Sensor Design in STK

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

This lesson requires STK 12.9 or newer to complete in its entirety. If you have an earlier version of STK, you can complete a legacy version of this lesson.

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.

Capabilities covered

This lesson covers the following STK Capabilities:

  • STK Pro

Problem statement

You are using STK for preliminary analysis of a future air traffic control radar system that will track aircraft flying through an airport's control zone. You are also interested in determining if a low earth orbit (LEO) satellite can take pictures of a ground site in the training area.

Solution

Use STK to model a scenario that allows you to consider and compare all of your system options. Simulate an aircraft traveling in the vicinity of the airport and use a Sensor object to simulate the radar's field of view. Determine which portion of the aircraft's route can be tracked by the various radars. Model a LEO satellite and use a Sensor object to model the satellite's camera. Determine if the LEO can take pictures of a ground site in the training area.

Video guidance

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

Creating a scenario

Start by creating a scenario.

  1. Click Create a Scenario in the Welcome to STK dialog box.
  2. Enter the following in the New Scenario Wizard:
    3. Option Value
    Name SensorIntro
    Location: Default
    Start 1 Jul 2016 16:00:00.000 UTCG
    End + 1 day
  3. Click OK when finished.
  4. Click Save () when the scenario loads. 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.
  6. Click Save.

Turning off Terrain Server

If you plan to complete the L3 quiz at the end of the tutorial, turn off the Terrain Server.Closed

  1. Right-click on the scenario () and open the Properties ().
  2. Select the Basic - Terrain page.
  3. Disable the Use terrain for analysis option.
  4. Click OK to apply changes and dismiss the Properties Browser.

Save Often!

Creating the Airport Radar Site

Start by creating the radar site.

  1. Insert a Place () object using the Insert Default method.
  2. Rename the Place object RadarSite.
  3. Open RadarSite's () properties ().
  4. Select the Basic - Definition page.
  5. Make the following changes:
    6. Option Value
    Latitude 38.8006 deg
    Longitude -104.6784 deg
    Height Above Ground: 50 ft

    The additional 50 feet of altitude above the ground is to simulate the height of the radar antenna.

  6. Click OK.

Viewing the Radar Site

View the Radar Site () in the 3D Graphics Window.

  1. Right click on RadarSite () in the Object Browser.
  2. Select Zoom To.
  3. Bring the 3D Graphics window to the front.
  4. Use your left and right mouse buttons to obtain situational awareness of where your radar site is located.

Creating waypoints

The test aircraft will fly between two waypoints. For the test, you will insert two additional Place objects using the City Database.

Inserting a Place object located at Cheyenne, Wyoming

  1. Insert a Place () object using the From City Database method ().
  2. Type Cheyenne in the Name: field in the Search Standard Object Data dialog box.
  3. Click Search.
  4. Select Cheyenne, Wyoming in the Results: list.
  5. Click Insert.

Inserting a Place object located at Raton, New Mexico

  1. Return to the Search Standard Object Database dialog box.
  2. Type Raton in the Name: field.
  3. Click Search.
  4. Select Raton, New Mexico in the Results: list.
  5. Click Insert.
  6. Click Close to close the Search Standard Object Data dialog box.

Viewing the places

View the three Place () objects in the 2D Graphics Window.

  1. Bring the 2D Graphics window to the front.
  2. Locate your Place objects on the 2D Graphics window.
  3. Zoom in until you are centered on RadarSite with Cheyenne and Raton visible at the top and bottom of your map.

Place Object Locations

Inserting an aircraft

Insert an aircraft into your scenario.

  1. Insert an Aircraft () object using the Insert Default method.
  2. Rename the Aircraft object "TestFlight".

Setting the aircraft Propagator

The aircraft performing the test flight will fly from Raton to Cheyenne. Since this is a preliminary analysis of the radar system, you can use the Great Arc Propagator.

  1. Open TestFlight's () properties ().
  2. Select the Basic - Route page.
  3. Note the Propagator is set to GreatArc.

Modeling the Test Flight Aircraft

You can also use the mouse to enter waypoints directly in the 2D Graphics window. Simply click anywhere in the 2D Graphics window to add new waypoints (latitude/longitude values) in the waypoint table. However, you must use the Route page to enter altitude, speed, and turn radius values. When you use the mouse to define a great arc route, it is recommended that you specify the altitude and speed for the first point before you create the second point, so that the initial route information become the default for all additional points.

If you plan to complete the L3 quiz at the end of the tutorial, follow these steps.Closed

  1. On the Basic - Route page, click Insert Point twice to add two waypoints.
  2. Manually enter the waypoint values in the table:
    3. Waypoint Latitude Longitude
    1 36.9034 deg -104.439 deg
    2 41.14 deg -104.82 deg
  3. Click OK.

If you do not plan to complete the L3 quiz at the end of this tutorial, follow the steps below to create the aircraft route:Closed

  1. Return to the 2D Graphics window.
  2. Click on the Place marker () for Raton.
  3. Click on the place marker () for Cheyenne.

    4. Be careful! Each time you click on the 2D Graphics window, you will create a new waypoint. Ensure you only click on the map where you want a waypoint.

  4. Return to TestFlight's () properties ().
  5. You will see your waypoints in the waypoints table on the Basic - Route page.
  6. Click OK.

Animating the test flight

Animate the test flight and view it in the 2D Graphics Window.

  1. Return to the 2D Graphics window.
  2. Make sure you can see the entire flight route of TestFlight.
  3. Use the Decrease Time Step () button in the Animation toolbar to decrease the time step to 3.00 sec.
  4. Click the Start () button.
  5. Observe your aircraft as it flies from Raton to Cheyenne.
  6. Click the Reset () button when finished.

Modeling a LEO Satellite

Add a Satellite object to the scenario. You need to analyze when the satellite's camera (Sensor object) can take pictures of Raton.

  1. Insert a Satellite () object using the Orbit Wizard () method.
  2. Make the following changes to the Orbit Wizard:
    3. Option Value
    Type Circular
    Satellite Name ImageSat
    Inclination 60 deg
    Altitude 800 km
    RAAN 20 deg
  3. Click OK.

Inserting a fixed sensor on a moving object

Use Sensor objects to model the various components that make up the detection system. Insert a default Sensor () object. The default Sensor Object that STK creates when you introduce a Sensor object is a simple conic sensor with a 45 degree cone angle. The default view is fixed at zero (0) degrees azimuth and 90 degrees elevation which is nadir pointing. When a Sensor object is attached to a moving object it points with respect to the parent object’s reference frame. A fixed sensor is always pointing in a fixed direction with respect to its parent object.

  1. Insert a Sensor () object using the Insert Default method.
  2. Select ImageSat () in the Select Object window.
  3. Click OK.
  4. Rename the Sensor1 () to Fixed.

Viewing the fixed sensor

View the sensor () in the 3D Graphics window.

  1. Bring the 3D Graphics window to the front.
  2. Right click on ImageSat () in the Object Browser.
  3. Select select Zoom To.
  4. Use your left and right mouse buttons to get a good view of ImageSat and the Sensor object's field of view and the locations of your ground sites.

Fixed Sensor

Calculating Access from Fixed sensor

The first analysis to perform is to check, whether or not, if Fixed will see Raton () during your analysis period (24 hours).

  1. Right click on Fixed () in the Object  Browser.
  2. Select Access... ().
  3. Select Raton () in the Associated Objects list in the Access Tool ().
  4. Click Access... . in the Reports panel.
  5. Take a look at the report. During the 24 hour exercise, Raton will be in Fixed's field of view (FOV) a couple of times.
  6. Note the Total Duration time in the report.
  7. Close the report.
  8. Close the Access Tool.

Modeling a moving sensor on a moving object

When you attached the Fixed () sensor, you used the default fixed pointing type. Many satellites can gimbal their sensors to track other objects (stationary and moving). STK provides a variety of Sensor object definitions and pointing types that allow you to model this type of movement.

Inserting the Targeted sensor on the satellite

First you will insert a sensor () object called Targeted on ImageSat ().

  1. Insert a Sensor () object using the Insert Default method.
  2. Select ImageSat () in the Select Object window.
  3. Click OK.
  4. Rename the Sensor1 () to Targeted.

Modeling the moving sensor

Update the sensor definition and pointing type to model the targeted sensor.

  1. Open Targeted's () properties ().
  2. Select the Basic - Definition page.
  3. Ensure the Sensor Type is set to Simple Conic.
  4. Change the Cone Half Angle: to 5 deg.
  5. Select the Basic - Pointing page.
  6. Change Pointing Type: to Targeted.
  7. Move () Raton () from the Available Targets list to the Assigned Targets list.
  8. Click OK.

Calculating Access from Targeted sensor

Compare the access time between Targeted () and Fixed ().

  1. Right click on Targeted () in the Object  Browser.
  2. Select Access... ().
  3. Select Raton () in the Associated Objects list.
  4. Click Access... in the Reports panel.
  5. Note the Total Duration time.

    6. How does the access time for Targeted compare to Fixed? When you target the Sensor object, it locks onto the assigned target using the Sensor objects boresight. It's a point-to-point access. You're using the line-of-site constraint. Therefore, Targeted accesses Raton from horizon to horizon. The field of view for Fixed had to pass over Raton. So, the access time for Targeted is much higher.

  6. Right-click on the first Access Start Time in the Access report.
  7. Select Start Time in the shortcut menu.
  8. Select Set Animation Time.

Viewing Access in the 3D Graphics Window

  1. Bring the 3D Graphics window to the front.
  2. Zoom To ImageSat () if required to reset your view.
  3. Use your left and right mouse buttons to get a good view of ImageSat and the Sensor object's field of view and the locations of your ground sites.
  4. Click the Start () button on the Animation Toolbar to view any accesses that occur.

    5. Targeted Access

  5. Click the Reset () button when finished.

Cleaning up your scenario

  1. Close the report.
  2. Close the Access Tool.
  3. Extend the Analysis menu.
  4. Select Remove All Accesses.
  5. Disable Fixed () in the Object Browser.
  6. Disable Targeted () in the Object Browser.

Your preliminary analysis shows that both cameras attached to ImageSat will have opportunities to take pictures of Raton.

Modeling the fixed sensor on a stationary object

You are now ready to model the radar field of view for RadarSite (). In the previous examples, you attached sensors to moving objects to model a fixed camera field of view and a camera that can gimbal. Sensors can also be used to model instruments attached to stationary objects, such as Facility, Place and Target objects. Fixed Sensor objects attached to stationary objects also point with respect to the parent object’s reference frame. Since stationary objects never change position or direction, a fixed Sensor object will always point in a fixed direction with respect to the parent object.

Inserting the Radar Dome sensor on the Radar Site

First you will insert a sensor () object called RadarDome on RadarSite ().

  1. Insert a Sensor () object using the Insert Default method.
  2. Select RadarSite () in the Select Object window.
  3. Click OK.
  4. Rename the Sensor3 () to RadarDome.

Updating the sensor's field-of-view

The Sensor object created here is similar to the fixed Sensor object attached to ImageSat (). However, it has a larger field-of-view. Change the Cone Half Angle to 90 deg.

  1. Open RadarDome's () properties ().
  2. Select the Basic - Definition page.
  3. Change the Cone Half Angle to 90 deg.
  4. Click Apply.

Adding constraints

RadarDome () points straight up from RadarSite (). It has an up looking field-of-view that covers everything above RadarSite (). That’s not very realistic. Let’s limit its range so that the field-of-view spans a constrained area mimicking the field-of-view of the actual air traffic control radar.

  1. Select the Constraints - Active page.
  2. Click Add new constraints () in the Active Constraints toolbar.
  3. Select Range in the Constraint Name list in the Select Constraints to Add dialog box.
  4. Click Add.
  5. Click Close to close the Select Constraints to Add dialog box.
  6. Select Max: in the Range panel of the Constraint Properties section.
  7. Enter 150 km in the Max: field.
  8. Click Apply.

Viewing RadarDome in the 3D Graphics Window

View RadarDome () in the 3D Graphics Window.

  1. Bring the 3D Graphics window to the front.
  2. Zoom To RadarSite ().
  3. Using your mouse, zoom out far enough so that you can see RadarDome's () full field-of-view.

Radar Dome Field-of-View

Setting 2D Projection properties

2D Graphics Projection properties for Sensor objects control the display of sensor projection graphics in the 2D Graphics window. Sensor objects attached to Facility, Place and Target objects differ in their display behavior from those attached to vehicles. The intersections of Sensor objects with the Earth are displayed during animation. The Extension Distances option indicates whether the Sensor object’s field-of-view crossings at specified distances are computed and displayed in the 2D Graphics window. When the Sensor object display is set to project to the range constraint, STK projects the Sensor object's field-of-view to the maximum range specified on the Basic Constraints properties page for the Facility, Place, or Target object.

  1. Bring the 2D Graphics window to the front.
  2. Locate your Place objects and zoom in until you are centered on RadarSite with Cheyenne and Raton visible at the top and bottom of your map. At this point, there is no indication of RadarDome's field-of-view.
  3. Return to RadarDome's () properties ().
  4. Select the 2D Graphics - Projection page.
  5. Select Use Range Constraint as the Project to: option.
  6. Click OK.
  7. Return to the 2D Graphics window.
  8. You can see the range constraint of 150 km projecting out from RadarDome.

2D Graphics Projection

Calculating RadarDome's Access

There's no doubt visually, that RadarDome can access TestFlight. For the purposes of the analysis, we need to know for how long.

  1. Right click on RadarDome () in the Object  Browser.
  2. Select Access... ().
  3. Select TestFlight () in the Associated Objects list.
  4. Click Access... in the Reports panel.

    5. This is pretty straight forward. The access report tells you when and for how long you have access to TestFlight. For briefing purposes, you might want to change the duration from seconds to minutes.

  5. Click Report Units () at the top of the access report.
  6. Ensure Time Dimension is selected on the left.
  7. Select Minutes (min) in the New Unit list.
  8. Click OK.

Saving as Quick Report

Sometimes it's useful to change report units. You can save the report inside or outside of STK. Later, you will be sending this scenario to someone who does not have STK. Therefore, you can create a Quick Report. If you make any property changes to the objects being used in the access calculation, the changes will appear in the Quick Report. Therefore, if you want to compare numbers, sometimes it's a good idea to save reports externally. For the purposes of this scenario, there's no need. Should you decide to do this, you can use the Save as .csv icon.

  1. Click Save as quick report () at the top of the access report.
  2. Close () the report.
  3. Click the Quick Report Manager () at the top of STK.

    4. All of your Quick Reports will be available by simply opening the Quick Report Manager. You can rename your reports, add descriptions, delete them, etc.

  4. Select the Access Quick Report.
  5. Click create.
  6. Return to the Quick Report Manager.
  7. Click OK.

Zooming to Access start time

You can use the report to quickly jump to the time in the scenario when RadarDome first accesses TestFlight.

  1. Return to the Access report.
  2. Right-click on the first Access Start Time in the Access report.
  3. Select Start Time in the shortcut menu.
  4. Select Set Animation Time.
  5. Bring the 3D Graphics window to the front.
  6. Zoom To TestFlight ().
  7. Using your mouse, move your view around so you can see TestFlight ()enter RadarDome ().

Generating an AER Report

This gives you a good idea of the location of TestFlight when it first enters RadarDome's field-of-view. You'll recall, that the maximum distance constraint for RadarDome is 150 km. Also, an air traffic controller might need to know TestFlight's azimuth and elevation data.

  1. Return to the Access Tool.
  2. Make sure RadarDome is selected as the Access For: object.
  3. Make sure TestFlight () is selected in the Associated Objects list.
  4. Click AER... in the Reports panel.
  5. Scroll through the report. This report not only tells you what time RadarDome accesses TestFlight, but it reports the azimuth, elevation, and range.

Cleaning up your scenario

  1. Close the report.
  2. Close the Access Tool.
  3. Extend the Analysis menu.
  4. Select Remove All Accesses.
  5. Disable RadarDome () in the Object Browser.

Modeling a moving sensor on a stationary object

Often, the dome created by a Sensor object is used to model a field-of-view, or the overall volume of space in which radar looks. The radar itself often sweeps or scans through that field-of-view in a repeating cycle. The area of space represented by such a scanning or spinning radar at any given instant is its field-of-view. Add another level of fidelity to your scenario and build a sweeping radar beam using a moving Sensor object.

Inserting the Radar Sweep sensor on the Radar Site

First you will insert a sensor () object called RadarSweep on RadarSite ().

  1. Insert a Sensor () object using the Insert Default method.
  2. Select RadarSite () in the Select Object window.
  3. Click OK.
  4. Rename the Sensor3 () to RadarSweep.

Defining the Sensor's definition

You want to simulate the actual field-of-view, antenna height, and spinning properties of your air traffic control radar. The antenna height was set when you increased RadarSite's () altitude earlier in the scenario.

Often, the area created by a sensor’s projection is used to model a field-of-view. Rectangular sensor types are typically used for modeling the field-of-view of instruments such as push broom sensors and star trackers. Rectangular sensors are defined according to specified vertical and horizontal half-angles.

The radar that you are modeling sweeps or scans in a repeating cycle. Since the radar “scans”, the full range of the radar is not always covered. You can configure the sensor’s field-of-view to provide a visual representation of the area that the radar does cover at any given point in time.

  1. Open RadarSweep's () properties ().
  2. Select the Basic - Definition page.
  3. Make the following changes:
    4. Option Value
    Sensor Type Rectangular
    Vertical Half Angle 5 deg
    Horizontal Half Angle 35 deg

The above configuration should create a wedge type field-of-view. Right now, that “wedge” is just pointing straight up.

Setting the Pointing Properties

Set the properties of the Sensor object to rotate and point at 35 degrees elevation. Set the RadarSweep's () Pointing Type to Spinning. You can set the spin axis elevation to 90 degrees for horizontal rotation with a cone angle of 55 degrees for a 35 degree elevation from the horizon.

  1. Return to RadarSweep's () properties ().
  2. Select the Basic - Pointing page.
  3. Make the following changes:
    4. Option Value
    Pointing Type Spinning
    Spin Rate (Revs/Min) 12 revs/min
    Spin Axis - Cone Angle 55 deg
  4. Click Apply.

Setting the Constraints of the Sensor

Right now, the field-of-view extends beyond the limits of the actual radar because you haven’t constrained it. The airport’s primary surveillance radar has a range of 150 km. You need to limit the range of the radar to model that constraint.

  1. Select the Constraints - Active page.
  2. Click Add new constraints () in the Active Constraints toolbar.
  3. Select Range in the Constraint Name list in the Select Constraints to Add dialog box.
  4. Click Add.
  5. Click Close to close the Select Constraints to Add dialog box.
  6. Select Max: in the Range panel of the Constraint Properties section.
  7. Enter 150 km in the Max: field.
  8. Click Apply.

Viewing the Radar Sweep sensor

View the RadarSweep () sensor in the 3D Graphics window.

  1. Bring the 3D Graphics window to the front.
  2. Zoom to RadarSite ().
  3. Use your mouse and mouse buttons to get a good view the RadarSweep's () field-of-view.

    4. Rectangular Sensor

  4. In order to view the RadarSweep () in real time, click the X Real-time Animation Mode icon in the Animation toolbar.
  5. Click the Start () to play the scenario. You can see RadarSweep as it turns 12 revolutions a minute.
  6. Reset () the scenario when finished.

Visualizing RadarSweep on the 2D Graphics Window

  1. Bring the 2D Graphics window to the front.
  2. Locate your Place objects and zoom in until you are centered on RadarSite with Cheyenne and Raton visible at the top and bottom of your map. At this point, there is no indication of RadarSweep's field-of-view.
  3. Return to RadarSweep's () properties ().
  4. Select the 2D Graphics - Projection page.
  5. Select Use Range Constraint as the Project to: option.
  6. Click OK.
  7. Return to the 2D Graphics window.
  8. Click the Start () button on the Animation Toolbar.
  9. Notice the sensor projection moving on the 2D Graphics Window.
  10. Click the Reset () button when finished.

Generating an access graph

Determine when RadarSweep () has access to TestFlight () using an access graph.

  1. Right click on RadarSweep () in the Object  Browser.
  2. Select Access... ().
  3. Select TestFlight () in the Associated Objects list.
  4. Click Access... in the Graphs panel.

    5. This graph is interesting because it's graphing each instance RadarSweep accesses TestFlight while it is spinning. The Zoom In tool is embedded in the functionality of the mouse.

  5. Hold down the left mouse button and hover over an item on the graph.
  6. Draw a box around the item and zoom closer.
  7. Close () the access graph.

Generating an access report

Generate an access report. You will then jump to an access time, so you can create a stored view at that time.

  1. Return to the Access Tool ().
  2. Click Access... in the Reports panel.
  3. Right-click on the first Access Start Time.
  4. Select Start Time in the shortcut menu.
  5. Select Set Animation Time.
  6. Close () the Access report.

Creating a Stored Views

At times, you may desire to quickly return to a particular 3D Graphics view. For instance, you might use this scenario for a briefing. During the briefing, you desire to jump to the 3D Graphics window view of when TestFlight is first detected by RadarSweep. Store a view that depicts just that.

  1. Bring the 3D Graphics window to the front.
  2. Zoom To RadarSite ().
  3. Mouse around until you are happy with the view.

    4. First Access

  4. Click Stored Views () on the 3D Graphics window toolbar.
  5. Click New .
  6. Rename View0 First Access.
  7. Click OK .
  8. Click Reset () in the Animation toolbar.
  9. Click Home View () in the 3D Graphics window toolbar.
  10. Select First Access in the Stored Views pull down menu.

Calculating multiple Accesses

You can quickly create an access graph that shows all the Sensor objects at the same time. You can create the graph from TestFlight to the Sensor objects. The Sensor properties will still be used.

  1. Return to the Access Tool ().
  2. Click the Select Object....
  3. Select TestFlight in the Select Object dialog box.
  4. Click OK.
  5. Using your Ctrl key and mouse, select all four Sensor objects in the Associated Objects list. You may need to expand ImageSat or RadarSite to see all the Sensor objects.
  6. Click Access... in the Graphs panel.

Multiple Access Graph

This graph shows you when each Sensor object accesses TestFlight. Your view may be different.

Saving Your Work

  1. When you are finished, close the Access graph and the Access Tool.
  2. Save () your work.