Advanced Options

Advanced properties allow you to adjust the manner in which access information is stored and computed. These properties can be used for large coverage problems where access computations are time-consuming and much memory would be needed to store access data.

Advanced coverage definition features

Field	Value
Automatically Recompute Accesses	If checked, STK automatically recomputes accesses every time an object on which the coverage definition depends (such as an asset) is updated.
Save Mode	Choices are: Don't save accesses - Access computations are not saved with the coverage definition. Don't save, compute access on load - Access computations are not saved with the coverage definition but are recalculated each time the coverage definition is opened in STK. Save accesses - Access computations are saved with the coverage definition. Saving Figure of Merit static values follows this setting on the Coverage Definition. Selecting “Save accesses” can therefore result in much faster subsequent loading of the scenario for cases where the static value of the Figure of Merit requires significant computation.
Use Light Time Delay	Enables light time delay. The default is not checked, or "off". Setting this option will significantly increase the time it takes to compute access. Its effect is to iteratively determine the accurate location of the transmitting and receiving objects in inertial space to properly model the signal path during the coverage access computations.
Regional Acceleration	Choices are: Automatic - Visibility intervals (using of line of sight) are first computed to the regions (interpreted as area targets) bounding the coverage grid points. Grid point visibility is then only computed over intervals when the bounding region enclosing the grid point is visible. This option can improve performance for many cases where visibility periods are short relative to the analysis interval (such as in LEO satellite applications). Regional acceleration is disabled (even if set to Automatic) for Latitude and Longitude Line grids. Line-of-sight accesses from an asset to the regions are modeled using access to an AreaTarget. The AreaTarget has been configured with an appropriate elevation angle constraint, whose value is obtained using the constraint settings of the grid instance. Off - Does not compute visibility to regions before computing visibility to the grid points themselves. Use this option if the coverage regions are very narrow.
Access Options...	Click to specify event detection and step size control parameters.
Data Retention	Choices are: All Data - Retains start and stop times for all accesses in virtual memory. Static Only - As access is computed for each point, STK also computes the static value for each figure of merit. Raw access data is then deleted to minimize memory usage.
Number of Assets	The condition on the number of assets covering a grid point that must be satisfied for a valid access. The number of assets can be At Least N or Exactly N (Equal to N), where N is greater than or equal to 1.

If the Data Retention option is set to Static Only and the Save Mode is set to Save Accesses, STK saves accesses to disk as they are being calculated, then deletes them from memory after calculations are complete. This means that the access data is saved to the hard disk but is not available in memory.

Time-dependent reports and graphs are not available if the Static Only option is selected in the Data Retention field.

The amount of data saved to disk can be quite large (approximately 20 bytes per access). A global coverage grid at 2 degrees of resolution with a constellation of 48 LEO satellites as assets provided slightly over one gigabyte of data for a 2-week analysis period.

If Data Retention is set to Static Only, figures of merit added to the coverage definition after accesses have been computed will not have defined values. In addition, changes to existing figures of merit or to the activation status of assigned assets will not be reflected in the reported values. You can use the Reload Accesses tool for the CoverageDefinition object to overcome these problems if the Save Mode is set to Save accesses.