Data Set Overview
      =================
      This is a compilation of mean U-B and B-V color indices of
      asteroids.  This data file was provided by E.F. Tedesco, MRC and
      is a *preliminary* version. The version actually published will
      include UBV observations published through 1994 and the
      Individual, referenced and commented, observations from which the
      average value was obtained. This dataset presents Johnson system
      U-B and B-V colors (or colors transformable to them) for
      asteroids, obtained between 1951 and 1989 and published through
      mid-1990.  In addition, it uses Ted Bowell's unpublished
      observations from the Lowell UBV Asteroid Survey. The 978 mean U-B
      color indices are derived from 3,476 U-B observations.  The 1,020
      mean B-V color indices are derived from 4,010 B-V observations.
      The details of this synthesis will be submitted for publication in
      the future. For additional information contact Ed Tedesco.
 
 
      Parameters
      ==========
      The data are presented in one ASCII file, 'ubvavg.tab'.  The file
      contains one entry for each asteroid, with fields for the
      following paramenters.  Catalog number of the asteroid,
      provisional designation (for data published under the provisional
      designation only), and for both U-B and B-V the mean color index,
      the standard deviation of the mean color index, the number of
      observations used to compute the mean value, and the minimum,
      maximum, and mean phase angles of the asteroid in the set of
      observations used to compute the mean.
 
 
      Processing
      ==========
      The U-B and B-V values presented here are the unweighted averages
      of color indices compiled from the published literature.  The full
      dataset including the source data and references will be
      incorporated into the PDS when the compilation has been published,
      sometime in the future.
 
      The 1.1 version of the dataset differed from version 1.0 only be
      cosmetic changes to this file and the label file. Nothing was
      changed in the data file.
 
 
      Data
      ====
      The data are included in the ASCII data table 'ubvmean.tab'.
 
 
      Media/Format
      ============
      This dataset is released in the form of ASCII files which may be
      stored on disk or other magnetic media and which may be
      distributed by ftp, email, realtime access by remote login, or by
      whatever means is most convenient.

Review
      ======
      This dataset underwent a formal external review on March 31, 1995.
 
 
      Data Coverage and Quality
      =========================
      This dataset includes data published through mid-1990.  The
      complete dataset including source data and references, which will
      be complete through 1994, will be released in the future.
 
 
      Limitations
      ===========
      This dataset is a compilation of data taken from the published
      literature, as well as unpublished data from the Lowell UBV
      Asteroid Survey.  It is a provisional data product and will be
      replaced with the complete product in the future.