SetState SGP4 (Satellites)
Set the orbit state of a satellite and propagate an SGP4 orbit
Syntax
SetState <SatObjectPath> SGP4 {NoProp | {TimeInterval}} <StepSize> <SSCNumber> TLESource {Automatic | DefineElements} [<Parameters>]
Related commands
Description
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.
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> | Specify the interval between calculated ephemeris output points in seconds, greater than or equal to 0.001 seconds. |
| <SSCNumber> | Enter the catalog number of the spacecraft. |
| TLESource {Automatic | DefineElements} | Indicate from where the parameters to define the orbit state 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 you enter File, then you must enter a "<Filename>", including the file path, containing element sets for the <SSCNumber>. You may use any file containing GP element data, including TLE files and files containing CCSDS OMM content in XML, KVN, (using file extension .omm), and CSV formats. "<FilePath>" can be the path to a file on your local drive or the path to a file on an SDF server. See Specifying Paths for "<SDFFilePath>" syntax information. |
| UseTLE {All | First} | Set the method for retrieving elements. The default value is All. |
| SwitchMethod {Epoch | Midpoint | TCA} | Set the method for switching between elements. The default value is Epoch. STK ignores the SwitchMethod option if you set UseTLE to First. |
| UseCatalogModel | Enter this keyword to load a satellite model based on the SSC number. If you do not enter this, then STK uses the default satellite model. |
| Routine {SGP4 | Default | <Name>} | Specify the implementation of the SGP4 propagator to be used, where SGP4 is the internal SGP4 routine implemented by STK, Default is the propagator selected in the Edit Preferences panel, and <Name> is an installed SGP4 plugin routine, e.g., ASTROSTDS_SGP4_V9.
Astro Standards routines may be available as an option if you properly configured STK to support it. It is only available if you have obtained the official SGP4 DLL (and related files) from USSF (US Space Force) and performed a minor install procedure. STK provides an interface to the USSF SGP4 routines; contact customer support for more information. |
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 you enter File, then you must enter one or more "<Filename>" values. The file(s) should contain element sets for the <SSCNumber> specified. You may use any file containing GP element data, including TLE files and files containing CCSDS OMM content in XML, KVN, (using file extension .omm), and CSV formats. "<FilePath>" can be the path to a file on your local drive or the path to a file on an SDF server. See Specifying Paths for "<SDFFilePath>" syntax information. If you enter DefaultFile, 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 elements. The default value is Epoch. STK ignores the SwitchMethod option if you set UseTLE to First. |
| UseCatalogModel | Enter this keyword to load a satellite model based on the SSC number. If you do not enter this, then STK uses the default satellite model. |
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. The ElementSet is required if you enter Source Elements. |
| OrbitEpoch <Date> | Enter the universal date and time at which the specified orbit elements are true. Enter the <Date> in Connect Date units. |
| OrbitEpochYYDDD <Date> | Enter the universal date and time at which the specified orbit elements are true. The format for <Date> is YYDDD.DDDDDDDD. |
| RevNumber <Value> | Enter an integer representing the current number of revolutions, or passes, of the vehicle. If you do not specify RevNumber <Value>, it is assumed to be the first pass. |
| Classification <Value> | Enter a one-letter classification indicator. |
| IntlDesignator <Value> | Enter 1-8 characters representing the international designation of the satellite. |
| MeanMotionDot <Value> | Specify the first time derivative of mean motion. |
| MeanMotionDotDot <Value> | Specify the second time derivative of mean motion. |
The following table describes the values used in Source Elements ElementSet.
| Element | Description |
|---|---|
| <MeanMotion> | Enter 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> | Specify the angle between the angular momentum vector, perpendicular to the plane of the orbit, and the inertial Z axis, in degrees. |
| <ArgOfPerigee> | Specify 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. Enter it in degrees. |
| <RAAN> | Specify 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. Enter it in degrees. |
| <MeanAnomaly> | Specify 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. Enter it in degrees. |
| <BStar> | Enter the drag term for the satellite. |
Examples
To set the state of the Shuttle in SGP4 coordinates automatically from the online AGIServer:
To set the state of the Shuttle in SGP4 coordinates automatically from the file specified:
To set the state of the Shuttle in SGP4 coordinates, obtaining the elements from the online AGIServer:
To set the state of the Shuttle in SGP4 coordinates using the specified element set:
To set the state of the Shuttle in SGP4 coordinates using the specified element set:
To set the state in SGP4 coordinates using the elements from the default source file:
To set the routine to preinstalled STK SGP4:
Return message
Group membership
This command belongs to the following group(s):
Version
11.5