Digital Mission Engineering (DME): Events and Time Components (Part 4 of 4)

STK Premium (Air) 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.

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.

If you have not completed Parts 1, 2 and 3 of the DME lessons, starter scenarios are provided. They require STK 12 or newer to open. The DME lessons are in the Training - Level 3 - Focused tutorials section of the STK Help.

This lesson requires STK 12.9 or newer to complete.

Capabilities covered

This lesson covers the following STK capabilities:

  • STK Pro
  • Communications
  • Analysis Workbench

Problem statement

Across the industry, the digital engineering process is becoming more complex. Systems of systems are changing and updating in different stages of the mission life cycle. In this series, you will address these challenges by creating a fully connected digital thread with a common mission environment at the core. You will design and test a new satellite constellation for persistent, stereo coverage of hypersonic vehicles across the world. You will address this topic in stages: satellite constellations, hypersonic flight, EOIR sensors, communications links, and triggering events and systems. The vision is to integrate the mission environment and operational objectives into the digital thread early and throughout the entire product life cycle. Through digital mission engineering, you are now capable of quickly evaluating the overall mission impact of the smallest change to any component. This lesson will look at event-based operations for mission or test and evaluation planning. You will be building on the previous scenarios to evaluate the series of events within a mission and how their dependencies on each other influence the overall mission effectiveness.

Solution

In this section of the Digital Mission Engineering (DME) series, you will focus on the test or mission planning phase of the life cycle. Using the same models constructed through the design phase, you will evaluate relationships between assets like communications link availability and how that influences the overall mission time line. You will look at the system response time of the mission as a whole.

What you will learn

Upon completion of this tutorial, you will be able to:

  • Understand the series of events taking place
  • Link the relevant events together
  • Understand the system as a whole

Required files

This lesson requires the following external file:

  • DME_Session3_Starter_AWB.vdf - This is the starter scenario for the event and time components portion of the DME series.

The external file is available for download from the STK Data Federate. The file path is Documents > STK 12 > Starter Tutorials > DME_Session3_Comms_and_Event_Analysis.

Opening the starter scenario

In this final section of the DME series, you will analyze how all the systems work together. To speed up the analysis, you can load the starter scenario which has been created for you.

  1. Launch STK ().
  2. Click Open a Scenario in the Welcome to STK dialog.

Loading the starter scenario from the STK Data Federate (SDF)

The STK scenario used with this tutorial is a Visual Data (VDF) file located in the SDF.

  1. Open the Location dropdown menu in the Open dialog.
  2. Select STK Data Federate.
  3. Select the Browse tab in the Open dialog. You can remain logged in as guest.
  4. Expand () the following: Sites > AGI > documentLibrary > STK 12 > Starter Tutorials > DME_Session3_Comms_and_Event_Analysis.

Opening the starter scenario VDF

  1. Select DME_Session4_Starter_AWB.vdf.
  2. Click Open. Be patient. This is a large scenario and might take a minute or two to load.

Saving the starter scenario VDF as a scenario file

When you save a scenario in STK, it will save in its originating format. That is, if you open a VDF, the default save format will be a VDF (.vdf). The same is true for a scenario file (*.sc). If you want to save a VDF as a file scenario file (or vice-versa), you must change the file format by using the Save As feature.

Choosing the location to save the starter scenario

  1. Open the File menu once the scenario has loaded.
  2. Select Save As... .
  3. Open the Location dropdown menu in the Save As dialog.
  4. Select File System.
  5. Select the STK > STK User folder in the Navigation Pane.
  6. Select the DME_Session4_Starter_AWB folder.
  7. Click Open.

Saving the starter scenario as a scenario file

  1. Open the Save as type dropdown menu.
  2. Select Scenario Files (*.sc).
  3. Enter X43_Mission_AWB in the File name field.
  4. Click Save.

Save () often during this lesson!

Understanding related events and time components

In this section, you will focus on understanding and relating all the events that occurred from the beginning of the X-43 (HXRV_X43 Aircraft object) test flight to when it was tracked, including any information relayed. The first lesson of the four-part series had you create a unique satellite constellation to track and monitor a hypersonic aircraft. The second lesson walked you through building the hypersonic flight and comparing it to a model from Ansys. In that lesson, you also created EOIR cameras to image the thermal properties of the hypersonic vehicle. In the third lesson, you created the communication system to convey the message to the necessary systems. This last section will bring it all together. You will model how the information will be passed from system to system, so the satellites have the opportunity to image the hypersonic aircraft.

Examining the starter scenario

Examine the scenario when it opens.

  1. You should see the hypersonic test flight (discussed in the DME: Hypersonics and EOIR (Part 2 of 4) lesson).
  2. You should see the eight relevant satellites from the SBIRS LEO constellation designed in the Constellation Design and Coverage (Part 1 of 4) lesson and refined in the Comm Analysis and Antenna Patterns (Part 3 of 4) lesson. These satellites are modeling the OmniInstalled transmitters and the Space-Based Infrared System (SBIRS).
  3. New to the mission are three geosynchronous satellites. These satellites are modeling the Defense Support Program (DSP) detection system.

All data and behavior is notional. The systems relate in this manner:

  • The mission is initiated by the takeoff of a B-52 aircraft carrying the Pegasus Hyper-X Launch Vehicle (HXLV), which accelerates the X-43 Hyper-X Research Vehicle (HXRV).
  • When the Pegasus HXLV ignites (begins its burn), it is detectable.
  • The DSP satellites in GEO orbit search for rocket plumes (ignition signature).
  • When a burn signature (something big and bright) is detected and processed, the DSP system sends that information to a ground terminal.
  • The ground terminal receives the information, processes it, and sends it to a constellation of SBIRS LEO satellites. The basis of this constellation is from first lesson, but with modifications that came about as the mission scope was expanded.
  • The satellites have IR cameras on board to track and follow the X-43 HXRV once it has been released from the Pegasus.
  • That information is transmitted back down to the ground terminal.
  • Once this entire system is modeled, you can assess the Total System Response Time, from the rocket ignition to full tracking by the SBIRS LEO satellites.

Adding the Pegasus HXLV burn interval to the Timeline View

The event that triggers the DSP and thus the entire series is the burn from the Pegasus HXLV launch. You can add that to the Timeline View to see when it occurs.

  1. Click the Timeline 1 tab in the lower left hand corner of STK to unhide the Timeline View.
  2. Right-click on the Timeline View title bar.
  3. Clear the Auto Hide checkbox. This will keep the Timeline View open.
  4. Click Add Time Components () in the Timeline View toolbar.
  5. Select the HXLV_Pegasus () in the object list when the Select Timeline Component dialog opens.
  6. Select PegasusBurn () in the Components for: HXLV_Pegasus list.

    7. This component was pre-built in the starter scenario. It has defined start and end time for the duration of the burn.

  7. Click OK to close the Select Timeline Component dialog.
  8. Look in the component rows section of the Time Display.

    9. Pegasus HXLV Burn

    This adds the first time component to the Time Display. This component was built to model the burn of the HXLV as it launches. This is also what the satellites in GEO detecting the burn sees. This is the initial trigger that sets the system in motion. This ignition burn is the initial event that triggers a detection system. It is what sets off the series events.

  9. Press and drag the rectangular markers on either side of the View Port to resize and focus on smaller periods of the scenario, if desired.

Creating a Chain between the DSP system and the Pegasus HXLV

Next, model how well the DSP system can detect the Pegasus HXLV. Once the Pegasus ignites and launches, the GEO satellites sweep and look for its signature. You can create a Chain between the system on the GEO satellite (Defense Support Program) and the Pegasus. The sensor is a specific system that is in the correct position to detect the Pegasus. Using a Chain object, you can do additional analysis.

  1. Bring the Insert STK Objects tool () to the front.
  2. Select Chain () in the Scenario Objects list.
  3. Select the Insert Default () method.
  4. Click Insert. . ..
  5. Right-click on Chain1 () in the Object Browser.
  6. Select Rename in the shortcut menu.
  7. Rename Chain1 () to DSP_to_Pegasus.

Defining the start and end objects

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

  1. Right-click on DSP_to_Pegasus () in the object Browser.
  2. Select Properties () in the shortcut menu.
  3. Select the Basic - Definition page when the Properties Browser opens.
  4. Click the Start Object ellipsis ().
  5. Select dsp_sweep3 () (attached to SBIRS_GEO-3_41937 ()) in the Select Object dialog.

    6. This is the specific system that is in the right location to detect the ignition.

  6. Click OK to close the Select Object dialog.
  7. Click the End Object ellipsis ().
  8. Select HXLV_Pegasus () in the Select Object dialog.
  9. Click OK to close the Select Object dialog.

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.

  1. Click Add in the Connections frame.
  2. Click the From Object ellipsis ().
  3. Select dsp_sweep3 () in the Select Object dialog.
  4. Click OK to close the Select Object dialog.
  5. Click the To Object ellipsis ().
  6. Select HXLV_Pegasus () in the Select Object dialog.
  7. Click OK to close the Select Object dialog.
  8. Click Apply to accept your changes and to keep the Properties Browser open.

Defining the interval component

This models the detection of the burn through each sensor sweep. This sensor is attached to a satellite spinning and sweeping the sensor over the earth. Through each sweep, the system is triggered when it detects the burn. You can add the burn interval to the chain analysis to make sure you are looking at it during the correct period.

  1. Select the Basic - Advanced page.
  2. Select the User Specified Time Period option in the Compute Time Period frame.
  3. Open the Start Stop dropdown menu.
  4. Select Interval Component... .
  5. Select the HXLV_Pegasus () in the object list when the Select Time Interval dialog opens.
  6. Select PegasusBurn () in the Intervals for: HXLV_Pegasus list.
  7. Click OK to close the Select Time Interval dialog.
  8. Click OK to accept your changes and to close the Properties Browser.

Adding the DSP to Pegasus complete chain access intervals to the Time Display

You can add the time component to the Time Display component rows to see how it compares to the data you have about the Pegasus burn.

  1. Click Add Time Components () in the Timeline View toolbar.
  2. Select the DSP_to_Pegasus () in the object list of the Select Timeline Component dialog.
  3. Select CompleteChainAccessIntervals () in the Components for: DSP_to_Pegasus list.
  4. Click OK to accept your changes and to close the Select Timeline Component dialog.

DSP_to_Pegaus Complete Chain Access Intervals

    This interval marks each time the sensor on the SBIRS_GEO-3_41937 () is able to scan and detect the burn signature from Pegasus.

Creating the DSP system processing time duration component

This component shows all the instances when the DSP system on board the satellite can detect the Pegasus burn. However, the system needs to verify that it is detecting a real ignition and process that information before it can relay it to the ground system. You can build a chain from the DSP to GroundStation while taking the processing time into account.

  1. Right-click on DSP_to_Pegasus () in the Object Browser.
  2. Select Analysis Workbench... () in the shortcut menu.
  3. Select the Time tab when the Analysis Workbench opens.
  4. Select DSP_to_Pegasus () in the object list.

    5. You can build the processing time on this chain access.

  5. Click Create new Interval () in the toolbar.

Adding a time component

You will define a time component that produces a single interval of time.

  1. Click Type: Select... in the Add Time Component dialog.
  2. Select Fixed Duration () in the Select Component Type list when the Select Component Type dialog opens.

    3. Fixed duration is an interval of fixed duration anchored at a time defined by a specified Time Instant component.

  3. Click OK to close the Select Component Type dialog.
  4. Type DSP_SystProcessing in the Name field.
  5. Click the Reference Time Instant ellipsis ().
  6. Select DSP_to_Pegasus () in the object list when the Select Reference Time Instant dialog opens.
  7. Expand () CompleteChainAccessTimeSpan () in the Time Instants for: DSP_to_Pegasus list.
  8. Select Start ().

    9. This enables you to build the processing time from the first detection of the burn.

  9. Click OK to close the Select Reference Time Instant dialog.
  10. Enter 30 sec in the Stop Offset field.
  11. Click OK to close the Add Time Component dialog.
  12. Click Close to close the Analysis Workbench.

Adding the DSP system processing time duration component to the Time Display

  1. Click Add Time Components () in the Timeline View toolbar.
  2. Select the DSP_to_Pegasus () in the object list in the Select Timeline Component dialog.
  3. Select DSP_SystProcessing () in the Components for: DSP_to_Pegasus list.
  4. Click OK to accept your changes and to close the Select Timeline Component dialog.

    DSP_to_Pegaus DSP_SystProcessing

    You built this component so that it is triggered during the first sweep and after the third one is prepared to relay the information. This interval accounts for how long the information takes to process on-board the SBIRS_GEO-3_41937 and when it is able to react.

Creating a chain between the DSP and the Ground Terminal

After the burn is verified and the information processed, the next stage is to send that signal to GroundTerminal. You do not have a specific transmitter built on this system, so the analysis focuses on the chain access between the geostationary satellite and GroundTerminal.

  1. Insert a Chain () object using the Insert Default () method.
  2. Rename Chain2 () to DSP_to_Ground.

Defining the start and end objects

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

  1. Open DSP_to_Ground's () Properties ().
  2. Select the Basic - Definition page when the Properties Browser opens.
  3. Click the Start Object ellipsis ().
  4. Select SBIRS_GEO-3_41937 () in the Select Object dialog.
  5. Click OK to close the Select Object dialog.
  6. Click the End Object ellipsis ().
  7. Select GroundTerminal () in the Select Object dialog.
  8. Click OK to close the Select Object dialog.

Creating the Chain object's connections

  1. Click Add in the Connections frame.
  2. Click the From Object ellipsis ().
  3. Select SBIRS_GEO-3_41937 () in the Select Object dialog.
  4. Click OK to close the Select Object dialog.
  5. Click the To Object ellipsis ().
  6. Select GroundTerminal () in the Select Object dialog.
  7. Click OK to close the Select Object dialog.
  8. Click Apply to accept your changes and to keep the Properties Browser open.

Defining the interval component

This models the access between a satellite in GEO and GroundTerminal. The access begins after the signal has been processed.

  1. Select the Basic - Advanced page.
  2. Select the User Specified Time Period option in the Compute Time Period frame.
  3. Open theStart Stop dropdown menu.
  4. Select Start Time in the shortcut menu.
  5. Select Time Component... in the Start Time submenu.
  6. Select the DSP_to_Pegasus () in the object list when the Select Time Instance dialog opens.
  7. Expand () DSP_SystProcessing () in the Time Instants for: DSP_to_Pegasus list.
  8. Select Stop ().

    9. You want the chain access to begin once the information from the geostationary satellite is processed and sent.

  9. Click OK to close the Select Time Instance dialog.

Defining the end of the chain

You can repeat the same process to set the Stop component. You want to define the end of the chain access.

  1. Open theStart Stop dropdown menu.
  2. Select Stop Time in the shortcut menu.
  3. Select Time Component... in the Stop Time submenu.
  4. Select the DSP_to_Pegasus () in the object list when the Select Time Instance dialog opens.
  5. Expand () CompleteChainAccessIntervals () in the Time Instants for: DSP_to_Pegasus list.
  6. Expand () Last ().
  7. Select Stop ().
  8. Click OK to close the Select Time Instance dialog.
  9. Click OK to accept your changes and to close the Properties Browser.

Adding the DSP to Ground complete chain access intervals to the Time Display

  1. Click Add Time Components () in the Timeline View toolbar.
  2. Select the DSP_to_Ground () in the object list when the Select Timeline Component dialog opens.
  3. Select CompleteChainAccessIntervals () in the Components for: DSP_to_Ground list.
  4. Click OK to accept your changes and to close the Select Timeline Component dialog.

DSP_to_Ground Complete Chain Access Intervals

    The interval added to the Time Display accounts for when SBIRS_GEO-3_41937 is able to send information down to GroundTerminal.

Setting the Ground Terminal system processing time duration component

Once GroundTerminal has the message from the Defense Support System, it processes and relays the message to the SBIRS LEO satellite constellation.

  1. Right-click on DSP_to_Ground () in the Object Browser.
  2. Select Analysis Workbench... () in the shortcut menu.
  3. Select the Time tab when Analysis Workbench opens.
  4. Select DSP_to_Ground () in the object list.

    5. You can build the processing time on this chain access.

  5. Click the Create new Interval () in the toolbar.

Creating a time component

  1. Click Type: Select... when the Add Time Component dialog opens.
  2. Select Fixed Duration () in the Select Component Type list when the Select Component Type dialog opens.
  3. Click OK to close the Select Component Type dialog.
  4. Type GroundTerminal_SystProcessing in the Name field when you return to the Add Time Component dialog.
  5. Enter 30 sec in the Stop Offset field.
  6. Click OK to accept your changes and to close the Add Time Component dialog.
  7. Click Close to close the Analysis Workbench.

Adding the Ground Terminal system processing time duration component to the Time Display

  1. Click Add Time Components () in the Timeline View toolbar.
  2. Select the DSP_to_Ground () in the object list when the Select Timeline Component dialog opens.
  3. Select GroundTerminal_SystProcessing () in the Components for: DSP_to_Ground list.
  4. Click OK to accept your changes and to close the Select Timeline Component dialog.

    DSP_to_Ground Ground Terminal System Processing

    This component accounts for the processing time at GroundTerminal before it relays the message. GroundTerminal processes the information it receives from SBIRS_GEO-3_41937. Once processed it can share it.

Creating a chain between the Ground Terminal and the SBIRS LEO constellation

GroundTerminal relays the message to the constellation of SBIRS LEO satellites. It doesn't matter which satellites get the message. You can send the message to any satellite overhead.

  1. Insert an Chain object () using the Insert Default () method.
  2. Rename Chain3 () to Ground_to_LEO.

Defining the start and end objects

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

  1. Open Ground_to_LEO's () Properties ().
  2. Select the Basic - Definition page in the Properties Browser.
  3. Click the Start Object ellipsis ().
  4. Select GroundTerminal () in the Select Object dialog.
  5. Click OK to close the Select Object dialog.
  6. Click the End Object ellipsis ().
  7. Select SBIRS_LEO () in the Select Object dialog.
  8. Click OK to close the Select Object dialog.

Creating the Chain object's connections

  1. Click Add in the Connections frame.
  2. Click the From Object ellipsis ().
  3. Select GroundTerminal () in the Select Object dialog.
  4. Click OK to close the Select Object dialog.
  5. Click the To Object ellipsis ().
  6. Select SBIRS_LEO () in the Select Object dialog.
  7. Click OK to close the Select Object dialog.
  8. Click OK to accept your changes and to close the Properties Browser.

Adding the Ground to LEO complete chain access intervals to the Time Display

Add the time component to the Time Display to see how it relates to the initial stages of the mission.

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

Ground_to_leo complete chain access intervals

    You confirmed that you can see this interval throughout the length of the mission. Now you can create a component that defines when the signal is transmitted.

Creating a chain from the Ground Terminal to the SBIRS LEO constellation when the message is relayed

This chain is similar to the previously built component. However, this time you can view the chain link after the signal is sent from GroundTerminal until the end of the previously built chain access.

  1. Insert an Chain object () using the Insert Default () method.
  2. Rename Chain4 () to Ground_to_LEORelay.

Defining the start and end objects

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

  1. Open Ground_to_LEORelay's () Properties ().
  2. Select the Basic - Definition page in the Properties Browser.
  3. Click the Start Object ellipsis ().
  4. Select GroundTerminal () in the Select Object dialog.
  5. Click OK to close the Select Object dialog.
  6. Click the End Object ellipsis ().
  7. Select SBIRS_LEO () in the Select Object dialog.
  8. Click OK to close the Select Object dialog.

Creating the Chain object's connections

  1. Click Add in the Connections frame.
  2. Click the From Object ellipsis ().
  3. Select GroundTerminal () in the Select Object dialog.
  4. Click OK to close the Select Object dialog.
  5. Click the To Object ellipsis ().
  6. Select SBIRS_LEO () in the Select Object dialog.
  7. Click OK to close the Select Object dialog.
  8. Click Apply to accept your changes and to keep the Properties Browser open.

Specifying the start time component

You want the chain access to begin once the information from GroundTerminal is processed and sent.

  1. Select the Basic - Advanced page.
  2. Select the User Specified Time Period option in the Compute Time Period frame.
  3. Open the Start Stop dropdown menu.
  4. Select Start Time in the shortcut menu.
  5. Select Time Component... in the Start Time shortcut menu.
  6. Select the DSP_to_Ground () in the object list when the Select Time Instance dialog opens.
  7. Expand () GroundTerminal_SystProcessing () in the Time Instants for: DSP_to_Ground list.
  8. Select Stop ().
  9. Click OK to close the Select Time Instance dialog.

Specifying the stop time component

This access takes place once the message is sent from GroundTerminal until the satellites are no longer in view.

  1. Open the Start Stop dropdown menu.
  2. Select Stop Time in the shortcut menu.
  3. Select Time Component... in the Stop Time submenu.
  4. Select the Ground_to_LEO () in the object list when the Select Time Instance dialog opens.
  5. Expand () CompleteChainAccessTimeSpan () in the Time Instants for: Ground_to_LEO list.
  6. Select Stop ().
  7. Click OK to close the Select Time Instance dialog.
  8. Click OK to accept your changes and to close the Properties Browser.

Adding the Ground to LEO Relay complete chain access intervals to the Time Display

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

    5. Ground_to_LEO_Relay Complete Chain Access Intervals

    This interval shows how long the GroundTerminal has to relay information to the constellation of LEO satellites.

Creating the SBIRS system processing time duration component

  1. Right-click on Ground_to_LEORelay () in the Object Browser.
  2. Select Analysis Workbench... () in the shortcut menu.
  3. Select the Time tab when Analysis Workbench opens.
  4. Select the Ground_to_LEORelay () in the object list.

    5. You can build the processing time on this chain access.

  5. Click Create new Interval () in the toolbar.

Creating a time component

  1. Click Type: Select... when the Add Time Component dialog opens.
  2. Select Fixed Duration () in the Select Component Type list when the Select Component Type dialog opens.
  3. Click OK to close the Select Component Type dialog.
  4. Type SBIRS_SystProcessing in the Name field when you return to the Add Time Component dialog.
  5. Enter 30 sec in the Stop Offset field.
  6. Click OK to close the Add Time Component dialog.
  7. Click Close to close the Analysis Workbench.

Adding the SBIRS system processing time duration component to the Time Display

  1. Click Add Time Components () in the Timeline View toolbar.
  2. Select Ground_to_LEORelay () in the object list when the Select Timeline Component dialog opens.
  3. Select SBIRS_SystProcessing () in the Components for: Ground_to_LEORelay list.
  4. Click OK to close the Select Timeline Component dialog.

    Ground_to_LEO_Relay SBIRS System Processing

    The LEO constellation isn’t able to react immediately. This interval accounts for how long it takes for it to take action.

Creating a chain from the SBIRS LEO system to the X-43 HXRV

Now that you know how long it takes the transmitters to react, you can create a chain access between SBIRS LEO system and the X-43. Once the SBIRS LEO system knows the Pegasus launch has taken place, it can lock on and begin to track the rest of the X-43's flight.

  1. Insert an Chain object () using the Insert Default () method.
  2. Rename Chain5 () to SBIRS_LEO_to_X43.

Defining the start and end objects

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

  1. Open SBIRS_LEO_to_X43's () Properties ().
  2. Select the Basic - Definition page when the Properties Browser opens.
  3. Click the Start Object ellipsis ().
  4. Select SBIRS_LEO () in the Select Object dialog.
  5. Click OK to close the Select Object dialog.
  6. Click the End Object ellipsis ().
  7. Select HXRV_X43 () in the Select Object dialog.
  8. Click OK to close the Select Object dialog.

Creating the Chain object's connections

Model the access between the SBIRS LEO system and the rest of the X-43 test flight. You are going to account for how long it takes for the SBIRS system to react to the message from GroundTerminal.

  1. Click Add in the Connections frame.
  2. Click the From Object ellipsis ().
  3. Select SBIRS_LEO () in the Select Object dialog.
  4. Click OK to close the Select Object dialog.
  5. Click the To Object ellipsis ().
  6. Select HXRV_X43 () in the Select Object dialog.
  7. Click OK to close the Select Object dialog.
  8. Click Apply to accept your changes and to keep the Properties Browser open.

Specifying the start time component

  1. Select the Basic - Advanced page.
  2. Select the User Specified Time Period option in the Compute Time Period frame.
  3. Open the Start Stop dropdown menu.
  4. Select Start Time in the shortcut menu.
  5. Select Time Component... in the Start Time submenu.
  6. Select Ground_to_LEORelay () in the object list when the Select Time Instance dialog opens.
  7. Expand () SIRBS_SystProcessing () in the Time Instants for: Ground_to_LEORelay list.
  8. Select Stop ().
  9. Click OK to close the Select Time Instance dialog.

Specifying the stop time component

This access takes place once the message is sent from GroundTerminal until the satellites are no longer in view.

  1. Open theStart Stop dropdown menu.
  2. Select Stop Time in the shortcut menu.
  3. Select Time Component... in the Stop Time submenu.
  4. Select HXRV_X43 () in the object list when the Select Time Instance dialog opens.
  5. Expand () AvailablityTimeSpan () in the Time Instants for: HXRV_X43 list.
  6. Select Stop ().
  7. Click OK to close the Select Time Instance dialog.
  8. Click OK to accept your changes and to close the Properties Browser.

Adding the SBIRS LEO to X-43 complete chain access intervals to the Time Display

  1. Click Add Time Components () in the Timeline View toolbar.
  2. Select SBIRS_LEO_to_X43 () in the object list when the Select Timeline Component dialog opens.
  3. Select CompleteChainAccessIntervals () in the Components for: SBIRS_LEO_to_X43 list.
  4. Click OK to close the Select Timeline Component dialog.

sbirs_leo_to_x43 complete chain access intervals

Examining the total system response time

You can now see how long it takes from the initial launch to when the SBIRS system can track the rest of the X-43 flight. You can measure this explicitly.

From the beginning of the DSP’s detection of the Pegasus launch to when the SBIRS system locks on is the total system response time. You can build this component in STK's Analysis Workbench capability.

  1. Right-click on X43_Mission_AWB () in the Object Browser.
  2. Select Analysis Workbench... () in the shortcut menu.
  3. Select the Time tab when Analysis Workbench opens.
  4. Select X43_Mission_AWB () in the object list.

    5. You can build the processing time on this chain access.

  5. Click Create new Interval () in the toolbar.

Creating a between time instants component

A between time instants component is an interval with start and stop times defined by two specified Time Instant components.

  1. Click Type: Select... when the Add Time Component dialog opens.
  2. Select Between Time Instants () in the Select Component Type list when the Select Component Type dialog opens.
  3. Click OK to close the Select Component Type dialog.
  4. Type SystemResponseTime in the Name field when you return to the Add Time Component dialog.
  5. Click the Start Time Instant ellipsis ().
  6. Select HXLV_Pegasus () in the object list when the Select Reference Time Instant dialog opens.
  7. Expand () PegasusBurn () in the Time Instants for: HXLV_Pegasus list.
  8. Select Start ().
  9. Click OK to close the Select Reference Time Instant dialog.
  10. Click the Stop Time Instant ellipsis ().
  11. Select SBIRS_LEO_to_X43 () in the object list when the Select Reference Time Instant dialog opens.
  12. Expand () CompleteChainAccessTimeSpan () in the Time Instants for: SBIRS_LEO_to_X43 list.
  13. Select Start ().
  14. Click OK to close the Select Reference Time Instant dialog.
  15. Click OK to close the Add Time Component dialog.

Adding the total system response time component to the Time Display

  1. Click Add Time Components () in the Timeline View toolbar.
  2. Select X43_Mission_AWB () in the object list when the Select Timeline Component dialog opens.
  3. Select SystemResponseTime () in the Components for: X43_Mission_AWB list.
  4. Click OK to close the Select Timeline Component dialog.

    5. X43_Mission System Response Time

    This is how long it would take for a space based system to know that a hypersonic vehicle has been launched. From the initial burn to when the LEO constellation is informed of the launch is the System Response Time.

  5. Examine the Time Display.

    6. The newly added component is the full closed loop of a system response. If you hover over the SystemResponseTime interval, you can see the total duration.

Showing the SBIRS LEO IR tracking and processing time duration component

You can complete the system. SBIRS _LEO has an IR Tracking system on it. It tracks HXRV_43, processes it, and sends the information back to GroundTerminal.

  1. Return to Analysis Workbench.
  2. Select SBIRS_LEO_to_X43 () in the object list.

    3. You can build the processing time on this chain access.

  3. Click Create new Interval () in the toolbar.

Creating a time component

  1. Click Type: Select... when the Add Time Component dialog opens.
  2. Select Fixed Duration () in the Select Component Type list when the Select Component Type dialog opens.
  3. Click OK to close the Select Component Type dialog.
  4. Type SBIRS_IR_SystProcessing in the Name field when you return to the Add Time Component dialog.
  5. Enter 30 sec in the Stop Offset field.
  6. Click OK to close the Add Time Component dialog.
  7. Click Close to the close the Analysis Workbench.

Adding the SBIRS LEO IR tracking and processing time component to the Time Display

  1. Click Add Time Components () in the Timeline View toolbar.
  2. Select SBIRS_LEO_to_X43 () in the object list when the Select Timeline Component dialog opens.
  3. Select SBIRS_IR_SystProcessing () in the Components for: SBIRS_LEO_to_X43 list.
  4. Click OK to close the Select Timeline Component dialog.

SBIRS_LEO_to_X43 SBIRS IR System Processing

Inserting a chain object to model the communications link

Model the communications link between the transmitters on the satellites and the receiver on the ground. You also want to take into account the time for the signal to process.

  1. Insert an Chain object () using the Insert Default () method.
  2. Rename Chain6 () to SBIRS_Tx_to_Ground_Rcvr.

Defining the start and end objects

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

  1. Open SBIRS_Tx_to_Ground_Rcvr's () Properties ().
  2. Select the Basic - Definition page when the Properties Browser opens.
  3. Click the Start Object ellipsis ().
  4. Select SBIRS_LEO_Tx () in the Select Object dialog.
  5. Click OK to close the Select Object dialog.
  6. Click the End Object ellipsis ().
  7. Select SatComRcvr () (attached to GroundTerminal ()) in the Select Object dialog.
  8. Click OK to close the Select Object dialog.

Creating the Chain object's connections

  1. Click Add in the Connections frame.
  2. Click the From Object ellipsis ().
  3. Select SBIRS_LEO_Tx () in the Select Object dialog.
  4. Click OK to close the Select Object dialog.
  5. Click the To Object ellipsis ().
  6. Select SatComRcvr () in the Select Object dialog.
  7. Click OK to close the Select Object dialog.
  8. Click Apply to accept your changes and to keep the Properties Browser open.

Specifying the start time component

You want the chain access to begin once the information is processed.

  1. Select the Basic - Advanced page.
  2. Select the User Specified Time Period option in the Compute Time Period frame.
  3. Open theStart Stop dropdown menu.
  4. Select Start Time in the shortcut menu.
  5. Select Time Component... in the Start Time submenu.
  6. Select SBIRS_LEO_to_X43 () in the object list when the Select Time Instance dialog opens.
  7. Expand () SBIRS_IR_SystProcessing () in the Time Instants for: SBIRS_LEO_to_X43 list.
  8. Select Stop ().
  9. Click OK to close the Select Time Instance dialog.

Specifying the stop time component

You already measured the inter visibility between the SBIRS satellites and GroundTerminal. The end time of this component works for the link.

  1. Open theStart Stop dropdown menu.
  2. Select Stop Time in the shortcut menu.
  3. Select Time Component... in the Stop Time submenu.
  4. Select Ground_to_LEO () in the object list when the Select Time Instance dialog opens.
  5. Expand () CompleteChainAccessTimeSpan () in the Time Instants for: Ground_to_LEO list.
  6. Select Stop ().
  7. Click OK to close the Select Time Instance dialog.
  8. Clear the Automatically Recompute Access checkbox in the Access frame.

    9. This chain is dependent on many earlier chains. When you make changes to the study, you want to manually update this calculation so it takes the latest configuration.

  9. Click OK to accept your changes and to close the Properties Browser.
  10. Select SBIRS_Tx_to_Ground_Rcvr () in the Object Browser.
  11. Open the Chain menu.
  12. Select Compute Accesses.

Adding the communication link chain access intervals to the Time Display

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

    5. SBIRS_Tx_to_Ground_Rcvr Complete Chain Access Intervals

    The LEO constellation is equipped with IR cameras. It will transmit that data back down to GroundTerminal.

  5. Take a look at the Time Display.

    6. You can see the total system of systems working together, sending information, relaying it, and processing it. This provides you with a holistic view of the mission design. You can also analyze what happens when events go awry.

Performing digital thread analysis: losing satellites

The basis of your constellation is that it will provide you with persistent coverage with at least two satellites covering the region of interest. That means, even if two satellites get knocked out, you will still be able to track out X-43. Test this out.

  1. Open SBIRS_LEO's () Properties ().
  2. Remove () the SBIRS_LEO12 () from the Assigned Objects list.
  3. Click OK to accept your change and to close the Properties Browser.
  4. Open Ground_to_LEO's () Properties ().
  5. Select the Basic - Advanced page.
  6. Clear the Automatic Recompute Accesses checkbox in the Access frame.
  7. Click OK to accept your change and to close the Properties Browser.
  8. Select Ground_to_LEO () in the Object Browser.
  9. Open the Chain menu.
  10. Select Compute Accesses.
  11. Recompute the other dependent chains:
    • Ground_to_LEORelay ()
    • SBIRS_LEO_to_X43 ()
    • SBIRS_Tx_to_Ground_Rcvr ()

Losing three satellites

  1. Open SBIRS_LEO's () properties ().
  2. Remove () the following satellites from the Assigned Objects list:
    • SBIRS_LEO21 ()
    • SBIRS_LEO36 ()
  3. Click Apply to accept your changes and to keep the Properties Browser open.
  4. Select Ground_to_LEO () in the Object Browser.
  5. Select the Chain menu.
  6. Select Compute Accesses.
  7. Recompute the other dependent chains:
    • Ground_to_LEORelay ()
    • SBIRS_LEO_to_X43 ()
    • SBIRS_Tx_to_Ground_Rcvr ()

    There is no change in the SBIRS_LEO_to_X43's () ability to track HXRV_X43 (). Ground_to_LEO () has become shorter.

Losing four satellites

  1. Bring SBIRS_LEO's () Properties () to the front.
  2. Remove () the SBIRS_LEO62 () from the Assigned Objects list.
  3. Click Apply to accept your change and to keep the Properties Browser open.
  4. Select Ground_to_LEO () in the Object Browser.
  5. Select the Chain menu.
  6. Select Compute Accesses.
  7. Recompute the other dependent chains:
    • Ground_to_LEORelay ()
    • SBIRS_LEO_to_X43 ()
    • SBIRS_Tx_to_Ground_Rcvr ()

    Now the SBIRS_LEO_to_X43's () ability to track HXRV_X43 () is shorter. You are no longer able to track HXRV_X43 () at the end of the flight.

Adding the satellites back into the system

You have the benefit of designing a system specifically to track launches, so the persistent coverage is very good. Even if you lose three satellites, you are able to track the objects. Once you lose that fourth satellite, you run into gaps in your data.

  1. Bring SBIRS_LEO's () properties () to the front.
  2. Move () the following Satellite () objects from the Available Objects list to the Assigned Objects list:
    • SBIRS_LEO12 ()
    • SBIRS_LEO21 ()
    • SBIRS_LEO36 ()
    • SBIRS_LEO62 ()
  3. Click OK to accept your changes and to close the Properties Browser.
  4. Select Ground_to_LEO () in the Object Browser.
  5. Select the Chain menu.
  6. Select Compute Accesses.
  7. Recompute the other dependent chains:
    • Ground_to_LEORelay ()
    • SBIRS_LEO_to_X43 ()
    • SBIRS_Tx_to_Ground_Rcvr ()

    You could also understand this behavior by generating an Individual Strand Access graph on Ground_to_LEO (). This graph gives a visual display of which satellites are overhead and when.

Performing digital thread analysis: communications link BER

You can also stress test the communication link that is relaying the message back down to GroundTerminal. Earlier you learned about the BER and how it could affect the information transmitted. You can incorporate a constraint on the BER and the constraints of the study. For this mission, the easiest way to do that is to set a constraint on the Receiver object. Then you can place all the Transmitter objects in a Constellation object, create a chain access, and generate a link budget on the chain.

The final stage of this mission is a communication link between the SBIRS LEO transmitters and SatCommRcvr. You know that the data will get worse with a higher BER and so you can add a constraint to the mission model that takes into account when you have bad data.

  1. Open SatCommRcvr's () properties ().
  2. Select the Constraints - Active page.
  3. Click Add new constraints () in the Active Constraints toolbar.
  4. Select Bit Error Rate in the Constraint Name list.
  5. Click Add.
  6. Click Close to close the Select Constraints to Add dialog.
  7. Select the Max checkbox in the Bit Error Rate frame.
  8. Enter 1e-09 in the Max field.
  9. Click OK to accept your changes and to close the Properties Browser.
  10. Recompute the SBIRS_Tx_to_Ground_Rcvr () object.

    11. Note how the BER constraint means that data transmitted at the beginning and end of the link is no longer valid. The total time to send the IR information is cut down.

    SBIRS_Tx_to_Ground_Rcvr Communication Constraint

  11. Examine the beginning and end of the interval.

    12. It is much shorter due to the constraint. With the BER constraint we can see how we will lose the ability to transmit data to GroundTerminal. The duration of the access interval is much shorter, not because the satellites aren’t there, but because the data quality is worse.

Saving your work

You can clean up and finish your scenario.

  1. Close any open reports, properties, and the Report & Graph Manager.
  2. Save () your work.

Summary

The purpose of this series and of this mission is to evaluate how all the components of the mission work together. In previous sessions, you built detailed models, and in this scenario were able to bring them all together to see how they affect one another. You can evaluate your mission’s outcomes through an integrated digital environment, STK.