Propagator Functions

The components within Propagator Functions are used to define propagation models.

Syntax

ComponentBrowser */ SetValue "Propagator Functions" {Component} {Attribute} <Value> [{Unit}]

ComponentBrowser */ Duplicate "Propagator Functions" {Component} <Duplicate Component Name>

Description

These components can be embedded into custom propagator components to define their characteristics. In addition, all of them can be duplicated and used in creating new models.

Components

The Propagator Functions components are:

Atmospheric Models

Component	Description
CIRA 72	Drag with Cira 72 Atmospheric Density Model. Empirical model of atmospheric temperature and densities as recommended by the Committee on Space Research (COSPAR). Similar to the Jacchia 1971 model but uses numeric integration rather than interpolating polynomials for some quantities.
Exponential	Drag with Exponential Atmospheric Density Model. This model uses the following equation to calculate atmospheric density: where = density at a specified altitude, h = specified altitude, = reference density, h0 = reference altitude, and H = scale altitude.
Exponential - Earth	Drag with Earth Exponential Atmospheric Density Model
Exponential - Jupiter	Drag with Jupiter Exponential Atmospheric Density Model
Exponential - Mars	Drag with Mars Exponential Atmospheric Density Model
Exponential - Venus	Drag with Venus Exponential Atmospheric Density Model
Harris-Priester	Drag with Harris-Priester Atmospheric Density Model. Takes into account a 10.7 cm solar flux level and diurnal bulge. Uses density tables. Valid range of 0-1000 km.
Jacchia-Roberts	Drag with Jacchia-Roberts Atmospheric Density Model. Similar to Jacchia 1971 but uses analytical methods to improve performance.
Jacchia 1960	Drag with Jacchia 1960 Atmospheric Density Model. An outdated atmospheric model provided for making comparisons with other software.
Jacchia 1970	Drag with Jacchia 1970 Atmospheric Density Model. Computes atmospheric density based on the composition of the atmosphere, which depends on altitude as well as seasonal variation. Valid range is 100-2500 km.
Jacchia 1971	Drag with Jacchia 1971 Atmospheric Density Model. Similar to Jacchia 1970, with improved treatment of certain solar effects.
MSISE 1990	Drag with MSISE 1990 Atmospheric Density Model. Empirical density model developed by Hedin based on satellite data. Finds the total density by accounting for the contribution of N2, O, O2, He, Ar and H. 1990 version, valid range of 0-1000 km.
MSIS 1986	Drag with MSIS 1986 Atmospheric Density Model. Empirical density model developed by Hedin based on satellite data. Finds the total density by accounting for the contribution of N2, O, O2, He, Ar and H. 1986 version, valid range of 90-1000 km.
NRLMSISE 2000	Drag with NRLMSISE 2000 Atmospheric Density Model. Empirical density model developed by the US Naval Research Laboratory based on satellite data. Finds the total density by accounting for the contribution of N, N2, O, O2, He, Ar and H. Includes anomalous oxygen. 2000 version, valid range of 0-1000 km. This implementation always calls the gtd7d routine (in contrast to switching between it and gtd7) per the recommendation of Mike Picone, one of the code authors.
US Standard Atmosphere	Drag with US 1976 Standard Atmospheric Density Model. Standard model with no user-specified parameters.

The MSIS models are available at http://modelweb.gsfc.nasa.gov/atmos/.

Gravity Models

Plugins

SRP Models

Third Bodies

This folder contains third body functions for each of the central bodies and for the Earth, Jupiter, Saturn, Neptune, Uranus, and Pluto planetary systems. In addition, if you create a central body, a third body function for it will automatically be created in this folder.

• Ariel
• Callisto
• Ceres
• Charon
• Deimos
• Earth
• Earth-Moon System
• Enceladus
• Europa
• Ganymede
• Hyperion
• Papetus
• Io
• Jupiter
• Jupiter System
• Mars
• Mercury
• Mimas
• Moon
• Neptune
• Neptune System
• Phobos
• Phoebe
• Pluto
• Pluto System
• Rhea
• Saturn
• Saturn System
• Sun
• Tethys
• Titan
• Titania
• Triton
• Uranus
• Uranus System
• Venus

Attributes

The attributes for each component are listed individually below.

Radiation Pressure

Atmospheric Models

For more details on the Atmospheric Models parameters, see the Astrogator GUI help.

Jacchia-Roberts, Jacchia 1970, Jacchia 1971, Cira 72, and MSIS

HarrisPriester

Jacchia 1960

US Standard

Exponential

Gravity Models

For more details on the Gravity Models parameters, see the Astrogator GUI help.

Gravitational Force

TwoBody Force

Note: the MuSource attribute has been deprecated in STK 9 and replaced with GravSource.

Plugins

SRP Models

For more details on the SRP Models parameters, see the Astrogator GUI help.

All SRP Models

Additional Spherical SRP Model Attributes

Third Bodies

The Third Body models are comprised of a set of parameters that is determined by the selected mode.

Note: the MuSource attribute has been deprecated in STK 9 and replaced with GravSource.

Examples

Duplicating a Propagator Functions component

ComponentBrowser */ Duplicate "Propagator Functions" "TwoBody Force" "My TwoBody Force"

Setting the Use Approximate Altitude control for a custom Harris-Priester component

ComponentBrowser */ SetValue "Propagator Functions" "My Harris-Priester" UseApproximateAltitude false

Selecting the shadow model for a custom Spherical SRP component

ComponentBrowser */ SetValue "Propagator Functions" "My Spherical SRP" ShadowModel "No Shadow"

Selecting a ground reflection model for a custom Radiation Pressure component

ComponentBrowser */ SetValue "Propagator Functions" "My Radiation Pressure" GroundReflectionModelFile STKData\CentralBodies\Earth\modelfile.txt

Defining the degree for the gravity field of a custom Third Body component

ComponentBrowser */ SetValue "Propagator Functions" "My Europa" GravityField.Degree 2

STK Programming Interface 11.0.1