We present a detailed analysis of the orbit of Charon where we show its orbit to be circular. This analysis explores the effects of surface albedo variations on the astrometry and the resulting errors in the orbital elements. We present two new epochs of data from the Hubble Space Telescope taken in 2008 and 2010 and combine that with a re-analysis of previously published data from 1992 and 2002. Our adopted two-body Keplerian orbital elements for Charon are P = 6.3872273 ± 0.0000003 days, a… CONTINUE READING
Figure 3. Eccentricity: this orbital element was poorly retrieved. The answer for the final fit depends on the data, on the map, and on every assumption. We can certainly rule out large eccentricities, and these tests suggest a credible upper limit of around 0.01 when no map corrections are applied.