NATIONAL INSTITUTE OF STANDARDS &

TECHNOLOGY

Research Information Center

Gaithersburg, MD 20099

Time & Frequency

Bulletin

No. 374 January 1989

(NISTIR 89-3910-1)

IP 

NIST TIMS & FREQUENCY BULLETIN

(Supersedes No. 373 December 1988)

NO. 374 JANUARY 1989

1. GENERAL BACKGROUND INFORMATION 1

2. TIME SCALE INFORMATION 1

International Timing Center comparisons via GPS common-view 2

3. UT1 CORRECTIONS AND LEAP SECOND ADJUSTMENTS 2

4. PHASE DEVIATIONS FOR WWVB AND LORAN-C 3

5. GOES TIME CODE INFORMATION 4

6. BROADCAST OUTAGES OVER FIVE MINUTES AND WWVB PHASE PERTURBATIONS .... 4

7. NOTES ON NIST TIME SCALES AND PRIMARY STANDARDS 5

8. SPECIAL ANNOUNCEMENTS 7

This bulletin is published monthly. Address correspondence to:

Gwen E. Bennett, Editor

Time and Frequency Division

National Institute of Standards & Technology

325 Broadway

Boulder, CO 80303

(303) 497-3295

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

with any correspondence regarding this bulletin.
1. GENERAL BACKGROUND INFORMATION

ABBREVIATIONS AND ACRONYMS USED IN THIS BULLETIN

APL John Hopkins University Applied Physics Laboratory

BIH - International Time Bureau, France

CCIR - International Radio Consultative Committee

CRL - Communications Research Laboratories, Japan

Cs - Cesium standard

CSIRO - Commonwealth Scientific and Industrial Research Organization, Australia

GOES - Geostat lonarv Operational Environmental Satellite

GPS - Global Positioning System

IEN - National Institute of Electronics, Italy

INPL - National Physical Laboratory, Israel

LORAN - Long Range Navigation

MC - Master Clock

MJD - Modified Julian Date

NIST - National Institute of Standards & Technology

NPL - National Physical Laboratory, England

NRC - National Research Council, Canada

NOAA - National Oceanic and Atmospheric Administration

OP - Paris Observatory, France

PTB - Physical Technical Federal Laboratory, Germany

SI - International System of Units ns nanosecond

SV - Space vehicle us microsecond

TA - Atomic Time ms millisecond

TAI - International Atomic Time s second

TAO - Tokyo Astronomical Observatory, Japan min - minute

TUG - Technical University of Graz, Austria h - hour

USNO - United States Naval Observatory d - day

UTC - Coordinated Universal Time

VLF - very low frequency

VSL ' Van Swinden Laboratory, Netherlands

2. TIME SCALE INFORMATION

The values listed below are based on data from the BIH, the USNO, and the NIST. The UTC - UTC(NIST) values are extrapolations since UTC is computed more than two months after the fact. The UTC(USNO.MC) - UTC(NIST) values

are averaged measurements from NAVSTAR satellites 3,4,6, and 8 (see references on page 6).

OOOO HOURS COORDINATED UNIVERSAL TIME

DECEMBER

1988 MJD

UT1 - UTC(NIST)

(± 5 ms)

UTC - UTC(NIST)

(± 0.2 us)

UTC ( USNO, MC) - UTC(NIST)*

(t 0.04 us)

1 47496 -76 ms -0.1 us 1.45 us

8 47503 -89 ms -0.1 us 1.40 us

15 47510 -97 ms 0.0 us 1.35 us

22 47517 -109 ms 0.0 us 1.30 us

29 47524 - 1 1 6 ms 0.0 us 1.25 us

^Values in this column reported in the November and December Bulletins should have been positive instead of

negative

.
INTERNATIONAL TIMING CENTER COMPARISONS VIA GPS COHION-VTEW

The table below is a weighted average of the indicated GPS satellites used as transfer standards to measure t time difference of Timing Center (i) - UTC(NIST) by the simultaneous common-view approach (see references, pa 6). The day-to-day variations of this technique are less than 10 ns. The time of the measurement is

interpolated to 0000 UTC for the particular MJD ending in 9. These data are prepared for the BIH for the

computation on TAI and of UTC. All differential delays are 0 unless otherwise noted.

UTC( i) - UTC(NIST) (ns) MJD

UTC( i) SV NUMBERS 47489 47499 47509 47519

UTC(APL) - UTC(NIST) 3,6,9,11,12,13 148 190 211 487

UTC ( CRL ) - UTC(NIST) 3,6,9, 12 1618 1616 1588 1550

UTC(CSIRO) - UTC(NIST) •Jc* 19632 19620 19566 19456

UTC(IEN) - UTC(NIST) 9,11,12 -1641 -1365 -1049 -647

UTC(INPL) - UTC(NIST) VIA OP -89135* -90540 -91981 -93416

UTC(NPL) - UTC(NIST) 9,11,12 - 3464* -3247 -3066 -2806

UTC(NRC) - UTC(NIST)*** 3,6,9,11,12,13 12010* 12368 12543 12717

UTC(OP) - UTC(NIST) 9,11,12 1664* 1711 1744 1793

UTC(PTB) - UTC (NIST) 9,11,12 -4314 -4245 -4237 -4235

UTC (TAO) - UTC(NIST) 3,6,9, 12 2354 2383 2414 0

UTC (TUG) - UTC (NIST) 9,11,12 -4896* -5121 4646 4385

UTC(USNO.MC) - UTC(NIST) 3,6,9,11,12,13 1490 1435 1363 1285

UTC(VSL) - UTC(NIST) 9,11,12 -3802* -3799 -3866 -3878

This value has been updated from that printed in last month's Bulletin.

** UTC(CSIRO) - UTC(NIST) is computed from the average by CRL, TAO and WWVH. However, no data has been

received from TAO after MJD 47515. Therefore, the value for MJD 47519 is computed using only

CRL and WWVH.

*** UTC(NRC) — UTC(NIST) has a differential delay of 41.2 ns; all other comparisons are computed using

zero (0).

0 No data has been received from TAO after MJD 47515.

3. UT1 CORRECTIONS AND LEAP SECOND ADJUSTMENTS

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 second 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 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 tl UTC timescale on 30 June 1972, 31 December 1972-1979, 30 June 1981-1983, 30 June 1985, and 31 December 1987 . When future leap seconds are scheduled, advance notice will be provided in this bulletin.

The use of leap seconds ensures that UT1 — UTC will always be held within i 0.9 s. The current value of

UT1 — UTC is called the DUT1 correction. DUT1 corrections are broadcast by WWV, WWVH, WWVB, and GOES and are printed below. These corrections may be added to received UTC time signals in order to obtain IJT1.

* 0.0 s beginning 0000 UTC 25 August 1988

DUT1 = UT1 - UTC = -0.1 s beginning 0000 UTC 10 November 1988

= -0.2 s beginning 0000 UTC 19 January 1989
4. PHASE DEVIATIONS FOR WWVB AND LGSAN-C

WWVB — The values shovm 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 t 0.5 us. The values listed are

for 1500 UTC.

LORAN-C - The values shown for Loran-C represent the time difference between the UTC(NIST) time pulses

and the 1 Hz output of the Loran-C receiver. The stations monitored are Dana, Indiana

(8970 M) and Fallon, Nevada (9940 M). The values shown are four-hour averages taken from

1600 to 2000 UTC daily. If data are lost, the symbol (-) is shown in place of the phase value

UTC (NIST) - RECEIVED PHASE (in us)

DECEMBER

1988 MJD

UTC (NIST) - WWVB( 60 kHz)

ANTENNA PHASE

(in us)

LORAN-C (DANA)

(LOO kHz)

LORAN-C (FALLON)

(100 kHz)

1 47496 5.74 5137.58 3948.63

2 47497 5.79 5137.43 3948.55

3 47498 5.67 5137.21 3948.32

4 47499 5.66 5137.25 3948.52

5 47500 5.66 5137.32 3948.75

6 47501 5.66 5137.23 3948.50

7 47502 5.34 5137.17 3948.77

8 47503 5.65 5137.22 3948.73

9 47504 5.58 5137.10 3948.72

10 47505 5.67 5136.97 3948.50

11 47506 5.61 5136.78 3948.47

12 47507 5.55 5136.98 3948.83

13 47508 5.68 5137.00 3948.85

14 47509 5.64 5137.11 3948.81

15 47510 5.72 5137.08 3948.83

16 47511 5.71 5137.02 3948.73

17 47512 5.68 5136.86 3948.56

18 47513 5.66 5136.97 3948.63

19 47514 5.63 5137.16 3948.80

20 47515 5.65 5137.23 3948.81

21 47516 5.63 5137.08 3948.75

22 47517 5.59 5137.20 3948.80

23 47518 5.58 5137.06 3948.77

24 47519 5.63 5136.99 3948.67

25 47520 5.62 5136.87 3948.61

26 47521 5.60 5136.99 3948.68

27 47522 5.59 5137.18 3948.90

28 47523 5.67 5137.11 3948.88

29 47524 5.63 5137.19 3948.97

30 47525 5.72 5137.24 3948.99

31 47526 5.70 5137.15 3948.95
5. GOES TIME CODE INFORMATION

A. TIME CODE PERPORMANCE (1-31 December 1988)

GOES/East : Performance within normal limits during this period except for the following outage periods:

(1) December 6: 2030-2230 UT Equipment relocation at Wallops Island.

(2) December 7: 1400-1515 UT Equipment relocation at Wallops Island.

(3) December 8: 1620-1810 UT Time code temporarily switched from GOES-5 to GOES-7 for antenna

calibrations at Wallops Island. Transmitted position data were updated for this change except for

few minutes at beginning and end of period.

GOES/West : Performance within normal limits during this period.

B. SPECIAL REMINDER: Current satellite locations are 65° W. for GOES/East and 135° W. for GOES/West.

C. SPECIAL ANNOUNCEMENT

At 1104 UT on October 26 NOAA switched the GOES/East time code from GOES-7 at 75° West longitude to GOES

at 65° West longitude. The transmitted position data were therefore in error until about 1430 UT. NOAA

informs us that the GOES/East time code will remain on GOES-5 indefinitely and that the orbital location

will stay at 65°. This change has the following consequences: (1) the path delay is now different for tl new location, but, in the case of automatic path-delay-correction receivers, is compensated for; (2) if

signal is lost or weakened, antenna repointing may be necessary; and (3) some receivers may show a blinking "East" satellite indicator light. This only indicates that the 65° position is "abnormal," but

the time data are still valid.

D. GOES STATUS REPORTS

A brief message from NIST giving current GOES time code status information is available from the U-.S. Naval Observatory's Automated Data Service computer system in Washington, DC. The message may be accesse

24 hours per day without charge by using a variety of terminals operating at 300, 1200, or 2400 Baud and even parity. Two different sets of telephone access numbers are available: (1) for 300 or 1200 Baud and

the Bell 103 standard use (202) 653-1079 (commercial), 653-1079 (FTS), or 294-1079 (Autovon); (2) for 120 or 2400 Baud with either the CCITT V.22 standard or the Bell standard use (202) 653-1783 (commercial),

653-1783 (FTS), or 294-1783 (Autovon). To receive the GOES status message, use the following procedure:

1. Access the USNO computer database by dialing one of the appropriate telephone numbers above;

2. In response to the prompt for identification, type your name and the name of your organization,

followed by a carriage return;

3. Type "@NBSGO" followed by a carriage return to receive the status message at your terminal;

4. Disconnect by typing Control-D.

6. BROADCAST OUTAGES OVER 5 MINUTES AND WWVB PHASE PERTURBATIONS

OUTAGES PHASE PERTURBATIONS WWVB 60 kHz

NOVEMBER BEGAN ENDED NOVEMBER BEGAN ENDED

STATION 1988 MJD (UTC) (UTC) FREQUENCY 1988 MJD (UTC) (UTC)

WWVB NONE NONE

WWV NONE NONE

WWVH NONE NONE

- 4 -
7. NOTES ON NIST TIME SCALES AND PRIMARY STANDARDS

he frequencies of the time scales, TA(NIST) and UTC(NIST), are calibrated with the NIST primary frequency

tandards. The UTC(NIST) scale is coordinated within a microsecond of the internationally coordinated time

cale, UTC, generated at the BIH. It is used to control all of the NIST time and frequency services. The last

alibration of the relative frequency offset, v, of UTC(NIST) as generated in Boulder, Colorado, gave:

) yuTC(NIST) ( July 198/) — yNBS-6 (July 1987) — (-0.6 ± 2 (1 sigma)) x 10 -13

the date shown. This calibration includes a correction for the systematic offset due to room temperature

:kbody radiation, which is approximately (delta vgg) = -1.7 x 10 . Using GPS 3

, the frequency of TAI for

dates shown were measured to be:

) y^Al (July 1987) — y»sjBS-6 (July 1987 on geoid) = ( + 1.7 ±2(1 sigma)) x 10 -13

•here account has been taken of the gravitational "red shift."

Starting 1 January 1975, an accuracy a jorithm was implemented t oring the second used in the generation of

TA(NIST) closer to the NIST "best est .ate" of the SI second (see references, p.6). The relative frequency

associated with this "best estimate" is denoted ycs(NIST) i l ast calibration (July 1987) covered the period

from October 1986 through July 1987.

3) yCs(NIST) “ yNBS-6 = ~ 2) x 10‘ 13 (July 1987)

and

yTAI " yCs(NIST) on geoid = (-K) - 3 4 °- 7) x 10

' 13 (July l987)

This algorithm should provide nearly optimum accuracy and stability for TA(NIST) since it uses all past

frequency calibrations with the NIST primary standards. These calibrations are weighted proportionately to the

frequency memory of the clock ensemble that generates atomic time. This algorithm, therefore, capitalizes on a weighted combination of all the frequency calibrations with the primary standards in order to gain a "best

estimate" of the SI Second while simultaneously obtaining the best uniformity available from the ensemble of

working clocks in the atomic time scale system. The relat frequency of T NIST) is steered toward ycs(NIST)

by slight frequency drift corrections of the order of 1 pa -i 10 13 /yr.

TA(NIST) and UTC(NIST) are no longer simply related by an tion. TA(NIST now computed each month using

i Kalman algorithm which minimizes the mean square time di_ rsion. UTC(NIST ,s now independently computed

ising a different algorithm and is steered in frequency to keep its time with a microsecond of UTC(BIH).

.’able 7.1 lists monthly values of the time difference between UTC(NIST) and TAvNIST). A linear interpolation

>etween monthly values will typically be within 10 ns of the actual time difference, TA(NIST) - UTC(NIST).

The primary standards of NIST (NBS-4 and NBS-6) are used in either of two modes: as calibrators of frequency to

provide a reference for the SI second; or as member clocks of the NIST clock ensemble, to help keep the proper

time for TA(NIST) and the coordinated time for UTC(NIST). Operating in the clock mode, NBS-4 and NBS-6 are only used and weighted according to their stability performance. Accuracy enters only when they are used as frequency calibrators, in which case clock operation is necessarily interrupted.

3 GPS is the Global Positioning System, a network of navigation satellites.

- 5 -
Table 7.1 is a list of changes in the time scale frequencies of both TA(SIST) and UTC(NIST) as well as a list of the time and frequency differences between TA(NIST) and UTC(NIST) at the dates of leap seconds,

and/or frequency or frequency drift changes.

TABLE 7.1

FREQUENCY CHANGES

DATE (MJD ) TA(NIST) UTC(NIST) TA(NIST) - UTC(NIST) v[UTC(NIST)] - v[TA( NIST )

]

1 Jul 87 46977 0 0.50 ns/d 23.045 099 849 s -3.56 E- 13

1 Aug 87 47008 0 0.75 ns/d 23.045 100 768 s -3.42 E- 13

1 Sep 87 47039 0 1.25 ns/d 23.045 101 681 s -3.44 E- 13

1 Oct 87 47069 0 1.25 ns/

d

23.045 102 583 s -3.47 E- 13

1 Nov 87 47100 0 0.50 ns/

d

23.045 103 512 s -3.38 E-13

1 Dec 87 47130 0 0.50 ns/d 23.045 104 367 s -3.40 E-13

1 Jan 88 47161 0 -1.00 ns/

d

24.045 105 306 s -3.56 E-13

1 Feb 88 47192 0 -1.00 ns/d 24.045 106 272 s -3.53 E-13

1 Mar 88 47221 0 -1.25 ns/

d

24.045 107 137 s -3.58 E-13

1 Apr 88 47252 0 -1.50 ns/d 24.045 108 130 s -3.85 E-13

1 May 88 47282 0 -1.50 ns/d 24.045 109 170 s -4.29 E-13

1 Jun 88 47313 0 -1.50 ns/

d

24.045 110 358 s -4.47 E-13

1 Jul 88 47343 0 -1.60 ns/

d

24.045 111 523 s -4.64 E-13

1 Aug 88 47374 0 -0.40 ns/

d

24.045 112 802 s -4.89 E-13

1 Sep 88 47405 0 -1.00 ns/

d

24.045 114 144 s -5.15 E-13

1 Oct 88 47435 0 1.00 ns/d 24.045 114 515 s -5.15 E-13

1 Nov 88 47466 0 1.25 ns/d 24.045 116 854 s -4.88 E-13

1 Dec 88 47496 0 1.50 ns/d 24.045 118 088 s -4.69 E-13

UTC(NIST) is steered in time toward UTC by occasional frequency changes of the order of a few nanosecond:

per day; 1 ns/d is approximately 1.16E-14. Otherwise, y[UTC(NIST)] is maintained as stable as possiDle

REFERENCES

Allan, David W. t et al., "An accuracy algorithm for an atomic time scale," Metrologia, Vol.ll, No. 3,

pp. 133-138 (September 1975).

Glaze, D.J., et al., "NBS-4 and NBS-6: The NIST primary frequency standards," Metrologia, Vol.13,

pp. 17-28 (1977).

Wineland, D.J., et al., "Results on limitations in primary cesium standard operation," IEEE Trans, on Instr. and Meas., Vol.IM-25, No. 4, pp. 453-458 (December 1976).

Allan, David W. and Weiss, Marc, "Accurate Time and Frequency Transfer During Common View of a GPS

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

Allan, David W. and Barnes, James A., "Optimal Time fit Frequency using GPS signals," Proc. 36th Annual

Symposium on Frequency Control, p.378 (1982).

- 6 -
8. SPECIAL ANNOUNCEMENTS

AUTOMATED COMPUTER TIME SERVICE (ACTS)

On March 9, 1988, NIST initiated operation of a telephone time service designed to provide computers with

telephone access to NIST time at accuracies approaching 1 ms. Features of the service include automated

compensation for telephone- line delay, advanced alert for changes to and from daylight savings time and

advanced notice of insertion of leap seconds. The ASCII-character time code should operate with standard

modems and most computer systems. While the system can be used to set computer tirae-of-day clocks, simple

hardware can also be developed to set other clock systems.

During the first six months, the service will be operated in a test phase to identify problems and obtain

feedback from users on both the format and operation of the service. After completion of the test phase, there

may be some revisions in the service. The service telephone number is (303) 494-4774. The number may be changed at a later date. A help message can be obtained by returning a ? during the first 6 s of transmission.

With appropriate user software, the NIST-ACTS service provides three modes for checking and/or setting

computer time-of-day clocks.

1. In the simplest form of the (1200 Baud) service, the user receives the time code and an on-time

marker/ character which has been advanced a fixed period to nominally account for modem and telephone- line

delays. Accuracy in this mode should be no worse than 0.1 s unless the connection is routed through a satellite

.

2. At 1200 Baud, if the user's system echoes all characters to NIST, the round-trip line delay will be

measured and the on-time marker advanced to compensate for that delay. The accuracy in this mode should be

better than 10 ms. Our experience to date indicates that the asymmetry in conventional, 1200-Baud modems

limits the accuracy at this level. Repeatability is about 1 ms.

3. At 300 Baud the user can obtain the same type of service as described in item 2 above, but there is

generally less problem with modem asymmetry at this rate and our experience indicates that the accuracy is

about 1 ms

.

The accuracy statements here are based upon the assumption that the telephone connection is reciprocal,

that is, that both directions of communication follow the same path with the same delay. Discussions with

telephone carriers indicate that this is the general mode of operation and our tests to date indicate that the

lines are both stable and reciprocal.

In order to assist users of the service, NIST has developed documentation of the features of the service,

some example software which can be used in conjunction with certain popular personal computers and simple

circuitry which can be used to extract an on-time pulse. This material is available on a 5|-in, 360-kbyte DOS

diskette with instructions for $35.00 from the NIST Office of Standard Reference Materials, B311-Chemistry

Bldg, NIST, Gaithersburg, MD, 20899, (301) 975-6776. Specify the Automated Computer Time Service, RM8101.

Further technical questions and comments should be directed to NIST-ACTS, NIST Time and Frequency Division, 325

Broadway, Boulder, CO 80303.

4 3RD ANNUAL FREQUENCY CONTROL SYMPOSIUM

CALL FOR PAPERS

The 43rd Annual Frequency Control will be held May 31- June 2, 1989, at the Denver Marriott City Center Hotel,

Denver, CO. The topics include:

• Crystal resonators

• Oscillators and filters

• SAW devices

• Atomic frequency standards

• Time coordination and distribution

Send a 500 word summary to T.R. Meeker, 2956 Lindberg Ave., Allentown, PA 18103. The deadline for summaries is

January 20, 1989.

NAME CHANGE

The name of the National Bureau of Standards (NBS) has already been changed to the National Institute of

Standards and Technology (NIST). The Bulletin covers reflect that change.
NBS«114A (REV. 2-80

U.S. DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. ort NoJ 3. Publication D ate BIBLIOGRAPHIC DATA

REPORT NO.

B89-0064

SHEET (See instructions) NISTIR 89-3910-1 January 1989

4. TITLE AND SUBTITLE

Time & Frequency Bulletin

5. AUTHOR(S)

6. PERFORMING ORGANIZATION (If joint or other than NBS

.

see in struction s) 7. Contract/Grant No.

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

10.

SUPPLEMENTARY NOTES

QT Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11.

ABSTRACT ( A 200-word or less factual summary of most si gnificant information. I f document includes a significant

bi bl lography or literature survey, mention it here)

The Time & Frequency Bulletin provides information on performance of time

scales and a variety of broadcasts (and related information) to users of the

NIST services.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capi ta I i ze on ly proper names; and separate key words by semi color s

clocks; dissemination; frequency; GPS; oscillators; time

13.

availability

Uni imi ted

(~y~1 For Official Distribution. Do Not Release to NTIS

1

I Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. I "~ 20402.

r Order From National Technical Information Service (NTIS), Springfield, VA. 22161

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PRINTED PAGES

8

15. Price

USCOMW •= 4

• -O J ;
fcSrw t

POSTAGE ft FEES PAID

NIST

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US Department of Commerce

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DIVI's ION 52 i NATL BUREAU ' > "Eb B ROADWAY

03

!