PG15-4 Inf. Session 기기기기기기 기기기기 UTC and Leap Second in Rep. of Korea Dai-Hyuk Yu Center for Time and Frequency Division of Physical Metrology Korea Research Institute of Standards and Science
APG15-4 Inf. Session
기반표준본부 시간센터
UTC and Leap Secondin Rep. of Korea
UTC and Leap Secondin Rep. of Korea
Dai-Hyuk Yu
Center for Time and FrequencyDivision of Physical Metrology
Korea Research Institute of Standards and Science
Generation of UTC
NMIs in the World
Time Scale UTC(k)Commercial clocks
Time transfer
Primary Frequency Standards
BIPM
Free Atomic Scale (EAL)
International Atomic Time (TAI)
Coordinated Universal Time (UTC)
Universal Time (UT1)
BIPM Circular TUTC – UTC(k)
Weighted Average of ~400 atomic clocks over 70 Labs.
Accuracy Evaluation
Leap Second|UTC- UT1| < 0.9 s
UTC(k) traceable to UTC
TA(k)
Atomic Clock 1
t1
t2
t3
tn
BIPMAtomic Clock 2
Atomic Clock 3
Atomic Clock n
UTC(k)
GPS receiver
Clock Comparison
9 atomic clocks: 5 Cs clocks + 4 H-masers
Circular Tissued monthly
Dissemination of the Korea Standard Time
5 MHz, 5 kW
Broadcasting of Time Signal (call sign: HLA)
Time service through internet
NTP time server at KRISS
260 million/day
Survey(2013)
Purpose
Current status of Time Sync. in civil area Opinions on the “Leap Second” issue Possible failure experiences during the “Leap Sec-
ond” insertion
Statistics
Period: August ~ September in 2013 Target: TV stations, Research Institutes, Companies,
Banks etc. 17 responses from 22
Survey(2013)
Quite Well47%Well
47%
No6%
Recognition of Leap Second
Survey(2013)
GPS58.8%
GPS/NTP11.8%
GPS/HF sta-tion
5.9%
NTP11.8%
Other5.9%
No resp.5.9%
Sources of Time Sync.
GPS: 76.5% NTP: 23.6% HF station: 5.9%
No problem reported so far can be attributed to the well functioning of GPS and receivers- expect some support in case needed
Survey(2013)
Yes29.4%
No17.6%
Indif-ference47.1%
No resp.5.9%
Cessation of Leap Second
Indifference - no problem so far - expect some support in case needed
Survey(2013)
Yes - troublesome to care for the insertion of “Leap Second” - avoid possible future catastrophe and the correction is possible with higher accuracy by using other method - need to carefully guide some equipment users to use “GPS Time” not “UTC” to avoid possible malfunction - transaction can be in a mess due to “causality problem”
Cessation of Leap Second
No - no problem so far - need to do extra work to the existing well functioning system
Possible problems
Judah Levine, NIST, ITU-leapsec, 2013.7
Possible problems
Judah Levine, NIST, ITU-leapsec, 2013.7
Possible problems
Judah Levine, NIST, ITU-leapsec, 2013.7
NTP time server at KRISS
~3000/s260 million/day
Impact - KRISS servers transmit ~2x3000 times messages with a time equivalent to 23:59:59 UTC - Some systems do not recognize advance notice parameter and do nothing at leap second (1 s error until next request) - system can request repeatedly - some system can crashes” - increasing number of users for NTP
Possible problems
Continue to do…
Current status - There are pros and cons for the cessation of “Leap Second” - There are no unanimous agreement in Korea - Direction : continue to study to “prevent possible future repetitive occurrence of catastrophe when the “Leap Second” is maintained