH 4UBUJPO TUBSUFE USBOTNJUUJOH B TUBOEBSE XBWF L)[ JO +VOF 5P QSPWJEF B CBDLVQ BOE TUSFOHUIFO UIF TJHOBM JO 5IF TUBUVT PG USBOTNJTTJPO JT BOOPVODFE POUIFXFCTJUF TPVUIXFTUFSO +BQBO UIF )BHBOFZBNB -' 4UBOEBSE 5JNF BOE IUUQTKKZOJDUHPKQ 'SFRVFODZ 5SBOTNJTTJPO 4UBUJPO DPNNFODFE USBOTNJTTJPO PG B TUBOEBSEXBWF L)[ JO0DUPCFS ++:JTUIFDBMMTJHOPGUIFSBEJPTUBUJPOBOEJTBSFHJTUFSFEUSBEF "O-'TUBOEBSEUJNFBOEGSFRVFODZUSBOTNJTTJPOTJHOBMJODMVEFTB NBSL 5 PGUIF/*$5
1,500km 40~50dBμV/m
1,000km 50~60dBμV/m 1,500km 43~53dBμV/m 500km >60dBμV/m 1,000km 500km 53~63dBμV/m >53dBμV/m>63dBμV/m Ohtakadoya-yama LF Standard Time and Frequency Transmission Station (40 kHz)
Hagane-yama LF Standard Time and Frequency Koganei-city, Tokyo Transmission Station (60 kHz)
A numerical value below each distance (km) shows the value by calculating theoretically assumed field strength.
)+45 OUFSOFU5JNF4FSWJDF 5IF +BQBO 4UBOEBSE 5JNF 4FSWJDF (SPVQ*ڦ *O UPEBZT DPNQVUFSJ[FE TPDJFUZ NPTU DPNQVUFST USBOTGFS PGGFST i5JNF*OGPSNBUJPO 4FSWJDF CZ /FUXPSLTw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i*OUFSOFU 5JNF 4FSWJDFw UP PDDVS JO GJMF JOGPSNBUJPO 5IFSFGPSF UIF /51 /FUXPSL 5JNF HFOFSBM VTFST TP UIBU UIFZ UPP BSF BCMF UP VTF BO /51 TFSWFS 1SPUPDPM JT XJEFMZ VTFE UP TZODISPOJ[F UIF UJNFT PG OUQOJDUKQ UIBUMJOLTVQXJUI+45 OFUXPSLFEDPNQVUFST Architecture of Time Information Service through Internet
National Institute of NTP service Users Internet Information and and others Communications Technology Leased Line NTP stratum 2 server Time information service UTC(NICT) throXgh Networks
NTP stratum 2 server Internet NTP stratum 1 Server Internet Time Service
5FMFQIPOF++:4FSWJDF %FEJDBUFESFDFJWFSTGPSDPNNFSDJBMVTFQFSGPSNUJNFTZODISP ڦ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■)JLBSJ5FMFQIPOF++:4FSWJDF 'PSIJHIFSQSFDJTJPOBOETUBCJMJUZPGUJNFEJTTFNJOBUJPO /*$5 IBEEFWFMPQFE)JLBSJUFMFQIPOF++:BOETUBSUFEFYQFSJNFOUBM PQFSBUJPOJO.BZ )JLBSJUFMFQIPOF++:IBTCFFOJOPGGJDJBMPQFSBUJPOTJODF 'FCSVBSZ"GUFS5FMFQIPOF++:FOETJO.BSDI )JLBSJ UFMFQIPOF++:XJMMCFUIFTJOHMFTFSWJDFVTJOHUIFUFMFQIPOF MJOF )JLBSJUFMFQIPOF++:SFBMJ[FEUIFTUBCMFEJTTFNJOBUJPO BOE SFEVDUJPOPGEPXOUJNFPGUIFTFSWJDFEVFUPIJHITQFFEEBUB DPNNVOJDBUJPOBOECBDLVQSFEVOEBODZPGUIFIPTUTZTUFN
JNQMFNFOUFECZUJNFDPNQBSJTPOVTJOH SFNPUFDBMJCSBUJPO C BMJCSBUJPOPGUIF'SFRVFODZ4UBOEBSE$ڦ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o DMJFOUTNBZTFMFDUFJUIFS +BQBOFTFWFSTJPOPOMZ
B DBMJCSBUJPOPGUIFGSFRVFODZTUBOEBSE DBSSJFEJOUPUIF/*$5 BOEDBSSJFEPVUXJUIUIF/*$5GBDJMJUJFT PS
Measurement CIPM-MRA Radio Law CommissionHd Law (ASNITE)
Calibration of Carried-in Carried-in Carried-in Carried-in frequency standard Remote Remote Remote
Measurement of N/A N/A N/A Carried-in short-term stability
“Carried-in” calibration is directly available Courier service is available “Remote” calibration is available “N/A (Not Available)”
'SFRVFODZ4UBOEBSE$BMJCSBUJPO4ZTUFN
The JSTG began disseminating JST, which is traceable to UTC, to the general public in February 2005. This has made it An possible to use precisely and socially authorized electronic time information. A system, in practice, is constructed as shown in the figure Information below. The NICT, as the National Time Authority (NTA), provides JST to the Time Assessment Authority (TAA) by publishing the measurement data on the Internet using a GPS Technology common-view method, and then provides users the precise time, which is traceable to JST via the TAA and the Time Stamp Authority (TSA). Society Since the time comparison method using the GPS common- view is able to measure 1 second with accuracy of about 10 nanoseconds but unable to measure the time label itself, the Telephone JJY, NTP, and JJY operated by the JSTG are used to .Electronic Time Authentication adjust time ڦ The concept of incorporating precise time into information In addition, the JSTG has promoted the use of traceability technology (IT) is referred to as new words “time business,” chains of UTC (NICT) to the TSA and the structure of the time which mainly consists of “time dissemination” and “time dissemination and the audit carried out by the TAA. Technical authentication” business. The IT community has been requirements for the TAA have already been established in encouraged to adopt precise time; e.g., as a timestamp. A Japanese Industrial Standards (JIS X 5094) and also established Japanese law on e-documents, which came into effect in April in ISO/IEC 18014-4 by the International Organization for 2005, requires time stamps to be put on electronic documents Standardization in 2015. to certify that they have not been altered, and it is inevitable for precise time information to be used for the time stamps.
Time Comparison Method using GPS common-view Time Assessment Authority Time Stamp Authority
Clock of TAA Internet and others Internet and others
GPS Time Comparison JJY +LNDUL7HOHSKRQH--<
Others +LNDUL7HOHSKRQH--< 7HOHSKRQH--< TAA/TSA server
National Institute of Information and Communications Technology 3BEJP3FTFBSDI*OTUJUVUF &MFDUSPNBHOFUJD4UBOEBSET3FTFBSDI$FOUFS Space-Time Standards Laboratory,Japan Standard Time 4FSWJDFGroup 4-2-1 Nukui-Kitamachi, Koganei, Tokyo 184-8795 Japan 63-IUUQTKKZOJDUHPKQ&NBJMIPSPOFU!NMOJDUHPKQ5FM 'BY The 1st edition: 0DUPCFS 2004
This brochure is printed on recycled paper. Revised: "QSJM