Cassini Trajectory Plots

Trajectory Plots

Trajectory Plots Description

The trajectories are plotted in the Saturn Equatorial System (SZS). The Z-axis is parallel to the Saturn spin axis. The Y-axis is then defined as the cross product of this vector with the Saturn-Sun vector. The X-axis completes the right-handed system and is directed “towards”, but not directly at, the Sun.

The data are taken from the University of Iowa “Cassini, Galileo, and Voyager ephemeris tool” website with settings of Origin: Saturn barycentric, Observer: Cassini, and Coordinate System: Equatorial.

Typical locations of the magnetopause and bow shock are shown and were taken from Arridge et al. (2006) and Masters et al., (2008). Standoff distances are 20.1 RS for the MP and 24.9 RS for the BS, corresponding to a solar wind pressure of 0.048 nPa. Those two models are defined in the Kronocentric Solar Magnetospheric (KSM) coordinate system which is Saturn-centered with positive X pointing at the sun, positive Y given by the cross product of the spin axis with X and pointing toward dusk, with Z completing the right hand system. The spin axis lies in the X-Z plane.

The KSM and SZS systems differ by a rotation about the common Y-axis. The Arridge and Masters models both assume that the surfaces are symmetric about the KSM X-axis. In the X-Y view of these trajectory plots, the magnetopause and bow shock are computed in the KSM Z=0 plane and then projected onto the SZS X-Y plane. In the X-Z view, they are computed in the KSM Y=0 plane and projected onto the SZS X-Z plane.

The tilt of Saturn’s equatorial plane relative to the solar direction is indicated by the departure from vertical of Saturn’s day-night terminator in the X-Z view.