Advanced CAT Filters | Log File | Ellipsoid Databases | Ellipsoid Scaling | Cross Reference Databases | Other Data Files | Sample Step Options| Additional Options
The Advanced Page allows you to select one or more pre-filters to be used to speed up the close approach processing and to define a pad for each filter selected. The use of the Out of Date TLE, Apogee/Perigee, Orbit Path and Time Pre-Filters, as well as filter Pads, is similar to the use of these devices in the Close Approach Tool.
Keeping a log file allows you to understand how filtering is affecting your computations. Information regarding how filters are affecting previously selected secondaries (i.e., a list of secondaries removed by each filter) is written to a log file as computations progress. To use this option, check the Use log file option and enter a path and file name in the File name field or click the ellipsis (...) button to browse for a file.
The Ellipsoid Databases frame enables you specify which database file to use for each of the dimension definition types that requires use of a database. The following databases are available:
| Dimension Definition Type | Applicable Database |
|---|---|
| Fixed | Does not use database. |
| Orbit Class | Fixed Orbit Class Database |
| Quadratic | Quadratic in Time Database |
| Quadratic Orbit Class | Quad / Orbit Class Database |
This option allows you to enter a scaling factor comprising any real number equal to or greater than zero, which is applied to the dimensions entered by the user, if the Fixed definition type is being used, or to those supplied by the selected database. In the case of the two quadratic databases, the scaling factor is applied to the calculated dimensions, not to the coefficients used in deriving them.
The ellipsoid scaling factor applies only when determining close approach event times, when determining the minimum separation between ellipsoids. The computation of uncertainties and probabilities do not incorporate the ellipsoid scaling factor—the 1-sigma values are obtained from the ellipsoid size as configured for each object without any scaling being applied.
This feature allows a cross-reference lookup of a TLE SSC number to retrieve the common name of the corresponding satellite. For example, if the SSC number of the satellite is 16609, the cross-reference feature gives you the common name 'Mir'. To use this option, check the Use Cross Reference Database option and enter a path and file name in the Database field or click the ellipsis (...) button to browse for a database.
This option allows you to load a text file in which a primary object and a list of related secondary objects are outlined. When a related objects file is loaded and the 'Ignore events involving related objects' option is active, the secondary objects listed in the file are excluded from consideration when determining close approach events with the specified primary object.
As illustrated in the sample file, a Related Objects (*.rel) file consists of one or more blocks of the form:
BEGIN RelationGroup
Member ...
...
END RelationGroup
BEGIN RelationObject
Name ...
RelatedObj ...
...
END RelationObject
where Member is the ssc number or file identifier of a member of the group, Name is the file name (e.g., an *.e or *.sa file) of the primary object, and RelatedObj is a related SSC number or file that should be ignored by Advanced CAT processing.
Note: The primary object in a RelationObject must be listed first or all secondary objects listed above it will be ignored.
This option allows you to load a text file containing hard body radius sizes for individual SSC numbers used to represent the size of the object when determining the likelihood of potential collisions. As illustrated in the sample file, a Hard Body Radius file (*.rad) consists of a series of lines, each containing two numbers: the SSC number of the spacecraft, followed by its HardBodyRadius in meters.
Note: Specification of hard body radius values only applies to primary and secondary objects which are specified as entries in a TLE or TCE file.
Starting with STK7, AdvCAT uses a sampling algorithm that is based on how much the relative position vector is allowed to rotate between samples, subject to maximum and minimum step sizes, while using at least 10 samples. You specify the minimum and maximum sample step sizes using the Max Sample Step and Min Sample Step fields. The resulting sampling uses much fewer samples but achieves the same accuracy. In addition, the tolerances associated with event detection have been tightened.
If Use Range Measured is set on the AdvCat Basic Main properties page, range is used as the measure for determining event start and stop times. (The filtering process does not include either object's threat volume sizes as part of the threshold used by the filters.) Using the Range measure results in the same computations as if the ellipsoid sizes for all objects were 0.0 (that is, points not volumes). Because the ellipsoid size is not being used during filtering when using the Range measure, you may want to examine the selection of the filter pad values to determine whether they need to be increased to achieve the same accuracy as previous versions of STK.
The following options appear at the bottom of the Advanced page of Advanced CAT Basic properties:
Note: In previous versions of Advanced CAT, satellite ephemeris was always regenerated. The ephemeris file (if any) was ignored. Beginning with STK version 5.0.4, Advanced CAT loads the ephemeris for satellites from the *.sa file and uses it in the computations (i.e. does not regenerate it). The Force Repropagation on Load option can be used to recover the previous behavior.