ASTROMETRY NETWORK I. INTRODUCTION A total of 1300 astrometric observations of comet Giacobini-Zinner that cover the interval from January 28, 1984 through March 31, 1987, were reported to the Astrometry Network of the International Halley Watch. These observations resulted from efforts by 199 observers working at 81 observatories throughout the world. Lists of the participating observers and observatories are given in Sec. IV. Astrometric observations were received at the Astrometry data pro- cessing center at the Jet Propulsion Laboratory, California Institute of Techno- logy, either directly from the observers or from B.G. Marsden and D.W.E. Green of the Minor Planet Center at the Harvard-Smithsonian Center for Astrophysics, who were unfailing in their efforts to relay the data expeditiously. At JPL, the data were received, verified, and added to the master data file. Observa- tions with orbit residuals smaller than three standard deviations (3-sigma) of the root mean square (RMS) residual were given an accept code (A) and employed in the weighted least squares differential correction procedure that was used to update the comet's existing orbit. Data with residuals greater than 3-sigma were given a delete code (D) and, if they retained this code during subsequent orbital updates, they were not included in these updates. Data with residuals exceeding 10 arcsec were not included in the master data file. Once verified, the data were put into the proper format (Sec. II) and added to the master data file. Observations were also sent to the Center for Astrophysics if they had not been relayed to us from there. Updated orbital information was sent elec- tronically to the NASA-Goddard Space Flight Center so that it could be used in the navigation of the International Cometary Explorer (ICE) spacecraft that flew through the tail of comet Giacobini-Zinner on September 11, 1985. The members of the Discipline Specialist Team of the Astrometry Network are listed in Table I. Modern techniques and procedures for making and reducing astrometric obser- vations are described in the reference. Table I. Discipline Specialist Team of the Astrometry Network ________________________________________________________________________________ Team Member Affiliation Responsibility ________________________________________________________________________________ Donald K. Yeomans Systems Division Discipline Specialist Jet Propulsion Laboratory California Institute of Technology Pasadena, CA 91109 U.S.A. Richard M. West European Southern Observatory Discipline Specialist D-8046 Garching bei Munchen Federal Republic of Germany Robert S. Harrington U.S. Naval Observatory Discipline Specialist Washington, DC 20392 U.S.A. Brian G. Marsden Harvard-Smithsonian Center Discipline Specialist for Astrophysics Cambridge, MA 02138 U.S.A. Paul W. Chodas Systems Division Computer Software Jet Propulsion Laboratory Assistant Michael S. Keesey Systems Division Data Reduction Jet Propulsion Laboratory Assistant Ravenel N. Wimberly Systems Division Communications Jet Propulsion Laboratory Assistant ________________________________________________________________________________ II. FITS HEADER DESCRIPTION AND DATA RECORD FORMAT Once complete, the comet Giacobini-Zinner master data file was written onto a tape using the FITS format in which each observation is represented by one file that includes header information followed by the data themselves. A hypothetical header record is used as an example in Table II below. Table II. Header Keyword Information __________________________________________ Keyword and Its Content __________________________________________ SIMPLE = T BITPIX = 8 NAXIS = 1 NAXIS1 = 2880 OBJECT = 'P/GIACOBINI-ZINNER' FILE-NUM= 102008 DATE-OBS= '21/ 7/84' TIME-OBS= 0.02708 DATE-REL= '26/ 9/88' DISCIPLN= 'ASTROMETRY' LONG-OBS= '289/11/23' LAT--OBS= '-30/09/43' SYSTEM = '18070000' OBSERVER= 'CLARKE,J.T/ET AL.' SUBMITTR= 'WIMBERLY,R.N' SPEC-EVT= F DAT-FORM= 'ASCII ' COMMENT ADD. OBS.: BRODIE,J/MCCARTHY,P COMMENT NOTES: VERY FAINT IMAGE END __________________________________________ The header key words SIMPLE, BITPIX, NAXIS, NAXIS1, OBJECT, DISCIPLN, SUBMITTR, SPEC-EVT, and DAT-FORM do not change from record to record for the Astrometry Network data. SIMPLE is a logical type (L) and conforms to basic FITS standards. BITPIX, NAXIS, NAXIS1 are integers (I) denoting, respectively, the number of bits per pixel in the data record, the number of axes in the data record and the number of pixels in the first axis row. OBJECT is a character field (C) giving the name of the object. FILE-NUM (I) begins with the integer 1 that identifies the Astrometry Network. The following five digits represent a unique sequential number used to identify the file. DATE-OBS (C) and TIME-OBS (real variable) give, respectively, the UT date (dd/mm/yy) and decimal fraction of a day. DATE-REL (C) is the date when the data were released to the IHW Lead Center and DISCIPLN (C) denotes the IHW discipline reporting the data. LONG-OBS and LAT--OBS give the east longitude (ddd/mm/ss) of the obser- vatory and its geographic (geodetic) latitude (sdd/mm/ss). When the geographic latitude was not available, we computed it from the parallax factors listed in each of our observation records. However, the parallax factors carry only enough significant figures to allow the geographic latitude to be computed to a few arcmin so that, in this case, we have rounded off the latitude to the nearest arcmin and placed zeros in the arcsec location. SYSTEM (C) is the system code in which the leading digit (1) identifies the Astrometry Network and the following three digits are a unique code for the reporting observatory (see Table V). The trailing four digits are zeroes for the Astrometry Network. OBSERVER (C) gives the name(s) of the observer(s), last name first followed by the initial(s) of their first (and middle) name(s) (see Tables V and VI). The observers are separated by a slash (/), whereas ET AL. indicates that additional observers (ADD. OBS.) are listed after the COMMENT keyword. Problems with the observation or data reduction process also are iden- tified after a COMMENT keyword. SUBMITTR (C) is R.N. Wimberly as the person who prepared the original data archive tape and submitted it to the IHW Lead Center at JPL. The SPEC-EVT (L) keyword is not used in the Astrometry Network. DAT-FORM (C) describes the format of the FITS data record which, for Astrometry, is to be interpreted as logical records of 80 ASCII characters. Following each FITS header record, there are five rows for each astro- metric position reported. The first line lists the time (Julian date in ephem- eris time) of the observation and the reported right ascension (hr, min, s) and the declination (deg, arcmin, arcsec). The first character of the second line is either an A or D, indicating whether the observation was accepted for, or deleted from, the final orbit solution. The second column of the second line contains either a blank or a code indicating the image quality. This code--C, D, S, and T--specifies whether the image is centrally condensed, diffuse, stellar, or trailed. An X code indicates that the observation is semi-accurate. The quality code is followed by the reported observation time (calendar date, UTC), by the ET-UTC correction in tenths of a second (see Table VII), and by the right ascension and declination that are corrected for the small effects of elliptic aberration. The right ascension and declination are referred to the mean equator and equinox of 1950.0. Next on the second line is the observatory code (see Table V) followed by the observatory's east longitude (deg) and by the parallax factors used to convert the computed geocentric positions to the topocentric observed positions. The last two entries on the second line are the 1-sigma standard deviations of the measurement noise (arcsec) for the right ascension and declination; these values are used to form weights in the orbit determina- tion process. The third line in the data record contains the name(s) of the observer(s), the name of the observatory, and the reported values for the total and nuclear magnitudes. When no magnitude was reported, a value of 99.0 fills this field. The fourth line in the data record begins with a reference which specifies how, or from whom, the data were obtained. The remainder of line four and all of line five contain further information on the observation, including any problems encountered, as well as additional observers involved whose names were not listed on line three. An example in Table III illustrates the five- line Astrometry format, which is described in Table IV. Table III. Example of Astrometry Data Record __________________________________________________________________________ 2445902.52771 135731.56+ 44348.1 AS1984 721.02708 542 135731.57+ 44348.2 807 289.19-369 213 1.0 1.0 CLARKE,J.T ET AL. CERRO TOLOLO OBSERVATORY, LA SERENA 99.00 23.0 LETTER DATED 9/13/84, IAUC 3979, 4M, CCD, REDUCED W/R TO AGK3 STARS ADDITIONAL OBSERVERS: BRODIE,J/MCCARTHY,P ;!VERY FAINT IMAGE! __________________________________________________________________________ Table IV. Five-line Astrometry format ________________________________________________________________________ Columns Description ________________________________________________________________________ Line 1: 1-13 Julian ephemeris day: xxxxxxx.xxxxx (Field length = 13, number of decimal places = 5) 14-21 Blank 22-30 Right ascension (hr, min, s), hhmmss.ss 31-39 Declination (sign, deg, arcmin, arcsec), sddmmss.s Line 2: 1 Accept code (A for accept, or D for delete) 2 Image quality code 3-16 UTC time of observation, yyyymmdd.ddddd 17 Blank 18-20 ET-UTC, nnn (542 = 54.2 s) 21 Blank 22-30 Right ascension, hhmmss.ss 31-39 Declination, sddmmss.s 40 Blank 41-43 Observatory code, nnn 44 Blank 45-50 East longitude of observatory, ddd.dd 51-58 Observatory parallax factors delta(xy) and deltaZ, snnnsnnn (cf. Note) 59 Blank 60-65 Right ascension data RMS in arcsec, ssss.s 66 Blank 67-72 Declination data RMS in arcsec, ssss.s Line 3: 1- 2 Blank 3-26 Name(s) of observer(s) 27 Blank 28-63 Name of observatory 64 Blank 65-69 Total visual magnitude estimate, xx.xx 70 Blank 71-74 Nuclear magnitude estimate, xx.x Lines 4 and 5: 1- 2 Blank 3-80 Supplemental information, character field of width 78 ________________________________________________________________________ Note: The parallax factors listed on line 2 are denoted delta(xy) and deltaZ and are used to transform the Earth-Sun vector from a geocentric origin to one that is topocentric: delta(xy) = -426.35E-07 * RHO * cos(LAT), deltaZ = -426.35E-07 * RHO * sin(LAT), where 426.35E-07 is the Earth's mean equatorial radius in AU, RHO the geocentric distance of the observatory in units of mean equatorial radii, and LAT the geo- centric latitude of the observatory. III. PRINTED ARCHIVE Contained in the printed version of the G-Z archive is a one-line sum- mary for each of the observations. Its format is described in Table V. Table V. Entries in the Printed Archive ________________________________________________________________________________ Heading Description ________________________________________________________________________________ Date(UT) Date (day & fraction of day) of middle of observation AN# Astrometry Network number--a unique number for each observa- tion. (The lead digit 1 indicates that the Discipline is Astrometry) RA (1950.0) Dec Right ascension and declination corrected for the small effects of elliptical aberration (referred to the mean equator and equinox of 1950.0) m1 Total magnitude m2 Nuclear magnitude System Observing System Code Observer(s) Name(s) of the observer(s) Notes Note reference(s) ________________________________________________________________________________ IV. OBSERVERS AND OBSERVATORIES PROVIDING ASTROMETRIC OBSERVATIONS Observatories that provided astrometric data for comet Giacobini-Zinner are listed in Table VI. Following the numeric code number of each observatory is its name and the total number of observations received. Under each observa- tory name is an alphabetical list of the observers and the total number of ob- servations in which they participated. In Table VII the observers are listed in alphabetical order followed by the codes of the relevant observatories and by the total number of observations they made. Differences between the ephemeris time (ET) and the UTC time applied to the observations of comet Giacobini-Zinner are presented in Table VIII. The first column shows the date on which the ET-UTC differences changed values by +1 s. Table VI. Observer List by Observatory ________________________________________________________________________________ Observatory Total Number of Observations Made Code Observatory and Observers --------------------------------- At Observatory By Observer ________________________________________________________________________________ 6 Fabra Observatory 46 Barcelona, Spain Codina, J.M. 37 Nunez, J. 19 Sanchez, F. 1 Torras, N. 11 12 Uccle Observatory 1 Uccle, Brussels, Belgium Debehogne, H. 1 Pauwels, T. 1 17 Hoher List Observatory 21 Hoher List, Federal Republic of Germany Decker, F. 21 Geffert, M. 21 Sterken, C. 21 22 Pino Torinese 24 Torino, Italy Ferreri, W. 10 Massone, G. 22 24 State Observatory at Konigstuhl 4 Heidelberg, Federal Republic of Germany Bastian, U. 4 Gorze, U. 4 Klare, G. 2 Mandel, H. 4 Roser, S. 4 26 Berne-Zimmerwald 12 Berne, Switzerland Wild, P. 12 43 Asiago Astrophysical Observatory 7 Padua, Italy Barbieri, C. 7 Kranjc, A. 7 Scardia, M. 7 46 Klet Observatory 78 Ceske Budejovice, Czechoslovakia Mrkos, A. 78 Vavrova, Z. 72 49 Uppsala-Kvistaberg 2 Uppsala, Sweden Lagerkvist, C.I. 2 Oja, T. 2 51 Cape of Good Hope, South Africa 2 Churms, J. 2 56 Skalnate Pleso Observatory 62 Skalnate Pleso, Czechoslovakia Cervak, G. 31 Kornos, L. 11 Rychtarcik, P. 53 Svoren, J. 3 57 Belgrade, Yugoslavia 7 Olevic, D. 1 Protitch-Benishek, V. 6 61 Uzhgorod, U.S.S.R. 36 Goroshchak, I.I. 36 63 Turku-Tuorla, Finland 5 Haarala, S. 5 Lappalainen, T. 5 Niemi, A. 5 Piironen, J. 5 Sillanpaa, A. 5 69 Baldone (near Riga), U.S.S.R. 20 Alksnis, A.K. 4 Eglitis, I.E. 2 Ozolinya, V. 14 71 Sofia, Bulgaria 34 Bonev, T. 16 Geffert, M. 6 Georgieva, A. 34 Ivanova, V. 34 Kirova, H. 2 Radeva, V. 14 Shkodrov, V. 28 83 Central Astrophysical Observatory 11 Golosseevo-Kiev, U.S.S.R. Izhakevich, E.M. 5 Kaltygina, S. 3 Ledovskaya, I. 2 Major, S.P. 1 Sereda, E. 3 Shatokhina, S.V. 1 84 Pulkovo Observatory 13 Leningrad, U.S.S.R. Bronikova, N.M. 9 Ipatova, I.A. 1 Kiseleva, T.P. 1 Koroleva, L.S. 8 Narizhnaya, N.V. 6 Nikiforov, I.I. 6 85 Kiev University Observatory 21 Kiev, U.S.S.R. Churyumov, K. 19 Izhakevich, E.M. 2 Sizonenko, Y. 2 Smirnova, K. 7 87 Helwan, Egypt 2 Bagus, B.B. 2 Bakhtigaraev, N.S. 2 El-Khilali, Y. 2 Tovadrus, M.Y. 2 94 Crimea-Simeis, U.S.S.R. 6 Fokanov, S.V. 6 Merezhina, L.S. 6 Shcherbanovskij, A.L. 6 95 Crimea-Nauchnij, U.S.S.R. 26 Chernykh, N.S. 20 D'yakonova, V.D. 6 Karachkina, L.G. 6 96 Merate, Italy 11 Barbieri, C. 11 Kranjc, A. 11 Scardia, M. 11 98 Cima Ekar, Asiago Astrophysical 11 Observatory Padua, Italy Barbieri, C. 11 Kranjc, A. 11 Scardia, M. 11 102 Zvenigorod, U.S.S.R. 32 Lyukhanov, K.B. 32 Osipenko, V.P. 32 Rusin, Y.V. 32 Yurevich, V.A. 32 114 Engelhardt Observatory, Zelenchuk 32 Station, U.S.S.R. Kitkin, V.N. 32 Zelishchev, I.E. 32 Zelishchev, I.G. 32 129 Ordubad, U.S.S.R. 1 Kiseleva, T.P. 1 168 Kourovskaya, U.S.S.R. 20 Tearo, A.R. 20 Timofeyev, S.N. 20 186 Kitab, U.S.S.R. 83 Mirmakhmudov, E. 47 Pattakhov, E. 27 Rakhmatov, E. 83 190 Gissar, U.S.S.R. 18 Gerasimenko, S.I. 18 191 Dushanbe, U.S.S.R. 3 Gerasimenko, S.I. 3 293 Burlington (Remote Site), 7 New Jersey, U.S.A. Handley, T. 7 323 Perth Observatory, Bickley 34 Western Australia, Australia Candy, M.P. 15 Jekabsons, P. 25 John, A. 13 Johnston, J. 11 Kinnear, G. 26 330 Purple Mountain Observatory 17 Nanking, China Lu, J.H. 4 Wang, D.C. 7 Wang, Q. 5 Wei, S.L. 9 Yang, J.X. 11 337 Zo-Se, China 1 Zhao, J.L. 1 372 Geisei, Japan 2 Seki, T. 2 376 Uenohara, Japan 2 Kawasato, N. 2 381 Tokyo-Kiso, Japan 2 Kosai, H. 2 Yamagata, T. 2 391 Sendai Observatory, Ayashi Station 17 Ayashi, Japan Hozono, K. 14 Koishikawa, M. 17 Kurosu, K. 14 Sato, T. 14 392 JCPM Sapporo Station 5 Sapporo, Japan Kaneda, H. 4 Watanabe, K. 1 397 Sapporo Science Center 17 Sapporo, Japan Watanabe, K. 17 415 Kambah (near Canberra) 2 New South Wales, Australia Herald, D. 2 474 Mount John Observatory 10 Lake Tekapo, New Zealand Gilmore, A.C. 10 482 St. Andrews, Scotland, 4 United Kingdom Stapleton, J.R. 4 490 Wimborne Minster, England, 2 United Kingdom Swan, M. 2 491 Centro Astronomico De Yebes 18 Yebes, Spain Cabanas, C. 18 De Pascual, M. 18 Garcia, J. 18 Martin-Pintado, J. 4 Sanchez, F. 14 493 Estacion Astronomica De Calar Alto 8 Calar Alto, Spain Kohoutek, L. 8 494 Stakenbridge, England, 13 United Kingdom Manning, B. 13 502 Colchester, England, United Kingdom 7 Hendrie, M.J. 7 552 Osservatorio San Vittore 15 Bologna, Italy Colombini, E. 15 Goretti, V. 11 Sassi, G. 15 Vacchi, C. 15 553 Chorzow, Poland 11 Firszt, T. 6 Szczepanski, M. 6 Wlodarczyk, I. 11 555 Cracow-Fort Skala, Poland 133 Kurpinska-Winiarska, M. 113 Kus, M. 94 Lapeta, A. 92 Waniak, W. 93 Winiarski, M. 111 Zola, S. 92 556 Reintal (near Munich), Federal 6 Republic of Germany Seiler, F. 6 562 Figl Observatory 22 Vienna, Austria Schnell, A. 22 Stockenhuber, H. 22 564 Herrsching (near Munich), Federal 3 Republic of Germany Stattmayer, P. 3 565 Brescia, Italy 25 Marinello, V. 25 Quadri, U. 25 567 Chaonis, Italy 2 Baur, C.R. 2 Baur, J.M. 2 571 Cavriana, Italy 5 Lai, L. 5 Ronchetti, I. 5 Ruzza, M. 5 Vesentini, G. 5 574 Gottolengo, Italy 2 Mattarozzi, G. 2 Quadri, U. 2 575 La Chaux Des Fonds, Switzerland 3 Behrend, A. 3 Behrend, R. 3 580 Graz, Austria 2 Ornig, C.W. 2 657 Victoria, British Columbia, Canada 69 Balam, D.D. 65 Lowe, T.B. 20 Rychtarcik, P. 1 Tatum, J.B. 60 662 Lick Observatory 16 Mount Hamilton, California, U.S.A. Djorgovski, S. 2 Harlan, E. 2 Jones, B. 12 McCarthy, P. 2 Spinrad, H. 2 675 Palomar Mountain, California, U.S.A. 11 Gibson, J. 2 Green, D.W.E. 6 Helin, E. 3 Schneeberger, D. 1 Singer-Brewster, S. 1 688 Lowell Observatory 9 Anderson Mesa, Arizona, U.S.A. Bowell, T. 2 Bus, S.J. 5 Kreidl, T.J.N. 5 Skiff, B.A. 7 691 Steward Observatory 16 Tucson, Arizona, U.S.A. Gehrels, T. 16 695 Kitt Peak National Observatory 17 Tucson, Arizona, U.S.A. Bailyn, C. 3 Belton, M.J.S. 5 Cohn, H. 3 Dacosta, G. 2 Djorgovski, S. 4 Ford, H. 2 Jacoby, G. 2 Jewitt, D. 2 Luggar, P. 3 Mateo, M. 3 Meech, K.J. 2 Spinrad, H. 4 Wehinger, P. 5 Will, G. 4 696 Whipple Observatory, Mt. Hopkins 9 Amado, Arizona, U.S.A. Schild, R. 9 707 Chamberlin Field Station 8 Bailey, Colorado, U.S.A. Briggs, J. 8 Everhart, E. 4 711 McDonald Observatory 22 Fort Davis, Texas, U.S.A. Mulholland, J.D. 12 Whipple, A.H. 22 786 United States Naval Observatory 1 Washington, District of Columbia, U.S.A. Harrington, R.S. 1 788 Mount Cuba Observatory 2 Greenville, Delaware, U.S.A. Bock, G. 1 Bruton, J. 1 Jackson, S. 2 Stock, R.F. 2 792 University Of Rhode Island 6 Quonochontaug, Rhode Island, U.S.A. Penhallow, W.S. 6 801 Oak Ridge Observatory 42 Harvard, Massachusetts, U.S.A. McCrosky, R.E. 40 Schwartz, G. 35 Shao, C.Y. 26 807 Cerro Tololo Observatory 4 La Serena, Chile Brodie, J. 4 Clarke, J.T. 4 McCarthy, P. 4 808 El Leoncito, Argentina 1 Lopez, C.E. 1 809 European Southern Observatory 1 La Silla, Chile Pederson, H. 1 West, R.M. 1 893 Sendai Municipal Observatory 7 Sendai, Japan Aisawa, K. 7 Kurosu, K. 6 978 Conder Brow, England, 9 United Kingdom Buczynski, D.G. 2 Greenwood, J.D. 7 984 West Chinnock, England, 1 United Kingdom Ridley, H.B. 1 993 Woolston, England, United Kingdom 1 Ridley, H.B. 1 ________________________________________________________________________________ Table VII. Observer Index _____________________________________________________ Observer Observatory Number of Code(s) Observations _____________________________________________________ Aisawa, K. 893 7 Alksnis, A.K. 69 4 Bagus, B.B. 87 2 Bailyn, C. 695 3 Bakhtigaraev, N.S. 87 2 Balam, D.D. 657 65 Barbieri, C. 43,96,98 29 Bastian, U. 24 4 Baur, C.R. 567 2 Baur, J.M. 567 2 Behrend, A. 575 3 Behrend, R. 575 3 Belton, M.J.S. 695 5 Bock, G. 788 1 Bonev, T. 71 16 Bowell, T. 688 2 Briggs, J. 707 8 Brodie, J. 807 4 Bronikova, N.M. 84 9 Bruton, J. 788 1 Buczynski, D.G. 978 2 Bus, S.J. 688 5 Cabanas, C. 491 18 Candy, M.P. 323 15 Cervak, G. 56 31 Chernykh, N.S. 95 20 Churms, J. 51 2 Churyumov, K. 85 19 Clarke, J.T. 807 4 Codina, J.M. 6 37 Cohn, H. 695 3 Colombini, E. 552 15 D'Yakonova, V.D. 95 6 Dacosta, G. 695 2 De Pascual, M. 491 18 Debehogne, H. 12 1 Decker, F. 17 21 Djorgovski, S. 662,695 6 Eglitis, I.E. 69 2 El-Khilali, Y. 87 2 Everhart, E. 707 4 Ferreri, W. 22 10 Firszt, T. 553 6 Fokanov, S.V. 94 6 Ford, H. 695 2 Garcia, J. 491 18 Geffert, M. 17,71 27 Gehrels, T. 691 16 Georgieva, A. 71 34 Gerasimenko, S.I. 190,191 21 Gibson, J. 675 2 Gilmore, A.C. 474 10 Goretti, V. 552 11 Goroshchak, I.I. 61 36 Gorze, U. 24 4 Green, D.W.E. 675 6 Greenwood, J.D. 978 7 Haarala, S. 63 5 Handley, T. 293 7 Harlan, E. 662 2 Harrington, R.S. 786 1 Helin, E. 675 3 Hendrie, M.J. 502 7 Herald, D. 415 2 Hozono, K. 391 14 Ipatova, I.A. 84 1 Ivanova, V. 71 34 Izhakevich, E.M. 83,85 7 Jackson, S. 788 2 Jacoby, G. 695 2 Jekabsons, P. 323 25 Jewitt, D. 695 2 John, A. 323 13 Johnston, J. 323 11 Jones, B. 662 12 Kaltygina, S. 83 3 Kaneda, H. 392 4 Karachkina, L.G. 95 6 Kawasato, N. 376 2 Kinnear, G. 323 26 Kirova, H. 71 2 Kiseleva, T.P. 84,129 2 Kitkin, V.N. 114 32 Klare, G. 24 2 Kohoutek, L. 493 8 Koishikawa, M. 391 17 Kornos, L. 56 11 Koroleva, L.S. 84 8 Kosai, H. 381 2 Kranjc, A. 43,96,98 29 Kreidl, T.J.N. 688 5 Kurosu, K. 391,893 20 Kurpinska-Winiarska, M. 555 113 Kus, M. 555 94 Lagerkvist, C.I. 49 2 Lai, L. 571 5 Lapeta, A. 555 92 Lappalainen, T. 63 5 Ledovskaya, I. 83 2 Lopez, C.E. 808 1 Lowe, T.B. 657 20 Lu, J.H. 330 4 Luggar, P. 695 3 Lyukhanov, K.B. 102 32 Major, S.P. 83 1 Mandel, H. 24 4 Manning, B. 494 13 Marinello, V. 565 25 Martin-Pintado, J. 491 4 Massone, G. 22 22 Mateo, M. 695 3 Mattarozzi, G. 574 2 McCarthy, P. 662,807 6 McCrosky, R.E. 801 40 Meech, K.J. 695 2 Merezhina, L.S. 94 6 Mirmakhmudov, E. 186 47 Mrkos, A. 46 78 Mulholland, J.D. 711 12 Narizhnaya, N.V. 84 6 Niemi, A. 63 5 Nikiforov, I.I. 84 6 Nunez, J. 6 19 Oja, T. 49 2 Olevic, D. 57 1 Ornig, C.W. 580 2 Osipenko, V.P. 102 32 Ozolinya, V. 69 14 Pattakhov, E. 186 27 Pauwels, T. 12 1 Pederson, H. 809 1 Penhallow, W.S. 792 6 Piironen, J. 63 5 Protitch-Benishek, V. 57 6 Quadri, U. 565,574 27 Radeva, V. 71 14 Rakhmatov, E. 186 83 Ridley, H.B. 984,993 2 Ronchetti, I. 571 5 Roser, S. 24 4 Rusin, Y.V. 102 32 Ruzza, M. 571 5 Rychtarcik, P. 56,657 54 Sanchez, F. 6,491 15 Sassi, G. 552 15 Sato, T. 391 14 Scardia, M. 43,96,98 29 Schild, R. 696 9 Schneeberger, D. 675 1 Schnell, A. 562 22 Schwartz, G. 801 35 Seiler, F. 556 6 Seki, T. 372 2 Sereda, E. 83 3 Shao, C.Y. 801 26 Shatokhina, S.V. 83 1 Shcherbanovskij, A.L. 94 6 Shkodrov, V. 71 28 Sillanpaa, A. 63 5 Singer-Brewster, S. 675 1 Sizonenko, Y. 85 2 Skiff, B.A. 688 7 Smirnova, K. 85 7 Spinrad, H. 662,695 6 Stapleton, J.R. 482 4 Stattmayer, P. 564 3 Sterken, C. 17 21 Stock, R.F. 788 2 Stockenhuber, H. 562 22 Svoren, J. 56 3 Swan, M. 490 2 Szczepanski, M. 553 6 Tatum, J.B. 657 60 Tearo, A.R. 168 20 Timofeyev, S.N. 168 20 Torras, N. 6 11 Tovadrus, M.Y. 87 2 Vacchi, C. 552 15 Vavrova, Z. 46 72 Vesentini, G. 571 5 Wang, D.C. 330 7 Wang, Q. 330 5 Waniak, W. 555 93 Watanabe, K. 392,397 18 Wehinger, P. 695 5 Wei, S.L. 330 9 West, R.M. 809 1 Whipple, A.H. 711 22 Wild, P. 26 12 Will, G. 695 4 Winiarski, M. 555 111 Wlodarczyk, I. 553 11 Yamagata, T. 381 2 Yang, J.X. 330 11 Yurevich, V.A. 102 32 Zelishchev, I.E. 114 32 Zelishchev, I.G. 114 32 Zhao, J.L. 337 1 Zola, S. 555 92 _____________________________________________________ Table VIII. Differences ET-UTC _______________________________ Date ET-UTC(s) _______________________________ 1983 July 1.0 54.18 1985 July 1.0 55.18 1988 Jan. 1.0 56.18 _______________________________ REFERENCE Yeomans, D.K., West, R.M., Harrington, R.S., and Marsden, B.G., eds. (1984). Cometary Astrometry, Proceedings of a Workshop held June 18-19, 1984 at the European Southern Observatory Headquarters in Garching bei Munchen, Federal Republic of Germany, JPL Publ. 84-82, 220pp.