InitialState

The InitialState Connect command enables you to import or export initial state data (i.e., epoch, position, and velocity) for satellites and missiles.

Syntax

InitialState <ObjectPath> {Import | Export} {Source} ["<FilePath>"] [{Options}]

Description

• Import

You can obtain the initial state from a vehicle's ephemeris (when Source is STKEphem), from an STK file (when Source is STKFile), or from one of several types of initial state files (when Source is one of the other valid values). See the Initial State Tool in the STK Desktop Help. If the vehicle uses the HPOP propagator, then STK will load any mass, drag, or solar radiation parameters contained as part of the initial state message into the vehicle as well, replacing any existing values. If the Source is CCSDS_OPM and that message contains position-velocity covariance, then STK will load it also into the vehicle, replacing any current values. STK will preserve the other HPOP Force Model settings.

• Export

You can export one or more initial states into an external file, formatted per the Source setting as specified by the corresponding authoritative organization. [These are not AGI-designed formats.] When the vehicle uses the HPOP or LOP propagator and the Source is EPV or CCSDS_OPM, then STK will include the vehicle's mass, drag, and solar radiation parameters in the file as part of the initial state message. Similarly, if the HPOP vehicle contains covariance, STK will include it as part of the CCSDS_OPM message.

The format used will depend on the whether you choose Import or Export. Formats are outlined below.

Generic Parameters

Valid values for {Source} are described in the table below.

The <FilePath> parameter includes the full path and name of the file to be imported or exported.

Import Options

For a satellite, you must use one of the following propagators: TwoBody, J2Perturbation, J4Perturbation, HPOP, LOP, or Astrogator. If you have not propagated the satellite, then STK will set the propagator to TwoBody.

When you use the TwoBody propagator for a satellite, STK uses the spacecraft parameters for mass, drag (Cd and area-to-mass ratio), and SRP (Cr and area-to-mass ratio) as well as the position-velocity covariance as read from the Initial State file. When you use Interpolate for epoch selection, STK obtains the parameters as if you chose ClosestPoint and determines the initial state through interpolation.

You must use the TwoBody or HPOP propagator for a missile. If you have not yet propagated the missile, then STK will set the propagator to TwoBody.

STK will set the ephemeris step size for the satellite or missile to 60.0 seconds, unless the propagator is LOP, in which case STK will use a step size of 1 day.

HPOP must propagate from the orbit epoch to the start time, so use caution when selecting a satellite or ephemeris file (i.e., check the epoch time in the file).

The following table describes the Import {Options}.

Import Deprecated Format

The format for the InitialState Import options was changed in STK 9. The following describes the format in previous versions of STK. You should avoid using this format; it appears here only for backward compatibility.

InitialState <ObjectPath> Import {Source} "<FilePath>" [{EpochSelect} "<TgtEpoch>" <InterpOrder>]

Export Options

If you are exporting an initial state file, the valid command format is:

InitialState <ObjectPath> Export {Source} "<FilePath>" {CrdnSystem} [{ExportOption} <Value> [{ExportOption} <Value>...]]

If you are exporting an initial state file, valid values for {CrdnSystem} will depend on the {Source} specified.

If {Source} is IIRV, valid {ExportOption} <Value> combinations are:

If {Source} is IIRV1, valid {ExportOption} <Value> combinations are:

If {Source} is IIRV9, valid {ExportOption} <Value> combinations are:

If {Source} is EPV, valid {ExportOption} <Value> combinations are:

If {Source} is NASAIIRV, valid {ExportOption} <Value> combinations are:

If {Source} is CCSDS_OPM, valid {ExportOption} <Value> combinations are:

Examples

Propagate Satellite2 using an external EPV file:

To propagate Satellite2 using the iirvIPC3.iirv file:

Propagate TestSat2 using the last ephemeris point from the file Satellite1.e:

The following series of commands will create a satellite with Astrogator propagator and set the Initial State for the satellite:

Use the closest data point, in the file Satellite1.e, following the Epoch to set the initial state:

Use the closest data point to the Epoch, from the ephemeris of TestSat1, to set the initial state:

Examples

Create an IIRV T9 file from Satellite SunSync, with an SRP of 1.234 and a defined start and stop time:

Create an IIRV file from Satellite Sat1, setting various parameters:

Create an IIRV T1 file from Missile Missile1:

Export an initial state file in NASA IIRV format, the following file will be created, ephmTc12009143:

Export an initial state file in EPV format:

Return message

Group membership

This command belongs to the following group(s):

Vehicles

Version

12.1