Description
The OrbitPeriselene method is a conditional property that can be used with the Step command to advance the Spacecraft to periselene, the point in the orbit where the Spacecraft is at its closest approach to the Moon. FreeFlyer determines this condition by monitoring the dot product between the position and velocity vectors of the Spacecraft and identifying when this value passes from negative to positive.
Note that as a general rule this method should only be used as a propagation stopping condition and should not be used as a means monitor whether or not a Spacecraft is at periselene at a particular epoch.
Timing Precision Mode
This page describes functionality in nanosecond timing precision mode.
Click here to see the documentation for this object in millisecond timing precision mode.
Note: This is a Stop-Propagation method. See the Stop-Propagation Properties and Methods page for more information.
Note: This method has a state. See the Methods and Properties with State page for more information.
Method Signature
Spacecraft.OrbitPeriselene( |
) |
Return Value
Type: |
number |
Units: |
km |
Returns the point in the orbit where the Spacecraft is at its closest approach to the Moon.
Syntax
Step mySpacecraft1 to ( mySpacecraft1.OrbitPeriselene()); |
The OrbitPeriselene property can be used to notify the user when the Spacecraft has reached the periselene of its orbit around the Moon. The following example shows how you can determine if a Spacecraft is at periselene.
The first Report command will report a 0, provided the Spacecraft is not initialized at the periselene of its orbit. The second Report command will report a 1, signifying the spacecraft has reached periselene.
Note: This example only works with orbits that have an eccentricity larger than 0.0001. |
See also
Stop-Propagation Properties and Methods
Coverage and Contact Analysis Guide