Using the Time 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 an Internet connection and STK 12.8.

Capabilities covered

This lesson covers the following STK Capabilities:

  • STK Pro
  • Analysis Workbench

Problem statement

Engineers and operators need a quick way to determine the response time of a Coast Guard Search and Rescue system.

Solution

Using the Time Tool in STK's Analysis Workbench (AWB) capability, you will analyze the response time of a Coast Guard Search and Rescue system. You will model a disabled vehicle that issues a distress call. The distress call will be picked up by the NOAA Search and Rescue Satellite Aided Tracking (SARSAT) constellation. Once the call is confirmed, a rescue helicopter will be dispatched to that location. From distress call to dispatched helicopter, each event will occur in a series, one triggering the next.

What you will learn

Upon completion of this tutorial, you will understand:

  • The Analysis Workbench and the Time Tool.
  • How to use the Chain object.
  • How to create an Interval From List component.
  • How to create a Fixed Time Offset component.
  • How to create merged interval lists.
  • How to use the Timeline View.

  • How to use the Great Arc Propagator and create waypoints.

Creating a new scenario

First, you must create a new STK scenario and then build from there.

  1. Launch STK ().
  2. Click Create a Scenario in the Welcome to STK dialog box.
  3. Enter the following in the STK: New Scenario Wizard:
    4. Option Value
    Name: SAR_Response
    Location: Default
    Start: 15 Dec 2023 16:00:00.000 UTCG
    Stop: +1day
  4. Click OK when you finish.
  5. Click Save () when the scenario loads. STK creates a folder with the same name as your scenario for you.
  6. Verify the scenario name and location in the Save As dialog box.
  7. Click Save.

Save () often during this lesson!

Disabling Terrain Server

You will not use Terrain in your analysis, so you can turn off the Terrain Server.

  1. Right-click on SAR_Response () in the Object Browser.
  2. Select Properties ().
  3. Select the Basic - Terrain page when the Properties Browser opens.
  4. Clear the Use terrain server for analysis check box.
  5. Click OK to accept your change and to close the Properties Browser.

Inserting a Target object

Use a Target () object to pinpoint the approximate location of the distress call.

  1. Select Target () in the Insert STK Objects Tool.
  2. Select the Insert Default () method.
  3. Click Insert... .
  4. Right-click on Target1 () in the Object Browser.
  5. Select Rename in the shortcut menu.
  6. Rename Target1 () to DistressLocation.

Setting the Distress Call location

The distress location is in the Atlantic Ocean east of New England.

  1. Open DistressLocation's () properties ().
  2. Select the Basic - Position page when the Properties Browser opens.
  3. Set the following in the Position frame:
    4. Option Value
    Latitude: 43 deg
    Longitude: -70 deg
  4. Click OK to accept your changes and to close the Properties Browser.

Inserting Satellite objects

Use the Standard Object Database tool to query a locally installed Spacecraft database, an online Spacecraft database, or both for a set of space objects from which to create new satellites in STK.

  1. Insert a Satellite () object using the From Standard Object Database () method.
  2. Type NOAA in the Name or ID: field when the Search Standard Object Data dialog box opens.
  3. Open the Operational Status: shortcut menu.
  4. Select Operational.
  5. Click Search.
  6. Select all the satellites in the Results: list.
  7. Select the Create Constellation from Selected check box in the Insert Options frame.
  8. Type NOAA_Sats in the Name: field.
  9. Click Insert.
  10. Click Close to close the Search Standard Object Data dialog box once the Satellite () objects are propagated.

Removing unneeded objects

Noaa19_33591 () has an attached Sensor () object which isn't used in your analysis. You can remove that object.

  1. Right-click on Noaa19_Avhrr3_Vir_FixedPt_FieldOfView () in the Object Browser.
  2. Select Delete () in the shortcut menu.
  3. Click Delete to confirm in the Delete Object dialog box.

Inserting a Chain object

You will create a Chain () object that starts at NOAA_Sats () and ends at DistressLocation ().

  1. Insert a Chain () object using the Insert Default () method.
  2. Rename Chain1 () to DistressCall.

Defining the start and end objects

Start by choosing the start object and end object in your chain.

  1. Open DistressCall's () properties ().
  2. Select the Basic - Definition page when the Properties Browser opens.
  3. Click the Start Object: ellipsis ().
  4. Select DistressLocation () in the Select Object dialog box.
  5. Click OK to close the Select Object dialog box.
  6. Click the End Object: ellipsis ().
  7. Select NOAA_Sats () in the Select Object dialog box.
  8. Click OK to close the Select Object dialog box.
  9. Click Apply to accept your changes and to keep the Properties Browser open.

Creating the Chain object's connections

After you choose the start and end objects in your chain, you need to build the chain's connections. It doesn't matter in which order you place the connections in the Connections list. What matters is the From Object must be able to access the To Object. In this simple chain, the from and to objects are your start and end objects.

  1. Click Add in the Connections frame.
  2. Click the From Object: ellipses ().
  3. Select DistressLocation () in the Select Object dialog box.
  4. Click OK to close the Select Object dialog box.
  5. Click the To Object: ellipses ().
  6. Select NOAA_Sats () in the Select Object dialog box.
  7. Click OK to close the Select Object dialog box.
  8. Click OK to accept your changes and to close the Properties Browser.

Using the Timeline View

You will use the Timeline View to visualize time intervals and time components within your scenario. You can adjust the display and content by using the toolbar, adjusting the timeline display, and adding rows of time components.

Display the Access times from the DistressLocation () to the NOAA_Sats () on the Timeline View.

  1. Click Add Time Components () in the Timeline View toolbar.
  2. Select DistressCall () in the objects list when the Select Timeline Component dialog box opens.
  3. Select CompleteChainAccessIntervals () in the Components for: DistressCall list.
  4. Click OK to close the Select Timeline Component dialog box.

Visualizing an access in the 3D Graphics window

You can use the Timeline View's gray pointer and the 3D Graphic window to visualize access between NOAA satellites and the distress location.

  1. Bring the 3D Graphics window to the front.
  2. Right-click on DistressLocation () in the Object Browser.
  3. Select Zoom To in the shortcut menu.
  4. Look at the Timeline View. You will see all the accesses between NOAA satellites in NOAA_Sats () and DistressLocation ().
  5. Place your cursor on the gray pointer in the Time Display.
  6. Hold down the left mouse button and drag the gray pointer to the first access.

    7. NOAA Satellite access

  7. Return to the 3D Graphics window.
  8. Hold down your mouse's right button and zoom out until you can see DistressLocation () and the NOAA satellite it is accessing.

    9. Distress location to a noaa satellite 3D graphics window view

Time Components

You will build time components using the Analysis Workbench and the Time Tool. Time components are built on two basic types: Instants and Intervals. An instant is any single moment in time (e.g. “Launch time”), whereas an Interval is a period of time bounded by two time Instants (e.g. “Launch Window”). In addition to those basic types, we also have

  • Interval list: A set of intervals, e.g. access intervals
  • Collection of Interval lists: A group of related interval lists, e.g. lighting intervals—Direct Sun, Umbra, and Penumbra intervals
  • Time Arrays: A set of time instants, e.g. threshold crossings, or Acquisition Of Signal times

Confirming the Distress Call

Due to the large number of false alarms received by the NOAA satellites, rescue response is only sent after a second satellite pass confirms a distress signal. Create a new Time Interval to capture the second satellite pass, confirming the distress signal.

  1. Right-click on DistressCall () in the Object Browser.
  2. Select Analysis Workbench... () in the shortcut menu.
  3. Select the Time tab when the Analysis Workbench opens.
  4. Click Create new Interval () in the Time Tool toolbar.

Creating an Interval From List component

An Interval From List component is a single interval created from an interval list defined by a specified Time Interval List component.

  1. Keep the default Type: Interval From List when the Add Time Component dialog box opens.
  2. Type Distress Confirmed in the Name: field.
  3. Click the Interval List: ellipsis ().
  4. Select DistressCall () in the object list when the Select Reference Interval List dialog box opens.
  5. Select CompleteChainAccessIntervals () in the Interval Lists for: DistressCall list.
  6. Click OK to close the Select Reference Interval List dialog box.

Confirming the distress call

You will confirm the distress call by using a second satellite pass. When an access displays on the Timeline view in the DistressConfirmed row, you will know the second satellite confirmed the distress call.

  1. Open the Interval Selection: shortcut menu when you return to the Add Time Component dialog box.
  2. Select Count forward from Start.
  3. Enter 2 in the Interval Number: field.
  4. Click OK to close the Add Time Component dialog box.
  5. Drag-and-drop DistressConfirmed () from the Components for: DistressCall list to the Timeline View's Time Display.

    6. Distress call Confirmed

Inserting a helicopter preparation time

To compensate for the time it takes to contact and prepare a rescue helicopter, create a new Time Instant that is delayed 20 minutes after the time of the distress confirmation. The helicopter will take off after this delay.

  1. Return to the Time Tool.
  2. Select DistressCall () in the object list.
  3. Click Create new Time Instant () in the Time Tool toolbar.
  4. Click Type: Select... when the Add Time Component dialog box opens.

Fixed Time Offset

A Fixed Time Offset component is a time instant offset by a fixed time relative to another time instant component.

  1. Select Fixed Time Offset () in the Select Component Type list when the Select Component Type dialog box opens.
  2. Click OK to close the Select Component Type dialog box.
  3. Type Rescue Launch Time in the Name: field when you return to the Add Time Component dialog box.
  4. Click the Reference Time Instant: ellipsis ().
  5. Select DistressCall () in the object list when the Select Reference Time Instant dialog box opens.
  6. Expand () DistressConfirmed () in the Time Instants for: DistressCall list.
  7. Select Stop ().
  8. Click OK to close the Select Reference Time Instant dialog box.

Setting the Rescue Launch time

The rescue launch time begins 20 minutes after the distress confirmed time.

  1. Enter 20 min in the Time Offset: field when you return to the Add Time Component dialog box.
  2. Click OK to close the Add Time Component dialog box.
  3. Drag-and-drop Rescue_Launch_Time () from My Components () to the Timeline View's Time Display.
  4. Keep the Analysis Workbench open.

    5. Rescue launch time

Coast Guard Air Station Cape Cod

A rescue helicopter will launch from Coast Guard Air Station Cape Cod and fly to the distress location.

  1. Insert a Place () object using the Search by Address () method.
  2. Type Coast Guard Air Station Cape Cod in the Enter an address or other search criteria below: field when the STK: Insert By Address dialog box opens.
  3. Select Coast Guard Air Station Cape Cod, MA in the Results list.
  4. Click Insert Place(s).
  5. Click Close to close the STK: Insert By Address dialog box.

If you choose to insert a Place () object manually, use the following steps:

  1. Insert a Place () object using the Insert Default () method.
  2. Rename Place1 () to Coast_Guard_Air_Station_Cape_Cod_MA.
  3. Open Coast_Guard_Air_Station_Cape_Cod_MA's () properties ().
  4. Select the Basic - Position page when the Properties Browser opens.
  5. Enter the following in the Position frame:
    6. Option Value
    Latitude: 41.66541 deg
    Longitude: -70.52475 deg
  6. Click OK to accept your changes and to close the Properties Browser.

Inserting an Aircraft object

Insert an Aircraft () object into your scenario.

  1. Insert an Aircraft () object using the Insert Default () method.
  2. Rename Aircraft1 () to RescueHelicopter.

Using the Great Arc propagator

The Great Arc Propagator defines the route of an aircraft that follows a point-by-point path over the surface of the Earth at a given altitude.

  1. Open RescueHelicopter's () properties ().
  2. Select the Basic - Route page when the Properties Browser opens.

Using the Time Component

You can change the takeoff time of your helicopter by using the launch time component you created.

  1. Open () the Start: Stop: shortcut menu.
  2. Select Start Time in the shortcut menu.
  3. Select Time Component... in the second shortcut menu.
  4. Select DistressCall () in the object list when the Select Time Instance dialog box opens.
  5. Select Rescue_Launch_Time () in the Time Instants for: DistressCall list.
  6. Click OK to close the Select Time Instance dialog box.
  7. Click Apply to accept you change and to keep the Properties Browser open.

Creating waypoints

The helicopter will take off from the Coast Guard Base, fly north along the coast, and then turn towards the distress location.

  1. Click Insert Point to create your first waypoint.
  2. Enter the following values for waypoint one:
    3. Option Value
    Latitude: 41.66541 deg
    Longitude: -70.52475 deg
    Altitude: 1000 ft
    Speed: 160 mi/hr
  3. Click Insert Point.
  4. Enter the following values for waypoint two:
    5. Option Value
    Latitude: 42.6 deg
    Longitude: -70.5 deg
    Turn Radius 500 ft
  5. Click Insert Point.
  6. Enter the following values for waypoint three:
    7. Option Value
    Latitude: 43 deg
    Longitude: -70 deg
    Altitude: 100 ft
    Speed: 10 mi/hr
  7. Click Apply to accept your changes and to keep the Properties Browser open.

Now the helicopter, instead of launching at the start of the scenario (default), will launch 20 minutes after the confirmation of the distress call. Furthermore, since the launch time depends on the distress call intervals, if those intervals change, the launch time will automatically update.

Change the Aircraft object's model

You will use a more realistic model for your helicopter and change its appearance in your scenario.

  1. Select the 3D Graphics - Model page.
  2. Click the Model File: ellipsis () in the Model frame.
  3. Select sh-60_seahawk.mdl in the File dialog box.
  4. Click Open.
  5. Click Apply to accept your changes and to close the Properties Browser.

View the rescue helicopter's flight route

View RescueHelicopter's () flight route in the 3D Graphics window.

  1. Select the Basic - Route page.
  2. Copy the time in waypoint 2.
  3. Paste the time in the Current Scenario Time field of the Animation toolbar.
  4. Press the Enter key on your keyboard.
  5. Click OK to close the Properties Browser.
  6. Bring the 3D Graphics window to the front.
  7. Zoom to RescueHelicopter ().
  8. Zoom out until you can see RescueHelicopter's () flight route.

Rescue helicopter flight route

Show Position Updates

Create a new Interval List to determine when the rescue helicopter might receive updates on the position of the distress location as it approaches. This is accomplished by merging DistressCall () chain intervals with the RescueHelicopter's () flight interval.

  1. Return to the Analysis Workbench.
  2. Select the Time tab.
  3. Select DistressCall () in the object list.
  4. Click Create new Interval List () in the Time Tool toolbar.

Creating a Merged interval list

A Merged interval list are intervals merged from multiple interval or Interval List Time Components using one of several merging operations.

  1. Click Type: Select... when the Add Time Component dialog box opens.
  2. Select Merged () in the Select Component Type list when the Select Component Type dialog box opens.
  3. Click OK to close the Select Component Type dialog box.
  4. Type Distress Position Updates in the Name: field when you return to the Add Time Component dialog box.
  5. Make sure AND is showing in the Operation: field (default).
  6. Select the first time component in the Time Components: list.
  7. Click Remove.
  8. Select the second time component in the Time Components: list.
  9. Click Remove.

Add Distress call to the Time Components: list

  1. Click Add... .
  2. Select DistressCall () in the object list when the Select Time Intervals dialog box opens.
  3. Select CompleteChainAccessIntervals () in the Components for: DistressCall list.
  4. Click OK to close the Select Time Intervals dialog box.

Add RescueHelicopter to the Time Components: list

  1. Click Add... .
  2. SelectRescueHelicopter () in the object list when the Select Time Intervals dialog box opens.
  3. Select EphemerisTimeSpan () in the Components for: RescueHelicopter list.
  4. Click OK to close the Select Time Intervals dialog box.
  5. Click OK to close the Add Time Component dialog box.
  6. Drag-and-drop Distress_Position_Updates () from My Components () to the Timeline View's Time Display.
  7. Click Close to close the Analysis Workbench.

    8. Distress position updates

    Updates are received when the next NOAA satellite accesses DistressLocation ().

Saving your work

You can clean up and finish your scenario.

  1. Close any open reports, properties, and tools.
  2. Save () your work.

Summary

You practiced using the Timeline View and the Time tool in Analysis Workbench to interact with your scenario. You used Time components to set access constraints and form timeline intervals for your reports or graphs. Also, you set your object behaviors and display properties with Time components.

On Your Own

In order for the RescueHelicopter () to receive updates on the position of the distress location as it approaches, the route needs to overlap with at least one of the Complete Chain Access Intervals. You can relocate the DistressLocation () and modify RescueHelicopter's () route so they overlap allowing time for the helicopter to get distress position updates. This will then display DistressPositionUpdate intervals. All the time components that you created will automatically update.