Target Vector Coordinate Types
Target Vector Incoming Asymptote
If you select Target Vector Incoming Asymptote as the Coordinate Type, you need to specify the following six components:
| Element | Description |
|---|---|
| Radius of Periapsis | This is the distance from the center of mass of the central body to the periapsis of the hyperbolic orbit (rp in the illustration). Enter a value in the selected distance unit. |
| C3 Energy | This is the energy of the orbit, computed as - /a, where is the gravity constant of the central body and a is the semimajor axis. Enter a value in the selected distance unit squared per selected time unit squared. |
| Right Ascension of Incoming Asymptote | This is the right ascension of the hyperbolic incoming asymptote in the selected coordinate system. Enter a value in the selected angle unit. If C3 Energy is less than zero, the orbit is elliptical, and this value provides the right ascension of the periapsis vector of that orbit. |
| Declination of Incoming Asymptote | This is the declination of the incoming asymptote in the selected coordinate system. Enter a value in the selected angle unit. If C3 Energy is less than zero, the orbit is elliptical, and this value provides the declination of the periapsis vector of that orbit. |
| Velocity Azimuth at Periapsis |
This is the spherical angle between the orbit plane and a plane of constant right ascension equal to the right ascension of the asymptote or apsis vector. Enter a value in the selected angle unit. For an explanation and graph of this angle, see Appendix B of the following reference. J. A. Atchison, M. T. Ozimek, C. J. Scott, F. E. Siddique, "Robust High-fidelity Gravity-assist Trajectory Generation Using Forward/Backward Multiple Shooting," AAS Paper 15-249, AAS/AIAA Space Flight Mechanics Meeting, Williamsburg, VA, January 2015. |
| True Anomaly | This is the angle from the periapsis of the orbit to the spacecraft's position vector, measured in the direction of spacecraft motion (the angle  in the illustration). Enter a value in the selected angle unit. |
In the drawing below, 
and 
represent the incoming and outgoing asymptotes, respectively:
Target Vector Outgoing Asymptote
If you select Target Vector Outgoing Asymptote as the Coordinate Type, the components you must specify are the same as those in the Incoming Asymptote type, except that right ascension and declination are defined in terms of the outgoing rather than the incoming asymptote. If C3 Energy is less than zero, the orbit is elliptical and the right ascension and declination are defined in terms of the apoapsis vector of the elliptical orbit.