The Status Output

The Status return value supports two types of segments: message and control. The message segment allows the script to send messages into the STK display window, and the control segment allows the script to control its use in the access calculation. Multiple segments are passed by separating the segments with semicolons.

A control segment has the form:

CONTROL: <controlType>;

Where <controlType> can be one of the control type keywords: OK, STOP or ERROR. Example:

CONTROL: Stop;

Control of Stop or Error will cause an error message indicating the problem and the Plugin will be turned off for the remainder of the run. It is not necessary to return OK on every successful iteration step. The Plugin is assumed to have succeeded when no control segment is returned.

A message segment has the form:

MESSAGE: [<messageType>] <message>;

Where <messageType> can be one of the message type keywords: ALARM, WARNING or INFO. Alarms cause the message to be displayed in the Message Viewer window and the window pops to the front. The <message> value can be any character string terminated by a semicolon. Example:

MESSAGE: [Alarm] My Plugin had an unexpected error!;

Information on Constraint Plugin Point Arguments

The following table gives representation (data type) and unit information for each constraint Plugin Point argument, together with a brief definition:

Name Representation Units Definition
Epoch Double epoch secs The STK epoch time for the current access iteration step.
fromCbName String --- The central body name for the from object.
fromAngularVelocity Double:3 1/sec The angular velocity for the from object's body, with respect to the reference frame specified.
fromCbAppSunPosition Double:3 m The apparent sun position with respect to the center of mass of the from object’s central body.
fromObjectPath String --- The from object path defined in STK fashion. Alternatively, the generic keyword “Access/fromObj” can be used.
fromPosition Double:3 m The from object's position in Cartesian coordinate system.
fromQuaternion Double:4 unitless The attitude defined by a quaternion for the from object.
fromRelPosition Double:3 m The to object's relative position in relation to the from object, in the Cartesian coordinate system of the central body of the from object.
fromRelVelocity Double:3 m/sec The to object's relative velocity in relation to the from object, in the Cartesian coordinate system of the central body of the from object.
maxRelMotion Double radians The maximum relative angular motion that the object should move between access iteration step samples (in radians). This number affects constraint sampling. This is an advanced feature and in most cases should not be used.
range Double m The range between the from and to objects.
Result Double unitless The result of the constraint script Plugin calculations, which will be compared to any minimum and/or maximum constraint values in effect.
Status String --- A status string that is parsed for message or control segment s . Each segment is separated by semicolons.
timeDelay Double secs The time delay between the from and to objects.
toAngularVelocity Double:3 1/sec The angular velocity for the to object's body, with respect to the reference frame specified.
toCbAppSunPosition Double:3 m The apparent sun position with respect to the center of mass of the to object’s central body.
toCbName String --- The central body name for the to object.
toObjectPath String --- The to object path defined in STK fashion. Alternatively, the generic keyword “Access/toObj” can be used.
toPosition Double:3 m The to object's position in the Cartesian coordinate system
toQuaternion Double:4 unitless The attitude defined by a quaternion for the to object
toRelPosition Double:3 m The from object's relative position in relation to the to object, in the Cartesian coordinate system of the central body of the to object.
toRelVelocity Double:3 m/sec The from object's relative velocity in relation to the to object, in the Cartesian coordinate system of the central body of the to object.
toVelocity Double:3 m/sec The to object's velocity in Cartesian coordinate system.

Velocities pulled from the Access plugin arguments fromVelocity and toVelocity are given as observed in the requested frame. The velocities pulled from the Vector Geometry Tool are given as expressed in the requested frame. The observed vector has the angular motion of the two frames taken into account, whereas the expressed vector simply has the components of the base vector rotated into the new frame. Take for example a geostationary satellite. The request for the velocity in the CBF frame will return a value near zero from the Access plugin argument. If the velocity is pulled from the Vector Geometry Tool, it simply rotates the components of the inertial velocity vector into the CBF frame. To get the same number out of the Vector Geometry Tool, one has to explicitly ask for the CBF Velocity vector, which is separately listed in the object's vector list. This is true for all requested frames however.

Expressed Vector Transformation (Vector Geometry Tool):

Observed Vector Transformation (Access arguments):

STK 11.2.1 Programming Interface