. Time & Frequency

Bulletin

No. 375 February 1989

(NISTIR 89-3910-2)

HIST TIME & FREQUENCY BULLETIN

(Supersedes No. 374 January 1989)

NO. 375 FEBRUARY 1989

1. GENERAL BACKGROUND INFORMATION

2. TIME SCALE INFORMATION

International Timing Center comparisons via GPS conmon-view

3. UT1 CORRECTIONS AND LEAP SECOND ADJUSTMENTS

4. PHASE DEVIATIONS FOR WWVB AND LORAN-C

5. GOES TIME CODE INFORMATION

6. BROADCAST OUTAGES OVER FIVE MINUTES AND WWVB PHASE PERTURBATIONS

7. NOTES ON NIST TIME SCALES AND PRIMARY STANDARDS

8. SPECIAL ANNOUNCEMENTS

This bulletin is puDlished 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.

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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 - r.nmmin i rations Research Laboratories, Japan

Cs - Cesium standard

CSIRO - Conxnonwealth Scientific and Industrial Research Organization, Australia

GOES - Geostationary 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 MS 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).

JANUARY

1989 MJD

0000 HOURS COORDINATED UNIVERSAL TIME

UT1 - UTC(NIST)

(± 5 ms)

UTC - UTC(NIST)

(± 0.2 us)

UTC(USNO.MC) -

( + 0.04

UTC(NIST)

us)

5 47531 -121 ms 0.0 us 1.20 us

12 47538 -131 ms 0.0 us 1.16 MS

19 47545 -137 ms 0.0 us 1.12 MS

26 47552 -145 ms 0.0 us 1.06 MS

- 1 -
INTERNATIONAL TIMING CENTER COMPARISONS VIA GPS CGMION-VIEW

The table below is a weighted average of the indicated GPS satellites used as transfer standards to measure the

time difference of Timing Center (i) - UTC(NIST) by the simultaneous common-view approach (see references, page

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 BIPM 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 47519 47529 47539 47549

UTC (APL) - UTC(NIST) 3,6,9,11,12,13 487 0 1038 931

UTC (CRL) - UTC(NIST) 3,6,9, 12 1550 1507 1452 1384

UTC(CSIRO) - UTC(NIST) ** 19467* 19424 19379 19347

UTC(IEN) - UTC (NIST) 9,11,12 -647 -230 187 598

UTC(INPL) - UTC (NIST) VIA OP -93416 -94877 -96295 -97665

UTC(NPL) - UTC(NIST) 9,11,12 -2806 -2530 -2287 -2032

UTC(NRC) - UTC(NIST)*** 3,6,9,11,12,13 12717 12870 13057 13194

UTC(OP) - UTC(NIST) 9,11,12 1793 1794 1711 1682

UTC(PTB) - UTC(NIST) 9,11,12 -4235 -4217 -4247 -4250

UTC (TAO) - UTC(NIST) 3,6,9, 12 2438 2471 2479 2492

UTC(TUG) - UTC(NIST) 9,11,12 4385 4134 3857 3605

UTC(USNO,MC) - UTC(NIST) 3,6,9,11,12,13 1285 1218 1156 1089

UTC(VSL) - UTC (NIST) 9,11,12 -3878 -911 -992 -1021

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

zero (0).

@ APL was experiencing a frequency step of approximately -1.05 E-12 during MJD's 47525 - 47529.

Therefore no value is computed for MJD 47529.

3. UT1 CORRECTIONS AND LEAP SECOND ADJUSTMENTS

The master clock pulses used by the WWV, WWVH, WVJVB, 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 the

UTC timescale on 30 June 1972, 3

1 December 1972-1979, 30 June 1981-1983, 30 June 1985, and 31 December 1987.

When future leap seconds am scheduled, advance notice will be provided in this bulletin.

The use of leap seconds ensures that UT1 — UTC will always be held within t 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 UT1.

= 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

- 2 -
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 ± 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)

JANUARY

1989 MJD

UTC(NIST) - WWVB( 60 kHz)

ANTENNA PHASE

(in us)

LORAN-C (DANA)

(100 kHz)

LORAN-C (FALLON)

(100 kHz)

1 47527 5.69 5137.12 3948.94

2 47528 5.67 5137.00 3948.96

3 47529 5.66 5137.30 3949.13

4 47530 5.63 5137.30 3949.20

5 47531 5.61 5137.39 3948.82

6 47532 5.54 5137.42 3948.97

7 47533 5.64 5137.24 3948.88

8 47534 5.60 5137.18 3948.88

9 47535 5.56 5137.52 3949.12

10 47536 5.71 5137.49 3949.12

11 47537 5.66 5137.63 3949.12

12 47538 5.66 5137.65 3949.24

13 47539 5.64 5137.68 (-)

14 47540 5.63 5137.61 3949.19

15 47541 5.61 5137.49 3949.11

16 47542 5.59 5137.40 3949.17

17 47543 5.58 5137.47 3949.45

18 47544 5.67 5137.53 3949.50

19 47545 5.68 5137.45 3949.57

20 47546 5.59 5137.38 3949.41

21 47547 5.69 5137.14 3949.40

22 47548 5.68 5137.18 3949.39

23 47549 5.67 5137.21 3949.62

24 47550 5.65 5137.22 3949.54

25 47551 5.62 5137.41 3949.54

26 47552 5.59 5137.25 3949.58

27 47553 5.69 5137.25 4949.57

28 47554 5.69 5137.17 (-)

29 47555 5.69 5137.22 (-)

30 47556 5.69 5137.39 3949.83

31 47557 5.66 5137.34 3949.79

- 3 -
5. GOES TIME CODE INFORMATION

'ff-z£rr>

A. TIME CODE PERFORMANCE (1-31 January 1989)

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

(1) 25 January, 1934-2330 UT: Satellite maneuver caused temporary time code deviations of about 100 us as observed in Boulder.

GOES/West : Performance within normal limits during this period. Failure of the GOES/West visual imaging

system on 21 January is not expected to impact the GOES/West time code operations in any way.

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-5

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 the 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 accessed

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 (conmercial) , 653-1079 (FTS), or 294-1079 (Autovon); (2) for 1200

or 2400 Baud with either the CCITT V.22 standard or the Bell standard use (202) 653-1783 (conmercial),

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

STATION

JANUARY

1989 MJD

BEGAN

(UTC)

ENDED

(UTC) FREQUENCY

JANUARY BEGAN

1989 MJD (UTC)

ENDED

(UTC)

WWVB NONE NONE

WWV NONE NONE

WWVH 12 47538 0059 0103 2.5 MHz NONE

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

The frequencies of the time scales, TA(NIST) and UTC(NIST) are standards The UTC(NIST) scale is coordinated within a microsecond of the

the

. NIST Pri**ry frequency

scale, UTC, generated at the BIH. It is used to control all of the NIST tim*

er^

a

£

lonally coordinated time calibration of the relative frequency offset, y, of UTC(NIST) as generated^ generated m

and frequency services. The last Boulder, Colorado, gave:

°

yOTC(NIST) (July 1987) - yNBS _ 6 (July 1987) - (-0.6 t 2 (1 sigma)) * 10 -13

blackbody

for the date shown. This calibration includes a correction ^ radiation, which is approximately (delta yBB ) « the dates -i 7 x shown were measured to be:

X 1U

^stematic offset due to room temperature sing GPS , the frequency of TAI for

2) yTAI (July 1987) - yNBS _ 6 (july 1987 on geoid) , (+1<? ± 2 (1 sigma)) x 1Q

_ 13

where account has been taken of the gravitational "red shift." — t»e. second used in th. gener.tioo of associated with this "best estimate" is denoted y' P ' 6) - Tha tclat uHreq^cy from October 1986 through July 1987.

yCs(NIST)- Th® last calibration (July 1987) covered the period

) yCs(NIST) “ yNBS-6 * (+1-* ± 2) x 1(T 13 (July i 987 ) and

) yTAI _ yCs(NIST) on geoid , (+Q.3 + 0.7) J 10 -13 (July 1987)

frequency^alibrations'with^the^IST pr^ £5£.“ it uses .U p.st frequency memory of the clock ensemble that een«.?I. . ^

calibrations are weighted proportionately to th. weighted combination of all the frequency J

1"*’ ThU al8orithm, therefore, c,pu“ues on ! estimate" of the SI Second while simultaneously Ptmery standards in order to gain a "best working clocks in the atomic time s^le“y«^ 5*“ u” ifoTMity ayailable from thT^embU of by slight frequency drift corrections of Le oMe^f !

NIST) is Peered toward yCs(NIST)

='2 ^«d

t^e“is

equati°n - W

1

lST) 15 touted each month using

PI '-I - kee^its t between monthly yalues will £,£££?*&S3T

typical ^""0“ .¥£".£i!“IL*?J

A< “ST)

- 7 i-Suo.

"" primary standards of NIST (NBS-S and NBS-6, a d ' OTC<NIST) - tI«1«\I(£j£)C* n°L

the SI SeCOnd! °r as n“ckn

nof“?rN?S

fT

tUonk

deS: “, Calibrators of frequency to

frequency calibrators, in which’case thay

lGPS is th® Global Positioning System, a network of navigation satellites.
Table 7.1 is a list of changes in the time scale frequencies of both TA(NIST) 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) y[UTC(NIST)] - y[TA(NIST)]

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/

23.045 101 681 s -3.44 E-13

1 Oct 87 47069 0 1.25 ns/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/

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/

24.045 106 272 s -3.53 E-13

1 Mar 88 47221 0 -1.25 ns/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/

24.045 109 170 s -4.29 E-13

1 Jun 88 47313 0 -1.50 ns/

24.045 110 358 s -4.47 E-13

1 Jul 88 47343 0 -1.60 ns/

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/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/24.045 116 854 s -4.88 E-13

1 Dec 88 47496 0 1.50 ns/24.045 118 088 s -4 . 69 E-13

1 Jan 89 47527 0 1.50 ns/24.045 119 325 s -4.57 E-13

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

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

REFERENCES

Allan, David W., et al., "/n 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 Conmon View of a GPS

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

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

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

- 6 -
8. SPECIAL AMKXJNCEMENTS

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 time-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 5i-in, 360-kbyte DOS

diskette with instructions for $35.00 from the NIST Office of Standard Reference Materials, B31 1-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.

A seminar on spectral analysis for physical applications will be given by Donald Percival, Ph.D., University of

Washington, based on a new book with A. Walden, Ph.D., featuring PiTSSa software on a Mac II. It will be held

March 13-17, 1989, 9am-3pm at the National Institute of Standards and Technology in Boulder, Colorado. Topics

in spectral analysis include:

SEMINAS ON SPECTRAL ANALYSIS FOB PHYSICAL APPLICATIONS

Stationary Processes

Deterministic Functions

Spectral Representation Theorem

Non- Parametric Spectral Analysis

Parametric Spectral Analysis

Multiple Taper Spectral Analysis

Linear Filtering

Power Law Spectral Density Est.

Unequally Spaced Data

The Allan Variance

Cost $500

Contact

DeeAnna Gibson, NIST, 576

325 Broadway

Boulder, CO 80303

(303) 497-3294
HSS.H4A i RE V. 2««Q

U.S. OEPT. Of COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NISTIR 89-3910-2

2. Performing Organ. Report No.

B89-0064

3. Publication Oate

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)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

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

10. SUPPLEMENTARY NOTES

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

11. ABSTRACT (A 200-word or less factual summary of most significant in formation. If document includes a significant

bibliography 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; capitalize only proper names; and separate key words by semicolon sj clocks; dissemination; frequency; GPS; oscillators; time

13. AVAILABILITY

[^J Unlimited

| y 1 For Official Distribution. Do Not Release to NTIS

!H Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

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

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PRINTED PAGES

8

15. Price

-8 -

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