Modeling Satellite Overflight Vulnerability using the Analysis Workbench

Information

 
QuestionHow can I model satellite overflight vulnerability for a naval transit using the Analysis Workbench?
Answer
This tutorial assumes the user has a basic understanding of STK capabilities or has completed the Level 1 - Beginner Training. The results of this tutorial may vary depending on the user inputs for the analysis period and the ship route. It is acceptable to have different results.  All pointing angles and gimbal limits are notional in this tutorial.

Task: Create a New Scenario
  1. Create a new scenario with an analysis period of at least 2 days.
  2. Insert two (2) Places (User-added image), San Diego, CA and Honolulu, HI, from the City Database (User-added image).
  3. Insert a ship (User-added image) using the Default Method.
  4. Using the 2D window (ensure the ship’s (User-added image) properties (User-added image) are open when you are clicking in the 2D window) or 3D window (3D object editing), click out a route from San Diego to Honolulu for your ship.
  5. Insert a Satellite (User-added image) using the Orbit Wizard (User-added image) Method.
    1. Select the Circular type from the dropdown (should be default)
    2. Set the Inclination to 98 degrees
    3. Set the Altitude to 600 km
    4. Accept all other defaults and click OK
  6. Verify that the satellite has visibility to the ship during its transit.

Create an Access Report

  1. Generate an access report from the satellite to the ship.
  2. Display the access times on the Timeline View (as of STK 11.1, the Access Tool now automatically adds the access time intervals to the Timeline View when ‘Auto Add to Timeline’ is enabled, so steps a. and b. below may not be necessary).
    1. Click on the Add Time Components button on the Timeline View.
  User-added image
      b. Select the access calc between the satellite and the ship on the left, and select Access Intervals on the right.  Click OK.
User-added image

Task: Create a Targeted Vector from a Satellite to a Ship
  1. Open the Analysis Workbench (User-added image).
    1. Extend the Analysis menu on the main menu bar and select Analysis Workbench.
  2. Use the Vector Geometry Tool (VGT) to create a displacement vector (User-added image) from the satellite to the ship:
    1. On the Vector Geometry tab,
      1. Select ‘Satellite1’ on the left
      2. Create a new Vector
      3. Type = Displacement
      4. Name = ‘FromSat_toShip’
      5. Origin Point = Satellite1 Center
      6. Destination Point = Ship1 Center
      7. Click OK
  3. Use VGT to create an angle (User-added image) between the targeted vector (‘FromSat_toShip’) and the satellite’s Body Z vector (pointing to nadir):
    1. Make sure you have ‘Satellite1’ selected on the left
    2. Create a new Angle
    3. Type = Between Vectors
    4. Name = ‘PointingAngle’
    5. From Vector = ‘FromSat_toShip’
    6. To Vector = ‘Satellite1 Body Z’ (under the satellite’s Body Axes)
    7. Click OK
User-added image
 
Task: Display Vectors/Angles in the 3D Graphics Window
  1. Display the custom vector components for the satellite in the 3D Graphics window.
    1. Right-click on Satellite1 (User-added image) in the Object Browser and select Properties (User-added image).
    2. On 3D Graphics – Vector page,
      1. Add the ‘FromSat_toShip’ vector and the ‘PointingAngle’ angle to the lists and show them.  The ‘FromSat_toShip’ vector will show up in the Vector tab, and ‘PointingAngle’ will show up in the Angles tab.
      2. Select “Show Angle Value” for ‘PointingAngle’
      3. In the Axes tab, click “Show” on the ‘Body Axes’
      4. Click OK
  2. Zoom To ‘Satellite1’ and animate (User-added image) the scenario and watch the vectors and angle dynamically changing.
    1. Note: If you need to zoom out to see the angle value and the vectors disappear, change the Detail (or Viewing) Thresholds in the 3D Graphics – Model tab.
Task: Create a New Condition for when the Satellite Gimbal Limit is Equal to or Less than 60 Degrees
We are going to create a new condition for when the angle between the ship and the satellite’s Body Z vector is equal to or less than 60 degrees to model the gimbal limit. We are arbitrarily building a condition for when the ship is vulnerable to the satellite.
  1. Add a Scalar Calculation that references the PointingAngle angle:
    1. Select the Calculation tab in Analysis Workbench (AWB).
    2. Select ‘Satellite1’ on the left.
    3. Create a new Scalar Calculation:
      1. Type = Angle
      2. Name = ‘PointingAngleScalar’
      3. Input Angle = ‘PointingAngle’
      4. Click OK
    4. Create a new Condition that represents when the angle is below 60 degrees:
      1. Type = Scalar Bounds
      2. Name = ‘Below60Degrees’
      3. Scalar = ‘PointingAngleScalar’
      4. Operation = Below Maximum
      5. Maximum = 60 deg
      6. Click OK
    5. Create a report that lists the times when the defined condition is met and add that condition to the Timeline View:
      1. Report: Right-click on the Scalar Condition, ‘Below60Degrees’, in Analysis Workbench (under My Components), select ‘Report/Graph...’ and click Create Report.
        1. The -1 value indicates times when the condition is not met (i.e. above 60 degrees), the +1 value indicates times when the condition is met.
      2. Add the ‘Below60Degrees’ Satisfaction Intervals to the Timeline View: Click on ‘SatisfactionIntervals’ under My Components (expand the items under ‘Below60Degrees’) in the Calculation tab, and drag the item down to the Timeline View.
 
Task: Create a Custom Interval Set that defines Tracking Opportunities/Vulnerability Times

We only want to display the times when our gimbal angle is below 60 degrees and when we have access from the satellite to the ship. This will represent the times when our satellite can see the ship and the gimbal angle is within the 60 degree limit…representing the ship vulnerability times.
  1. Create a new Interval List:
    1. Select the Time tab in AWB.
    2. Select ‘Satellite1’ on the left.
    3. Create a new Interval List:
      1. Type = Merged
      2. Name = ‘VulnerabilityTimes’
      3. Remove any Time Components that are currently listed
      4. Click Add...
      5. Select the Satellite1 to Ship1 Access Intervals (select the Access icon on the left, and ‘AccessIntervals’ on the right)
      6. Click Apply
      7. Select the Satellite1 > Below60Degrees > Satisfaction Intervals (select Satellite1 on the left and Below60Degrees > Satisfaction Intervals on the right)
      8. Click OK
      9. Operation = AND
      10. Click OK
  2. Add the new Interval List to the Timeline View: Click on ‘VulnerabilityTimes’ under My Components in the Time tab, and drag the item down to the Timeline View.
  3. You should now be able to see all three (3) time components displayed on the Timeline View (Satellite to Ship access, Below 60 Degrees Satisfaction Intervals, and the Vulnerability Times).
 
 
 
 
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