Collection Define
This command is an action option (Define) of the Collection Connect command. Use the Define action option with the Collection command to create a satellite collection object.
Syntax
Collection <objPath> Define {Walker <Parameters> | SatDb <Parameters> | Custom <Parameters> | SP3 <Parameters>}
Description
This defines the method for creating a satellite collection. Below are descriptions and examples for the four methods: Walker, Satellite Database, Custom, and SP3.
Walker
The following table provides descriptions of the applicable parameters for the Walker method:
| Optional Parameters | Description |
|---|---|
| Propagator <Propagator Name> | You can specify the propagator to use for all entries within a shell. Use this when adding or modifying a shell. The choices are TwoBody, J2Perturbation, and J4Perturbation. The default is J2Perturbation. |
| PropagationFrame | This is the coordinate frame of propagation. STK will apply the analytic orbit equations to the orbit initial conditions and interpret the results in the propagation frame. Choose from Inertial, TrueOfDate, TrueOfEpoch, and TrueOfOrbitEpoch (where TrueOfEpoch is simply an alias for TrueOfOrbitEpoch). |
| AddShell <Shell Name> | Use this to add a new shell; the parameters NumPlanes and either NumSatsPerPlane or TotalNumSats are required. |
| Type {Delta, Star, Custom} | Choose a pattern type. |
| NumPlanes <num> | This is the number of planes in a new shell, and it is required when you select AddShell. |
| NumSatsPerPlane <num> | This is the number of satellites in each plane in the new shell. You must specify either this or TotalNumSats when adding a shell. |
| TotalNumSats <num> | This is the total number of satellites in the shell. You must specify either this or NumSatsPerPlane when adding a shell. |
| InterPlanePhaseIncrement <num> | This is the number of slots (less than or equal to NumPlanes-1) representing the relative angular spacing between satellites in adjacent planes. The change in true anomaly is <num>*360/T deg, where T is the total number of satellites in the shell. This parameter is required for Delta and Star patterns and is not applicable for Custom patterns. |
| InterPlanePhaseAngle <value> | This is the relative angular spacing between satellites in adjacent planes. It is required for Custom patterns and not applicable for Delta and Star patterns. The <value> must be in degrees. |
| RAANSpacing <value> | This is the spacing between adjacent planes in a Custom pattern shell. The <value> must be in degrees. You must specify either this or RAANSpread when adding a Custom pattern shell. |
| RAANSpread <value> | This is the total spread of the planes within a shell. The <value> = RAANSpacing * NumPlanes, and must be in degrees. You must specify either this or RAANSpacing when adding a Custom pattern shell. |
| Epoch <epoch> | This is the epoch of the initial conditions, and the default is the scenario epoch. You can specify <epoch> as either an explicit date in Connect units or as a Time Instant time component. |
| Semimajoraxis <a> | This is the semimajoraxis of the initial conditions. The value is in Connect units. |
| Eccentricity <e> | This is the eccentricity of the initial conditions. |
| Inclination <i> | This is the inclination of the initial conditions. The value is in degrees. |
| RAAN <ra> | This is the RAAN of the initial conditions. The value is in degrees. |
| ArgumentOfPerigee <aop> | This is the argument of perigee of the initial conditions. The value is in degrees. |
| MeanAnomaly <ma> | This is the mean anomaly of first satellite in the first plane. The value is in degrees. |
| ModifyShell <Shell Name> | Use this to modify certain settings of the specified shell. It works with the same optional settings as in AddShell. |
| ClearShells | Select this to remove all prior shells and start a new collection. |
| RemoveShell <Shell Name> | Use this to remove a specified shell. |
| Subsets {None | Shell | ShellsAndPlanes | All} | This sets the mode for automatically creating subsets. "All" is equivalent to "ShellsAndPlanes." |
| Prefix <NamePrefix> | This is the prefix used in naming collection members; the default is "Sat_". |
SatDb
The Satellite Database (SatDb) algorithm searches the satellite database for SSCs having field values that match specified search criteria. It then obtains GP data for those SSCs meeting all the search criteria and discards any data deemed out of date (controlled by the Out Of Date Duration setting). Those SSCs meeting all search criterion and data timeliness requirements are then considered the entries of the satellite collection.
The following table provides descriptions of the applicable parameters for the Satellite Database method:
| Optional Parameters | Description |
|---|---|
| "Name or ID" <"value"> or NameOrID <"value"> | This requires that at least one field (SSCNumber, International Designator, Common Name, or Official Name) from the satellite database file contain the specified value in order for an SSC to be included as part of the satellite collection. |
| Owner <value> | This requires that the Owner field of the satellite database file match the specified value in order for an SSC to be included as part of the satellite collection. It must be an exact match of letters, without regard for case. |
| Mission <value> | This requires that the Mission field of the satellite database file match the specified value in order for an SSC to be included as part of the satellite collection. It must be an exact match of letters, without regard for case. |
| "Launch Site" <value> or LaunchSite <value> | This requires that the Launch Site field of the satellite database file match the specified value in order for an SSC to be included as part of the satellite collection. It must be an exact match of letters, without regard for case. |
| "Operational Status" <value> or OperationalStatus <value> or Status <value> | This requires that the Operational Status field of the satellite database file match the specified value in order for an SSC to be included as part of the satellite collection. It must be an exact match of letters, without regard for case. This field supports three choices: Active, Inactive, and Unknown. These use '|' as a separator. As an example, you could search for both active and inactive status, but exclude the unknown status, using "Active|Inactive" as the value. |
| "Launch Date" <MinValue> <MaxValue> or LaunchDate <MinValue> <MaxValue> | This requires that the LaunchDate field of the satellite database file meet the specified minimum and maximum launch dates in order for an SSC to be included as part of the satellite collection. The <MinValue> and <MaxValue> are in Connect units. |
| "Periapsis Altitude" <MinValue> <MaxValue> or PeriapsisAltitude <MinValue> <MaxValue> or Perigee <MinValue> <MaxValue> | This requires that the nominal perigee altitude meet the specified minimum and maximum values in order for an SSC to be included as part of the satellite collection. The <MinValue> and <MaxValue> are in Connect units. Both <MinValue> and <MaxValue> must be nonnegative and less than 999,999 km. |
| "Apoapsis Altitude" <MinValue> <MaxValue> or ApoapsisAltitude <MinValue> <MaxValue> or Apogee <MinValue> <MaxValue> | This requires that the nominal apogee altitude meet the specified minimum and maximum values in order for an SSC to be included as part of the satellite collection. The <MinValue> and <MaxValue> are in Connect units. Both <MinValue> and <MaxValue> must be nonnegative and less than 1,000,000 km. |
| Period <MinValue> <MaxValue> | This requires that the nominal period meet the specified minimum and maximum values in order for an SSC to be included as part of the satellite collection. The <MinValue> and <MaxValue> are in Connect units. Both <MinValue> and <MaxValue> must be nonnegative and less than 100,000 minutes. |
| Inclination <MinValue> <MaxValue> | This requires that the nominal inclination meet the specified minimum and maximum values in order for an SSC to be included as part of the satellite collection. The <MinValue> and <MaxValue> are in Connect units. Both <MinValue> and <MaxValue> must be nonnegative and not greater than 180 degrees. |
| AgiServer | This sets the method for retrieving GP data for each SSC to be the AGI Online TLE server. |
| DefaultSatDb | This sets the method for retrieving GP data for each SSC to be the default satellite database file, as defined by the scenario properties. |
| SourceFile <"filename"> | This sets the file used for retrieving GP data for each SSC. |
| SwitchMethod [Epoch | MidPoint | TCA] | This sets the method for switching between different GP element sets if more than one element set is available for an SSC. |
| RetrieveMethod [First | All] | This sets the method for utilizing GP element sets provided by the GP data source. |
| TimeStep <value> | This sets the time step in seconds to use when propagating GP data. By default, when you do not use this option, STK automatically chooses the time step to be appropriate for the period of the orbit. |
| OutOfDateDuration <value> | STK uses this duration as the maximum age (SSC epoch relative to the analysis interval) of GP element sets provided by the GP data source; if older, STK excludes them. Provide the <value> in days or set the value to "Off", which turns this feature off [actually, sets the value at 100 years]. When off, no GP element set will be considered out of date regardless of how far its epoch is from the analysis interval. |
| NameStyle {SSCNumber | CommonName | CommonNameSSCNumber | SSCNumberCommonName | PrefixSSCNumber <prefix> | SSCNumberSuffix <suffix>} | This sets the naming convention for satellite collection entries. When you choose CommonName, STK may append an integer to the name so that the name of each satellite collection entry remains unique. The default is CommonNameSSCNumber. |
Custom
The following table provides descriptions of the applicable parameters for the Custom method:
| Optional Parameters | Description |
|---|---|
| File <"filename"> | This sets the file name of the Orbit Definition file that defines the members of the satellite collection. |
| Propagator <Propagator Name> | If TrajectorySource is OrbitElements [TwoBody, J2Perturbation, J4Perturbation], it defaults to the prior value. If new, it defaults to J2Perturbation. |
| Epoch <epoch> | This is the default epoch of the initial conditions for orbit definition files of type OrbitElements. You can specify <epoch> as either an explicit date in Connect units or as a Time Instant time component. |
| EphemerisDirectory <"Directory"> | If TrajectorySource is Ephemeris, it defaults to the prior value. If new, it defaults to the scenario directory. |
| EphemerisSubDirectory <"SubDirectory"> | Sets the ephemeris directory as the specified subdirectory relative to the scenario directory. |
| AgiServer | If TrajectorySource is SSC, this sets the method for retrieving GP data for each SSC to be the AGI Online TLE server. |
| DefaultSatDb | If TrajectorySource is SSC, this sets the method for retrieving GP data for each SSC to be the default satellite database file, as defined by the scenario properties. |
| SourceFile <"filename"> | If TrajectorySource is SSC, this sets the file used for retrieving GP data for each SSC. |
| SwitchMethod [Epoch | MidPoint | TCA] | If TrajectorySource is SSC, this sets the method for switching between different GP element sets if more than one element set is available for an SSC. |
| RetrieveMethod [First | All] | If TrajectorySource is SSC, this sets the method for utilizing GP element sets provided by the GP data source. |
| TimeStep <value> | If TrajectorySource is SSC, this sets the time step in seconds to use when propagating GP data. By default, when you do not use this option, STK automatically chooses the time step to be appropriate for the period of the orbit. |
| Propagate <option> | If TrajectorySource is SSC, you can specify the name of the SGP4 implementation for propagating TLEs. Valid options are SGP4 (STK internal version), Default (SGP4 version specified in SGP4 default), or the name of an externally registered version of SGP4. |
| OutOfDateDuration <value> | If TrajectorySource is SSC, STK uses this duration as the maximum age (SSC epoch relative to the analysis interval) of GP element sets provided by the GP data source; if older, STK excludes them. Provide the <value> in days or set the value to "Off", which turns this feature off [actually, sets the value at 100 years]. When off, no GP element set will be considered out of date regardless of how far its epoch is from the analysis interval. |
| NameStyle {SSCNumber | CommonName | CommonNameSSCNumber | SSCNumberCommonName | PrefixSSCNumber <prefix> | SSCNumberSuffix <suffix>} | If TrajectorySource is SSC, this sets the naming style for satellite collection entries. When you choose CommonName, STK may append an integer to the name so that the name of each satellite collection entry remains unique. |
SP3
The following table provides descriptions of the applicable parameters for the SP3 method:
| Optional Parameters | Description |
|---|---|
| Extrapolate {Yes | No} | If you enter Yes, STK will calculate an additional ephemeris step beyond the last data point provided by the SP3 file(s) assigned to the satellite. In place of Yes/No, you can also use On/Off or True/False. |
| InterpAcrossBoundaries {Yes | No} | If you enter Yes, STK allows interpolation samples to span different SP3 files; if No, then STK restricts interpolation samples to be in the same SP3 file as the requested time. In place of Yes/No, you can also use On/Off or True/False. |
| InterpMethod {Lagrange | Hermitian} | Enter the interpolation method. The default value is Lagrange.
InterpMethod Hermitian is only valid if all files are configured to use it, i.e., they all have velocity natively in the file. |
| InterpOrder <value> | Enter a value representing the interpolation order. The value must be an integer between 1 and 13. |
| EphemerisDirectory <"Directory"> | If TrajectorySource is Ephemeris, it defaults to the prior value. If new, it defaults to the scenario directory. |
| EphemerisSubDirectory <"SubDirectory"> | Sets the ephemeris directory as the specified subdirectory relative to the scenario directory. |
| NameStyle {SysIDSatID | PrefixSysIDSatID {prefix} | SysIDSatIDSuffix {suffix} | SatID | PrefixSatID {prefix} | SatIDSuffix {suffix}} | Sets the convention for assigning names to satellite entries. When you choose SatID or PrefixSatID or SatIDSuffix, STK may append an integer to the name so that the name of each satellite collection entry remains unique. |
Examples
Define a Satellite Collection object using Walker.
Collection */SatelliteCollection/SatCon1 Define Walker Propagator "J2Perturbation" ClearShells AddShell "1" Type Delta NumPlanes 10 NumSatsPerPlane 10 InterPlanePhaseIncrement 1 Epoch "28 May 2020 16:00:00.000" Semimajoraxis 18000000 Eccentricity 0.001 Inclination 68.0 RAAN 22.0 ArgumentOfPerigee 123.4 MeanAnomaly 45.8
Collection */SatelliteCollection/SatCon1 Define Walker AddShell "2" Type Star NumPlanes 30 NumSatsPerPlane 30 InterPlanePhaseIncrement 1 Epoch "28 May 2020 16:00:00.000" Semimajoraxis 9000000 Eccentricity 0.001 Inclination 88.0 RAAN 222.0 ArgumentOfPerigee 23.4 MeanAnomaly 145.8
Collection */SatelliteCollection/SatCon1 Define Walker ClearShells
Collection */SatelliteCollection/SatCon1 Define Walker ModifyShell "1" Semimajoraxis 18000000
Examples
Define the SatDB for a Satellite Collection object.
Collection */SatelliteCollection/SatCon1 Define SatDB DefaultSatDb Status Active
Collection */SatelliteCollection/SatCon1 Define SatDB DefaultSatDb Inclination 80.0 100.0
Examples
Define a Collection with a Custom File.
Collection */SatelliteCollection/SatCon1 Define Custom Propagator "J2Perturbation" File "C:\Users\user\Documents\STK 12\LargeConstellation\CustomSatConTest.csv"
Examples
Define a Collection with SP3 files.
Collection */SatelliteCollection/SatCon1 Define SP3 Extrapolate Yes InterpAcrossBoundaries No InterpOrder 3 EphemerisDirectory "C:\Users\user\Documents\STK 12\LargeConstellation\SatConSP3Files" NameStyle SysIDSatID
Group membership
This command belongs to the following group(s):
Version
12.4