The longitude discrepancy for mutual satellite phenomena resolved

The systematic differences between Io and Europa longitudes, as derived from near-simultaneous mutual occultations and eclipses of the satellites in 1973, are presently traced to phase effects on the satellites. Attention is given to phase corrections for published observations of minimum satellite separations in orbital longitude, and the equivalent changes in the observed midtimes. Expressions are given for calculating the satellite separations in right ascension and declination from rectangular coordinates, along with a detailed discussion of the light-aberration effects. Ordinary satellite eclipses in Jupiter's shadow are noted to also require phase corrections by means of one of the formulas presented.