For the OrbitState property, select either Cartesian or Keplerian as the coordinate type. In the former case, enter position values in the selected distance unit and velocity values in the selected distance unit per selected time unit. In the latter case, enter the orbit elements in the table below.

Use the central body selector to specify the primary gravitational body for use in orbit integration. The orbit state of the satellite will be estimated relative to the center of mass of the selected body. Prior to using ODTK for deep space trajectories, the limitations of various functional areas for deep space orbit determination should be reviewed.

For the primary central body for trajectory generation and the origin of the reference frame for the initial conditions, select between:

- Earth
- Moon
- Sun

For either type of orbital element, select from among the following available coordinate frames:

- J2000
- True of Date
- Mean of Date
- Inertial (Moon only)
- Fixed (e.g. Earth Centered Fixed - for Cartesian input only)
- True Equator Mean Equinox (TEME) of Date (Earth only)

The epoch defaults to the scenario start time.

Keplerian Orbit Elements | |
---|---|

Element | Value |

SemiMajorAxis | Enter the semimajor axis of the orbit in the selected distance unit. |

Eccentricity | Enter a value (unitless) representing the orbit's eccentricity. |

TrueArgofLatitude | Enter the true argument of latitude in the selected angle unit. |

Inclination | Enter the orbit's inclination in the selected angle unit. |

RAAN | Enter the right ascension of ascending node in the selected angle unit. |

ArgofPerigee | Enter the argument of perigee (W) in the selected angle unit. |

The coordinate systems for non-Earth central bodies follow the IAU reports on Cartographic coordinates for the planets. The Inertial coordinate system uses axes defined as follows:

- The Inertial Z axis is aligned with the Fixed Z axis at the J2000 epoch.
- The X axis lies along the intersection of the plane perpendicular to the Inertial Z axis and the J2000 XY plane.

The conversion from the Inertial frame to the Mean of Date frame is performed by turning off the contribution of the trigonometric terms in the motion of the spin axis and ignoring motion about the spin axis. The conversion from the Inertial frame to the True of Date frame is performed by considering all terms in the motion of the spin axis, but ignoring motion about the spin axis.

The Fixed frame is defined by the set of rotational parameters defined by a Rotational Coefficients File (that is, a file with the extension .rot) in the central body directory under \STKData\CentralBodies. The values of these parameters derive from the IAU 2003 and 2000 reports.

ODTK 6.5