Use the Initial State segment to define the initial conditions of your MCS or of a subsequence within the MCS. For an STK/Astrogator® satellite, on the Properties page Basic - Orbit, the Initial State segment defaults to the Elements tab, where you can specify the state at a given epoch in a variety of coordinate types and in any coordinate system. On other tabs, you can also configure the spacecraft’s physical values, user variables, and stochastic parameters. The segment adds the defined state to the ephemeris and then passes the state to the next segment.
Elements tab
Selecting a coordinate system
The name of the currently selected coordinate system appears in the text box for Coord.System. To select a different coordinate system, click 
to the right of this field and make the desired selection in the Select Reference dialog box that appears. The name of that coordinate system will then appear in the Coordinate System field. For more information on coordinates systems, see STK Technical Notes.
Selecting a coordinate type
You can define the initial state using Cartesian, Geodetic, or Spherical elements if the coordinate system is fixed, or by Cartesian, Spherical, and several other element sets if the coordinate system is inertial. Select the desired element set from the Coordinate Type drop-down menu and then define an Orbit Epoch and values for the elements of the selected set.
Initial State Tool
Click to do one of the following:
- Change the initial state of the satellite by reading ephemeris from a file
- Move the epoch of the initial state using a vehicle's propagated ephemeris
- Set the initial state using a Flight Dynamics Record
If you want to set the initial state of an Astrogator satellite from a Flight Dynamics Record, then select "Flight Dynamics Record" as the Source Type. You can then choose a Flight Dynamics Record from the Component Browser.
See the Initial State Tool topic for more information.
Set Full State
You can define all six elements of the initial state at once using the following steps:
- Click to open an MCS Initial State Input dialog box.
- In the upper left, specify the coordinate system of your input data by clicking and choosing from a list of available types.
- In the upper right, select either Cartesian or Keplerian for the state element type of your input data.
- In the input text box, enter the six elements using km for distances, km/s for velocities, and degrees for angles; you must use these units. You must also follow the input order for the state variables as shown above the input text box. Separate the state elements by commas, spaces, or return characters.
- After entering the initial state into the text box, click to preview the resulting Cartesian state in the coordinate system chosen on the Elements tab of the Initial State segment (not your input data coordinate system).
- If the preview is satisfactory, click to import the result into the initial state.
Spacecraft Parameters and Fuel Tank tabs
Use the Spacecraft Parameters and Fuel Tank tabs to manually define the Spacecraft Configuration.
User Variables tab
Click the User Variables tab to set initial values for user variables that you want to define for the mission.
Stochastic Parameters tab
Click the Stochastic Parameters tab to see read-only and definable stochastic propagation parameters for the mission.