MPEC 2010-U20 : EDITORIAL NOTICE
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M.P.E.C. 2010-U20 Issued 2010 Oct. 19, 02:20 UT
The Minor Planet Electronic Circulars contain information on unusual
minor planets and routine data on comets. They are published
on behalf of Commission 20 of the International Astronomical Union by the
Minor Planet Center, Smithsonian Astrophysical Observatory,
Cambridge, MA 02138, U.S.A.
Supported in part by the Steven and Michele Kirsch Foundation
Prepared using the Tamkin Foundation Computer Network
MPC@CFA.HARVARD.EDU
URL http://cfa-www.harvard.edu/iau/mpc.html ISSN 1523-6714
EDITORIAL NOTICE
The rules defining who discovered a particular object have evolved over
the past two centuries. In the days of visual observation, discovery was
credited to the first person to report an observation of a new object. If
a subsequent report emerged of an earlier observation, the discovery credit
was switched to the earlier observer. This reassignment of discovery credit
was applied somewhat arbitrarily and there are a number of cases where
earlier observations are simply listed as "prediscovery". Designations would
be assigned on the basis on single-night approximate measures. When the Minor
Planet Center (MPC) was founded, discoveries continued to be credited on the
basis of single approximate positions (e.g., Minor Planet Circular 2). After
the MPC moved to Cambridge in 1978, an Editorial Notice (Minor Planet Circular
4845-4846) informed observers that approximate observations were no longer
eligible for discovery credit. In 1995, the decision was taken to no longer
assign designations to single-night detections (Minor Planet Circular 24597).
The Minor Planet Center (MPC) recently changed the way discovery credit
was assigned to new discoveries. Rather than being the earliest observation
in the initial two-night linkage, the discovery credit was to be given to
the earliest observation at that opposition. In practice, it is often
difficult to determine which observation is the earliest at the time the
designation needs to be assigned.
Effective immediately, the MPC will separate the concept of discovery
credit from the assignment of asterisks. Asterisks will revert to being
simply an indication of the initial assignment of a new designation and will
not be associated with any discoverer.
In addition, the MPC will begin adding timetags to all archived and
newly-received observations, to indicate when they were received at the MPC.
For the moment, these timetags will be maintained only on internal datasets.
External availability of the timetags will depend on certain professional
users of the observational datasets indicating that their software will cope
with the extended format. For newly-submitted observations, the timetags will
indicate when the observation was accepted by the AUTOACK routine. For
previously-submitted observations, a timetag will be constructed that is
related to the date of observation. Known cases of delayed submission of
observations will be accounted for in these constructed timetags.
Discoverers will be defined only when an object is numbered. At that
time, the timetags on all the observations included in the solution will be
examined. The discovery observation will be that observation which is the
earliest-reported observations at the opposition with the earliest-reported
second-night observation. The discovery observation will then define the
discoverer. This scheme, which will be entirely automatic, is consistent
with the following resolution adopted by Commission 20 at the 1979 IAU
General Assembly: "The Commission defines the discovery as the earliest
apparition at which an orbit useful in the establishment of identifications
was calculated" (taken from Minor Planet Circular 4845-4846).
The new scheme removes one common complaint with the current scheme: that
the assignment of discovery credit depended, to some degree, on the ability
of either the MPC or the observer to make the initial night-to-night linkages.
In addition, it removes the apparent arbitrary nature of the order of
designations in new identifications.
Objects that have multiple-opposition orbits as of now will be
grandfathered into the old scheme of assigning discovery credit.
Timothy B. Spahr (C) Copyright 2010 MPC M.P.E.C. 2010-U20
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