pm0014

Contents.
      planet: 9 - Pluto
  satellites: 1 - P1 Charon : 28
total number: 28
        type: relative
       dates: 1991-1993
 observatory: 250 - HST

Reference.
   Null, G. W.; Owen, W. M., Jr.; Synnott, S. P. (1993)
   Masses and Densities of Pluto and Charon.
   The Astronomical Journal. 1993. V. 105. P. 2319-2335.
   1993AJ____105_2319N
   
   Null, G. W.; Owen, W. M., Jr. (1996)
   Charon/Pluto Mass Ratio Obtained with HST CCD Observations in 1991 and 1993.
   The Astronomical Journal. 1996. V. 111. P. 1368-1381.
   1996AJ____111_1368N

Informations.
         relative to: Pluto
     reference frame: astrometric
     centre of frame: topocentre
    epoch of equinox: J2000
          time scale: UTC
           reduction: distortion and albedo corrections for Pluto,
                      distortion and image overlap corrections for Charon
         coordinates: sample and line coordinates on the CCD image
                      as well as relative coordinates of Charon deduced from
                      published data.
    diff. refraction: no information
            receptor: CCD
           telescope: WFC CCD 1 of the HST
           observers: Null, G. W.; Owen, W. M., Jr.

 data included in standard data file: no

Comments.
  1. The mutual distance s (in arcseconds) between Charon and Pluto can be obtained as:

\begin{equation*} s=m\times\sqrt{(X_C-X_P)^2+(Y_C-Y_P)^2} \end{equation*}

     where: m = 0.1016 arcsec/pixel is the scale for the WFC,
           (X_P, Y_P) and (X_C, Y_C) are pixel coordinates of Pluto and Charon on the CCD frame (see the values X_P, Y_P, X_C, Y_C in the data).
  2. Charon's position angle P can be obtained as:

\begin{equation*} P=P_{axis}-225^\circ+\frac{180^\circ}{\pi}\arctan\left(\frac{Y_C-Y_P}{X_C-X_P}\right) \end{equation*}

     where P_axis is the WFC roll angle (see the value P_axis in the data) measured in degrees. 
  3. Values for s and P obtained in this way are given in the data file.

Format.
  1. Year of the date of observation
  2. Month of the date of observation
  3. Day of the date of observation 
  4. Hour (h) of the date of observation
  5. Minute (m) of the date of observation 
  6. Seconds (s) of the date of observation with decimals (UTC)
  7. Geocentric x-coordinate of the HST (X, km)
  8. Geocentric y-coordinate of the HST (Y, km)
  9. Geocentric z-coordinate of the HST (Z, km)
 10. x-coordinate of Pluto in the image (X_P, pixels)
 11. y-coordinate of Pluto in the image (Y_P, pixels)
 12. x-coordinate of Charon in the image (X_C, pixels)
 13. y-coordinate of Charon in the image (Y_C, pixels)
 14. WFC roll angle, i.e. position angle of the HST's V3 axis (P_axis, degrees)
 15. The mutual apparent topocentric (HST) distance Charon-Pluto, s, arcsec
 16. The mutual apparent topocentric (HST) position angle of Charon relative to Pluto, P, degrees
 
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Year   Day   Time          X       Y      Z        X_P     Y_P      X_C     Y_C     P_axis    s         P
  Month    h  m  s         km      km     km      pixels  pixels   pixels  pixels   degrees  arcsec   degrees
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