Apokrone

The original plan in the primary mission to look for the existence of an internal liquid layer called for four flybys to measure the Love number k₂: two equatorial passes -- one when Titan was at perikrone and one at apokrone, and two inclined passes – also at perikrone and apokrone.

In order to obtain the value of k₂ with high accuracy, four flybys of the Cassini spacecraft will be devoted to measuring Titan's gravity field near both apokrone and perikrone (Castillo et al., 2002).