NIST TIME AND FREQUENCY BULLETIN 

NlSTlR 5082-1 1 

NO. 504 NOVEMBER 1999 

1. GENERALBACKGROUND INFORMATION ............................................ 2 

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

3. UT1 CORRECTIONS AND LEAP SECOND ADJUSTMENTS ................................ 2 

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

5. BROADCAST OUTAGES OVER FIVE MINUTES AND WWVB 

PHASEPERTURBATIONS ....................................................... 5 

6. NOTES ON NlST TIME SCALES AND PRIMARY STANDARDS .............................. 5 

7. BIBLIOGRAPHY ............................................................... 5 

8. SPECIALANNOUNCEMENTS .................................................... 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 80303-3328 

(303) 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, Gary R. Bachula, Acting Under Secretary for Technology 

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY, Karen Brown, Deputy Director 

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2 

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 

18 51500 +409 ms 14 ns 

25 51507 +398 ms 16 ns 

 

 The master clock pulses used by the WWV, WWVH, WWVB and GOES 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 rate of 

rotation of the Earth. 

 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. There have been 22 leap seconds inserted in total. 

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 GOES are printed below. These corrections 

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

_______________________________________________________________________________________________________ 

 +0.6 s beginning 0000 UTC 04 March 1999 

DUT1 = UT1 - UTC = +0.5 s beginning 0000 UTC 27 May 1999 

 +0.4 s beginning 0000 UTC 14 October 1999 

 
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The deviation of 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 

Dec. 2, 1998 51149 4 

Dec. 12, 1998 51159 3 

Dec. 22, 1998 51169 10 

Jan. 1, 1999 51179 10 

Jan. 11, 1999 51189 19 

Jan. 21, 1999 51199 22 

Jan. 31, 1999 51209 25 

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 

 
4. PHASE DEVIATIONS FOR WWVB AND LORAN-C 

WWVB - The values shown for WWVB are the time difference 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 k0.5 ,us. 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 (-1 is printed. 

The master stations monitored are Dana, IN (8970) and Fallon, NV (9940). The monitoring is done from 

the NlST laboratories in Boulder, CO. 

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

UTC(NIST)-WWVB (60 kHZl UTC(NIST) - LORAN PHASE (nsl 

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

DATE MJD (PS) (8970) (9940) 

lOlO1199 51452 5.71 -131 + 565 

10102199 5 1453 5.70 +400 +452 

10103199 5 1454 5.70 +431 -165 

10104199 51455 5.69 -569 + 297 

mnr;/qq 51 AGfi F. 71 + 3F.R RQ 

10106199 51457 5.67 + 623 + 366 

10107199 51458 5.69 +359 + 582 

1 OlO8l99 51459 5.68 -480 -111 

1 OlO9l99 51460 5.70 -17 +41 

in/? nmq 61Afil c, 7n 747 3x6 

10111l99 51462 5.71 -138 +105 

10112199 51463 5.72 -103 + 40 

10113199 51464 5.74 -115 -510 

10114199 51465 5.70 -499 -217 

in/iww FLlAfifi C, 71 + 7fi5 - 

1011 6/99 51467 5.72 (-) + 395 

1011 7/99 51468 5.72 +61 -326 

1011 8/99 51469 5.73 + 326 -149 

1011 9/99 51470 5.72 (4 - 67 

199 61 A71 6 71 1-1 i -4n 

10121l99 51472 5.70 (4 - 24 

10122199 51473 5.69 (-) + 435 

10123199 51474 5.69 + 86 + 122 

10124199 51475 5.66 -257 + 202 

innyqs 6- C, fi.G All6 A 

10126199 51477 5.70 - 565 -641 

10127199 51478 5.72 (-) +659 

10128199 51479 5.74 (-1 -441 

10129199 51 480 5.72 (-) +661 

10130199 51481 5.73 (-1 + 46 

10/31/99 51482 5.74 + 45 -513 

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5. BROADCAST OUTAGES OVER 5 MINUTES AND WWVB PHASE PERTURBATIONS 

I I I I I 

WWVH 

1 I I 

6. NOTES ON NlST TIME SCALE 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 cesiumbeam standard. The uncertainty of the new standard is currently 1 part in IOl4. 

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 22 nslday. 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. 

7. 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 (1 980). 

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 is a list of the 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 To column and less than the 

entry in the last column. The values of xis, 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 x,, 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 - To) 

Valid until 0000 on: 

Nov 99 - 32 -1 97896.5 

Dec 99 -32 - 199096.5 -40.0" 51 51 3 51 544 

*Provisional rate 

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8. SPECIAL ANNOUNCEMENTS 

TRACEABLE FREQUENCY CALIBRATIONS 

(Now NVLAP Certified) 

Anyone 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 to 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 NET. Users must provide their own oscillator(s) 

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

calibrated at the same time. Radio signals from either Loran-C or GPS satellite are used. Results for either are at 

about the same accuracy. 

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 any needed system spares. Equipment that fails is 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 to nearly all 

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

at (303) 497-321 2, E-mail at lombardi@boulder.nist.gov, or write to: Michael Lombardi, NIST, Division 847, 325 

Broadway, Boulder, CO 80303. 

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