The Additional tab of the HPOP Force Model Properties window includes a miscellany of optional properties that you can enable or define for use in an HPOP trajectory calculation.
Central Body Radiation Pressure
| Option | Description |
|---|---|
| Include Albedo | Determines whether albedo effects (i.e., radiation pressure caused by sunlight reflected off the lit part of the central body) will be considered. |
| Include Thermal | Determines whether thermal radiation pressure effects (i.e., radiation pressure caused by blackbody heat radiation of the central body) will be considered. |
| Ck | Coefficient of radiation pressure reflectivity of the satellite. A value of 1 indicates full absorption; a value of 2 indicates full reflection. |
| Area to Mass Ratio | The area exposed to radiation pressure (nominally along the radial direction) divided by the mass. |
| Ground Reflection Model File | File containing parameters defining a ground reflection model that defines albedo and emissivity properties of the central body surface. |
Satellite Options
| Option | Description |
|---|---|
| Include Relativistic Accelerations | Select this option to model the effects of general relativity in accordance with IERS Technical Note 32, IERS Conventions (2003). |
| Satellite Mass |
Enter a value for mass, in the desired units, to be used in atmospheric drag and solar radiation pressure calculations when using a non-spherical model, such as a GPS specific solar radiation pressure model or a custom plugin. When the spherical model is specified for drag and solar pressure, the associated area to mass ratios specified on the Force Model page are retained and the mass specified here is only used to determine the compatible area. When the HPOP propagator is selected, the value entered in this field overrides any value for mass entered on the satellite Mass page. |
Propagator Plugin
The Propagator Plugin option is unavailable if you are defining a force model vector.
A single force model plugin point is provided for the customization of the accelerations used in the propagation of the satellite trajectory. Typical uses of the force model plugin are to implement satellite specific solar pressure, drag and lift models.
Plugins can be written in Perl, VB script, C++, etc.
Using the Plugin Force Model
A plugin must be registered. Register the script by opening the Command Prompt window, navigate to the folder where the plugin is stored and enter
regsvr32 <plugin name>. For example, if the plugin is named
SatXXXBoxWingPlugin.wsc, enter:
regsvr32 SatXXXBoxWingPlugin.wsc
The plugin interface offers the following options:
| Option | Description |
|---|---|
| Use | Select to use the Plugin model. |
| Plugin Name | Enter the complete plugin name, e.g.
SatXXXBoxWingPlugin.wsc.
|
| Plugin Settings | Click to open the HPOP Plugin Settings window and set parameters for the selected plugin. |
For detailed help on the HPOP force model plugin, navigate to Library Reference -> STK Plugins -> STK Engine Plugins -> AGI AgAsHpopPlugin 11 in the STK Programming Interface Help.
Regsvr32.exe requires administrator rights in order to register a plugin. Once registered, it's available to all users on that machine (provided that the actual file location on the disk does not change).
It's sometimes difficult to find a system administrator to register the plugin though. In this case we have provided a VBScript utility "register_wsc_hkcu.vbs" located in your install under <STK install folder>\CodeSamples\Extend (where <STK install folder> is typically C:\Program Files\AGI\ODTK <version number> ).
The utility will register a Windows Script Component to the HKEY_CURRENT_USER area of the Windows registry rather than HKEY_LOCAL_MACHINE. To run the utility, open up a command prompt and change directories to the location of the utility. Then enter
cscript register_wsc_hkcu.vbs "Your WSC Name.wsc"
replacing "Your WSC Name.wsc" with the actual full path to the location of your Windows Script Component (WSC) file. The utility will parse your WSC file and make the appropriate entries into the Windows registry. This utility must be run for each user on the machine if they want to use that plugin.