The 1983 June 15 Occultation by Neptune. II - the Oblateness of Neptune

The oblateness and radius of Neptune were determined from an analysis of photoelectric observations of the 15 June 1983 occultation by Neptune at six stations, combined with the results of the 7 April 1968 Neptune occultation of BD - 17°4388. The oblateness is 0.0191±0.0017 and the equatorial radius is 25268±12 km at the level probed by the occultation. The results are consistent with recent determinations of Neptune's rotation period and J2 (the second-order gravitational harmonic coefficient) and suggest that Neptune is far less centrally condensed than Uranus. Temperature profiles for Neptune's upper atmosphere were also derived from these data.