Time & Frequency

Bulletin

No. 390 May 1990

(NISTIR 90-3940-5)

NIST TIME & FREQUENCY BULLETIN

(Supersedes No. 389 April 1990)

NO. 390 MAY 1990

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 Frequencv Division

National Institute of Standards & Technology

325 Broadway

Boulder, CO 80303

(303) 497-3295

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

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

ABBREVIATIONS AND ACRONYMS USED IN THIS BULLETIN

APL _ John Hopkins University Applied Physics Laboratory

BIH - International Time Bureau, France

CC1R - 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

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

1990 MJD

UT1 - UTC(NIST)

( + 5 ms)

UTC - UTC(NIST)

( + 0.2 us

)

UTC ( USNO ,MC ) - UTC(NIST)

(± 0.04 us)

5 47986 +128 ms 0.4 us 1.62 us

12 47993 +111 ms 0.4 us 1.59 us

19 48000 +97 ms 0.4 us 1.54 us

26 48007 +79 ms 0.4 us 1.51 us
INTERNATIONAL TIMING CENTER COMPARISONS VIA GPS COt«ON-VIEW

The fable 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) bv the simultaneous common-view approach (see references, page

6). The day-to-day variations of this technique are a few nanoseconds and the accuracy is about 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 47979 47989 47999 48009

UTC(APL) - UTC(NIST) 3,6,9,11,12,13,14 -515 -648@ -888 -798

UTC (CRL) - UTC (NIST) 3,6,9 12 833+ 823 758 754

UTC(CSIRO) - UTC ( NIST

)

-H- 24876+ 24970 24967 25158

UTC(IEN) - UTC (NIST) 11,12,13,14 1371 + 1385 1411 1427

UTC(INPL) - UTC (NIST) VIA OP -162636+ -164729 -166875 -169067//

UTC(NPL) - UTC(NIST) 3, 11,12,13,14 2728 2791 2813 2833

UTC(NRC) - UTC ( NIST )+++ 3,6,9,11,12,13,14 798+ 693 543 362

UTC (OP) - UTC(NIST)! 3, 11,12,13,14 1104+ 1150 1153 1152

UTC(PTB) - UTC (NIST) 11 -3280 -3248 -3234 -3212

UTC(TAO) - UTC (NIST) 3,6,9, 12, 5006 4835 4668 4522

UTC (TUG) - UTC (NIST

)

3, 11,12,13,14 2839+ 2592 2346 2103

UTC(USNO.MC) - UTC(NIST) 3,6,9,11,12,13,14 1662 1618 1550 1503

UTC(VSL) - UTC (NIST) 3, 11,12,13,14 -2214+ -2220 -2234 -2222

+ These values have been updated from those printed in last month's Bulletin. ++ UTC(CSIRO) - UTC(NIST) is computed from the average of CRL, TAO, & WWVH. +++ UTC(NRC) - UTC(NIST) has a differential delay of 41.2 ns; all other comparisons are computed using zero

( 0 ). @ APL experienced a frequency shift of approximately 30.0 E-14 (NET) between MJD's 47988 - 47998.

Therefore, the value for MJD 47989 was computed from the raw, unfiltered data.

! OP experienced a frequency shift of approximately -10.0 E-14 on MJD 47983.

It The value for this station for MJD 48009 was extrapolated forward from MJD 48007.

3. UTI 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 .eap

second. Its purpose is to keep the UTC time scale within t 0.9 s of the UTI 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 'he

UTC timescale on 30 June 1972, 31 December 1972-1979. 30 June 1981-1983, 30 June 1985, 31 December 1987 anc

1989. When future leap seconds are scheduled, advance notice will be provided in this bulletin.

The use of leap seconds ensures that UTI — UTC will alwavs be held within t 0.9 s. The current value of

UTI — UTC is called the DUT1 correction. DUT1 corrections are broadcast by WWV, WWVH, WWVB, and GOES and irp

printed below. These corrections may be added to received UTC time signals in order to obtain UTI.

DUT1 = UTI - UTC

= +0.2 s beginning 0000 UTC on 1 March 1990

= +0.1 s beginning 0000 UTC on 12 April 1990

= 0.0 s beginning 0000 UTC on 10 May 1990
4. PHASE DEVIATIONS EOR WWVR AND LORAN-C

WWVB - The values shown tor WWVB are the time difference between the t ime markers ol the L'TC(NIST)

time scale and the t irst positive-going zero voltage crossover measured at the transmitting

antenna. The uncertainty or the individual measurements is ± 0.5 us. the values Listed are

for 1300 UTC

.

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

The phase shift is measured by comparing the output ot a Loran receiver to the b'TC(NEST) time

scale for a period ot 24 hours. If data were not recorded on a particular day, the symbol

( - ) is printed

.

The stations monitored are Dana, Indiana (8970 M) and Fallon, Nevada (9940 M). The

monitoring is done from the NIST laboratories i.n Boulder, Colorado.

UTC(NIST) - WWVB(60 kHz)

UTC ( NIST ) - LORAN PHASE ( in us

)

DATE MJD

ANTENNA PHASE

( us

)

LORAN-C (DANA)

( 8970 M)

LORAN-C (FALLON)

(9940 M)

04/01/90 47982 5.67 +0.32 +0.31

04/02/90 47983 5.66 -0.03 +0.03

04/03/90 47984 5.63 +0.09 -0.02

04/04/90 47985 5.75 +0.01 -0.08

04/05/90 47986 5.69 -0.01 (-)

04/06/90 47987 5.67 -0.23 -0.44

04/07/90 47988 5.65 +0.13 -0.46

04/08/90 47989 5.64 +0.09 +0.15

04/09/90 47990 5.63 -0.01 +0.00

04/10/90 47991 5.74 -0.10 -0.04

04/11/90 47992 5.73 -0.13 +0.03

04/12/90 47993 5.70 +0.05 -0.00

04/13/90 47994 5.69 (-) (-)

04/14/90 47995 5.68 (-) (-)

04/15/90 47996 5.66 (-) (-)

04/16/90 47997 5.65 -0.07 +0.05

04/17/90 47998 5.64 +0.03 -0.28

04/18/90 47999 5.61 +0.16 +0.24

04/19/90 48000 5.68 +0.07 -0.07

04/20/90 48001 5.68 -0.36 -0.34

04/21/90 48002 5.66 +0.09 +0.05

04/22/90 48003 5.64 +0.26 +0.25

04/23/90 48004 5.62 -0. 15 -0.08

04/24/90 48005 5.73 -0.08 +0.10

04/25/90 48006 5.75 -0.10 +0.06

04/26/90 48007 5.73 +0.03 +0.05

04/27/90 48008 5.68 -0.21 -0.08

04/28/90 48009 5.68 +0.13 -0.08

04/29/90 48010 5.67 +0.24 +0.26

04/30/90 48011 5.67 +0.24 +0.13

- 3 -
5. GOES TIME CODE INFORMATION

A. TIME CODE PERFORMANCE ( I - JO April 1990)

JOES/' East : Performance within normal limits

was transmitted briefly from about 2100-2145

to lock to the signal. The GOES-5 satellite

longitude on 30 April.

during this period. An erroneous code synchronization word

UTC on 23 April, which may have affected receivers' ability

is still drifting westward and was at about 74 degrees west

GOES/West

:

Performance within normal limits during this period, except for the period from about 1700-

1800 UTC on 27 April when erroneous position data were transmitted. Also, see note about erroneous synchronization word under GOES/East above.

B. SPECIAL REMINDER: Current satellite locations are 74° West longitude for GOES/East and 135° West

longitude for GOES/West.

C. SPECIAL NOTE

In response to concerns from time code users about GOES/East coverage in Europe and Africa

if GOES/East operations are shifted to GOES-7, NOAA has reconsidered its previous decision.

Currently, the plan is to transfer GOES/East operations from GOES-5 to GOES-2 (an older

standby satellite) when GOES-2 drifts into its new location at about 60° West longitude.

This transfer of operations is expected to occur about May-July time period and will remain

in effect indefinitely. Exact dates will be announced in the GOES status file (NBSGO)

maintained in the U.S. Naval Observatory's Automated Data Service (see below for access information) as soon as it is known.

D. FUTURE SATELLITE LAUNCHES: NOAA's present launch schedule for replacement of the current East and West

satellites is July 1991 and February 1992, respectively.

E. GOES STATUS REPORTS

A brief message from the 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 "0NBSGO" 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

APRIL

1990 MJD

BEGAN

( UTC

)

ENDED

( UTC

)

FREQUENCY

APRIL

1990

BEGAN

MJD (UTC)

ENDED

( UTC )

WWVB NONE NONE

wwv 23-24 48004 2355:00 0205:00 2.5 MHz NONE

23-24 48004 2355:00 0145:00 20.0 MHz

WWVH NONE NONE
7. NOTES ON NIST TIME SCALES AND PRIMARY STANDARDS

The frequencies of the time scales, TA(NIST) ana L'TC(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 contro' 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:

1 ) y UTC (NIST) (

3

U 1 Y 1987 ) — v NBS . 6 (July 1987) = (-0.6 ± 2 (1 si gma ) ) x 10 ^ 3

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

blackbodv radiation, which is approximately (delta Vgg) = -L.7 x 10" . Using GPS 3

, the frequency of TAI for

the dates shown were measured to be:

2) (July 1987 ) - y^jBs-6 (July 1987 on geoid) = ( + 1.7 ±2(1 sigma)) x 10’ 33

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)* 3ast calibration (July 1987) covered the period

from October 1986 through July 1987.

3) yCs(NIST) “ ^NBS-6 = ( + 3,4 ± 2) x 10 33 (July 1987)

and

4) yTAI " yCs(NIST) on geoid = < +0 - 3 1 °- 7) x 30

' 13

^ Jul y 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 relative frequency of TA(NIST) is steered toward Ycs(NIST)

by slight frequency drift corrections of the order of 1 part in 10 33 /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.

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

- 5 -
Tabli-i l is a list of changes in the time scare f requen;lies or Doth TA( N 1ST) ind 1 TC( 'US'T> as we i L is list of t he : ime and frequency di f ferences between TA(NIST) ind UTC(NIST) ac r-ne dates \ £ . eap seconds

ind/ 1or f requencv or frequency dri ft change;

TABLE 7 . 1

FREQUENCY CHANGES

DATE ( MJD

)

TA(NIST) UTC (NIST) TA(NIST) - UTC (NIST) y[ UTC (NIST) ! -- y[TA( NIST) |

1 Nov 88 4 7466 0 1.25 ns/d _ *4 ..045 116 854 s ~ u . 88 E- L 3

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- 1 3

1 Feb 89 47558 0 1.00 ns/d 24,.045 120 538 s -4. 51 E- 13

1 Mar 89 47586 0 -1.25 ns/d 24,.045 121 622 s -4. 58 E-13

1 Apr 89 47617 0 -1.50 ns/d 24,.045 122 871 s - 4 . 66 E- 13

1 May 89 47647 0 -1.50 ns/d 24,.045 124 078 s -4. 75 E-13

1 Jun 89 47678 0 -1.00 ns/d 24,.045 125 375 s -4. 92 E-13

1 Jul 89 47708 0 -1.00 ns/d 24

,

.045 126 670 s -5

.

09 E-13

1 Aug 89 47739 0 -1.00 ns/d 24,,045 128 060 s -5. 35 E-13

1 Sep 89 47770 0 -1.00 ns/d 24.,045 129 538 s -5

.

58 E-13

1 Oct 89 47800 0 1.00 ns/d 24.,045 131 001 s -5. 68 E-13

1 Nov 89 47831 0 1.00 ns/d 24.,045 132 534 s -5. 85 E-13

1 Dec 89 47861 0 1.00 ns/d 24.,045 134 082 s -6. 05 E-13

1 Jan 90 47892 0 1.00 ns/d 24,,045 135 724 s -6. 16 E-13

1 Feb 90 47923 0 1.00 ns/d 24,,045 137 382 s -6. 21 E-13

1 Mar 90 47951 0 1.00 ns/d 24..045 138 888 s -6. 23 E-13

1 Apr 90 47982 o

• 1.00 ns/d 24,,045 140 560 s -6.,36 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, v ( UTC( NIST ) ] is maintained as stable as possible.

REFERENCES

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

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

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

standards," Metrologia, Vol.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, on Instr. and Meas., Vol.IM-25, No. 4, pp. 453-458 (December 19/6'.

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

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

- 6-
8. SPECIAL ANNOUNCEMENTS

44TH ANNUAL FREQUENCY CONTROL SYMmsniM

...e 44th Annual Frequency Control Symposium will be held May "3 - ^ , qqn , „

. sympos aim is the leading technical conference addressing all aspects of frJn

Baitimore> MD - This

tinekeeping. Authors are invited to submit papers dealing w irh

^equencv control and precision

applications in areas represented by the following topics:

r ecent progress in research, development ana

Fundamental properties of piezoelectric crystals Theory and design of piezoelectric resonators

Resonator processing techniques

Filters

Surface acoustic wave devices (SAW)

Quartz crystal oscillators

Microwave and millimeter wave oscillators

Signal processing and frequency control circuitry Atomic and molecular frequency standards

Frequency and time coordination and distribution

Sensors and transducers

Applications of frequency control

Measurement and specifications

Contact: Dr. R. L. Filler, US Army Electronics Technology and Devices Laboratory ATTN Monmouth, NJ 07703-5000; (201) 544-2467. Laboratory, ATTN: SLCET-EQ, Fort

NOBEL PRIZE WINNERS to SPEAX at the 44th ANNUAL

SYMPOSIUM on FREQUENCY CONTROL

advancements in alojc clo^ S^

TrltlssTr L^ev Th"

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W° lf

^

Paul f ° r University of Washington (and possiblfProfessor pJl TZ the Snivels uHflonn^

Pr° feSS° r

HDet”eU ° f the

present their Nobel lectures at the 44th Annual Symposium on Frequency Control -Jhwe wUl'be'a ""''‘“D"’

5 ”

reduced registration fee for the Nobel lectures. The lectures w!ll be p^e«ed FUdTy ^ning?

Masers.

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proLs^rDetaeltU

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I. PEAFQA.minC OAGaniZaTiOn nf ; o • ( o' o • ' t*t* Nil, im i* i(/«ctio« i; National Institute of Standards &

Technology

325 Broadway

Boulder, CO 80303

1. Cont'icv'C'ant Na.

1. T/m *f A**en & Pan©4

». SPONSOAinC O^CAWiZATION name AND COMPLETE ADOAESS rSutat, Cm,. 2iPj

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Th« Tiae 4 Frequency Bulletin provides informetion on performance of t 1m

• caltt aad a veriety of broedcutA (tod related information) to users of tht

NIST services.

j

12. KEY *OAOS (S'f to t wtlrt ttlfltt, tip* tPtliCtt prttf; C *p llllll o*.'r « «mt 1 ; l»t«r«tf tl; »©^l ©r l«^-ce O' »;

clocks; diseeainetlon; frequency; CFS; oeclll«tors; time

1). AVAILABILITY

[ 1 U<Mimu*e

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f ~1 Fr©n< S^o#' Iruar4«nt af Documents, U.S» OevammaAi PrlMlng Office. WaeM*ii«n. O.C.

20402.

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*1 Qfdtr From National TacKmcal lnf©»mati©n Sarvlca (NTlS), Se'infflaH, VA. 22141

14. NO. OF

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