Set the orbit state of a satellite and propagate an SGP4 orbit
SetState <SatObjectPath> SGP4 {NoProp | {TimeInterval}} <StepSize> <SSCNumber> TLESource {Automatic | DefineElements} [<Parameters>]
The SetState SGP4 command sets the orbit state of the specified satellite and propagates the orbit over the specified time period. The propagated ephemeris data is spaced by the <StepSize> parameter.
Warning: The STK orbit propagator doesn't completely validate the correctness of the orbit state specified. This means that Connect may return a positive acknowledgment even if the orbit track can't be displayed. Connect performs the same validation that occurs from the entry of state data via the user interface.
| Parameter | Description |
|---|---|
| {NoProp | {TimeInterval}} |
Enter NoProp to set the state of the vehicle but not propagate it. Enter {TimeInterval} to define the beginning and end of the satellite's time period for propagation. For valid {TimeInterval} values see Time Options. |
| <StepSize> | The interval between calculated ephemeris output points. Entered in seconds and must be greater or equal to 0.001 seconds. |
| <SSCNumber> | The catalog number of the spacecraft. |
| TLESource {Automatic | DefineElements} | Indicate where the parameters to define the orbit state will originate. The following tables describe the additional parameters for each source. |
If TLESource is Automatic, then the following <Parameters> are valid:
| Parameter | Description |
|---|---|
| Source {AGIServer | File "<Filename>"} | The default value is AGIServer.
If File is entered then a "<Filename>", including the file path, containing TLEs for the <SSCNumber> must be entered. |
| UseTLE {All | First} | Set the method for retrieving TLEs. The default value is All. |
| SwitchMethod {Epoch | Midpoint | TCA} | Set the method for switching between TLEs. The default value is Epoch. The SwitchMethod option is ignored if UseTLE is set to First. |
| UseCatalogModel | Enter this keyword to load a satellite model based on the SSC number. If not entered then the default satellite model is used. |
If TLESource is DefineElements, then the following <Parameters> are valid:
| Parameter | Description |
|---|---|
| Source {AGIServer | File "<Filename>" | DefaultFile | Elements <Parameters>} | Specify the source of the elements. The
default AGIServer.
If File is entered then one or more "<Filename>" must be entered. The file(s) should contain TLEs for the <SSCNumber> specified. If DefaultFile is entered then the current default source file will be set as the Source. See SetPropagatorDefaults command. The tables below describe the <Parameters> for the Elements option. |
| SwitchMethod {Epoch | Midpoint | TCA} | Set the method for switching between TLEs. The default value is Epoch. The SwitchMethod option is ignored if UseTLE is set to First. |
| UseCatalogModel | Enter this keyword to load a satellite model based on the SSC number. If not entered then the default satellite model is used. |
If Source is Elements then the following <Parameters> are valid.
| Parameter | Description |
|---|---|
| ElementSet <MeanMotion> <Eccentricity> <Inclination> <ArgOfPerigee> <RAAN> <MeanAnomaly> <BStar> | Specify the elements that describe the
orbit state. These values are described in the table below.
Note: The ElementSet is required if Source Elements is entered. |
| OrbitEpoch <Date> | The universal date and time at which the specified orbit elements are true. The <Date> is entered in Connect Date units. |
| OrbitEpochYYDDD <Date> | The universal date and time at which the specified orbit elements are true. The format for <Date> is YYDDD.DDDDDDDD. |
| RevNumber <Value> | An integer representing the current number of revolutions, or passes, of the vehicle. If RevNumber <Value> is not included, it is assumed to be the first pass. |
| Classification <Value> | A one-letter classification indicator. |
| IntlDesignator <Value> | 1-8 characters representing the international designation of the satellite. |
| MeanMotionDot <Value> | The first time derivative of mean motion. |
| MeanMotionDotDot <Value> | The second time derivative of mean motion. |
The following table describes the values used in Source Elements ElementSet.
| Element | Description |
|---|---|
| <MeanMotion> | A measure of the osculating period of the orbit, expressed as an angular rate. |
| <Eccentricity> | Describes the shape of the ellipse. A value of 0 represents a circular orbit; values greater than 0 but less than 1 represent ellipses of varying degrees of ellipticality. |
| <Inclination> | The angle between the angular momentum vector (perpendicular to the plane of the orbit) and the inertial Z-axis. Entered in degrees. |
| <ArgOfPerigee> | The angle from the ascending node to the eccentricity vector (lowest point of orbit) measured in the direction of the satellite's motion. The eccentricity vector points from the center of the Earth to perigee with a magnitude equal to the eccentricity of the orbit. Entered in degrees. |
| <RAAN> | The angle from the inertial X-axis to perigee. The ascending node is the point where the satellite passes through the inertial equator moving from south to north. Right ascension is measured as a right-handed rotation about the inertial Z-axis. Entered in degrees. |
| <MeanAnomaly> | The angle from the eccentricity vector to a position vector where the satellite would be if it were always moving at its average angular rate. Entered in degrees. |
| <BStar> | The drag term for the satellite. |
To set the state of the Shuttle in SGP4 coordinates automatically from the online AGIServer:
SetState */Satellite/SGP4Sat SGP4 "1 Jul 2009 15:00:00.00" "1 Jul 2009 19:00:00.00" 60.0 11536 TLESource Automatic
To set the state of the Shuttle in SGP4 coordinates automatically from the file specified:
SetState */Satellite/SGP4Sat SGP4 UseScenarioInterval 60.0 11417 TLESource Automatic Source File "c:\MyTemp\B44150.tle" UseTLE All SwitchMethod Midpoint
To set the state of the Shuttle in SGP4 coordinates, obtaining the elements from the online AGIServer:
SetState */Satellite/SGP4Sat SGP4 "1 Jul 2009 15:00:00.00" "1 Jul 2009 19:00:00.00" 60.0 28470 TLESource DefineElements Source AGIServer
To set the state of the Shuttle in SGP4 coordinates using the specified element set:
SetState */Satellite/SGP4Sat SGP4 "1 Jul 2009 15:00:00.00" "1 Jul 2009 19:00:00.00" 60.0 12345 TLESource DefineElements Source Elements OrbitEpochYYDDD 09182.62500000 ElementSet 0.0625 0.0 28.5 0.0 0.0 0.0 0 IntlDesignator 79017A MeanMotionDot 0.00011563
To set the state of the Shuttle in SGP4 coordinates using the specified element set:
SetState */Satellite/SGP4Sat SGP4 UseScenarioInterval 60.0 12345 TLESource DefineElements Source Elements OrbitEpochYYDDD 09182.62500000 ElementSet 0.0625 0.0 28.5 0.0 0.0 0.0 0
To set the state in SGP4 coordinates using the elements from the default source file:
SetState */Satellite/SGP4_FileC SGP4 "1 Jul 2007 12:00:00.000" "2 Jul 2007 12:00:00.000" 60.0 25577 TLESource DefineElements Source DefaultFile
If activated, Connect returns an acknowledgement message.
This command belongs to the following group(s):
10.1
STK Programming Interface 11.0.1