                 THE CIRCUMSTANCES OF MINOR PLANET DISCOVERY

                             Frederick Pilcher
                             Illinois College
                        Jacksonville, IL 62650 USA

     This file of minor planet discovery data has been prepared in machine
readable form for NSSDC and in hardcopy for ASTEROIDS II, (1988), ed. R. P.
Binzel, T. Gehrels, and M. S. Mathews (Tucson: Universiy of Arizona Press).
The machine readable list contains complete data for all numbered minor planets.
The hard copy contains complete data only for planets 2125 and forward, and
notes pertaining to these planets.  Those for the preceding planets were listed
by the writer in ASTEROIDS, (1979), ed. T. Gehrels (Tucson: University of
Arizona Press), pp 1130-1154.  A few mistakes in the first book have since been
found and corrected in the machine readable version, and the reader will note
small changes in the numbering of some of the NOTES.  Diacritical marks for the
names of planets, increasingly omitted from machine readable lists, have been
added by hand to the hardcopy.

     The first column, 4 characters, contains the permanent number; the second,
l6 characters, the official name; the third, for planets 330 and forward, the
provisional designation attached to the discovery apparition; the fourth, the
year, month, and day of discovery according to criteria explained below; the
fifth, the name of the discoverer, discoverers, or institution of discovery;
the sixth, the discovery place. The seventh column is used when needed for
notes referencing two or more discoverers with names of combined length too
great to fit in the discoverer column, to give a more complete description of
programs involving several persons, and to reference cases in which two
numbered planets were subsequently discovered to be identical and the number
and name of one of these was reassigned to a newly-discovered planet.  Notes
have also been used to reference conflicting discovery claims and list
important independent discoveries which are no longer regarded as official.

     The discovery date is in local mean time prior to 1 January 1925, and
in UT thereafter, and refers to the time of mid-exposure for planets discovered
by photographic means.  In many cases the permanent number was assigned only
when several unnumbered planets observed in different years were found to be
identical, often many years after the discovery photographs were made.  In
these cases the discovery date is the first of that series of photographic
observations from which the preliminary orbit was computed, and the provi-
sional designation is that associated with this particular set of observations.
Often earlier observations exist, but they are considered prediscoveries.
In some cases the discovery and subsequent observations permitted images to be
found on photographs obtained at the same observatory earlier in the discovery
apparition; these earlier observations are considered prediscoveries.

     The following literature has been examined comprehensively to determine
the discovery data:

     STRACKE, G., Identifizierungsnachweis der Kleinen Planeten (Berlin, 1938).
     HERGET, P., Names of Minor Planets (University of Cincinnati Observatory,
        1957, 1967).
     Astronomische Nachrichten.
     Astronomische Nachrichten Indices.
     Monthly Notices of the Royal Astronomical Society.
     Rechen-Institut Circulars.
     Beobachtungs Zircular.
     Minor Planet Circulars.
     Lick Research Surveys on Minor Planets.
     Turku Informo.

Acknowledgments.  The authors wish to thank the following people for valuable
contributions to this work.  B. Marsden has arduously searched the literature,
resolved various errors and discrepancies, and has passed judgment on con-
flicting discovery claims.  J. Meeus and M. Combes have prepared an earlier
list of discovery data from which the present list was adapted and expanded,
and J. Meeus has provided a complete list of diacritical marks of names of
minor planets.  K. Kelly and J. LoGuirato have proofread the material, and
provided coninuing advice and counsel.
