Setting Up Advanced CAT
The Main page under Advanced CAT Basic properties contains fields for defining various general parameters and selecting and defining analysis objects.
General Parameters
At the top of the Main page of Advanced CAT Basic properties, you can set a Time Period, define a Threshold, select one or both of two additional options, and launch the close approach computation process.
Basic Advanced CAT Parameters
| Parameter | Description |
|---|---|
| Time Period | Enter a time Interval or Start and Stop times to define the time frame for the close approach analysis. This is the time period for which the primary and secondary objects selected for the analysis will be propagated when you compute close approaches. For more information on the options available for intervals and start and stop times, see Time Options. |
| Threshold | Enter the desired Threshold in the selected distance unit. A warning is given whenever the distance between the threat volumes of the primary and secondary objects falls below the threshold. The Threshold must fall within a range of 0 km to 1000 km; otherwise an error message will appear. |
| Use Range Measure | STK performs the close approach computation using range between objects as the criterion rather than the ellipsoid separation. |
| Display acknowledgement when done | Select this option to have a message box appear when close approach computation is completed. |
| Compute |
Click this button to launch the close approach computation process. If you do not choose an item from the secondary list before clicking Compute, the close approach computations will not be performed. However, the ephemerides for each object in the primary list will be created, and hence each object’s ellipsoid can be made to display in the 3D Graphics window. |
Selecting and Defining Analysis Objects
Most of the Main page is comprised of two lists: a Primary List and a Secondary List. The selection of analysis objects consists principally of moving satellite objects and TLE sets back and forth between the left (Available) and right (Chosen) columns of each of these lists.
Display of Primary and Secondary Objects
Primary objects are the satellites of interest to you, such as those that you own or wishes to use. Secondary objects are those that present a potential risk of collision with, or unacceptably close approach to, your primary objects. The Primary and Secondary List panes display the following information for each analysis object:
Analysis object attributes
| Field | Description |
|---|---|
| Name | The name of a satellite object or group or external file. |
| Class | Select one of the following dimension definition types:
AdvCAT checks to make sure that an object that uses covariance data to determine its threat volume ellipsoid has such data over the entire analysis interval. If the object does not, then that object is removed from consideration in the analysis. |
| Tangential | The dimension of the threat volume ellipsoid along the X axis, i.e., parallel to the object's velocity vector. Used only for the Fixed Dimension Definition Type. |
| Cross Track | The dimension of the threat volume ellipsoid along the Y axis, i.e., parallel to the orbit normal vector, or the cross product of the radius and velocity vectors. Used only for the Fixed Dimension Definition Type. |
| Normal | The dimension of the threat volume ellipsoid along the Z axis, i.e., parallel to the cross product of the X and Y axes. Used only for the Fixed Dimension Definition Type. |
| Type | The type of the object or group. Types include:
|
| HardBodyRadius | Displays the Hard Body Radius value for each object in the Primary and Secondary lists. |
| NumberID | Allows you to assign a number, which appears in reports, to each object in the Primary and Secondary lists. |
| StringID | Allows you to assign a character string definition, which appears in reports, to each object in the Primary and Secondary lists. |
To edit the Tangential, Cross Track, and/or Normal dimensions of an object's threat volume (with Fixed selected as the Class), enter the desired values directly in the grid. The default values for these fields define an ellipsoid with a tangential dimension of 20 km, a cross track dimension of 10 km, and a normal dimension of 5 km. You can set new defaults for the current Advanced CAT object using the text boxes provided below each list.
Selection of New Analysis Objects
The available objects columns list available satellites and external files by type, date, and name. This group includes any satellites objects and any external files that Advanced CAT finds by searching, in order:
- the current scenario
- your STK scenario directory,
- the tce subdirectory of your user directory (this is the path of the SGP4 registry entry)
- C:\ProgramData\AGI\STK <version no.>\Databases\Satellite
- <GENDB>\Satellite (where GENDB is the path of the STKGENDB registry entry)
To select an object in the Primary or Secondary list, highlight it in the Available column and move it to the Chosen column by clicking the appropriate right arrow. To de-select an object, highlight it in the Chosen column and double-click it or use the appropriate left arrow.
Advanced CAT does not add any objects to the scenario. It merely propagates ephemerides for the primary and secondary objects that you select from those available, for the specified time frame.
STK will not repeat the propagation of a satellite object over the analysis interval; only its current ephemeris interval will be used in the analysis.