Charon/Pluto Mass Ratio Obtained with HST CCD Observations in 1991 and 1993

Abstract

We have analyzed Hubble Space Telescope Wide Field Camera observations of Pluto, Charon, and a reference star, acquired in 1991 and 1993, to observe Pluto's barycentric motion and determine the Charon/Pluto mass ratio, 0.124±0.008. Solution values for Charon orbital elements include the semimajor axis, 19662±81 km inclination, 96.57±0.24 deg; eccentricity, 0.0072±0.0067; longitude of periapsis, 2±35 deg; and mean longitude, 123.58±0.43 deg. These elements are referred to the J2000 Earth equator and equinox at epoch JED 2446600.5.