Data Set Overview
  =================
    During the period 1985-1990, the earth entered the orbital plane of Pluto
    and its moon Charon, and the mutual eclipse events were observed from
    ground-based observatories.  A subset of these data are included in this
    data set, and more will be added in future updates.  The current version
    contains photoelectric photometry data from thirty-nine events observed at
    Mauna Kea Observatory by Tholen, CCD photometry data from fifteen events
    observed at Palomar Observatory by Buratti and colleagues, and
    photoelectric photometry data from ten events observed at McDonald
    Observatory by Young and Binzel.
 
      Data
      ====
 
    The Mauna Kea data is in the file pcmemko.tab, and includes standard B
    magnitudes and errors, and Julian date at mid-observation, corrected for
    light-travel time.  The Palomar data is in the file pcmepal.tab, and
    includes differential magnitudes and errors, and Julian date at
    mid-observation (uncorrected).  The McDonald Observatory data, taken from
    Young (1992), includes differential B and V photometry.
 
    Individual lightcurves are included in the subdirectory 'indiv'.  These
    contain the same data as in the full data files.  The filenaming system is
    as follows: obs_yyyymmdd_f.tab, where obs is an abbreviation of the
    observatory, yyyymmdd is the date of observation, and f is the filter.
 
      Modification History
      ====================
 
    In January 2002 SBN personnel calculated UTC based on the Julian dates
    provided and added it to the data files. At the time resolution of the
    Julian date (less than 1.e-05), UTC and UT are equivalent. START_TIME and
    STOP_TIME values were updated throughout as appropriate. No other data
    values were changed.
 
    In 2008, the data from McDonald Observatory, from Young (1992) and with
    additional discussion of the data given in Young and Binzel (1993), was
    added to the data set.
 
    In 2012, the data were broken into individual lightcurves, supplied in a
    separate subdirectory in addition to the original data files.  This change
    was made to facilitate loading the data into the data Ferret.
 
      References
      ==========
 
    Young, E.F., An albedo and frost model of Pluto, Ph.D. thesis,
    Massachusetts Institute of Technology, 1992.  [YOUNG1992]
 
    Young, E.F. and R.P. Binzel, Comparative mapping of Pluto's sub-Charon
    hemisphere: Three least-squares models based on mutual event lightcurves,
    Icarus 102, 134-149, 1993.  [YOUNG&BINZEL1993]

Confidence Level Overview
  =========================
    Data Coverage and Quality
    =========================
 
        The data set is eventually intended to be a complete collection of
    groundbased observations of the Pluto-Charon mutual events.  At present,
    it contains visual photometric data from Mauna Kea Observatory, Palomar
    Observatory, and McDonald Observatory.  The collection includes both
    calibrated and uncalibrated data.  Additional data will be added in future
    updates.