1 

NIST TIME AND FREQUENCY BULLETIN 

 NISTIR 5082-12 

 NO. 505 DECEMBER 1999 

 

1. GENERAL BACKGROUND INFORMATION .......................................................................................... 2 

 

2. TIME SCALE INFORMATION ............................................................................................................... 2 

 

3. PHASE DEVIATIONS FOR WWVB AND LORAN-C .............................................................................. 4 

 

4. BROADCAST OUTAGES OVER FIVE MINUTES AND WWVB 

 PHASE PERTURBATIONS .................................................................................................................... 5 

5. NOTES ON NIST TIME SCALES AND PRIMARY STANDARDS .......................................................... 5 

6. BIBLIOGRAPHY....................................................................................................................................... 5 

 

7. SPECIAL ANNOUNCEMENTS............................................................................................................... 7 

 

This bulletin is published monthly. Address correspondence to: 

 

Gwen E. Bennett, Editor 

Time and Frequency Division 

National Institute of Standards and Technology 

325 Broadway 

Boulder, CO 8O3O5-3328 

(3O3) 497-3295 

NOTE TO SUBSCRIBERS: Please include your address label (or a copy) 

with any correspondence regarding this bulletin. 

U.S. DEPARTMENT OF COMMERCE, William M. Daley, Secretary

TECHNOLOGY ADMINISTRATION, Dr. Cheryl L. Shavers, Under Secretary of Commerce for Technology 

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY, Raymond G. Kammer, Director 

 
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1. GENERAL BACKGROUND INFORMATION

_______________________________________________________________________________________________________ 

ACRONYMS AND ABBREVIATIONS USED IN THIS BULLETIN

BIPM - Bureau International des Poids et Mesures 

CCIR - International Radio Consultative Committee 

Cs - Cesium standard 

GOES - Geostationary Operational Environmental Satellite 

GPS - Global Positioning System 

IERS - International Earth Rotation Service 

LORAN - Long Range Navigation 

MC - Master Clock 

MJD - Modified Julian Date 

NVLAP - National Voluntary Laboratory Accreditation Program 

NIST - National Institute of Standards and Technology 

NOAA - National Oceanic and Atmospheric Administration ns - nanosecond 

SI - International System of Units μs - microsecond 

TA - Atomic Time ms - millisecond 

TAI - International Atomic Time s - second 

USNO - United States Naval Observatory min - minute 

UTC - Coordinated Universal Time 

_______________________________________________________________________________________________________ 

 2. TIME SCALE INFORMATION

 The values listed below are based on data from the IERS, the USNO, and NIST. The UTC(USNO,MC) - UTC(NIST) values are 

averaged measurements from all available common-view GPS satellites (see bibliography on page 5). UTC - UTC(NIST) data are 

on page 3.

 0000 HOURS COORDINATED UNIVERSAL TIME 

NOV 1999 MJD UT1-UTC(NIST) 

 (±5 ms) 

UTC(USNO,MC) - UTC(NIST) 

 (±20 ns) 

4 51486 +428 ms 13 ns 

11 51493 +418 ms 14 ns 

28 51500 +409 ms 14 ns 

25 51507 +398 ms 16 ns 

 

 The master clock pulses used by the WWV, WWVH, and WWVB time-code transmissions are referenced to the UTC(NIST) time 

scale. Occasionally, 1 s is added to the UTC time scale. This second is called a leap second. Its purpose is to keep the UTC time 

scale within ±0.9 s of the UT1 astronomical time scale, which changes slightly due to variations in the Earth’s rotation. 

 Positive leap seconds, beginning at 23 h 59 min 60 s UTC and ending at 0 h 0 min 0 s UTC, were inserted in the UTC 

timescale on 30 June 1972, 1981-1983, 1985, 1992, 1993, 1994, and 1997, and on 31 December 1972-1979, 1987, 1989, 

1990,1995, and 1998. 

NOTE: There will NOT be a leap second on December 31, 1999 

 The use of leap seconds ensures that UT1 - UTC will always be held within ±0.9 s. The current value of UT1 - UTC is called the 

DUT1 correction. DUT1 corrections are broadcast by WWV, WWVH, WWVB, and ACTS and are printed below. These corrections 

may be added to received UTC time signals in order to obtain UT1. 

_______________________________________________________________________________________________________ 

 +0.1 s beginning 0000 UTC 19 October 2000 

 +0.0 s beginning 0000 UTC 01 March 2001 

DUT1 = UT1 - UTC = -0.1 s beginning 0000 UTC 04 October 2001 

 -0.2 s beginning 0000 UTC 14 February 2002 

 -0.3 s beginning 0000 UTC 24 October 2002 

 -0.4 s beginning 0000 UTC 03 April 2003 

 
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The difference between UTC(NIST) from UTC has been within +/–100 ns since July 6, 1994. The table below shows 

values of UTC - UTC(NIST) as supplied by the BIPM in their Circular T publication for the most recent 310-day period in 

which data are available. Data are given at ten-day intervals. Five-day interval data are available in Circular T. 

0000 Hours Coordinated Universal Time 

DATE MJD UTC-UTC(NIST) ns 

Feb. 10, 1999 51219 25 

Feb. 20, 1999 51229 26 

Mar. 2, 1999 51239 24 

Mar. 12, 1999 51249 21 

Mar. 22, 1999 51259 15 

Apr. 1, 1999 51269 10 

Apr. 11, 1999 51279 2 

Apr. 21, 1999 51289 -9 

May 1, 1999 51299 -18 

May 11, 1999 51309 -18 

May 21, 1999 51319 -18 

May 31, 1999 51329 -16 

Jun. 10, 1999 51339 -16 

Jun. 20 1999 51349 -14 

Jun. 30, 1999 51359 -12 

Jul. 10, 1999 51369 -6 

Jul. 20, 1999 51379 -3 

Jul. 30, 1999 51389 -1 

Aug. 9, 1999 51399 -2 

Aug. 19, 1999 51409 4 

Aug. 29, 1999 51419 12 

Sep. 8, 1999 51429 15 

Sep 18, 1999 51439 13 

Sep. 28, 1999 51449 15 

Oct. 8, 1999 51459 9 

Oct. 18, 1999 51469 9 

Oct. 28, 1999 51479 10 

Nov. 7, 1999 51489 7 

Nov. 17, 1999 51499 6 

Nov. 27, 1999 51509 -1 

 

 
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3. PHASE DEVIATIONS FOR WWVB AND LORAN-C

WWVB - The values shown for WWVB are the time differences between the time markers of the UTC(NIST) time scale 

and the first positive-going zero voltage crossover measured at the transmitting antenna. The uncertainty of 

the individual measurements is ±0.5 μs. The values listed are for 1300 UTC. 

LORAN-C - The values shown for Loran-C represent the daily accumulated phase shift (in ns). The phase shift is 

measured by comparing the output of a Loran receiver to the UTC(NIST) time scale for a period of 24 h. If data 

were not recorded on a particular day, the symbol (-) is printed. The stations monitored are Baudette, ND 

(8970-Y) and Fallon, NV (9940). The monitoring is done from the NIST laboratories in Boulder, Colorado. 

Note: The values shown for Loran-C are in nanoseconds. 

 

 UTC(NIST)-WWVB (60 kHz) UTC(NIST) - LORAN PHASE (ns)

 

 ANTENNA PHASE LORAN-C (BAUDETTE) LORAN-C (FALLON) 

DATE MJD (μs) (8970) (9940) 

11/01/99 51483 5.74 -266 +126 

11/02/99 51484 5.73 +247 +411 

11/03/99 51485 5.75 +131 -223 

11/04/99 51486 5.75 +112 +4 

11/05/99 51487 5.75 -17 +149 

 

11/06/99 51488 5.75 - -279 

11/07/99 51489 5.76 +158 +537 

11/08/99 51490 5.75 -302 +183 

11/09/99 51491 5.76 +157 +405 

11/10/99 51492 5.76 +191 -338 

 

11/11/99 51493 5.75 -283 +433 

11/12/99 51494 5.74 -366 +58 

11/13/99 51495 5.74 -69 +304 

11/14/99 51496 5.75 +252 -408 

11/15/99 51497 5.71 -465 +229 

 

11/16/99 51498 5.76 +234 -67 

11/17/99 51499 5.72 +48 +37 

11/18/99 51500 5.73 +461 -508 

11/19/99 51501 5.73 -69 +344 

11/20/99 51502 5.76 -332 -125 

 

11/21/99 51503 5.78 -7 +227 

11/22/99 51504 5.76 -384 -648 

11/23/99 51505 5.78 -540 +660 

11/24/99 51506 5.75 +246 +304 

11/25/99 51507 5.74 -427 -217 

 

11/26/99 51508 5.74 +285 -173 

11/27/99 51509 5.74 -65 +158 

11/28/99 51510 5.75 +77 +211 

11/29/99 51511 5.74 -205 +381 

11/30/99 51512 5.75 +341 +279 

 
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4. BROADCAST OUTAGES OVER FIVE MINUTES AND WWVB PHASE PERTURBATIONS

OUTAGES OF 5 MINUTES OR MORE 

 

PHASE PERTURBATIONS 

2 ms 

Station NOV 

1999 

 MJD Began 

UTC 

Ended 

UTC 

Freq. NOV 

1999 

MJD Began 

 UTC 

End 

UTC 

WWVB 

WWV 

WWVH 

5. NOTES ON NIST TIME SCALES AND PRIMARY STANDARDS 

Primary frequency standards developed and maintained by NlST are used to provide accuracy (rate) input to the 

BIPM. NBS-6, which served as the US. primary standard from 1975 through 1992, has been replaced by NIST-7, 

an optically pumped cesium-beam standard. The uncertainty of the new standard is currently 1 part in 10-14. 

The AT1 scale is run in real time using data from an ensemble of cesium standards and hydrogen masers. It is a 

free-running scale whose frequency is maintained as constant as possible by choosing the optimum weight for each 

clock that contributes to the computation. 

UTC(NIST) is generated as an offset from our real-time scale ATI. It is steered in frequency towards UTC using 

data published by the BlPM in its Circular T. Changes in the steering frequency will be made only at 0000 UTC on 

the first day of any month, and the change in frequency in any month is limited to ±2 ns/day. The frequency of 

UTC(NIST) is kept as stable as possible at other times. 

UTC is generated at the BlPM using a post-processed time-scale algorithm and is not available in real-time. The 

parameters that we use to generate UTC(NIST) in real-time are therefore based on an extrapolation of UTC from 

the most recent data available. 

6. BIBLIOGRAPHY 

Allan, D.W.; Hellwig, H.; and Glaze, D.J., "An accuracy algorithm for an atomic time scale," Metrologia, Vol.11, 

No.3, pp.133-138 (September 1975). 

Allan, D.W. and Weiss, M.A., "Accurate time and frequency transfer during common view of a GPS satellite," 

Proc. 34th Annual Symposium on Frequency Control, p.334 (1980). 

Allan, D.W. and Barnes, J.A., "Optimal time and frequency using GPS signals," Proc. 36th Annual Symposium 

on Frequency Control, p.378 (1982). 

Drullinger, R.E.; Glaze, D.J.; Lowe, J.P.; and Shirley, J.H., "The NlST optically pumped cesium frequency 

standard," IEEE Trans. Instrum. Meas., IM-40, 162-164 (1991). 

Glaze, D.J.; Hellwig, H.; Allan, D.W.; and Jarvis, S., "NBS-4 and NBS-6: The NlST primary frequency 

standards," Metrologia, Vo1.13, pp.17-28 (1977). 

Wineland, D.J.; Allan. D.W.; Glaze, D.J.; Hellwig, H.; and Jarvis, S., "Results on limitations in primary cesium 

standard operation," IEEE Trans. Instrum. Meas., IM-25, pp.453-458 (December 1976). 
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Table 7.1 lists parameters that are used to define UTC(NIST) with respect to our real-time scale AT1. To find the value of 

UTC(NIST) - AT1 at any time T (expressed as a Modified Julian Day, including a fraction if needed), the appropriate 

equation to use is the one for which the desired T is greater than or equal to the entry in the T0 column and less than the 

entry in the last column. The values of xls, x, and y for that month are then used in the equation below to find the desired 

value. The parameters x and y represent the offset in time and in frequency, respectively, between UTC(NIST) and AT1; 

the parameter xls is the number of leap seconds applied to both UTC(NIST) and UTC as specified by the IERS. Leap 

seconds are not applied to AT1. 

Table 7.1 

UTC(NIST) - AT1 = xls + x + y*(T −T0

) 

Month xls

(s) 

x 

(ns) 

y 

(ns/d) 

 T0

(MJD) 

Valid until 0000 on: 

(MJD) 

Feb 98 -31 -171573 -42.5 50845 50873 

Mar 98 -31 -172763 -42.5 50873 50904 

Apr 98 -31 -147080.5 -42.0 50904 50934 

May 98 -31 -175340.5 -42.0 50934 50965 

Jun 98 -31 -176642.5 -41.5 50965 50995 

Jul 98 -31 -177887.5 -41.5 50995 51025 

Aug 98 -31 -179174 -41.0 51025 51057 

Sep 98 -31 -180445 -41.0 51057 51087 

Oct 98 -31 -181675 -41.5 51087 51118 

Nov 98 -31 -182961.5 -41.5 51118 51148 

Dec 98 -31 -184206.5 -41.5 51148 51179 

Jan 99 -32 -185493 -41.5 51179 51210 

Feb 99 -32 -186779.5 -41.0 51210 51238 

Mar 99 -32 -187927.5 -40.5 51238 51269 

Apr 99 -32 -189183 -40.0 51269 51299 

May 99 -32 -190383 -41.0 51299 51330 

Jun 99 -32 -191654 -41.0 51330 51360 

Jul 99 -32 -192884 -41.0 51360 51391 

Aug 99 -32 -194155 -41.0 51391 51422 

Sep 99 -32 -195426 -40.5 51422 51452 

Oct 99 -32 -196641 -40.5 51452 51483 

Nov 99 -32 -197896.5 -40.0 51483 51513 

Dec 99 -32 -199096.5 -40.0 51513 51533† 

Dec 99 -32 -199896.5 -41.0 51533 51544 

Jan 00 -32 -200347.5 -40.5* 51544 51575* 

† Rate change in mid-month 

†† Rate change one day early 

*Provisional value 
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8. SPECIAL ANNOUNCEMENTS 

TRACEABLE FREQUENCY CALIBRATIONS 

(Now NVLAP Certified) 

Laboratories needing traceable frequency calibrations can get them by subscribing to the NlST Frequency 

Measurement and Analysis Service. This service is offered on a lease basis by NlST to provide an easy and 

inexpensive means t o obtain traceability of a laboratory main oscillator and, in addition, to calibrate other devices 

in the lab. This service has been designed for ease of operation and as a practical lab calibration tool. 

 All the equipment and software needed are provided by NIST. Users must provide their own oscillator(s) 

and an ordinary telephone line so that NIST can access the system by modem. A total of five oscillators can be 

calibrated at the same time. Radio signals from GPS satellites are used and the measurement uncertainty is ±5 x 

10-13 per day. 

The calibration data are displayed in color and a graph is plotted daily for each oscillator connected. Data 

are also stored on disk. The user can call up any of the data and view them onscreen or in the form of plots. Many 

months of data can be plotted. 

 The system plots are easy to read and understand. The system manual is written for easy understanding 

and the NlST staff is available by telephone to assist. The modem connection allows NlST to access the data and 

to prepare a monthly traceability report which is mailed to the user. 

Frequency sources of any accuracy can be calibrated. The FMAS is particularly useful at the highest levels 

of performance. This is because each user of the system contributes information and calibration data for the others. 

If an uncertainty arises, it is possible for NlST to call by modem to another user nearby. In this way problems in 

data interpretation can be resolved. 

NVLAP certification requirements for frequency measurement are met by following the NET-FMAS 

operating manual. This service does not eliminate the NVLAP audits but, when installed and operated per the NlST 

guidelines, audit requirements are easily met. 

NlST retains title to the equipment and supplies. All necessary replacement parts are replaced by overnight 

shipment. Training for use of the system is available if requested by the user. 

The NlST Frequency Measurement and Analysis Service provides a complete solution t o nearly all 

Frequency measurement and calibration problems. For a free information package, please contact Michael 

Lombardi at (303) 497-3212, E-mail at lombardi@boulder.nist.gov, or write to: Michael Lombardi, NIST, Division 

847, 325 Broadway, Boulder, CO 80303. 

______________________________________________________________ 

IMPORTANT NOTICE! 

The Time and Frequency Bulletin is not available online at: 

www.boulder.nist.gov/timefreq/pubs/bulletin/index.htm