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                                                                                             
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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)                                                                                             
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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                                                                                           
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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.