Digital Mission Engineering (DME): Comm Analysis and Antenna Patterns, Events, and Time Components (Part 3 of 3)

STK Premium (Air) 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.

Additional installation - EOIR. You can obtain the necessary install by visiting http://support.agi.com/downloads or calling AGI support.

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 and 2 of the DME lessons, starter scenarios are provided. It requires 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 12.8 or newer to complete.

Capabilities covered

This lesson covers the following STK capabilities:

STK Pro
Communications
Analysis Workbench
Aviator
Aviator Pro
Electro-Optical Infrared Sensor Performance (EOIR)

Overview

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 lifecycle. 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 lifecycle. Through digital mission engineering, you are now capable of quickly evaluating the overall mission impact of the smallest change to any component. This session 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 lifecycle. 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 timeline.

The communication system will be an important factor in the system response time of a detection and tracking system. Once you figure out how well your communication system works and which satellites are doing the communicating, you will look at the system response time of the mission as a whole.

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

Build and analyze a communication link
Apply external antenna gain pattern files
Generate a Link Budget
Understand the series of events taking place
Link the relevant events together.
Understand the system as a whole

External files

This lesson requires several external files:

DME_Session3_Starter_Comms.vdf - This is the starter scenario for the STK Communications capability portion of this lesson
DME_Session3_Starter_AWB.vdf - This is the starter scenario for the event and time components portion of the DME series
stss.mdl - This is the custom satellite model
SatCom_Omni_2p2G_Isolated.pattern - Simple antenna model to be loaded into the scenario
SatCom_Omni_2p2G_Installed.pattern - Antenna model using ANSYS tools to account for absorption / reflection off the satellite body

The external files are available for download from the STK Data Federate, at AGI - Document Library- STK 12 - Starter Tutorials - DME_Session3_Comms_and_Event_Analysis.

Video guidance

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

Open a starter scenario

We built a starter scenario for you that contains the flight and the Pegasus hypersonic vehicle. You can open the scenario from the SDF or from a local copy, and open the downloaded scenario from the SDF or the completed scenario from DME: Hypersonics and EOIR (Part 2 of 3) Lesson.

Launch STK ().
Click Open a Scenario when the Welcome to STK dialog box opens.

Open a starter scenario from the STK Data Federate (SDF)

Open the starter scenario from the SDF. You can log in as Guest.

Open the Location: shortcut menu when the Open dialog box opens.
Select STK Data Federate.
Select the Browse tab when the SDF opens.
Expand () the following: Sites>AGI>documentLibrary>STK 12>Starter Tutorials>DME_Session3_Comms_and_Event_Analysis.
Select DME_Session3_Starter_Comms.vdf.
Click Open . Be patient. This is a large scenario and might take a minute or two to load.

Examine the scenario. This mission is a continuation of what was built in DME: Hypersonics and EOIR. In the scenario, you should see the hypersonic test flight. Later in this mission, you can assess a system detecting and tracking the hypersonic aircraft.

Save a VDF as a SC File

When you save a scenario in STK, it will save in the format in which it originated. In other words, 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 SC file (or vice-versa), you must change the file format when you are performing the Save As procedure.

Open the File menu once the scenario has loaded.
Select Save As... .
Open the Location: shortcut menu when the Save As dialog box opens.
Select File System.
Select STK User on the left side of the Save As dialog box.
Select DME_Session3_Starter_comms.

Use this folder. There are files needed later in the scenario.

Click Open.
Open the Save as type: shortcut menu.
Select Scenario Files (*.sc).
Type X43_Mission_Comms in the File name: field.
Click Save .

Save often!

Inserting a Facility object

Use a Facility () object to simulate the location of your ground station.

Bring the Insert STK Objects tool () to the front.
Select Facility () in the Scenario Objects list.
Select the Define Properties () method.
Click Insert... .
Select the Basic - Position page when the Properties Browser opens.

Creating the ground station location

The focus of this section is to create a communication system. You can begin creating the communication system by building a ground station. The ground station houses the receiver. The satellite communicates with the ground station receiver, and you can use it to compare the coverage between the antenna models.

Set the following in the Position frame:

Option	Value
Latitude	34.1084 deg
Longitude	-119.065 deg

Click OK to accept your changes and to close the Properties Browser.
Right click on Facility1 () in the Object Browser.
Select Rename in the shortcut menu.
Rename Facility1 () to GroundTerminal.

This location is near Point Mugu.

Viewing in 3D

Bring the 3D Graphics window to the front.
Right click on GroundTerminal () in the Object Browser.
Select Zoom To.
Mouse around the 3D Graphics window to understand the location of the ground terminal.

3D View: Ground Terminal

Inserting a Receiver object

GroundTerminal () is receiving signals from multiple satellites. Use a Simple Receiver model that autotracks to all frequencies. A Simple Receiver model (default) uses an isotropic, omnidirectional antenna which is an ideal spherical pattern antenna with constant gain.

Insert an Receiver () object using the Insert Default () method.
Select GroundTerminal () in the Select Object dialog box.
Click OK.
Rename Receiver1 () to Receiver.

Inserting a Satellite object

The Satellite () object is the vehicle for the transmitter. It also functions as a seed satellite for a satellite constellation you set up later.

Insert a Satellite () object using the Orbit Wizard () method.
Set the following when the Orbit Wizard opens:

Option	Value
Type:	Circular
Satellite Name:	LEO_Sat
Inclination:	50 deg
Altitude:	1734 km

Click the 3D Model: ellipsis () in the Graphics frame.
Select stss.mdl when the File dialog box opens.
Click Open.
Click OK to close the Orbit Wizard.

The orbital values were found from another optimization of the satellite constellation. After the initial study in DME: Constellation Design, the parameters for the mission were updated and a new constellation for the system was designed. You can use this satellite to seed the constellation later in this lesson.

Inserting a Transmitter object

Attach a Transmitter () object to LEO_Sat ().

Insert a Transmitter () object using the Define Properties () method.
Select LEO_Sat () in the Select Object dialog box.
Click OK.

Adding a transmitter to model accessibility

You can now begin by building the communication system. Initially, you want to model a simple omnidirectional transmitter and analyze the communications link. The Simple Transmitter model (default) uses an isotropic, omnidirectional antenna which is an ideal spherical pattern antenna with constant gain.

Select the Basic - Definition page when the Properties Browser opens.
Select the Model Specs tab.
Enter 2.2 GHz in the Frequency: field. This is a short range S-Band frequency.
Click OK to accept your changes and to close the Properties Browser.
Rename Transmitter1 () to Transmitter.

Computing the link budget to the ground terminal

First, generate a link budget using the simple transmitter model. Then update it with a unique antenna pattern.

Right click on Transmitter () in the Object Browser.
Select Access... () in the shortcut menu.
Expand () GroundTerminal () in the Associated Objects list when the Access Tool opens.
Select Receiver ().
Click .
Click Link Budget...in the Reports frame.

This generates communication values between the two objects: Receiver () and Transmitter (). You can see various values, like Carrier to Noise (C/N) Ratio. For this case, you are primarily going to look at the Bit Error Rate (BER) as the quality metric. BER shows that, for this case, as long as line of sight is maintained, any sort of signal can be maintained. BER is effectively zero. This is primarily because you are using the Simple Transmitter model.

Inserting an Antenna object

Insert an Antenna () object and attach it to LEO_Sat (). The Antenna () object models the properties and behavior of an antenna.

Insert an Antenna () object using the Define Properties () method.
Select LEO_Sat () in the Select Object dialog box.
Click OK.

Using an external antenna model

With a Simple Transmitter model, you can get an initial analysis of the satellite communications system. With DME in mind, you can modify your system and see how things change when you load an external antenna model into the scenario.

Select the Basic - Definition page when the Properties Browser opens.
Click the Antenna Model Component Selector ().
Select External Antenna Pattern () in the Antenna Models list when the Select Component dialog box opens.
Click OK to close the Select Component dialog box .
Enter 2.2 GHz in the Design Frequency field.
Click the External Filename: ellipsis ().
Browse to the location of your scenario (typically <C:\Users\username\STK 12\DME_Session3_Starter_Comms>) when the Select File dialog box opens.
Select SatCom_Omni_2p2G_Isolation.pattern.
Click Open.
Click Apply to accept your changes and to keep the Object Browser open.

External Antenna Pattern Files

Within STK's Communications capability you can specify an external pattern file that contains user-defined data. The antenna data must form a rectangular matrix in order for STK to process it.

Open Windows File Explorer.
Browse to the location of your scenario.
Right click on SatCom_Omni_2p2G_Isolation.pattern.
Select Open with.
Select Notepad.
Click OK.

SatCom_Omni_2p2G_Isolation Pattern File

The pattern file is isolated from the body of the vehicle to which it is attached. This external antenna pattern could be provided by a third party, like a test lab. It could also be defined in another file type such as a CSV file. To turn this into an antenna gain pattern for STK, use Notepad and ensure the following header is in the data. The external antenna pattern file you are using is a PhiThetaPattern. This format is commonly used to model traditional antennas such as parabolic.

STK works well with the Phi-Theta sweep pattern of data. STK supports a wide variety of industry antenna gain formats. Contact support@agi.com if you have questions about other formats.

Close Notepad when you are finished viewing the data.
Close Windows File Explorer.

Orienting the antenna

By default, STK places the antenna in a fixed 90-degree elevation on the satellite. You can reorient it and change the position of the antenna. Realistically, the antenna is not placed on the center of the model.

Select the Basic - Orientation page.
Set the following options:

Option	Value
Azimuth	270 deg
Elevation	90 deg

Set the following Position Offset values:

Option	Value
X	-0.57 m
Y	0.93 m
Z	0.55 m

Click Apply to accept your changes and to keep the Properties Browser open.

Displaying Contours

The 2D Graphics Contours properties page for the antenna allows you to define the display of contour lines and antenna patterns.

Select the 2D Graphics - Contour page.
Select the Show Contour Graphics check box.
Set the following in the Level Adding frame:

Option	Value
Start:	-10
Stop:	11
Step:	3

Click Add Level.
Clear the Relative to Maximum check box.
Click Apply to accept your changes and to keep the Properties Browser open.

Contours and Antenna Beams

The 3D Graphics Attributes page for the antenna allows you to control the 3D display of contour lines and antenna patterns.

Select the 3D Graphics - Attributes page.
Select the Show Lines check box in the Contour Graphics frame.
Select the Show Volume check box in the Volume Graphics frame.
Set the following options:

Option	Value
Gain Scale (per dB):	4 cm
Minimum Displayed Gain:	-30 dB

Enter 180 deg in the Stop: field in the Elevation frame.
Open the Min Color: shortcut menu.
Select red.
Open the Max Color: shortcut menu.
Select blue.
Click OK to accept your changes and to close the Properties Browser.
Rename Antenna1 () to OmniIsolated.

Viewing in 3D

View the antenna pattern in the 3D Graphics window.

Bring the 3D Graphics window to the front.
Right click on LEO_Sat () in the Object Browser.
Select Zoom To.
Mouse around the 3D Graphics dialog box to understand the antenna pattern.

Omni isolated antenna pattern

The model is isolated from the model of the satellite. It does not take into account any aspect of the satellite that may affect the signal. The "perfect omni" antenna assumption may not be sufficient for RF link budget modeling.

Modifying the transmitter

You will analyze the behavior of this system to quantify it in detail. You can model a transmitter to house the antenna and compute the link budget. Transmitter objects can pull in configuration of antennas modeling in the scenario.

Open Transmitter's () properties ().
Select the Basic - Definition page when the Properties Browser opens.
Click the Transmitter Model Component Selector ().
Select Complex Transmitter Model in the Transmitter Models list when the Select Component dialog box opens.
Click OK to close the Select Component dialog box.

Model Specs

Select the Model Specs tab.
Enter the following options:

Option	Value
Frequency:	2.2 GHz
Power	2 W

Click Apply to accept your changes and to keep the Properties Browser open.

Antenna

Select the Antenna tab.
Open the Reference Type: shortcut menu.
Select Link.

There are many default antenna gain patterns available in STK. Instead of these, you can load an external antenna pattern that is relevant to the mission.

Notice that Antenna/OmniIsolated is set as the Antenna Name.
Click Apply to accept your changes and to keep the Properties Browser open.

Refresh the Link Budget report

Bring the Link Budget report to the front.
Click Refresh (F5) () in the report's toolbar.

Notice the greater variation in the BER with this updated model. Rather than the constant value, see how the BER varies throughout the satellites pass. This is still an idealized mission model. Realistically, the behavior of the antenna changes depending on how it is placed on the body of the satellite. You can analyze that behavior next.

Modeling the installed antenna

To take the satellite model behavior into account, you are using the OmniIsolated file. This file was created using ANSYS HFSS SBR+ that uses Shooting and Bouncing Rays to solve the antenna interaction with the satellite it is attached to. However, the source of the antenna behavior data could come from a multitude of sources. You created your own data in STK, loaded external models, and could have loaded results from system tests.

Antenna performances can be altered dramatically and impact the associated system because of the relationship between vehicle and payload. This is important to take into account in the mission model. This file is the OmniInstalled model because it is takes into account the antenna behavior. Assuming the antenna was installed at a specific location on the body of the vehicle, it would take into account the interference from that location.

The figures above demonstrate the results from the HFSS SBR+ using Shooting and Bouncing Rays analysis.

Reusing STK Objects

You can reuse objects in STK.

Right click on OmniIsolated () in the Object Browser.
Select Copy () in the shortcut menu.
Right click on LEO_Sat () in the Object Browser.
Select Paste () in the shortcut menu.
Rename OmniIsolated1 () to OmniInstalled.
Clear the OmniIsolated () in the Object Browser.

Updating OmniInstalled's properties

Open OmniInstalled's () properties ().
Select the Basic - Definition page when the Properties Browser opens.
Click the External Filename: ellipsis ().
Browse to the location of your scenario when the Select File dialog box opens.
Select SatCom_Omni_2p2G_Installed.pattern.
Click Open.

If you were to open the pattern file in a text editor, you'd notice that the values change throughout the file.

Pattern file in Text editor

Click OK to accept your changes and to close the Properties Browser.

Viewing in 3D

Bring the 3D Graphics window to the front.
Right-click LEO_Sat () in the Object Browser.
Select Zoom To.
Mouse around the 3D Graphics dialog box to understand the new antenna pattern.

Notice the dramatic difference between the two antenna models. It is also important to understand the effect the interaction of the antenna and satellite can have on the signal. This is visualized with the contours on the surface of the Earth. The effects can also be measured in the data.

Omni Installed antenna pattern

Switching to the OmniInstalled antenna

Open Transmitter's () properties ().
Select the Antenna tab when the Properties Browser opens.
Select the Model Specs sub tab.
Open the Antenna shortcut menu.
Select Antenna/OmniInstalled.
Click OK to accept your changes and to close the Properties Browser.
Bring the Link Budget report to the front.
Click Refresh (F5) () in the report's toolbar.

Examine the data. Notice the variations in the Bit Error Rate. To understand how this antenna model affects the data, you can generate a Bit Error Rate graph.

Viewing in 3D

Bring the 3D Graphics window to the front.
Right-click LEO_Sat () in the Object Browser.
Select Zoom To.
Mouse around the 3D Graphics window to view the contours on the Earth.

Omni installed Antenna Contours

Over time, the antenna pattern passes over the Ground Terminal. You can assess this in more detail with a BER graph.

Generating the BER graph

Right click on OmniInstalled () in the Object Browser.
Select Report & Graph Manager... () in the shortcut menu.
Open the Object Type: shortcut menu when the Report & Graph Manager opens.
Select Access.
Select Satellite-LEO_Sat-Transmitter-Transmitter-To-Facility-GroundTerminal-Receiver-Receiver () in the Object Type: list.
Expand () Installed Styles () in the Styles frame if needed.
Select the Bit_Error_Rate () graph.
Click Generate... .
Enter 1 sec in the Step: field.
Click the Enter key on your keyboard.

bit error rate graph throughout the scenario

Hold down your left mouse button and draw a box around one of the peaks. This zooms into the graph to show the data values.

bit error rate graph zoomed in

Viewing in 3D

You can jump to a time in your graph and obtain situational awareness in the 3D Graphics window.

Right-click the sharp peak in the graph.
Select Set Animation Time in the shortcut menu.
Bring the 3D Graphics window to the front.
Zoom to LEO_sat ().
Mouse around in the 3D Graphics window to note the dip in the antenna pattern as it passes over the GroundTerminal ().

3D View: Antenna Pattern over Ground Terminal

It is important to consider how you would not have known when bit error rates increased had you not used a custom external antenna model and generated the BER graph.

Clear the OmniInstalled () check box in the Object Browser.

Designing the satellite constellation

You have defined a satellite with the characteristics and orbit you need. You will use the Satellite Collection () object and the Walker tool to generate a Walker constellation. For your preliminary analysis, six (6) satellites in six (6) orbital planes are required for a total of 36 satellites. The Satellite Collection object models a group of satellites as a single object in the Object Browser. The associated satellites do not appear in the Object Browser, but are available for analysis purposes within other computational tools such as STK's Coverage capability, CommSystem, DeckAccess, and AdvCAT.

Insert a SatelliteCollection () object using the Walker Tool () method.
Click Select Object... when the Walker Tool opens.
Select LEO_Sat () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Set the following:

Option	Value
Number of Sats per Plane	6
Number of Planes:	6

Type LEO_Sats in the Name field in the Container Options frame.
Click Create / Modify Walker.
Click Close to close the Walker Tool.

Satellite Collection Labels

You can control the graphical display of a satellite collection. You want to have STK place the satellites' names next to their markers for each satellite in the subset for situational awareness.

Open LEO_Sats () properties ().
Select the Graphics - Attributes page when the Properties Browser opens.
Select the AllSatellites Label check box.
Click OK to accept your change and to close the Properties Browser.
Bring the 3D Graphics window to the front.
Use you mouse to view the constellation of satellites.

satellite collection object constellation

Creating a Chain Object

The Walker tool enables you to design constellations of satellites using the behavior of a seed satellite. It will also model any payloads on the seed satellite. In this mission, that would be the Transmitter and Antennas.

You built a global constellation to provide as much coverage as possible to track the hypersonic vehicle. However, not all of these satellites are overhead during the time of the flight. You only care about a subset of the satellites, not all 36 satellites.

To quantify the relationship between all satellites in the constellation and the ground terminal, you can compute a chain access.

Insert a Chain () object using the Insert Default () method.
Rename Chain1 () to LEO_to_Ground.

Define the start and end objects

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

Open LEO_to_Ground's () properties ().
Select the Basic - Definition page when the Properties Browser opens.
Click the Start Object: ellipsis ().
Select AllSatellites () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click the End Object: ellipsis ().
Select GroundTerminal () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click Apply to accept your changes and to keep the Properties Browser open.

Create 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.

Click Add in the Connections frame.
Click the From Object: ellipses ().
Select AllSatellites () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click the To Object: ellipses ().
Select GroundTerminal () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click OK to accept your changes and to close the Properties Browser.

You can calculate this analysis with the transmitters and receivers. When you use an entry of a satellite collection in your analysis, that entry will inherit the properties of a reference object. By default, the reference object is simply the default satellite object. However, if you choose a default subset reference object, STK will associate the entries with that specific satellite in the scenario. Using a specified satellite provides a way to customize settings (attitude, access constraints, etc.) when you use the satellite collection member in an analysis. Moreover, when the reference object contains child objects (sensors, transmitters, receivers, etc.), STK also associates these children with the satellite entry.

Strand Access

Strand access reports the time intervals for each strand in a chain that completes the chain.

Right click Leo_to_Ground () in the Object Browser.
Select Report & Graph Manager... () in the shortcut menu.
Select the Individual Strand Access () graph in the Installed Styles list.
Click Generate... .

individual strand access graph

Close the Individual Strand Access graph when done viewing the data.

Defining the custom intervals

Throughout the period of analysis, you can see all the links between your satellites and the ground terminal. However, you care about how these systems communicate during the period of the X-43's test flight. Figure out which satellites are relevant during the flight.

Return to the Report & Graph Manager.
Select the Specify Time Properties option in the Time Properties frame.
Open the Select Type: shortcut menu.
Select Custom Interval List.
Click the ellipsis ().
Select HXRV_X43 () in the object list when the Select Interval List dialog box opens.
Select AvailabilityIntervals () from the Interval Lists for: HXRV_X43 list.
Click OK to close the Select Interval List dialog box.
Select the Individual Strand Access () graph in the Installed Styles list.
Click Generate... .

Modified Individual Strand Access

Now you are just looking at the eight satellites overhead during the time of the flight. Through each stage of the analysis, you needed to reevaluate the outcomes of the mission. Through modifications of the antenna and examining the link budget, you can see the effects through each iteration. This falls directly in line with the DME workflow. Within one system (STK), changing the necessary systems (transmitters) maintain the required mission metrics (Link Budget - BER).

Saving your work

You can clean up and finish your scenario.

Close any open graphs, properties, and tools.
Save () your work.
Close STK.

DME: Events and Time Components

In this section, you will focus on understanding and relating all the events that occurred from the beginning of the X43 (HXRV_X43 aircraft object) test flight to when it was tracked, including any information relayed. The first session of the three-part series had you create a unique satellite constellation to track and monitor a hypersonic aircraft. The second session walked you through building the hypersonic flight and comparing it to a model from Ansys. In that session, you also created EOIR cameras to image the thermal properties of hypersonic. Finally, in the first section of Session 3, you created the communication system to convey the message to the necessary systems. This last section of Session 3 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.

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 have a starter scenario to load.

Launch STK ().
Click Open a Scenario when the Welcome to STK dialog box opens.

Open a starter scenario from the STK Data Federate (SDF)

Open the starter scenario from the SDF. You can log in as Guest.

Open the Location: shortcut menu when the Open dialog box opens.
Select STK Data Federate.
Select the Browse tab when the SDF opens.
Expand () the following: Sites>AGI>documentLibrary>STK 12>Starter Tutorials>DME_Session3_Comms_and_Event_Analysis
Select DME_Session3_Starter_AWB.vdf.
Click Open . Be patient. This is a large scenario and might take a minute or two to load.

Save a VDF as a SC File

Open the File menu once the scenario has loaded.
Select Save As... .
Click Yes to confirm.
Open the Location: shortcut menu when the Save As dialog box opens.
Select File System.
Click STK User on the left side of the Save As dialog box.
Select DME_Session3_Starter_AWB ().
Click Open.
Open the Save as type: shortcut menu.
Select Scenario Files (*.sc).
Type X43_Mission_AWB in the Filename: field.
Click Save .

Save often!

Examining the scenario

Examine the scenario when it opens.

You should see the hypersonic test flight (discussed in DME session 2).
You should see the eight relevant satellites from the SBIRS LEO Constellation designed in DME session 1 and refined earlier in this session. These satellites are modeling the OmniInstalled transmitters and the Space-Based Infrared System (SBIRS).
New to the mission are 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 a launch of a B2 carrying the HXLV Pegasus, which accelerates the HXRV X43.
When the Pegasus 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 Session 1, but with modifications that came about as the mission scope was expanded.
The satellites have IR cameras on board to track and follow the X43 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 burn to the Timeline View

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

Click Timeline 1 in the lower left hand corner of STK to open the Timeline View.
Click Auto Hide on the right side of the Timeline View title bar if desired. This will keep the Timeline View open.
Click Add Time Components () in the Timeline View toolbar.
Select the HXLV_Pegasus () in the object list when the Select Timeline Component dialog box opens.
Select PegasusBurn () in My Components () in the Components for: HXLV_Pegasus list. This component was prebuilt in the starter scenario. It has defined start and end time for the duration of the burn.
Click OK to close the Select Timeline Component dialog box.

Pegasus Burn

This ignition burn is the initial event that triggers a detection system. It is what sets off the series of following events.

You can use the Timeline View Port markers to focus on smaller periods of the scenario. You need to move forward in time of the scenario to see the rectangular marker on the left.

Click and drag the markers on either side to re-size the timeline.

This adds the first-time component to the Timeline. This component was built to model the burn of the Pegasus as it takes off. This is also what the satellites in GEO detecting the burn sees. This is the initial trigger that sets the system in motion. Next, model how well the DSP system can detect the Pegasus.

Creating a Chain between the DSP and Pegasus

Once the Pegasus ignites and takes off, 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.

Bring the Insert STK Objects tool () to the front.
Select Chain () in the Scenario Objects list.
Select the Insert Default () method.
Click Insert... .
Right click on Chain1 () in the Object Browser.
Select Rename in the shortcut menu.
Rename Chain1 () to DSP_to_Pegasus.

Defining the start and end objects

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

Open DSP_to_Pegasus's () properties ().
Select the Basic - Definition page when the Properties Browser opens.
Click the Start Object: ellipsis ().
Select dsp_sweep3 () (attached to SBIRS_GEO-3_41937 ()) in the Select Object dialog box.

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

Click OK to close the Select Object dialog box.
Click the End Object: ellipsis ().
Select HXLV_Pegasus () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click Apply to accept your changes and to keep the Properties Browser open.

Creating the Chain object's connections

Click Add in the Connections frame.
Click the From Object: ellipses ().
Select dsp_sweep3 () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click the To Object: ellipses ().
Select HXLV_Pegasus () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
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.

Select the Basic - Advanced page.
Select the User Specified Time Period option in the Compute Time Period frame.
Open the Start: Stop: shortcut menu.
Select Interval Component... .
Select the HXLV_Pegasus () in the object list when the Select Time Interval dialog box opens.
Select PegasusBurn () in the Intervals for: HXLV_Pegasus list.
Click OK to close the Select Time Interval dialog box.
Click OK to accept your changes and to close the Properties Browser.

Adding the time component to the Timeline View

You can add the time component to the Timeline View to see how it compares to the data you have about the Pegasus burn.

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

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 the burn.

Creating system processing duration

This component shows all the instances when the DSP 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 the chain between the DSP to GroundStation () while taking the processing time into account.

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

You can build the processing time on this chain access.

Click Create new Interval () in the toolbar.

Adding a time component

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

Click Type: Select... when the Add Time Component dialog box opens.
Select Fixed Duration () in the Select Component Type list when the Select Component Type dialog box opens.
Click OK to close the Select Component Type dialog box.
Type DSP_SystProcessing in the Name: field.
Click the Reference Time Instant: ellipsis ().
Select DSP_to_Pegasus () in the object list when the Select Reference Time Instant dialog box opens.
Expand () CompleteChainAccessTimeSpan () in the Time Instants for: DSP_to_Pegasus list.
Select Start ().

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

Click OK to close the Select Reference Time Instant dialog box.
Enter 30 sec in the Stop Offset: field.
Click OK to close the Add Time Component dialog box.
Using your left mouse button, drag and drop DSP_SystProcessing () from the Components for: DSP_to_Pegasus list to the Timeline View.
Click Close to close the Analysis Workbench.

You built this component so that it is triggered during the first sweep and after the third one is prepared to relay the information.

DSP_to_Pegaus DSP_SystProcessing

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 ().

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

Define the start and end objects

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

Open DSP_to_Ground's () properties ().
Select the Basic - Definition page when the Properties Browser opens.
Click the Start Object: ellipsis ().
Select SBIRS_GEO-3_41937 () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click the End Object: ellipsis ().
Select GroundTerminal () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click Apply to accept your changes and to keep the Properties Browser open.

Creating the Chain object's connections

Click Add in the Connections frame.
Click the From Object: ellipses ().
Select SBIRS_GEO-3_41937 () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click the To Object: ellipses ().
Select GroundTerminal () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
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.

Select the Basic - Advanced page.
Select the User Specified Time Period option in the Compute Time Period frame.
Open the Start: Stop: shortcut menu.
Select Start Time in the shortcut menu.
Select Time Component... in the next shortcut menu.
Select the DSP_to_Pegasus () in the object list when the Select Time Instance dialog box opens.
Expand () DSP_SystProcessing () in the Time Instants for: DSP_to_Pegasus list.
Select Stop (). You want the chain access to begin once the information from the geostationary satellite is processed and sent.
Click OK to close the Select Time Instance dialog box.

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.

Open the Start: Stop: shortcut menu.
Select Stop Time in the shortcut menu.
Select Time Component... in the next shortcut menu.
Select the DSP_to_Pegasus () in the object list when the Select Time Instance dialog box opens.
Expand () CompleteChainAccessIntervals () in the Time Instants for: DSP_to_Pegasus list.
Expand () Last ().
Select Stop ().
Click OK to close the Select Time Instance dialog box.
Click OK to accept your changes and to close the Properties Browser.

Adding the component to the Timeline View

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

DSP_to_Ground Complete Chain Access Intervals

The interval added to the timeline accounts for when the SBIRS_GEO-3_41937 () is able to send information down to the Ground Terminal.

Setting the Ground Terminal processing time

Once the Ground Terminal has the message from the Defense Support System, it processes and relays the message to the SBIRS LEO constellation. You can build that component next.

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

You can build the processing time on this chain access.

Click the Create new Interval () in the toolbar.

Creating a time component

Click Type: Select... when the Add Time Component dialog box opens.
Select Fixed Duration () in the Select Component Type list when the Select Component Type dialog box opens.
Click OK to close the Select Component Type dialog box.
Type GroundTerminal_SystProcessing in the Name: field when you return to the Add Time Component dialog box.
Enter 30 sec in the Stop Offset: field.
Click OK to accept your changes and to close the Add Time Component dialog box.
Drag and drop GroundTerminal_SystProcessing () to the Timeline View.
Click Close to close the Analysis Workbench.

This component accounts for the processing time at the Ground Terminal before it relays the message.

DSP_to_Ground Ground Terminal System Processing

The Ground Terminal processes the information it receives from the SBIRS_GEO-3_41937 (). Once processed it can share it.

Creating a chain between Ground Terminal and SBIRS LEO Satellites

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.

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

Defining the start and end objects

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

Open Ground_to_LEO's () properties ().
Select the Basic - Definition page when the Properties Browser opens.
Click the Start Object: ellipsis ().
Select GroundTerminal () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click the End Object: ellipsis ().
Select SBIRS_LEO () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click Apply to accept your changes and to keep the Properties Browser open.

Creating the Chain object's connections

Click Add in the Connections frame.
Click the From Object: ellipses ().
Select GroundTerminal () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click the To Object: ellipses ().
Select SBIRS_LEO () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click OK to accept your changes and to close the Properties Browser.

Viewing the interval

Add the time component to the Timeline View to see how it relates to the initial stages of the mission.

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

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 looks at just when the signal is transmitted.

Creating a chain from Ground Terminal to SBIRS LEO 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.

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

Defining the start and end objects

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

Open Ground_to_LEORelay's () properties ().
Select the Basic - Definition page when the Properties Browser opens.
Click the Start Object: ellipsis ().
Select GroundTerminal () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click the End Object: ellipsis ().
Select SBIRS_LEO () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click Apply to accept your changes and to keep the Properties Browser open.

Creating the Chain object's connections

Click Add in the Connections frame.
Click the From Object: ellipses ().
Select GroundTerminal () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click the To Object: ellipses ().
Select SBIRS_LEO () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
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.

Select the Basic - Advanced page.
Select the User Specified Time Period option in the Compute Time Period frame.
Open the Start: Stop: shortcut menu.
Select Start Time in the shortcut menu.
Select Time Component... in the next shortcut menu.
Select the DSP_to_Ground () in the object list when the Select Time Instance dialog box opens.
Expand () GroundTerminal_SystProcessing () in the Time Instants for: DSP_to_Ground list.
Select Stop ().
Click OK to close the Select Time Instance dialog box.

Specifying the stop time component

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

Open the Start: Stop: shortcut menu.
Select Stop Time in the shortcut menu.
Select the Time Component option.
Select Time Component... in the next shortcut menu.
Select the Ground_to_LEO () in the object list when the Select Time Instance dialog box opens.
Expand () CompleteChainAccessTimeSpan () in the Time Instants for: Ground_to_LEO list.
Select Stop ().
Click OK to close the Select Time Instance dialog box.
Click OK to accept your changes and to close the Properties Browser.

Adding the time component to the Timeline View

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

Ground_to_LEO_Relay Complete ChainA ccess Intervals

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

Creating SBIRS system processing time

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

You can build the processing time on this chain access.

Click Create new Interval () in the toolbar.

Creating a time component

Click Type: Select... when the Add Time Component dialog box opens.
Select Fixed Duration () in the Select Component Type list when the Select Component Type dialog box opens.
Click OK to close the Select Component Type dialog box.
Type SBIRS_SystProcessing in the Name: field when you return to the Add Time Component dialog box.
Enter 30 sec in the Stop Offset: field.
Click OK to close the Add Time Component dialog box.
Drag and drop SBIRS_SystProcessing () to the Timeline View.
Click Close to close the Analysis Workbench.

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 to the HXRV_X43

Now that you know how long it takes the transmitters to react, you can create a chain access between SBIRS LEO () and HXRV_X43 ().

Once the SBIRS LEO system knows the Pegasus launch has taken place, it can lock on and begin to track the rest of the X43 flight.

Insert an Chain object () using the Insert Default () method.
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.

Open SBIRS_LEO_to_X43's () properties ().
Select the Basic - Definition page when the Properties Browser opens.
Click the Start Object: ellipsis ().
Select SBIRS_LEO () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click the End Object: ellipsis ().
Select HXRV_X43 () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click Apply to accept your changes and to keep the Properties Browser open.

Creating the Chain object's connections

Model the access between the SBIRS_LEO system and the rest of the X43 test flight. You are going to account for how long it takes for the SBIRS system to react to the message from GroundTerminal ().

Click Add in the Connections frame.
Click the From Object: ellipses ().
Select SBIRS_LEO () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click the To Object: ellipses ().
Select HXRV_X43 () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click Apply to accept your changes and to keep the Properties Browser open.

Specifying the start time component

Select the Basic - Advanced page.
Select the User Specified Time Period option in the Compute Time Period frame.
Open the Start: Stop: shortcut menu.
Select Start Time in the shortcut menu.
Select Time Component... in the next shortcut menu.
Select Ground_to_LEORelay () in the object list when the Select Time Instance dialog box opens.
Expand () SIRBS_SystProcessing () in the Time Instants for: Ground_to_LEORelay list.
Select Stop ().
Click OK to close the Select Time Instance dialog box.

Specifying the stop time component

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

Open the Start: Stop: shortcut menu.
Select Stop Time in the shortcut menu.
Select Time Component... in the next shortcut menu.
Select HXRV_X43 () in the object list when the Select Time Instance dialog box opens.
Expand () AvailablityTimeSpan () in the Time Instants for: HXRV_X43 list.
Select Stop ().
Click OK to close the Select Time Instance dialog box.
Click OK to accept your changes and to close the Properties Browser.

Add the time component to the Timeline View

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

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.

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

You can build the processing time on this chain access.

Click Create new Interval () in the toolbar.

Creating a between instants component

Click Type: Select... when the Add Time Component dialog box opens.
Select Between Time Instants () in the Select Component Type list when the Select Component Type dialog box opens.
Click OK to close the Select Component Type dialog box.
Type SystemResponseTime in the Name: field when you return to the Add Time Component dialog box.
Click the Start Time Instant: ellipsis ().
Select HXLV_Pegasus () in the object list when the Select Reference Time Instant dialog box opens.
Expand () PegasusBurn () in the Time Instants for: HXLV_Pegasus list.
Select Start ().
Click OK to close the Select Reference Time Instant dialog box.
Click the Stop Time Instant: ellipsis ().
Select SBIRS_LEO_to_X43 () in the object list when the Select Reference Time Instant dialog box opens.
Expand () CompleteChainAccessTimeSpan () in the Time Instants for: SBIRS_LEO_to_X43 list.
Select Start ().
Click OK to close the Select Reference Time Instant dialog box.
Click OK to close the Add Time Component dialog box.
Drag and drop SystemResponseTime () to the Timeline View.

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.

Examine the timeline.

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

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 ().

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

You can build the processing time on this chain access.

Click Create new Interval () in the toolbar.

Creating a Time Component

Click Type: Select... when the Add Time Component dialog box opens.
Select Fixed Duration () in the Select Component Type list when the Select Component Type dialog box opens.
Click OK to close the Select Component Type dialog box.
Type SBIRS_IR_SystProcessing in the Name: field when you return to the Add Time Component dialog box.
Enter 30 sec in the Stop Offset: field.
Click OK to close the Add Time Component dialog box.
Drag and drop SBIRS_IR_SystProcessing () to the Timeline View.
Click Close to the close the Analysis Workbench.

SBIRS_LEO_to_X43 SBIRS IR System Processing

Inserting a chain object to model the communication link

Model the communication 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.

Insert an Chain object () using the Insert Default () method.
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.

Open SBIRS_Tx_to_Ground_Rcvr's () properties ().
Select the Basic - Definition page when the Properties Browser opens.
Click the Start Object: ellipsis ().
Select SBIRS_LEO_Tx () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click the End Object: ellipsis ().
Select SatComRcvr () (attached to GroundTerminal ()) in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click Apply to accept your changes and to keep the Properties Browser open.

Creating the Chain object's connections

Click Add in the Connections frame.
Click the From Object: ellipses ().
Select SBIRS_LEO_Tx () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
Click the To Object: ellipses ().
Select SatComRcvr () in the Select Object dialog box.
Click OK to close the Select Object dialog box.
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.

Select the Basic - Advanced page.
Select the User Specified Time Period option in the Compute Time Period frame.
Open the Start: Stop: shortcut menu.
Select Start Time in the shortcut menu.
Select Time Component... in the next shortcut menu.
Select SBIRS_LEO_to_X43 () in the object list when the Select Time Instance dialog box opens.
Expand () SBIRS_IR_SystProcessing () in the Time Instants for: SBIRS_LEO_to_X43 list.
Select Stop ().
Click OK to close the Select Time Instance dialog box.

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.

Open the Start: Stop: shortcut menu.
Select Stop Time in the shortcut menu.
Select Time Component... in the next shortcut menu.
Select Ground_to_LEO () in the object list when the Select Time Instance dialog box opens.
Expand () CompleteChainAccessTimeSpan () in the Time Instants for: Ground_to_LEO list.
Select Stop ().
Click OK to close the Select Time Instance dialog box.
Clear the Automatically Recompute Access check box in the Access frame.

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.

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

Adding the time component to the Timeline View

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

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 ().

Take a look at the timeline.

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 X43. Let’s test this out.

Open SBIRS_LEO () properties ().
Remove () the SBIRS_LEO12 () from the Assigned Objects list.
Click OK to accept your change and to close the Properties Browser.
Open Ground_to_LEO's () properties ().
Select the Basic - Advanced page.
Clear the Automatic Recompute Accesses check box in the Access frame.
Click OK to accept your change and to close the Properties Browser.
Select Ground_to_LEO () in the Object Browser.
Open the Chain menu.
Select Compute Accesses.
Recompute the other dependent chains:

Ground_to_LEORelay ()
SBIRS_LEO_to_X43 ()
SBIRS_Tx_to_Ground_Rcvr ()

Losing three satellites

Open SBIRS_LEO's () properties ().
Remove () the following satellites from the Assigned Objects list:

SBIRS_LEO21 ()
SBIRS_LEO36 ()

Click Apply to accept your changes and to keep the Properties Browser open.
Select Ground_to_LEO () in the Object Browser.
Select the Chain menu.
Select Compute Accesses.
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

Bring SBIRS_LEO's () properties () to the front.
Remove () the SBIRS_LEO62 () from the Assigned Objects list.
Click Apply to accept your change and to keep the Properties Browser open.
Select Ground_to_LEO () in the Object Browser.
Select the Chain menu.
Select Compute Accesses.
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.

Bring SBIRS_LEO's () properties () to the front.
Move () the following Satellite () objects from the Available Objects list to the Assigned Objects list:

SBIRS_LEO12 ()
SBIRS_LEO21 ()
SBIRS_LEO36 ()
SBIRS_LEO62 ()

Click OK to accept your changes and to close the Properties Browser.
Select Ground_to_LEO () in the Object Browser.
Select the Chain menu.
Select Compute Accesses.
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 Bit Error Rate (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.

Open SatCommRcvr's () properties ().
Select the Constraints - Comm page.
Select the Max: check box in the Bit Error Rate frame.
Enter 1e-09 in the Max: field.
Click OK to accept your changes and to close the Properties Browser.
Recompute the SBIRS_Tx_to_Ground_Rcvr () object.

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

Examine the beginning and end of the interval.

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.

Close any open reports, properties, and the Report & Graph Manager.
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.