Part 4: Compute Access

Compute Access

Calculating object-to-object visibility in STK is called Access (). An access is defined FROM one object TO another object. STK calculates the times that an object can access, or "see," another object based on their properties and constraints.

The Access tool provides quick links to reports, graphs, and Timeline View.

Compute Access for a sensor on a Ground Site

Watch the following video, then follow the steps below incorporating the systems and missions you work on (sample inputs provided).

  1. Compute Access from a ground site's sensor to a vehicle (any type: , , ).Closed
    1. Click the Access tool icon () or extend the Analysis menu and select Access.
    2. On the Access page, click the Select Object... button and select the sensor () on the ground site as the Access For object (From).
    3. Select a vehicle object (, , ) as the To object.
    4. Click the Compute button.
  2. Generate an Access () report.Closed
    1. In the Reports section, click Access...
    2. Click the Save as Quick Report () button to save the report as a Quick Report.
      1. Click the down arrow on the Quick Report Manager () to see the report has been added to the list.
    3. In the report, right-click on an Access Start Time and extend the Start Time menu to select the Set Animation Time option.

      4. If your report says "No Access Found," modify the vehicle's properties so that the vehicle flies through the sensor field-of-view.

    4. Bring the 3D Graphics window to the front and look for the access lines between the objects.
    5. Click the Access tab at the bottom of the Integrated Workspace to bring the Access Tool to the front.
    6. In the Reports section, click the AER... button to create an AER report.
  3. Create a New Stored View ()Closed
    1. Click the Stored Views () button on the 3D Graphics toolbar.
    2. Click the New button to create a new Stored view.
    3. Double-click on the View Name "view0" and rename it (e.g. AccessView).
    4. Click OK.
  4. Add Access Intervals () to the Timeline ViewClosed.
    1. If your Timeline View is not open, extend the STK View menu and select Timeline View.
    2. In the Timeline View toolbar, select Add Time Components ().
    3. Select the access () object on the left.
    4. Select AccessIntervals in the Components for section on the right.
    5. Click OK to add the Access Intervals to the Timeline View and dismiss the Add Time Components tool.
  5. Animate () the scenario and watch the acces Intervals start and end.
  6. Decrease the Max Range constraint and observe the effects of the constraint.Closed
    1. In the STK Object Browser, right-click on the ground site’s sensor () and select Properties.
    2. Select the Constraints - Basic page.
    3. Enter the desired Max range constraint value in the textbox (e.g. 500 km).
    4. Click OK to apply changes and dismiss the Properties Broswer.
    5. Refresh () the AER report to see the effects of the updated constraint.
    6. Notice any changes to the report and Timeline View after the constraint was applied.
    7. Close the Timeline view.

You can generate commonly used Access-specific reports directly from the Access tool without opening the Report & Graph Manager.

Light time delay and the directionality of the signal transmission are considered when computing the times one object can access another object. Moreover, the effects of refraction will be considered for objects specifying its use in access in their refraction settings.

If any of the access objects are changed, the access is automatically computed. But if you have an access report or graph open, it is not automatically regenerated. You will need to do that manually.

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