Tim0 & FrcQuency

Bulletin

No. 376 March 1989

(NISTIR 89-3910-3)

HIST TIMB & FREQUENCY BULLETIN

(Supersedes No. 375 February 1989)

NO, 376 MARCH 1989

1. GENERAL BACKGROUND INFORMATION 1

2. TIME SCALE INFORMATION 1

International Timing Center comparisons via GPS conmon-view 2

3. UTl CORRECTIONS AND LEAP SECOND ADJUSTMENTS 2

A. 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 - Geostationary Operational Environmental Satellite

GPS - Global Positioning System

lEN - 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. TDffi SCALE INF08MATIGN

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).

0000 HOURS COORDINATED UNIVERSAL TIME

FEBRUARY

1989 MJD

UTl - UTC(NIST)

(± 5 ms)

UTC - UTC (NIST)

(± 0.2 us)

UTC(USNO,MC) - UTC(NIST)

(± 0.04 us)

2 47559 -155 ms -0.1 us 1.01 us

9 47566 -168 ms -0.1 us 0.95 us

16 47573 -178 ms -0.1 us 0.89 us

23 47580 -187 ms -0.1 us 0.82 us

- 1 -
INTERNATIONAL TTKING CENTER COMPARISONS VIA GPS COItlON-VIEH

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

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

6). The day-to-day variations of this technique are Less than LO ns. The time of the measurement is

interpolated to 0000 UTC for the particular MJD ending in 9. These data are prepared for the BIFM 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 47549 47559 47569 47579

UTC(CRL) - UTC(NIST) 1372* 1295 1202 1083

UTC(CSIRO) - UTC(NIST) 19347 19225 19156 19115

LTC(IEN) - UTC(NIST) 9,11,12 598 604 581 562

UTC(INPL) - UTC(NIST) VIA OP -97665 -1021371 -1021281 -1021226

UTC(NPL) - UTC(NIST) 9,11,12 -2032 -1726 -1450 -1133

LT'C(NRC) - UTC(NIST)*** 3,6,9,11,12,13 13194 13211 13207 13185

UTC(OP) •- UTC(NIST) //# 1682 1650 1599 1532

UTC(PTB) - UTC(NIST) mi -4250 -4321 -4385 -4482

UTC(TAO) - UTC(NIST) mi 2492 2483 2477 2443

UTC (TUG) - UTC(NIST) 9,11,12 3605 3324 3015 2684

UTC(USN0 ,MC) - UTC(NIST) mi 1089 1011 922 829

UTC(VSL) - UTC(NIST) 9,11,12 -1021 -1121 -1237 -1301

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

IHf These values have been computed using around-the-world time transfer techniques.

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

( 0 ).

3. UTl CORRECTIONS AND LEAP SECOND ADJUSTMENTS

The master clock pulses used by the WWV, WWVH, WVTVB, 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 t 0.9 s of the UTl 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, 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 UTl — UTC will always be held within ± 0.9 s. The current value of

UTl - UTC is called the DUTl correction. DUTl 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 UTl.

DUTl = UTl - UTC

= 0.0 s beginning 0000 UTC 25 August 1988

= -0.1 s beginning 0000 UTC 10 November 1988

= -0.2 s beginning 0000 UTC 19 January 1989
4. PHASE DEVIATIONS FOR WWVB AND LORAH-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 1 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)

FEBRUARY

1989 MJD

UTC(NIST) - WWVB(60 kHz)

ANTENNA PHASE

(in us)

LORAN-C (DANA)

(100 kHz)

LORAN-C (FALLON)

(100 kHz)

1 47558 5.64 5137.55 3949.85

2 47559 5.71 5137.61 3949.94

3 47560 5.68 5137.49 3949.80

4 47561 5.68 5137.43 3949.64

5 47562 5.68 5138.35 3949.70

6 47563 5.68 5137.48 3949.76

7 47564 5.66 5137.62 3950.00

8 47565 5.62 5137.77 3950.16

9 47566 5.71 5137.81 3950.25

10 47567 5.65 5138.03 3950.29

11 47568 5.64 5138.03 (-)

12 47569 5.62 5138.18 (-)

13 47570 5.61 5138.51 3950.35

14 47571 5.58 5138.40 3950.35

15 47572 5.69 5138.18 3950.31

16 47573 5.65 5137.86 3950.33

17 47574 5.68 5137.94 3950.38

18 47575 5.66 5137.88 3950.16

19 47576 5.64 5138.09 3950.14

20 47577 5.62 5138.33 3950.16

21 47578 5.60 5138.37 3950.28

22 47579 5.69 5138.04 3950.21

23 47580 5.64 5137.90 (-)

24 47581 5.63 5138.08 3950.27

25 47582 5.63 5138.19 3950.14

26 47583 5.63 5138.23 3950.10

27 47584 5.63 5138.34 3950.20

28 47585 5.57 5138.39 3950.19

- 3 -
5. GOES TIME CODE INFORMATION

A. TIME CODE PERFORMANCE (1-28 February 1989)

GOES/East : Performance within normal limits during this period. Time code deviations for the corrected

code as observed in Boulder were near the normal 100 microsecond limits at times due to quality of the

GOES-5 orbital elements available.

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 REMINDEIR: Current satellite locations are 65“ W. for GOES/East and 135“ W. for GOES/West.

C. SPECIAL ANNOUNCEMENT

Spring 1989 eclipse operations are not expected to impact the time code operations for either GOES/East or GOES/West, since no time code transfers to spare satellites are being done during eclipse periods.

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 (commercial), 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 (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. BItQADCAST CXJTAGES OVER 5 MINUTES AND UUVB PHASE PERTUIBATIGNS

OUTAGES PHASE PERTURBATIONS WWVB 60 k.Hz

STATION

FEBRUARY

1989

BEGAN

MJD (UTC)

ENDED

(UTC) FREQUENCY

FEBRUARY BEGAN

1989 MJD (UTC)

ENDED

(UTC)

WWVB NONE NONE

WWV NONE NONE

WWVH NONE

-4 -
-if-'

7. NOTES ON NIST TINE SCALES AND PRIMARY STANDARDS

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

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

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

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

yUTC(NIST) 1987) - y^BS-b 1-987) = (-0.6 ±2(1 sigma)) x 10"^^

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

blackbody radiation, which is approximately (delta ygg) = -1.7 x 10"^^. Using GPS^, the frequency of TAI for

the dates shown were measured to be:

2) (July 1987) - y^Bs-b (J^^y 1-987 on geoid) = (+1.7 ±2(1 sigma)) x 10"^^

where account has been taken of the gravitational "red shift."

Starting 1 January 1975, an accuracy algorithm was implemented to bring the second used in the generation of

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

associated with this "best estimate" is denoted ycs(NIST)’ last calibration (July 1987) covered the period

from October 1986 through July 1987.

yCs(NIST) ” yNBS-6 = ± 2) x 10"^^ (July 1987)

and

yTAI - yCs(NIST) on geoid “ (+0*3 ± 0.7) x 10‘^3

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 gam 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 relative frequency of TA(NIST) is steered toward ycs(NIST)

by slight frequency drift corrections of the order of 1 part in 10^^/yr.

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

a Kalman algorithm which minimizes the mean square time dispersion. UTC(NIST) is now independently computed

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

Table 7.1 lists monthly values of the time difference between UTC(NIST) and TA(NIST). A linear interpolation

between 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.

1 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(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 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 no 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

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

1 Feb 89 47558 0 1.00 ns/d 24.045 120 538 s -4.51 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[LTC(NIST)] is maintained as stable as possible.

REFERENCES

Allan, David W., 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 primarv frequency standards," Metrologia, Vol.l3,

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 i Frequency using GPS signals," Proc. 36th Annual

Symposium on Frequency Control, p.378 (1982).
8. SPECIAL ANN0UNCB1EIITS

43rd Annual Syaposiua on Frequency Control

The 43rd Annual Symposium on Frequency Control will be held on May 31 - June 2, 1989. The site for this vears symposium will be the Marriott Hotel City Center in Denver, Colorado.

The number of summaries submitted to the technical program committee reached an all time high. The

quality of these submissions proves to make the 43rd the best symposium ever. Ninety papers will be presented

in 21 sessions. Highlights will be a specially organized session on environmental effects and their

measurement, a session on surface preparation of quartz, including a tutorial on abrasive processes, and a session on two-way time transfer.

The symposium will begin with a plenary session at which three prestigious awards will be presented. The

Cady award is presented annually by the technical program conmittee to frequency control devices. This year

the award recipient will be Dr. D.E. Newell. The Rabi award is presented to recognize outstanding

contributions related to fields such as atomic and molecular frequency standards, time transfer, and frequency

and time metrology. This year's recipient is Dr. L. Cutler. The third award, sponsored by Sawyer Applied

Research Products, is presented in honor of C.B. Sa%ryer for the most outstanding recent contribution to

advancement in the field of quartz crystals and devices. The recipient of the C.B. Sawyer award is selected by an independent conmittee and will be announced at the symposium.

Special invited presentations will include "Spacecraft Gravitational Wave Experiments" by J.W. Armstrong,

JPL; "Shear Mode Grinding" by N.J. Brown and B.A. Fuchs, LLNL; "A High Stability Microwave Oscillator Based on

a Sapphire Loaded Superconducting Cavity" by D.G. Blair, A.J. Giles, and S.K. Jones, U. of Western Australia;

"Stacked Crystal Filters Implemented with Thin Films" by K.M. Lakin, G.R. Kline, J.T. Martin, and K.T.

McCarron, Iowa State U. ; and "Low-Cost High-Performance Resonator and Coupled-Resonator Designs: NSPUDT and

Other Innovative Structures" by P.V. Wright, RF Monolithics.

The social program will be extra special due to the proximity of the National Institute of Standards and

Technology (formerly the National Bureau of Standards). There will be a tour of NIST, including a visit to the

nation's time standard, tentatively scheduled for Wednesday evening. May 31. Dinner on Thursday, June 1, will

be at a famous Denver attraction The Fort. The Fort is a restaurant specializing in authentic foods of the

American West including buffalo. Rocky Mt. oysters and Rocky Mt. trout. This will be an experience to be

enjoyed by all.

- 7 -
u.»: bear, ox comm. 1. PUBLICATION OR 2. Performing Organ. Raport NoJ S. Publication Data

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NISTIR 89-3910-3

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4, TITLE AND SUBTITLE

T1*€ i Frequency Bulletin

S. AUTHOR(S)

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NATIONAL BUREAU OF STANDARDS

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If. SUPPLEMENTARY NOTES

I I Documam daicribaa a computar program; SF*I85. FlPS Softwara Summary, la actachad.

11. ABSTRACT (A 200-word or lass factual tummary of most tignificant Information, If documant Includas a significant

bibliography or litaratura survey, mention it hare)

The Tlae & Frequency Bulletin provides InforBStlon on perforaence of tlae

sceles end e verlety of broedcestt (end releted Informetion) to ueere of the

NIST services.

12. KEY WORDS (Six to twelve entries; aiphebetical order; capitalize only proper names; and separate key words by temicoionti

clocks; dlssemlnetlon; frequency; GPS; oscllletors; tlae

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