InitialState

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

Syntax

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

Description

• Import

The initial state may be obtained 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 any mass, drag, or solar radiation parameters contained as part of the initial state message will be loaded into the vehicle as well, replacing any existing values. If the Source is CCSDS_OPM and that message contains position-velocity covariance, then it too will be loaded into the vehicle replacing any current values. Note that the other HPOP Force Model settings will be preserved.

• Export

One or more initial states may be exported 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 the vehicle's mass, drag, and solar radiation parameters will be output in the file as part of the initial state message. Similarly, if the HPOP vehicle contains covariance, it will be output as part of the CCSDS_OPM message.

The format used will depend on the whether Import or Export is specified. 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

A Satellite must be using one of the following propagators: TwoBody, J2Perturbation, J4Perturbation, HPOP, LOP or Astrogator. If the Satellite has not been propagated then the propagator will be set to TwoBody.

When the satellite is a TwoBody satellite, the spacecraft parameters for mass, drag (Cd and area-to-mass ratio), and SRP (Cr and area-to-mass ratio) and the position-velocity covariance as read from the Initial State file are used. When Interpolate is used for for epoch selection, the parameters are obtained as if ClosestPoint was chosen while the initial state is found through interpolation.

A Missile must be using the TwoBody or HPOP propagator. If the Missile has not been propagated then the propagator will be set to TwoBody.

The ephemeris step size for the Satellite or Missile will be set to 60.0 seconds, unless the propagator is LOP, in which case the step size will be set to 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. This format should no longer be used but is included for backward compatibility.

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

Export Options

If you are exporting an initial state file, 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