Using the AzEl Mask Tool

STK Pro, STK Premium (Air), STK Premium (Space), or STK Enterprise
You can obtain the necessary licenses for this training by contacting AGI Support at support@agi.com or 1-800-924-7244.

The results of the tutorial may vary depending on the user settings and data enabled (online operations, terrain server, dynamic Earth data, etc.). It is acceptable to have different results.

This lesson requires STK 12.0 or newer to complete it in its entirety.

Capabilities Covered

This lesson covers the following STK Capabilities:

  • STK Pro

Problem Statement

Engineers and operators need a quick way to determine if structures or vehicles affect visibility between sites, vehicles, or satellites. This gives insight about communications, imaging, radar, and general situational awareness. A ship is deploying a satellite tracking sensor. You need to determine how much of the sensor is blocked by the ship's superstructure.

Solution

Use STK and the AzEl Mask Tool to determine if the ship's superstructure interferes with the sensor's access times to the satellite.

What You Will Learn

Upon completion of this tutorial, you will understand the following:

  • The AzEl Mask Tool
  • The Sensor AzEl Mask Constraint
  • How to visualize the Sensor AzEl Mask Constraint in the 3D Graphics window

Video Guidance

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

Create a Scenario

  1. Click the Create a New Scenario button.
  2. Enter the following in the New Scenario Wizard:
    3. Option Value
    Name AzElMaskTool
    Location C:\Users\<username>\Documents\STK 12\
    Start 1 Jul 2020 16:00:00.000 UTCG
    End + 1 day

    Accept the default Start and End times if you are not completing the L3 quiz at the end of the tutorial.

  3. When you finish, click OK.
  4. When the scenario loads, click Save (). A folder with the same name as your scenario is created for you in the location specified above.
  5. Verify the scenario name and location and click Save.

    6. If you plan to complete the L3 quiz at the end of the tutorial, disable the Terrain Server.

  6. Right-click on the scenario () and open the Properties ().
  7. Select the Basic - Terrain page.
  8. Clear the Use terrain for analysis check box.
  9. Click  OK to apply changes and dismiss the Properties Browser.

Insert a Satellite

  1. Using the Insert STK Object Tool () insert a Satellite () object using the From Standard Object Database method.
  2. When the Search Standard Object Data window opens, enter Iridium 109 in the Name or ID: field.
  3. Click Search.
  4. In the Results: field, select IRIDIUM 109.
  5. Click Insert.
  6. When finished, close the Search Standard Object Data window.

Insert a Ship

  1. Using the Insert STK Objects tool (), insert a default Ship.
  2. Open the Ship's () properties ().
  3. Select the Basic - Route page.
  4. Change the Altitude Reference - Reference: to MSL.
  5. Set Route Calculation Method: to Specify Time.
  6. Click Insert Point and set the following:
    LatitudeLongitude
    31.0 deg-70.5 deg
  7. Click Insert Point. The Latitude and Longitude will be duplicated.
  8. Change point two's Time to 2 Jul 2020 16:00:00.000 UTCG.
  9. Click OK to accept the changes and close the Properties Browser.

Model a Sensor

  1. Using the Insert STK Objects tool (), attach a default sensor () to the Ship object.
  2. Bring the 3D Graphics window to the front.
  3. Zoom To the Ship () object.
  4. Open the sensor’s () Properties ().
  5. Select the Basic - Location page.
  6. Select Fixed at the Location Type.

    7. You can also select 3D Model as the Location Type and use the ship model's attach points or the sensor's 3D Graphics Vertex Offset properties to position the sensor.

    When you position the sensor origin, make certain that it is outside the shell of the model; otherwise the AzEl Mask tool will not work.

    For this exercise you will position the sensor origin on or slightly above the forward deck, close to the superstructure. You can check your settings by clicking Apply and viewing the 3D Graphics window.

  7. Set the X axis adjustment of 0.04 km.
  8. Set the Z axis adjustment of 0.01 km.

  9. Select the Basic - Definition page.
  10. Set the Sensor Type to Complex Conic.
  11. Set the Outer Half Angle to 180 deg.
  12. Click OK to accept those changes and close the Properties Browser.

Sensor to Satellite Access

Create an access from the sensor to the satellite without taking the ship's 3D graphics model into consideration.

  1. In the Object Browser, right click on the Sensor () object and select Access ().
  2. When the Access Tool opens, in the Associated Objects list, select IRIDIUM_109_41919 ().
  3. Click Compute.
  4. In the Reports section, click Access.
  5. Note the Total Duration time.
  6. Click Save as text ().
  7. When the Save Report window opens, ensure Save in: is using your scenario folder.
  8. Change File name: to Access_No_BodyMask.
  9. Click Save.
  10. When finished, close the access report and the Access Tool.

Create a BMSK File

Next you will use the AzEl Mask tool to create a BMSK file that can be used in access computations and visualization.

  1. Right-click the sensor () in the Object Browser.
  2. Select Sensor - AzEl Mask… A white window, possibly containing one or more black shapes, will appear, along with the AzElMask dialog. (If no black shape appears, it only means there is no obstruction in the direction being shown in the window.)

    3. For targeted sensors, it is important to show the sensor at a time at which it is targeted to an object. The sensor is not displayed when there are no targets in view.

  3. Select the ship as the Obscuring Object.
  4. Set the Window Dim field to 800, so that the entire window is shown and not extended off the screen and not obscured by other screen objects. This will allow for the most accurate mask with the finest possible detail.
  5. Click Apply to set the new window dimensions, and then click Compute to create the BMSK file.
  6. When the Select Body Mask File window opens, click Save.
  7. Close the AzEl Mask tool.
  8. Close the Az/El Mask View window.

Use the BMSK File to Constrain Access

Now you will configure the sensor to use the BMSK file as a limiting factor in visibility calculations.

  1. Open the sensor's () Properties ()
  2. Select the Basic - Sensor AzEl Mask page
  3. Set the Use option to MaskFile.
  4. Click the Mask File: ellipsis button ().
  5. Select the .bmsk file (e.g. Sensor1.bmsk).
  6. Click Open.
  7. Enable the Use Mask for Access Constraint option.
  8. Click Apply to accept the changes, and keep the Properties Browser open.
  9. Select to the Constraints - Basic page to see that the Sensor AzElMask has been enabled.

Visualize the Body Mask in 3D

Finally, create a 3D representation of the body mask and superimpose it on the view of the sensor cone.

  1. Select the 2D Graphics - Projection page.
  2. Enable the Use Constraints under Field of View.
  3. Select SensorAzElMask.
  4. Click Apply to accept the changes and keep the Properties Browser open.
  5. On the 3D Graphics - Projection page.
  6. Set Type to None.
  7. Enable Use Extension Distance as Maximum.
  8. Set the Space Projection to a small value (e.g., 35 m) to show only the mask immediately around the ship.
  9. Click OK to accept changes and close the Properties Browser.
  10. Check out the view in the 3D Graphics window. (You may need to click Reset () to refresh the sensor display.)

Create an Access Report

Create a new access report taking into account the affects of the body mask file.

  1. In the Object Browser, right click on the Sensor () object and select Access ().
  2. When the Access Tool opens, in the Associated Objects list, select IRIDIUM_109_41919 ().
  3. Click Compute.
  4. In the Reports section, click Access.
  5. Note the Total Duration time.
  6. Click Save as text ().
  7. When the Save Report window opens, ensure Save in: is using your scenario folder.
  8. Change File name: to Access_With_BodyMask.
  9. Click Save.
  10. When finished, close the access report and the Access Tool.
  11. Save () your scenario.

Summary

You modeled a ship deploying a sensor that tracks satellites. Using STK Pro, you:

  • Used a sensor object to create the field of view.
  • Propagated a single satellite.
  • Generated an access between the sensor and the satellite to create a benchmark access time.
  • Used the AzEl Mask tool to determine if the ship's superstructure blocked the sensor's field of view.
  • Generated another access report which determined that the substructure affects your overall access time.