ASTROMETRY NETWORK 1. OVERVIEW Through the dedicated efforts of a great many individuals, the Astrometry Network of the International Halley Watch (IHW) successfully carried out its goal of coordinating astrometric observations of comet Halley and archiving the collected data. The astrometric data were used to update continually the orbit of Halley's comet with the resulting ephemerides being made available to a wide community of researchers to make observations using ground-based, Earth orbital, and interplanetary instruments. Astrometric data were received via telegram, Telex, electronic mail message, computer-to-computer links as well as by telephone and postal delivery. Many observers went to extraordinary efforts to see that their data were reduced and transmitted to the orbit determination center within the shortest possible time. Some of these observations were less than a day old when received at the data collection center at the Jet Propulsion Laboratory (JPL). These outstanding efforts were most obvious just prior to the spacecraft encounters of comet Halley in early March 1986. As an example of the personal efforts that made the Astrometry Network a success, we note that an English amateur astronomer often took astrometric photographs, measured the images, reduced the measurements into positional data and telephoned the information to JPL before finally going to bed. As of mid-1989, a total of 6475 astrometric observations of comet Halley covering the interval from October 16, 1982 through January 9, 1989 had been reported to the Astrometry Network. These observations resulted from efforts by 430 observers working at 148 observatories throughout the world. It is a credit to the IHW Astrometry Network members that 90% of the data received were used in the comet's most recent orbit updates. Lists of the participating observers and observatories are given in Sec. III of the Astrometry Network Appendix. The members of the Discipline Specialist Team of the Astrometry Network are listed in Table I below. Table I. Discipline Specialist Team of the Astrometry Network ___________________________________________________________________________ Team Member Affiliation Responsibility ___________________________________________________________________________ Donald K. Yeomans Systems Division Discipline Jet Propulsion Laboratory Specialist California Inst. of Technology Pasadena, CA 91109 U.S.A. Richard M. West European Southern Observatory Discipline D-8046 Garching bei Munchen Specialist Federal Republic of Germany Robert S. Harrington U.S. Naval Observatory Discipline Washington, DC 20392 Specialist U.S.A. Brian G. Marsden Harvard-Smithsonian Center Discipline for Astrophysics Specialist Cambridge, MA 02138 U.S.A. Paul W. Chodas Systems Division Computer Software Jet Propulsion Laboratory Cognizant Michael S. Keesey Systems Division Data Reduction Jet Propulsion Laboratory Cognizant Ravenel N. Wimberly Sterling Software Communications Palo Alto, CA 94303 Cognizant U.S.A. ___________________________________________________________________________ 2. PREPARATIONS FOR OBSERVING PROGRAMS In preparation for the extensive observations of comet Halley, IHW Hand- books were issued giving circumstances, brightness predictions and ephemeris information (Yeomans 1981; Yeomans 1983). Updated ephemeris information was distributed to all IHW members in periodic Newsletters and self-contained, two-body ephemeris generation computer software was made available to IHW Discipline Specialists enabling them to generate accurate ephemeris information from frequently updated orbital elements. Up-to-date orbital elements were maintained in the IHW electronic mail system. Visual stellar occultation predictions were provided by Bowell and Wasserman (1985) and also by Dunham, De Pater et al. (1985) provided occultation predictions for radio sources. R.M. West hosted an Astrometry Network Workshop at the European Southern Observatory in June 1984. Experts in the field presented papers on modern techniques for making astrometric observations, using star catalogs, reducing plates as well as computing orbits. At the conclusion of the Workshop, recommendations were made in each of these areas to assist those wishing to make contributions. The Workshop Proceedings were printed and distributed to each Astrometry Network member to serve as a useful guide (Yeomans et al. 1984). 3. FLIGHT PROJECT SUPPORT The critical nature of astrometric data, in support of the various flight projects, was recognized at the inception of the IHW since uncertainties in the comet's ephemeris would dominate spacecraft targeting errors at the encounters with Halley. These ephemeris errors are due to imperfectly modeled nongravitational forces acting upon the comet's nucleus, systematic offsets between the measured center of light and the comet's (unseen) center of mass, errors in the existing star catalogs used in reducing the data and non- standard imaging and data reduction techniques. It was critically important to provide for the rapid communication of up- to-date Halley astrometric data to the flight project orbit-determination centers at the European Space Operations Center (ESOC) in Darmstadt, Federal Republic of Germany, and the Space Research Institute (IKI) in Moscow, U.S.S.R. Accurate spacecraft targeting relied upon the use of recent astrometric data to improve constantly the knowledge of the comet's orbital motion. Astrometric data and recent IHW orbit updates were transmitted from JPL to ESOC via a direct computer-to-computer link and these data were, in turn, transmitted to IKI via a direct ESOC-IKI data line. This latter line was also important for the success of the Pathfinder navigation effort (Munch et al. 1986). Mention must also be made of the considerable help from Dr. B.G. Marsden and D.W.E. Green at the IAU immediately relaying astrometric data of comet Halley, via an electronic mail service, to the IHW orbit determination center at JPL. Astrometric data and recent orbits were also sent, via telex, from JPL to the Soviet astrometric center in Kiev, U.S.S.R. Y.S. Yatskiv and S.P. Major then forwarded this information directly to Moscow for a redundant flow of information to the VEGA flight project. The astrometric data were used by the Giotto and VEGA comet Halley flight projects to update existing cometary ephemerides; orbital parameters of Halley's comet provided by the Astrometry Network were used for comparisons with similar efforts by ESOC and IKI. Halley ephemeris data were also provided to the flight projects of the Japanese Sakigake and Suisei spacecraft, as well as the spacecraft flight projects for the Pioneer Venus Orbiter, Solar Maximum Mission, and the International Ultraviolet Explorer. 4. DATA REDUCTIONS Beginning with the work of Marsden et al. (1973), the obvious rocket-like thrusting, or nongravitational effects, affecting the motions of active comets has been successfully represented using a model based upon the sublimation of water ice. Because a solution for nongravitational effects in comet Halley's motion requires astrometric data from at least three apparitions (Yeomans 1977), an effort was made to improve the existing data from 1835-36 and 1909- 11, as well as to provide accurate reductions during the current apparition. For this apparition, improved reference star catalogs were generated and all data were reduced to a consistent coordinate system (FK4, equinox 1950.0). 4.1 Improvement of the 1835-36 and 1909-11 Astrometric Data Morley (1983) used the SAO star catalog to improve upon the positions taken at Cordoba, Argentina, during 1909-11, and Vashtova and Latinov (1984) reduced a few 1910 Tashkent observations using more modern star catalogs. Complete re- measurements and reductions were done by Klare et al. (1983) for some of the 1909-11 Heidelberg plates, and by Bowell (1982) for some of the 1910-11 Lowell Observatory plates that had never been used for astrometric positions. Pereyra and West (1984) re-measured approximately 70 plates taken at Cordoba in 1910, and Roeser (1984) and Roeser and Morley (1985) re-reduced many of the 1835-36 and 1909-11 visual data on comet Halley using modern reference star catalogs. 4.2 Star Catalog Improvement In order to provide accurate reference stars for the reduction of the astrometric data, special comet Halley star catalogs were generated and distributed to all Network members. Reference star catalogs were distributed in printed form, on magnetic tape and on micro computer disks (in 18 different formats and sizes!). R.S. Harrington, of the U.S. Naval Observatory, coordinated all star catalog efforts for the Astrometry Network. For a degree on either side of the comet's celestial path, A.R. Klemola, B.F. Jones, S.P. Francic, E.A. Harlan and T. Nakajima used plates taken with the Lick Observatory astrograph and compiled a Lick Observatory reference star catalog that required measurements and reductions for 5148 stars covering the path of comet Halley from January 1984 until late October 1985. The stars were mostly in the visual magnitude range 13-14 and all were in the range 11-15. Their density was approximately 30-40 stars per square degree, the reference catalog used was the AGK3R and the approximate mean epoch was 1983.2 (equinox B1950). For the period from November 1985 till January 1986, AGK3 stars were used for the Halley catalog that was distributed in advance and N. Zacharias and C. de Vegt provided, in early 1986, an improved catalog (reduced with respect to the AGK3N) for this same time period. For the critical period just prior to and during the spacecraft encounters (January through mid-March 1986), the U.S. Naval Observatory generated a special supplemental star catalog from transit circle observations with some additional positions being determined from a set of overlapping plates taken with their twin 20 cm astrograph (Holdenried and Crull 1986). 5. DATA PROCESSING Comet Halley astrometric data, received by the orbit determination center at JPL, were processed before being archived and sent onto ESOC< FRG, and Kiev, U.S.S.R. The processing included assigning an ephemeris time to the observed UTC time, assignment of the observatory's coordinates, and correcting for the small effects of elliptic aberration. On January 1, 1984, the International Astronomical Union formally switched from using Ephemeris Time (ET) to Terrestrial Dynamical Time (TDT) for the time scale of ephemerides for observations made from the Earth's surface. To the level of the observational accuracy, these two time scales can be considered equal and continuous. Once verified and weighted, the observations were stored in reverse chronological order on the JPL master data file for use by the orbit determination program. This latter program takes into account the comet's nongravitational perturbations, as well as planetary perturbations, at each time step. The local error allowed at each time step can be input and the time steps of the numerical integration are va- ried to limit the local error to the input tolerance. The partial derivatives of the observables are integrated numerically along with the comet's equations of motion. To be consistent with the various flight projects to Comet Halley and Giacobini-Zinner, the comet's equations of motion also include general relativistic effects by means of the parameterized space-time metric of the Eddington-Robertson-Schiff formalism. The orbit determination program uses a batch processed, weighted least squares technique and can store and employ a priori information matrices and map covariance matrices to specified epochs. 6. COMET HALLEY OBSERVATION SETS The sets of observations used in the various comet Halley orbit determination solutions are given in Table II. The columns in this table give the time interval covered by the observations, the total number of observations from each apparition used in the computations, the number of observatories contributing observations, and the root mean square (rms) data noise used in the weighting of the data. Table II. Observation Schedule for Comet Halley ______________________________________________________________________ Number Number rms data Observation Interval of obser- of obser- noise vations vatories (arcsec) ______________________________________________________________________ Jan. 9, 1989 - Oct. 16, 1982 6475 148 1.0 May 30, 1911 - Aug. 29, 1909 1696 34 1.5-3.0 Apr. 15, 1836 - Aug. 21, 1835 158 5 2.0-5.5 June 3, 1759 - Jan. 23, 1759 206 5 31.5 Sep. 19, 1682 - Aug. 30, 1682 13 1 35 Oct. 23, 1607 - Sep. 28, 1607 9 3 300 ______________________________________________________________________ The data noise during the 1909-11 apparition depended not only upon the skill of the observers, but also upon whether the photographic plates had been remeasured (1.5 arcsec) or whether the available observations had only been rereduced using more modern star catalogs (2.0-3.0 arcsec). For the 1835-36 apparition, the observations of F.W. Bessel at Konigsberg were assigned a noise value of 2.0 arcsec, those of F.G.W. Struve at Dorpat 2.8 arcsec, T. Maclear at the Cape of Good Hope and J. Encke at Berlin 4.5 arcsec, and B. Nicolai at Mannheim 5.5 arcsec. After being re-reduced by Roeser (1984, 1987) and by Roeser and Morley (1985), many of the 1835-36 and 1909-11 positions were kindly forwarded from ESOC to JPL by T. Morley. In addition to the 1982- 89 astrometric data on the digital IHW Astrometry archive, the 1835-36 and 1909-11 astrometric data are included as well. Although detailed information on the observers and observing conditions is necessarily absent from these early data sets, all data have been re-reduced to be consistent with the 1982- 89 data. In large part, the availability of the 1835-36 and 1909-11 data is due to the considerable efforts of S.F. Roeser of the Astronomisches Rechen- Institut in Heidelberg. Observations 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 from 1982-89 with residuals exceeding 10 arcsec were not included in the master data file. Once verified, the astrometric data were put into the proper format and added to the master data file. The master data file was then used to write the IHW archive on magnetic tapes in FITS format (Sec. II of Astrometry Appendix). These tapes, in turn, were used to generate the digital Astrometry archive on compact optical disks. 7. ARCHIVING Once received at JPL, the IHW astrometric data were entered into a master data file in reverse chronological order. This file was updated whenever new data arrived and the updated files were used to generate a total of 61 orbital solutions using data that spanned the interval from August 21, 1835 through the most current astrometric observation then residing in the file. The five line format of this master data file is outlined in Tables II and III below. Once the master data file was completed and verified, the data from August 21, 1835 through January 9, 1989 were written in FITS format to a magnetic tape. 7.1 Astrometry FITS Header Description and Data Record Format Each astrometric observation in the FITS format consists of one file that includes header information (36 records of 80 ASCII bytes each) followed by the data themselves (another 36 records of 80 bytes each). A hypothetical header is used as an example in Table III below. Table III. Header Keyword Information ______________________________________ Keyword and Its Content ______________________________________ SIMPLE = T BITPIX = 8 NAXIS = 1 NAXIS1 = 2880 OBJECT = 'P/HALLEY' FILE-NUM= 102008 DATE-OBS= '12/ 8/85' TIME-OBS= 0.88403 DATE-REL= '26/ 9/89' DISCIPLN= 'ASTROMETRY' LONG-OBS= '116/ 8/24' LAT--OBS= '-32/00/30' EQUINOX = 'B1950.0' SYSTEM = '18070000' OBSERVER= 'CANDY,M.P ET AL.' SUBMITTR= 'WIMBERLY,R.N' SPEC-EVT= F DAT-FORM= 'ASCII ' COMMENT ADD. OBS.: SMITH,P/DOE,J COMMENT NOTES: VERY FAINT IMAGE END ______________________________________ The header key words SIMPLE, BITPIX, NAXIS, NAXIS1, OBJECT, DISCIPLN, EQUINOX, SUBMITTR, SPEC-EVT, and DAT-FORM do not change from file to file 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 observatory 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. EQUINOX (C) identifies the origin of the equatorial coordinate system used for the astrometric data; for each record, the FK4-1950.0 origin has been abbreviated as B1950.0. 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 VI). 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 VI and VII). The observers are separated by a slash (/), whereas ET AL. indicates that additional observers (ADD. OBS.) are listed after the COMMENTS keyword. Problems with the observation or data reduction process also are iden- tified after a keyword COMMENTS. 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 astrometric position reported. The first line lists the time (Julian date in ephemeris 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 orbital 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 (Table VIII), 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 IV) 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 determination 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 valuse 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 4 and all of line 5 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 IV illustrates the five-line Astrometry format, which is described in Table V. Table IV. Example of Astrometry Data Record __________________________________________________________________________ 2446290.38467 55914.61+19 4 9.3 A 1985 812.88403 552 55914.59+19 4 9.3 323 116.14-362 225 1.0 1.0 CANDY,M.P ET AL. PERTH OBSERVATORY, BICKLEY 15.00 99.0 IAU CENTRAL BUREAU FILE TRANSFER 9-18-85 ADDITIONAL OBSERVERS: SMITH,P/DOE,J ;!VERY FAINT IMAGE! __________________________________________________________________________ Table V. 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 (552 = 55.2 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 DXY and DZ, 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 DXY and DZ and are used to transform the Earth-Sun vector from a geocentric origin to one that is topocentric: DXY = -426.35E-07 * RHO * cos(LAT), DZ = -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 geocentric latitude of the observatory. 7.2 Observers and Observatories Participating in the Astrometry Network Observatories that provided astrometric data for comet Halley 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 observatory name is an alphabetical list of the observers and the total number of observations which they contributed. In Table VII the observers are listed in alphabetical order followed by the codes of the observatories where they observed 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 Halley 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 Code Observatory and Observers ---------------------------- At Observatory By Observer ________________________________________________________________________ 6 Fabra Observatory 190 Barcelona, Spain Cepa, J. 1 Codina, J.M. 123 Heras, A.M. 1 Hernandez, M. 13 Moreno, M. 11 Nunez, J. 40 Sanchez, F. 1 10 CERGA 6 Caussols, France Bartheleme, A. 5 Heudier, J. 5 Le Fevre, O. 1 Pollas, C. 6 12 Uccle Observatory 30 Uccle, Brussels, Belgium Debehogne, H. 22 Pauwels, T. 20 17 Hoher List Observatory 36 Hoher List Federal Republic of Germany Elst, E. 14 Geffert, D. 5 Geffert, M. 21 Geyer, E. 14 Haenel, A. 34 20 Nice 1 France Benest, D. 1 22 Pino Torinese 64 Torino, Italy Ferreri, W. 29 Massone, G. 35 24 State Observatory at Konigstuhl 8 Heidelberg Federal Republic of Germany Goerze, M. 1 Gorze, U. 2 Kiefer, E. 2 Kiefer, P. 2 Madejsky, R. 1 Mandel, H. 8 Mandel, U. 1 Schiffer, H.J. 5 26 Berne-Zimmerwald 20 Berne, Switzerland Wild, P. 20 33 Karl Schwarzschild Observatory 25 Tautenburg German Democratic Republic Boerngen, F. 25 Ludwig, F. 13 Mau, K.H. 12 Tanzer, G. 10 45 Vienna (since 1879) 33 Austria Jackson, P. 33 46 Klet Observatory 283 Ceske Budejovice Czechoslovakia Landgraf, W. 6 Mrkos, A. 267 Vavrova, Z. 32 47 Poznan 25 Poland Czelusniak, H. 1 Gromadzinski, M. 3 Hurnik, H.H. 2 Matz, D. 11 Ochnik, R. 5 Swierkowska, S. 9 49 Uppsala-Kvistaberg 14 Uppsala, Sweden Lagerkvist, C.I. 14 Oja, T. 14 51 Cape of Good Hope 100 South Africa Churms, J. 83 Roberts, G. 17 56 Skalnate Pleso Observatory 128 Skalnate Pleso Czechoslovakia Cervak, G. 110 Kornos, L. 41 Rychtarcik, P. 110 Svoren, J. 47 57 Belgrade 35 Yugoslavia Olevic, D. 1 Protitch-Benishek, V. 34 61 Uzhgorod 88 U.S.S.R. Galas, T.Y. 37 Goroshchak, I.I. 81 Gvardionov, A.B. 9 Ignatovich, S.I. 72 Polishchuk, N.D. 73 Vorinka, S.I. 27 63 Turku-Tuorla 12 Finland Haarala, S. 6 Lappalainen, T. 6 Niemi, A. 12 Piironen, J. 6 Sillanpaa, A. 6 69 Baldone (near Riga) 70 U.S.S.R. Alksnis, A.K. 26 Eglitis, I.E. 14 Grasberg, E.K. 17 Ozolinya, V. 29 Platajs, I.K. 23 Pundure, I. 2 Rydzinskis, A. 3 Urgitis, I.I. 16 71 Sofia 114 Bulgaria Bonev, T. 21 Cirova, H. 16 Georgieva, A. 62 Ivanova, V. 107 Kirova, H. 17 Major, S.P. 5 Radeva, V. 12 Shkodrov, V. 98 73 Bucharest 4 Romania Alexiu, A. 2 Bocsa, G. 2 75 Tartu 4 U.S.S.R Maazik, M. 4 Raudsaar, X. 4 83 Central Astrophysical Observatory 58 Golosseevo-Kiev, U.S.S.R. Golovnya, V.V. 12 Ivashchenko, Y.N. 10 Izhakevich, E.M. 13 Kaltygina, S.V. 1 Kizyun, L.N. 1 Ledovskaya, I.V. 7 Major, S.P. 9 Safronov, Y.I. 9 Sereda, E.M. 11 Shatokhina, S.V. 15 Sizonenko, Y.V. 5 Yatsenko, A.I. 1 84 Pulkovo Observatory 40 Leningrad, U.S.S.R. Bobylyev, V.V. 3 Bronikova, N.M. 7 Kiseleva, T.P. 8 Kiselyev, A.A. 8 Lepeshnikova, S.A. 16 Narizhnaya, M.V. 3 85 Kiev University Observatory 28 Kiev, U.S.S.R. Churyumov, K.I. 5 Smirnova, K.E. 2 Telnyuk, V.V. 25 87 Helwan 10 Egypt Bagus, B.B. 10 Bakhtigaraev, N.S. 10 El-Khilali, Y. 10 Tovadrus, M.Y. 10 89 Nikolaev 194 U.S.S.R. Gorel, G.K. 67 Gudkova, L.A. 21 Kalinenkov, N.D. 93 Voronenko, V.I. 128 90 Mainz 5 Federal Republic of Germany Landgraf, W. 4 Riemann, R. 5 91 St. Etienne 14 France Chanal, R. 14 92 Torun-Piwnice Observatory 26 Poland Antal, M. 19 Krawczyk, S. 24 Muciek, M. 20 Woszczyk, A. 11 93 Skibotn Observatory 37 Skibotn, Norway Aksnes, K. 5 Havnes, O. 18 Henriksen, K. 17 Solheim, J.E. 16 94 Crimea-Simeis 25 U.S.S.R. Fokanov, S.V. 23 Merezhina, L.S. 17 Nagornyuk, S. 5 Nikolenko, I.V. 6 Shcherbanovskij, A.L. 13 95 Crimea-Nauchnij 293 U.S.S.R. Chernykh, L.I. 51 Chernykh, N.S. 188 Karachkina, L.G. 114 Lyukhanov, K. 3 Pavlenko, E. 56 Ponomarev, D.N. 19 Prokofyeva, V. 47 Smirnova, T.M. 5 Tarashchuk, V. 56 Zhuravlyeva, L.V. 67 96 Merate 45 Italy Barbieri, C. 3 Kranjc, A. 3 Scardia, M. 45 98 Cima Ekar - Asiago Astrophys. Obs. 18 Padua, Italy Barbieri, C. 17 Kranjc, A. 17 Scardia, M. 18 99 Lahti 3 Finland Salmi, J. 3 101 Kharkov 34 U.S.S.R. Pavlenko, P.P. 34 102 Zvenigorod 17 U.S.S.R. Bakhtigaraev, N.S. 2 Burg, B. 2 Osipenko, V.P. 15 Panferova, V.I. 1 105 Moscow 7 U.S.S.R. Shokin, Y.A. 7 114 Engelhardt Observatory 171 Zelenchuk Station U.S.S.R. Kitkin, V.N. 86 Rizvanov, N. 8 Zelishchev, I.E. 85 115 Zelenchukskaya 6 U.S.S.R. Karachentsev, I.D. 2 Nazarchuk, G.K. 4 Shapovalova, A.I. 3 Shcherbanovskij, A.L. 3 Shokin, Y.A. 3 119 Abastuman 34 U.S.S.R. Inasaridze, R.Y. 13 Kiladze, R.I. 2 Majsuradze, G.A. 19 123 Byurakan 30 U.S.S.R. Akhverdyan, L.G. 30 Ledovskaya, I.V. 14 129 Ordubad 153 U.S.S.R. Bobylyev, V.V. 30 Kiselyev, A.A. 56 Malkov, A.A. 4 Novikov, S.B. 2 Shokin, Y.A. 2 Tolbin, S.V. 63 Yagudin, L.I. 44 Yagudina, E.I. 1 136 Engelhardt Observatory 9 Kazan, U.S.S.R. Tokhtasyev, S.S. 7 Zelishchev, I.E. 9 168 Kourovskaya 164 U.S.S.R. Barkhatova, K.A. 3 Blym, M.E. 1 Kajzer, G.T. 11 Kalinina, N.D. 36 Levitskaya, T.I. 113 Matkin, N.V. 18 Pyatkes, S.A. 30 Ryazanov, A.P. 12 Seleznev, A.F. 24 Sobolenko, G.M. 15 Tearo, A.R. 24 Timofeyev, S.N. 54 Vasilevskij, A.E. 46 Yuminova, O.G. 26 Zhukova, G.A. 12 Zvonareva, E.V. 40 186 Kitab 333 U.S.S.R. Bashtova, L. 22 Ivanov, Y. 13 Kadyrova, N. 40 Kamalov, M. 27 Khamidov, E. 13 Khamidov, T. 4 Lejko, V. 1 Major, S.P. 37 Mirmakhmudov, E. 144 Pattakhov, E. 26 Rakhmatov, E. 179 Saidov, G. 23 Shatokhina, S.V. 32 188 Majdanak 22 U.S.S.R. Bugaenko, O.I. 3 Novikov, S.B. 22 Shokin, Y.A. 22 190 Gissar 196 U.S.S.R. Gerasimenko, S.I. 196 191 Dushanbe 1 U.S.S.R. Churyumov, K.I. 1 Rspaev, F.K. 1 192 Tashkent 180 U.S.S.R. Azizov, S.K. 111 Baltabaev, Y. 10 Khamidov, T. 125 Rakhimov, A.G. 164 Rakhmatov, A. 16 193 Sanglok 23 U.S.S.R. Chernova, G.P. 23 Gerasimenko, S.I. 23 Kiselyev, N.N. 23 210 Alma-Ata 47 U.S.S.R. Churyumov, K.I. 13 Gorodetskaja, N.S. 5 Gorodetskij, D.I. 39 Meleyev, H. 5 Mileyev, H. 3 Rozhkovskij, D.A. 4 Rspaev, F.K. 1 Ryabenko, I.B. 3 Solodovnikov, V.V. 5 214 Kazakh Astrophy. Inst. Coronal Sta. 4 U.S.S.R. Gorodetskij, D.I. 3 Ryabenko, I.B. 4 Solodovnikov, V.V. 1 217 Assah 30 U.S.S.R. Churyumov, K.I. 30 Gorodetskij, D.I. 6 Meleyev, H. 4 Rspaev, F.K. 30 219 Japal-Rangapur Observatory 6 Japal, India Sanwal, N.B. 6 286 Yunnan Observatory 16 Kunming, China Yan, L.S. 15 Zhang, B.L. 1 293 Burlington (Remote Site) 7 New Jersey, U.S.A. Handley, T. 7 302 U. Of The Andes Astronomical Sta. 3 Venezuela Ferrin, I. 3 303 Merida 17 Venezuela Abad, C. 17 Contreras, O. 6 Moreno, F. 9 Stock, J. 17 305 Purple Mt. Observatory 27 Hainan Island Station China Ge, Y.L. 27 Lu, J.H. 27 Wang, D.C. 27 Wang, Q. 27 Wang, S.C. 27 Wei, S.L. 27 Yang, J.X. 27 Zhang, J.X. 27 312 Xisha Islands (Paracel Is.) 20 South China Sea Dong, C.Z. 2 Huei, Y.Q. 2 Shao, Y.J. 2 Sun, S.S. 20 Zhang, B.L. 2 323 Perth Observatory 548 Bickley, Western Australia Australia Birch, P. 6 Candy, M.P. 412 Harwood, D. 4 Jekabsons, P. 426 John, A. 146 Johnston, J. 39 Kinnear, G. 55 Martin, R. 2 McGrath, A. 372 Stevens, L. 287 324 Beijing Observatory 1 Shaho Station, China Dong, Z.Z. 1 Hao, X.L. 1 Tang, D.Y. 1 330 Purple Mountain Observatory 149 Nanking, China Ge, Y.L. 60 Li, G.Y. 2 Lu, J.H. 63 Luo, G.S. 5 Wang, D.C. 79 Wang, Q. 84 Wang, S.C. 19 Wang, W. 2 Wei, S.L. 65 Yang, J.X. 104 Yang, J.Z. 6 Zhang, J.X. 21 334 Qingdao 176 China Cheng, L. 11 Dong, C.Z. 11 Huei, Y.Q. 111 Ma, X.Y. 83 Shao, Y.J. 168 Song, W.Q. 113 Sun, S.S. 176 Wang, Z.L. 102 Zhang, B.L. 102 337 Zo-Se 48 China Zhao, J.L. 48 371 Tokyo-Okayama 5 Japan Kosai, H. 3 Watanabe, E. 2 372 Geisei 22 Japan Seki, T. 22 378 Murou 2 Japan Nakamura, M. 2 379 Hamamatsu 2 Japan Tashiro, T. 2 381 Tokyo-Kiso 9 Japan Kosai, H. 9 Yamagata, T. 3 391 Sendai Observatory 134 Ayashi Station Ayashi, Japan Koishikawa, M. 134 392 JCPM Sapporo Station 10 Sapporo, Japan Kaneda, H. 9 Watanabe, K. 1 396 Asahikawa 1 Japan Tsuchiya, K. 1 397 Sapporo Science Center 30 Sapporo, Japan Watanabe, K. 30 399 Kushiro 2 Japan Ueda, S. 2 413 Siding Spring Observatory 26 New South Wales, Australia Hartley, M. 1 Russell, K. 25 414 Mount Stromlo 20 A.C.T., Australia Ge, Y.L. 20 Lu, J.H. 20 Wang, D.C. 20 Wang, Q. 20 Wang, S.C. 20 Wei, S.L. 20 Yang, J.X. 20 Zhang, J.X. 20 415 Kambah (near Canberra) 76 New South Wales Australia Herald, D. 76 420 Sydney 3 New South Wales Australia Bembrick, C.S. 3 425 Taylor Range Observatory 3 Brisbane, Queensland Australia Anderson, P. 3 474 Mount John Observatory 41 Lake Tekapo, New Zealand Gilmore, A.C. 40 Kilmartin, P. 15 482 St. Andrews 14 Scotland, United Kingdom Stapleton, J.R. 14 483 Carter Observatory 12 Black Birch Station New Zealand Douglass, G.G. 12 491 Centro Astronomico De Yebes 44 Yebes, Spain Cabanas, C. 44 De Pascual, M. 44 Garcia, J. 44 Martin-Pintado, J. 29 493 Centro Astronomico Hispano-Aleman 114 Calar Alto, Spain Birkle, K. 60 Graser, U. 4 Groote, D. 4 Gruen, E. 4 Hagen, H.J. 4 Haug, U. 1 Kohoutek, L. 30 Lingenfelder, G. 2 Pauls, R. 4 Quetsch, A. 1 Thiele, U. 11 494 Stakenbridge 37 England, United Kingdom Manning, B. 37 501 Royal Greenwich Observatory 12 Herstmonceux, England United Kingdom Jones, D.H.P. 12 502 Colchester 20 England, United Kingdom Hendrie, M.J. 20 503 Cambridge 24 England, United Kingdom Argue, A.N. 11 Shanklin, J.D. 21 509 La Seyne Sur Mer 5 France Pinson, J. 5 528 Gottingen 3 Federal Republic of Germany Landgraf, W. 3 544 Wilhelm Foerster Observatory 2 Berlin Federal Republic of Germany Dreyhsig, J. 2 Leder, N. 2 552 Osservatorio San Vittore 53 Bologna, Italy Colombini, E. 24 Sassi, G. 49 Vacchi, C. 49 553 Chorzow 36 Poland Firszt, T. 1 Kaminski, R. 1 Pawicka, B. 1 Sieron, W. 1 Stanek, K. 1 Syroczynski, R. 1 Szczepanski, M. 3 Wlodarczyk, I. 27 555 Cracow-Fort Skala 34 Poland Kurpinska-Winiarska, M. 6 Waniak, W. 3 Winiarski, M. 21 Zola, S. 4 561 Piszkesteto 5 Hungary Toth, I. 5 562 Figl Observatory 15 Vienna, Austria Schnell, A. 15 Stockenhuber, H. 11 Stoll, M. 2 565 Brescia 20 Italy Marinello, V. 20 Quadri, U. 20 567 Chions 3 Italy Baur, C.R. 3 Baur, J.M. 3 568 Mauna Kea 23 Hawaii, U.S.A. Alvarez, E.M. 3 Baudrand, J. 14 Belton, M.J.S. 3 Le Fevre, O. 9 Lecacheux, J. 9 Lelievre, G. 9 Lemonnier, D. 9 Mathez, G. 9 Meech, K.J. 6 Piscitelli, J. 1 Racine, R. 1 Sicardy, B. 5 571 Cavriana 12 Italy Lai, L. 12 Ronchetti, I. 12 Ruzza, M. 12 Vesentini, G. 12 574 Gottolengo 1 Italy Mattarozzi, G. 1 575 La Chaux De Fonds 13 Switzerland Behrend, A. 13 Behrend, R. 13 576 Burwash 16 England, United Kingdom Young, A. 16 577 Metzerlen Observatory 3 Switzerland Trefzger, C.F. 3 580 Graz 4 Austria Hanslmeier, A. 4 Ornig, C.W. 4 581 Sedgefield Observatory 38 South Africa Hers, J. 38 583 Odessa - Mayaki 58 U.S.S.R. Kramer, E. 7 Shestaka, I.S. 51 586 Pic Du Midi 2 France Laffont, E. 2 Martinez, P. 2 656 Near Victoria 4 British Columbia, Canada Newton, J. 4 657 Victoria 18 British Columbia, Canada Balam, D.D. 14 Lowe, T.B. 2 Tatum, J.B. 10 662 Lick Observatory 73 Mount Hamilton California, U.S.A. Harland, G. 39 Jones, B.F. 32 Miller, J. 2 675 Palomar Mountain 28 California, U.S.A. Danielson, G.E. 12 Gibson, J. 14 Helin, E. 2 Jewitt, D.C. 12 686 U. Of Minn. Ir Obs. 1 Mt. Lemmon, Arizona U.S.A. Levy, D. 1 Wisniewski, W. 1 688 Lowell Observatory 8 Anderson Mesa, Arizona U.S.A. Bus, S.J. 5 Gullixson, C. 8 Skiff, B.A. 3 691 Steward Observatory 11 Kitt Peak, Tuscon, Arizona U.S.A. Scotti, J.V. 11 693 Catalina Station 5 Tucson, Arizona, U.S.A. Fink, U. 1 Karkoschka, E. 4 Schultz, P. 4 Tyler, A. 5 695 Kitt Peak National Observatory 35 Tucson, Arizona, U.S.A. Alvarez, E.M. 1 Baum, S. 2 Beauchemin, M. 1 Belton, M.J.S. 11 Borra, E. 1 Burks, J. 2 Bushouse, H. 2 Butcher, H. 3 Djorgovski, S.G. 3 Gallagher, J. 3 Goad, J. 1 Heckman, T.M. 2 Holleran, P. 2 Howell, S. 2 Jacoby, G.H. 1 Junkkarinen, V.T. 3 Kaluzny, J. 3 Kennicutt, R.C. 1 Smith, E. 2 Spinrad, H. 4 Szkody, P. 4 Waller, W. 1 Wehinger, P.A. 4 Wyckoff, S. 3 707 Chamberlin Field Station 20 Bailey, Colorado, U.S.A. Briggs, J. 19 Everhart, E. 2 711 McDonald Observatory 27 Fort Davis, Texas, U.S.A. Frueh, M.L. 21 Whipple, A. 6 771 Boyeros 18 Habana, Cuba Donal, H.P. 18 Farinyas, R. 18 Kulish, A.P. 18 Nikonov, O.V. 18 Sid, M.A. 18 Tolbin, S.V. 18 Zhilinskij, E.G. 18 781 Quito 8 Ecuador Davila, U. 8 Espin, L. 8 Kaltygina, S.V. 8 Sizonenko, Y.V. 8 782 Comet Astrographic Station 4 Quito, Ecuador Davila, U. 4 Espin, L. 4 Kaltygina, S.V. 4 Sizonenko, Y.V. 4 788 Mount Cuba Observatory 5 Greenville, Delaware U.S.A. Bock, G. 5 Jackson, S. 5 Stock, R.F. 5 792 University of Rhode Island 11 Quonochontaug, Rhode Island U.S.A. Penhallow, W.S. 11 801 Oak Ridge Observatory 33 Harvard, Massachusetts U.S.A. McCrosky, R.E. 31 Schwartz, G.. 29 Shao, C.Y. 27 805 Santiago-Cerro El Roble 273 Chile Torres, C. 241 Wroblewski, H. 143 807 Cerro Tololo Observatory 4 La Serena, Chile Meech, K.J. 4 808 El Leoncito 32 Argentina Cesco, M.R. 13 Lopez, C.E. 32 Sanguin, J.G. 13 Vicentela, J.A. 13 809 European Southern Observatory 139 La Silla, Chile Danziger, J. 2 Debehogne, H. 3 Ferreri, W. 16 Louys, L. 15 Monderen, P. 15 Pedersen, H.E. 29 Shaver, P. 2 West, R.M. 107 820 Tarija 23 Bolivia Potter, H.I. 23 821 Cordoba-Bosque Alegre 16 Argentina Pereyra, Z.M. 16 822 Cordoba 11 Argentina Pereyra, Z.M. 11 881 Toyota 3 Japan Suzuki, K. 3 889 Karasuyama 1 Japan Inoda, S. 1 892 YGCO Hoshikawa and Nagano Stations 2 Japan Hayakawa, S. 2 Kojima, T. 2 893 Sendai Municipal Observatory 5 Sendai, Japan Koishikawa, M. 3 Yusa, T. 5 950 La Palma 1 Canary Islands Argyle, R. 1 Wall, J.V. 1 975 Valencia 15 Spain Artes, P.J. 15 Lopez, G.A. 15 Lopez, M.R. 15 Lopez, O.J.A. 15 976 Leamington Spa 3 England, United Kingdom Johnstone, G. 3 978 Conder Brow 9 England, United Kingdom Buczynski, D.G. 9 Greenwood, J.D. 9 979 South Wonston 1 England, United Kingdom Arbour, R.W. 1 980 Lancaster 2 England, United Kingdom Waddington, W.G. 2 984 Eastfield 15 England, United Kingdom Buczynski, D.G. 1 Ridley, H.B. 15 993 Woolston Observatory 1 England, United Kingdom Dykes, M.R. 1 Waterfield, R. 1 996 Oxford 36 England, United Kingdom Waddington, W.G. 36 ________________________________________________________________________ Table VII. Observer Index ________________________________________________________ Observer Observatory Number of Code(s) Observations ________________________________________________________ Abad, C. 303 17 Akhverdyan, L.G. 123 30 Aksnes, K. 93 5 Alexiu, A. 73 2 Alksnis, A.K. 69 26 Alvarez, E.M. 568,695 4 Anderson, P. 425 3 Antal, M. 92 19 Arbour, R.W. 979 1 Argue, A.N. 503 11 Argyle, R. 950 1 Artes, P.J. 975 15 Azizov, S.K. 192 111 Bagus, B.B. 87 10 Bakhtigaraev, N.S. 87,102 12 Balam, D.D. 657 14 Baltabaev, Y. 192 10 Barbieri, C. 96,98 20 Barkhatova, K.A. 168 3 Bartheleme, A. 10 5 Bashtova, L. 186 22 Baudrand, J. 568 14 Baum, S. 695 2 Baur, C.R. 567 3 Baur, J.M. 567 3 Beauchemin, M. 695 1 Behrend, A. 575 13 Behrend, R. 575 13 Belton, M.J.S. 568,695 14 Bembrick, C.S. 420 3 Benest, D. 20 1 Birch, P. 323 6 Birkle, K. 493 60 Blym, M.E. 168 1 Bobylyev, V.V. 84,129 33 Bock, G. 788 5 Bocsa, G. 73 2 Boerngen, F. 33 25 Bonev, T. 71 21 Borra, E. 695 1 Briggs, J. 707 19 Bronikova, N.M. 84 7 Buczynski, D.G. 978,984 10 Bugaenko, O.I. 188 3 Burg, B. 102 2 Burks, J. 695 2 Bus, S.J. 688 5 Bushouse, H. 695 2 Butcher, H. 695 3 Cabanas, C. 491 44 Candy, M.P. 323 412 Cepa, J. 6 1 Cervak, G. 56 110 Cesco, M.R. 808 13 Chanal, R. 91 14 Cheng, L. 334 11 Chernova, G.P. 193 23 Chernykh, L.I. 95 51 Chernykh, N.S. 95 188 Churms, J. 51 83 Churyumov, K.I. 85,191,210,217 49 Cirova, H. 71 16 Codina, J.M. 6 123 Colombini, E. 552 24 Contreras, O. 303 6 Czelusniak, H. 47 1 Danielson, G.E. 675 12 Danziger, J. 809 2 Davila, U. 781,782 12 De Pascual, M. 491 44 Debehogne, H. 12,809 25 Djorgovski, S.G. 695 3 Donal, H.P. 771 18 Dong, C.Z. 312,334 13 Dong, Z.Z. 324 1 Douglass, G.G. 483 12 Dreyhsig, J. 544 2 Dykes, M.R. 993 1 Eglitis, I.E. 69 14 El-Khilali, Y. 87 10 Elst, E. 17 14 Espin, L. 781,782 12 Everhart, E. 707 2 Farinyas, R. 771 18 Ferreri, W. 22,809 45 Ferrin, I. 302 3 Fink, U. 693 1 Firszt, T. 553 1 Fokanov, S.V. 94 23 Frueh, M.L. 711 21 Galas, T.Y. 61 37 Gallagher, J. 695 3 Garcia, J. 491 44 Ge, Y.L. 305,330,414 107 Geffert, D. 17 5 Geffert, M. 17 21 Georgieva, A. 71 62 Gerasimenko, S.I. 190,193 219 Geyer, E. 17 14 Gibson, J. 675 14 Gilmore, A.C. 474 40 Goad, J. 695 1 Goerze, M. 24 1 Golovnya, V.V. 83 12 Gorel, G.K. 89 67 Gorodetskaja, N.S. 210 5 Gorodetskij, D.I. 210,214,217 48 Goroshchak, I.I. 61 81 Gorze, U. 24 2 Grasberg, E.K. 69 17 Graser, U. 493 4 Greenwood, J.D. 978 9 Gromadzinski, M. 47 3 Groote, D. 493 4 Gruen, E. 493 4 Gudkova, L.A. 89 21 Gullixson, C. 688 8 Gvardionov, A.B. 61 9 Haarala, S. 63 6 Haenel, A. 17 34 Hagen, H.J. 493 4 Handley, T. 293 7 Hanslmeier, A. 580 4 Hao, X.L. 324 1 Harland, G. 662 39 Hartley, M. 413 1 Harwood, D. 323 4 Haug, U. 493 1 Havnes, O. 93 18 Hayakawa, S. 892 2 Heckman, T.M. 695 2 Helin, E. 675 2 Hendrie, M.J. 502 20 Henriksen, K. 93 17 Herald, D. 415 76 Heras, A.M. 6 1 Hernandez, M. 6 13 Hers, J. 581 38 Heudier, J. 10 5 Holleran, P. 695 2 Howell, S. 695 2 Huei, Y.Q. 312,334 113 Hurnik, H.H. 47 2 Ignatovich, S.I. 61 72 Inasaridze, R.Y. 119 13 Inoda, S. 889 1 Ivanov, Y. 186 13 Ivanova, V. 71 107 Ivashchenko, Y.N. 83 10 Izhakevich, E.M. 83 13 Jackson, P. 45 33 Jackson, S. 788 5 Jacoby, G.H. 695 1 Jekabsons, P. 323 426 Jewitt, D.C. 675 12 John, A. 323 146 Johnston, J. 323 39 Johnstone, G. 976 3 Jones, B.F. 662 32 Jones, D.H.P. 501 12 Junkkarinen, V.T. 695 3 Kadyrova, N. 186 40 Kajzer, G.T. 168 11 Kalinenkov, N.D. 89 93 Kalinina, N.D. 168 36 Kaltygina, S.V. 83,781,782 13 Kaluzny, J. 695 3 Kamalov, M. 186 27 Kaminski, R. 553 1 Kaneda, H. 392 9 Karachentsev, I.D. 115 2 Karachkina, L.G. 95 114 Karkoschka, E. 693 4 Kennicutt, R.C. 695 1 Khamidov, E. 186 13 Khamidov, T. 186,192 129 Kiefer, E. 24 2 Kiefer, P. 24 2 Kiladze, R.I. 119 2 Kilmartin, P. 474 15 Kinnear, G. 323 55 Kirova, H. 71 17 Kiseleva, T.P. 84 8 Kiselyev, A.A. 84,129 64 Kiselyev, N.N. 193 23 Kitkin, V.N. 114 86 Kizyun, L.N. 83 1 Kohoutek, L. 493 30 Koishikawa, M. 391,893 137 Kojima, T. 892 2 Kornos, L. 56 41 Kosai, H. 371,381 12 Kramer, E. 583 7 Kranjc, A. 96,98 20 Krawczyk, S. 92 24 Kulish, A.P. 771 18 Kurpinska-Winiarska, M. 555 6 Laffont, E. 586 2 Lagerkvist, C.I. 49 14 Lai, L. 571 12 Landgraf, W. 46,90,528 13 Lappalainen, T. 63 6 Le Fevre, O. 10,568 10 Lecacheux, J. 568 9 Leder, N. 544 2 Ledovskaya, I.V. 83,123 21 Lejko, V. 186 1 Lelievre, G. 568 9 Lemonnier, D. 568 9 Lepeshnikova, S.A. 84 16 Levitskaya, T.I. 168 113 Levy, D. 686 1 Li, G.Y. 330 2 Lingenfelder, G. 493 2 Lopez, C.E. 808 32 Lopez, G.A. 975 15 Lopez, M.R. 975 15 Lopez, O.J.A. 975 15 Louys, L. 809 15 Lowe, T.B. 657 2 Lu, J.H. 305,330,414 110 Ludwig, F. 33 13 Luo, G.S. 330 5 Lyukhanov, K. 95 3 Ma, X.Y. 334 83 Maazik, M. 75 4 Madejsky, R. 24 1 Major, S.P. 71,83,186 51 Majsuradze, G.A. 119 19 Malkov, A.A. 129 4 Mandel, H. 24 8 Mandel, U. 24 1 Manning, B. 494 37 Marinello, V. 565 20 Martin, R. 323 2 Martin-Pintado, J. 491 29 Martinez, P. 586 2 Massone, G. 22 35 Mathez, G. 568 9 Matkin, N.V. 168 18 Mattarozzi, G. 574 1 Matz, D. 47 11 Mau, K.H. 33 12 McCrosky, R.E. 801 31 McGrath, A. 323 372 Meech, K.J. 568,807 10 Meleyev, H. 210,217 9 Merezhina, L.S. 94 17 Mileyev, H. 210 3 Miller, J. 662 2 Mirmakhmudov, E. 186 144 Monderen, P. 809 15 Moreno, F. 303 9 Moreno, M. 6 11 Mrkos, A. 46 267 Muciek, M. 92 20 Nagornyuk, S. 94 5 Nakamura, M. 378 2 Narizhnaya, M.V. 84 3 Nazarchuk, G.K. 115 4 Newton, J. 656 4 Niemi, A. 63 12 Nikolenko, I.V. 94 6 Nikonov, O.V. 771 18 Novikov, S.B. 129,188 24 Nunez, J. 6 40 Ochnik, R. 47 5 Oja, T. 49 14 Olevic, D. 57 1 Ornig, C.W. 580 4 Osipenko, V.P. 102 15 Ozolinya, V. 69 29 Panferova, V.I. 102 1 Pattakhov, E. 186 26 Pauls, R. 493 4 Pauwels, T. 12 20 Pavlenko, E. 95 56 Pavlenko, P.P. 101 34 Pawicka, B. 553 1 Pedersen, H.E. 809 29 Penhallow, W.S. 792 11 Pereyra, Z.M. 821,822 27 Piironen, J. 63 6 Pinson, J. 509 5 Piscitelli, J. 568 1 Platajs, I.K. 69 23 Polishchuk, N.D. 61 73 Pollas, C. 10 6 Ponomarev, D.N. 95 19 Potter, H.I. 820 23 Prokofyeva, V. 95 47 Protitch-Benishek, V. 57 34 Pundure, I. 69 2 Pyatkes, S.A. 168 30 Quadri, U. 565 20 Quetsch, A. 493 1 Racine, R. 568 1 Radeva, V. 71 12 Rakhimov, A.G. 192 164 Rakhmatov, A. 192 16 Rakhmatov, E. 186 179 Raudsaar, X. 75 4 Ridley, H.B. 984 15 Riemann, R. 90 5 Rizvanov, N. 114 8 Roberts, G. 51 17 Ronchetti, I. 571 12 Rozhkovskij, D.A. 210 4 Rspaev, F.K. 191,210,217 32 Russell, K. 413 25 Ruzza, M. 571 12 Ryabenko, I.B. 210,214 7 Ryazanov, A.P. 168 12 Rychtarcik, P. 56 110 Rydzinskis, A. 69 3 Safronov, Y.I. 83 9 Saidov, G. 186 23 Salmi, J. 99 3 Sanchez, F. 6 1 Sanguin, J.G. 808 13 Sanwal, N.B. 219 6 Sassi, G. 552 49 Scardia, M. 96,98 63 Schiffer, H.J. 24 5 Schnell, A. 562 15 Schultz, P. 693 4 Schwartz, G. 801 29 Scotti, J.V. 691 11 Seki, T. 372 22 Seleznev, A.F. 168 24 Sereda, E.M. 83 11 Shanklin, J.D. 503 21 Shao, C.Y. 801 27 Shao, Y.J. 312,334 170 Shapovalova, A.I. 115 3 Shatokhina, S.V. 83,186 47 Shaver, P. 809 2 Shcherbanovskij, A.L. 94,115 16 Shestaka, I.S. 583 51 Shkodrov, V. 71 98 Shokin, Y.A. 105,115,129,188 34 Sicardy, B. 568 5 Sid, M.A. 771 18 Sieron, W. 553 1 Sillanpaa, A. 63 6 Sizonenko, Y.V. 83,781,782 17 Skiff, B.A. 688 3 Smirnova, K.E. 85 2 Smirnova, T.M. 95 5 Smith, E. 695 2 Sobolenko, G.M. 168 15 Solheim, J.E. 93 16 Solodovnikov, V.V. 210,214 6 Song, W.Q. 334 113 Spinrad, H. 695 4 Stanek, K. 553 1 Stapleton, J.R. 482 14 Stevens, L. 323 287 Stock, J. 303 17 Stock, R.F. 788 5 Stockenhuber, H. 562 11 Stoll, M. 562 2 Sun, S.S. 312,334 196 Suzuki, K. 881 3 Svoren, J. 56 47 Swierkowska, S. 47 9 Syroczynski, R. 553 1 Szczepanski, M. 553 3 Szkody, P. 695 4 Tang, D.Y. 324 1 Tanzer, G. 33 10 Tarashchuk, V. 95 56 Tashiro, T. 379 2 Tatum, J.B. 657 10 Tearo, A.R. 168 24 Telnyuk, V.V. 85 25 Thiele, U. 493 11 Timofeyev, S.N. 168 54 Tokhtasyev, S.S. 136 7 Tolbin, S.V. 129,771 81 Torres, C. 805 241 Toth, I. 561 5 Tovadrus, M.Y. 87 10 Trefzger, C.F. 577 3 Tsuchiya, K. 396 1 Tyler, A. 693 5 Ueda, S. 399 2 Urgitis, I.I. 69 16 Vacchi, C. 552 49 Vasilevskij, A.E. 168 46 Vavrova, Z. 46 32 Vesentini, G. 571 12 Vicentela, J.A. 808 13 Vorinka, S.I. 61 27 Voronenko, V.I. 89 128 Waddington, W.G. 980,996 38 Wall, J.V. 950 1 Waller, W. 695 1 Wang, D.C. 305,330,414 126 Wang, Q. 305,330,414 131 Wang, S.C. 305,330,414 66 Wang, W. 330 2 Wang, Z.L. 334 102 Waniak, W. 555 3 Watanabe, E. 371 2 Watanabe, K. 392,397 31 Waterfield, R. 993 1 Wehinger, P.A. 695 4 Wei, S.L. 305,330,414 112 West, R.M. 809 107 Whipple, A. 711 6 Wild, P. 26 20 Winiarski, M. 555 21 Wisniewski, W. 686 1 Wlodarczyk, I. 553 27 Woszczyk, A. 92 11 Wroblewski, H. 805 143 Wyckoff, S. 695 3 Yagudin, L.I. 129 44 Yagudina, E.I. 129 1 Yamagata, T. 381 3 Yan, L.S. 286 15 Yang, J.X. 305,330,414 151 Yang, J.Z. 330 6 Yatsenko, A.I. 83 1 Young, A. 576 16 Yuminova, O.G. 168 26 Yusa, T. 893 5 Zelishchev, I.E. 114,136 94 Zhang, B.L. 286,312,334 105 Zhang, J.X. 305,330,414 68 Zhao, J.L. 337 48 Zhilinskij, E.G. 771 18 Zhukova, G.A. 168 12 Zhuravlyeva, L.V. 95 67 Zola, S. 555 4 Zvonareva, E.V. 168 40 ________________________________________________________ Table VIII. Differences TDT-UTC (ET-UTC) _________________________________________ Date ET-UTC(s) TDT-UTC(s) _________________________________________ 1982 July 1.0 53.18 1983 July 1.0 54.18 1985 July 1.0 55.18 1988 Jan. 1.0 56.18 _________________________________________ 8. REFERENCES Bowell, E. (1982). Minor Planet Circular No. 6841. Bowell, E., and Wasserman, L. (1985). Predictions of occultations of stars by comet Giacobini-Zinner and prediction updates for comet Halley. IHW Astro- metry Network Newsletter, May 1985. De Pater, I., Schloerb, F.P. and Johnson, A.H. (1985). A catalog of radio sources to be occulted by comets P/Halley and P/Giacobini-Zinner. Astron. J. 90, 846-868. Holdenried, E.R., and Crull, H.E. (1986). U.S. Naval Observatory Halley Watch Astrometric Catalog. Astron. J. (Nov., 1986, in press). Klare, G., Roser, S., Schwehm, G., and West, R. (1983). Private communication, Dec. 13. Marsden, B.G., Sekanina, Z., and Yeomans, D.K. (1973). Comets and nongravitational Forces. V. 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