Digital Mission Engineering (DME): Comm Analysis and Antenna Patterns (Part 3 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.

This lesson requires version 12.9 of the STK software or newer to complete.

Capabilities covered

This lesson covers the following capabilities of the Ansys Systems Tool Kit® (STK®) digital mission engineering software:

  • STK Pro
  • Communications

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 session will focus on creating a communications system. This communications system will be an important factor in the system response time of a detection and tracking system. After you figure out how well your communications system works and which satellites are doing the communicating, you will look at the system response time of the mission as a whole in the next part of the Digital Mission Engineering (DME) series.

Solution

Using the same models constructed through the design phase, you will evaluate relationships between assets like communications link availability and determine which satellites in a constellation of satellites can talk to a ground terminal during the flight of the X-43 Hyper-X Research Vehicle (HXRV).

What you will learn

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

  • Build and analyze a communications link
  • Use external antenna gain pattern files
  • Generate a Link Budget

Video guidance

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

Downloading the required starter scenario

A partially created scenario containing the X-43's test flight has been provided for you. The scenario is saved as a visual data file (VDF).

  1. Download the zipped folder here: https://support.agi.com/download/?type=training&dir=sdf/help&file=DME_Session3_Starter_Comms.zip

    If you are not already logged in, you will be prompted to log in to agi.com to download the file. If you do not have an agi.com account, you will need to create one. The user approval process can take up to three (3) business days. Please contact support@agi.com if you need access sooner.

  2. Navigate to the downloaded folder.
  3. Right-click on DME_Session3_Starter_Comms.zip.
  4. Select Extract All... in the shortcut menu.
  5. Set the Files will be extracted to this folder: path to the location of your choice. The default path is C:\Users\<username>\Downloads\DME_Session3_Starter_Comms).
  6. Click Extract.
  7. Go to the chosen folder.
  8. DME_Session3_Starter_Comms.vdf will be in the extracted folder.

Opening the starter scenario

Open the downloaded scenario in the STK application.

  1. Launch the STK application ().
  2. Click Open a Scenario () in the Welcome to STK dialog box.
  3. Browse to location of your extracted VDF file.
  4. Select DME_Session3_Starter_Comms.vdf.
  5. Click Open.

Saving a VDF file as a Scenario file

Save your scenario in an appropriate location for your work. When you save a scenario in the STK application, 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.

  1. Open the File menu.
  2. Select Save As....
  3. Select the STK User folder in the navigation pane when the Save As dialog box opens.
  4. Select the DME_Session3_Starter_Comms folder.

    5. A folder with the same name as the VDF file was created for you when you opened the VDF in the STK application.

  5. Click Open.
  6. Select Scenario Files (*.sc) as the Save as type.
  7. Click Save.

Save () often during this lesson!

The following files will be in the DME_Session3_Starter_Comms folder:

  • SatCom_Omni_2p2G_Installed.pattern - This is a simple antenna pattern model file you will load into the scenario.
  • SatCom_Omni_2p2G_Isolation.pattern - This is an antenna pattern model file created using the ANSYS HFSS™ 3D high-frequency simulation software to account for absorption / reflection off the satellite body.

When saving a VDF containing additional data files, like the Ansys HFSS antenna pattern files included in the VDF used in this tutorial, as a Scenario file, you must save your scenario file to the folder the STK application automatically creates for you in the STK User folder. This allows the non-STK files packaged with the VDF to unpack to the scenario folder. While you can save the scenario file to another location, the additional data files will not be included. See the VDF Setup Considerations page for more information.

Modeling the communications ground terminal

You will begin building your communications system by creating a ground terminal. The ground terminal houses a receiver.

Inserting a Facility object

Use a Facility object to simulate the location of your ground terminal.

  1. Bring the Insert STK Objects tool () to the front.
  2. Select Facility () in the Scenario Objects list.
  3. Select the Define Properties () method.
  4. Click Insert. . ..
  5. Select the Basic - Position page in the Properties Browser.

Setting the ground terminal's location

Update the ground terminal's properties to place it at the correct location.

  1. Set the following options in the Position panel:
    2. Option Value
    Latitude 34.1084 deg
    Longitude -119.065 deg
  2. Click OK to accept your changes and to close the Properties Browser.
  3. Right-click on Facility1 () in the Object Browser.
  4. Select Rename in the shortcut menu.
  5. Rename Facility1 () GroundTerminal.

Viewing the ground terminal in the 3D Graphics window

Gain situational awareness by viewing the ground terminal's location on Laguna Peak, near Naval Base Ventura County - Point Mugu.

  1. Bring the 3D Graphics window to the front.
  2. Right-click on GroundTerminal () in the Object Browser.
  3. Select Zoom To in the shortcut menu.
  4. Move around in the 3D Graphics window to understand the location of the ground terminal.

    5. 3D Graphics View of GroundTerminal

Inserting a Receiver object

Attach a Receiver object to GroundTerminal. GroundTerminal is receiving signals from multiple satellites. Use a Simple Receiver model that auto-tracks to all frequencies. The default Simple Receiver model uses an isotropic, omnidirectional antenna which is an ideal spherical pattern antenna with constant gain.

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

Modeling a communications satellite

The satellite collection communicates with the ground terminal receiver. Use a single Satellite object to compare the coverage between antenna models. It also functions as a seed satellite for a satellite collection you will set up later.

Inserting a Satellite object

A Satellite object is the vehicle for the transmitter.

  1. Insert a Satellite () object using the Orbit Wizard () method.
  2. Set the following options in the Orbit Wizard:
    3. Option Value
    Type Circular
    Satellite Name LEO_Sat
    Inclination 50 deg
    Altitude 1734 km

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

Updating the satellite's 3D model

Change the satellite's 3D model to more close visualize a satellite that is part of the Space Tracking and Surveillance System, which your satellite collection will model. This 3D model was also used in the Ansys HFSS software to model the antenna patterns used later in this lesson.

  1. Click the 3D Model ellipsis () in the Graphics panel.
  2. Select stss.glb in the File dialog box.
  3. Click Open.
  4. Click OK to close the Orbit Wizard.

Inserting a Transmitter object

Attach a Transmitter object to LEO_Sat.

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

Defining the transmitter model

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

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

Generating a Link Budget to the ground terminal

Create a Link Budget report using the simple transmitter model, then update it with a unique antenna pattern.

  1. Right-click on Transmitter () in the Object Browser.
  2. Select Access... () in the shortcut menu.
  3. Expand () GroundTerminal () in the Associated Objects list in the Access tool dialog box.
  4. Select Receiver ().
  5. Click .
  6. Click Link Budget. . . in the Reports panel.

    7. This generates communications values between the two objects: Receiver and Transmitter. You can see various values, like the 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. The bit error rate shows that, for this case, as long as line of sight is maintained, any sort of signal can be maintained; the BER is effectively zero. This is primarily because you are using the simple transmitter model.

Using an external antenna pattern file

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. Within STK's Communications capability, you can employ an external antenna pattern file that contains user-defined data.

Inserting an Antenna object

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

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

Loading the OmniIsolated antenna pattern

Use the OmniIsloated antenna pattern included with your scenario to model LEO_Sat's antenna. The OmniIsolated pattern file models an antenna isolated from the body of the vehicle to which it is attached. It is a Phi-Theta pattern, which is commonly used to model parabolic antennas and other traditional antenna types. The STK software works well with the Phi-Theta sweep pattern of data.

External antenna pattern files can also be provided by a third party, like a test lab; they can also be defined in another file type, such as a CSV file. The STK software supports a wide variety of industry antenna gain formats. Contact support@agi.com if you have questions about other formats.

  1. Select the Basic - Definition page in the Properties Browser.
  2. Click the Antenna Model Component Selector ().
  3. Select External Antenna Pattern () in the Antenna Models list in the Select Component dialog box.
  4. Click OK to close the Select Component dialog box.
  5. Enter 2.2 GHz in the Design Frequency field.
  6. Click the External Filename ellipsis ().
  7. Browse to the location of your pattern file (e.g. C:\Documents\STK 12\DME_Session3_Starter_Comms\DME_CommAnalysis_Part3) in the Select File dialog box.
  8. Select SatCom_Omni_2p2G_Isolation.pattern.
  9. Click Open.
  10. Click Apply to accept your changes and to keep the Object Browser open.

Viewing the external antenna pattern file

Using the 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 the STK software to process it.

  1. Open File Explorer in Windows.
  2. Browse to the location of your pattern file (e.g. C:\Documents\STK 12\DME_Session3_Starter_Comms\DME_CommAnalysis_Part3).
  3. Right-click on SatCom_Omni_2p2G_Isolation.pattern.
  4. Select Open with in the shortcut menu.
  5. Select a text editor, such as Notepad.
  6. Click OK.
  7. View the antenna pattern data. The antenna data forms a rectangular matrix so that the STK software can process it.

    8. OmniIsolated Pattern File

  8. Close your text editor when you are finished viewing the data.
  9. Close File Explorer.

Orienting the antenna

By default, the STK application 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.

  1. Select the Basic - Orientation page.
  2. Set the following options:
    3. Option Value
    Azimuth 270 deg
    Elevation 90 deg
  3. Set the following Position Offset values:
    4. Option Value
    X -0.57 m
    Y 0.93 m
    Z 0.55 m
  4. Click Apply to accept your changes and to keep the Properties Browser open.

Displaying contour graphics in the 2D Graphics window

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

  1. Select the 2D Graphics - Contours page.
  2. Select the Show Contour Graphics check box.
  3. Clear the Relative to Maximum check box.
  4. Set the following dB values in the Level Adding panel:
    5. Option Value
    Start -10
    Stop 11
    Step 3
  5. Click Add Level.
  6. Click Apply to accept your changes and to keep the Properties Browser open.

Displaying contour graphics in the 3D Graphics window

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

  1. Select the 3D Graphics - Attributes page.
  2. Select the Show Lines check box in the Contour Graphics panel.
  3. Select the Show Volume check box in the Volume Graphics panel.
  4. Set the following options:
    5. Option Value
    Gain Scale (per dB) 4 cm
    Minimum Displayed Gain -30 dB
  5. Enter 180 deg in the Stop field in the Elevation panel.
  6. Open the Min Color drop-down list in the Gain Coloring panel.
  7. Select red.
  8. Open the Max Color drop-down list.
  9. Select blue.
  10. Click OK to accept your changes and to close the Properties Browser.

Renaming the Antenna

Rename the Antenna object to reflect that it is using the OmniIsolated antenna pattern.

  1. Right-click on Antenna1 () in the Object Browser.
  2. Select Rename in the shortcut menu.
  3. Rename Antenna1 () OmniIsolated.

Viewing the OmniIsolated antenna pattern in the 3D Graphics window

View the OmniIsolated antenna pattern in the 3D Graphics window.

  1. Bring the 3D Graphics window to the front.
  2. Right-click on LEO_Sat () in the Object Browser.
  3. Select Zoom To in the shortcut menu.
  4. Move around in the 3D Graphics window to understand the antenna pattern.

    5. OmniIsolated antenna pattern

    The antenna 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.

Using a Complex Transmitter model

Change the transmitter to use a Complex Transmitter model. A Complex Transmitter model allows you to select among a variety of analytical and realistic antenna models, and to define the characteristics of the selected antenna type.

  1. Open Transmitter's () Properties ().
  2. Select the Basic - Definition page in the Properties Browser.
  3. Click the Transmitter Model Component Selector ().
  4. Select Complex Transmitter Model () in the Transmitter Models list in the Select Component dialog box.
  5. Click OK to close the Select Component dialog box.

Changing the model specs

Update the model specs of the transmitter for your Complex Transmitter model.

  1. Select the Model Specs tab.
  2. Set the following options:
    3. Option Value
    Frequency 2.2 GHz
    Power 2 W
  3. Click Apply to accept your changes and to keep the Properties Browser open.

Linking to an antenna object

You can select to embed an antenna model from the Component Browser or you can link to an antenna object.

  1. Select the Antenna tab.
  2. Open the Reference Type drop-down list.
  3. Select Link.

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

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

Refreshing the Link Budget report

Refresh your Link Budget report to examine the effects of your changes.

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

Notice the increased variation in the BER with this updated model. Rather than a constant value, see how the BER varies throughout the satellite's passage. However, 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 will analyze that behavior next.

Modeling the OmniInstalled antenna

The relationship between the vehicle and its payload can dramatically alter antenna performance and impact the associated system. This is important to take into account in the mission model. To account for the satellite model behavior, you must use the OmniInstalled antenna pattern file. This file models the antenna's 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 OmniInstalled file was created using the ANSYS HFSS™ SBR+ asymptotic high-frequency electromagnetic (EM) simulator for modeling EM interaction in electrically large environments. The SBR+ software uses shooting and bouncing rays to solve the antenna interaction with the satellite to which it is attached.

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

However, the antenna behavior data could come from a multitude of sources: you can create your own data using the STK software, load external models, and load results from system tests.

Reusing the OmniIsolated antenna

You can reuse objects in the STK software.

  1. Right-click on OmniIsolated () in the Object Browser.
  2. Select Copy () in the shortcut menu.
  3. Right-click on LEO_Sat () in the Object Browser.
  4. Select Paste () in the shortcut menu.
  5. Rename OmniIsolated1 () OmniInstalled.
  6. Clear the OmniIsolated () check box in the Object Browser.

Updating OmniInstalled's properties

Update the OmniInstalled antenna to use the OmniInstalled antenna pattern.

  1. Open OmniInstalled's () Properties ().
  2. Select the Basic - Definition page in the Properties Browser.
  3. Click the External Filename ellipsis ().
  4. Browse to the location of your pattern file (e.g. C:\Documents\STK 12\DME_Session3_Starter_Comms\DME_CommAnalysis_Part3) in the Select File dialog box.
  5. Select SatCom_Omni_2p2G_Installed.pattern.
  6. Click Open.

    7. If you open the pattern file in a text editor, you will notice that the values change throughout the file.

    OmniINstalled Pattern file

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

Viewing the OmniInstalled antenna pattern in the 3D Graphics window

See the dramatic difference between the two antenna models.

  1. Bring the 3D Graphics window to the front.
  2. Right-click on LEO_Sat () in the Object Browser.
  3. Select Zoom To in the shortcut menu.
  4. Move around in the 3D Graphics window to understand the new antenna pattern.

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.

OmniInstalled antenna pattern

Switching to the OmniInstalled antenna

Set your transmitter to use the OmniInstalled antenna.

  1. Open Transmitter's () Properties ().
  2. Select the Antenna tab in the Basic - Definition page of the Properties Browser.
  3. Select the Model Specs sub tab.
  4. Open the Antenna drop-down list.
  5. Select Antenna/OmniInstalled.
  6. Click OK to accept your changes and to close the Properties Browser.

Viewing the OmniInstalled antenna contours in the 3D Graphics window

View the changes to the antenna contours in the 3D Graphics window.

  1. Bring the 3D Graphics window to the front.
  2. Right-click on LEO_Sat () in the Object Browser.
  3. Select Zoom To in the shortcut menu.
  4. Move around in the 3D Graphics window to view the contours on the Earth.

OmniInstalled Antenna Contours

Over time, the antenna pattern passes over the Ground Terminal. You can assess it in more detail with a bit error rate graph.

Refreshing the Link Budget report

Examine the changes to your Link Budget report.

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

Notice the variations in the bit error rate. To understand how this antenna model affects the data, you can generate a BER graph.

Generating a BER graph

A BER graph plots the bit error rate over time, during each access interval.

  1. Right-click on OmniInstalled () in the Object Browser.
  2. Select Report & Graph Manager... () in the shortcut menu to open the Report & Graph Manager.
  3. Select Access in Object Type drop-down list.
  4. Select Satellite-LEO_Sat-Transmitter-Transmitter-To-Facility-GroundTerminal-Receiver-Receiver () in the Object Type list.
  5. Expand () Installed Styles () in the Styles panel if needed.
  6. Select the Bit_Error_Rate () graph.
  7. Click Generate. . ..
  8. Enter 1 sec in the Step field.
  9. Refresh (F5) () in the report's toolbar.

    10. bit error rate graph throughout the scenario

  10. Hold down your left mouse button and draw a bounding outline around one of the peaks. This zooms into the selected region to show the data values.

    11. zoomed-in bit error rate graph

Obtaining situational awareness with the 3D Graphics window

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

  1. Right-click on the sharp peak in the graph.
  2. Select Set Animation Time in the shortcut menu.
  3. Bring the 3D Graphics window to the front.
  4. Zoom to LEO_Sat ().
  5. Move around in the 3D Graphics window to note the dip in the antenna pattern as it passes over the GroundTerminal ().

    6. 3D Graphics 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.

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

Designing a satellite collection

From your preliminary analysis, you found that six satellites in six orbital planes are required to maintain worldwide coverage, for a total of 36 satellites. You can model this constellation with a Satellite Collection object. A 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 those in the STK software's Coverage and Communications capabilities, the Deck Access tool, and the Advanced CAT tool.

Inserting a Satellite Collection object

Insert a new Walker satellite collection to model the satellites from your earlier analysis. The Walker selection 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, those are the transmitter and antennas.

  1. Insert a () object using the Walker Tool () method.
  2. Click Select Object. . . in the Walker Tool dialog box.
  3. Select LEO_Sat () in the Select Object dialog box.
  4. Click OK to close the Select Object dialog box.
  5. Set the following options:
    6. Option Value
    Number of Sats per Plane 6
    Number of Planes 6
  6. Enter LEO_Sats in the Name field in the Container Options panel.
  7. Click Create / Modify Walker.
  8. Click Close to close the Walker Tool dialog box.

Displaying the satellite collection labels

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

  1. Open LEO_Sats' () Properties ().
  2. Select the Graphics - Attributes page in the Properties Browser.
  3. Select the AllSatellites Label check box.
  4. Click OK to accept your change and to close the Properties Browser.

Viewing the satellite collection

View the labeled satellites in the 3D Graphics window.

  1. Bring the 3D Graphics window to the front.
  2. Move around in the 3D Graphics window to the constellation of satellites.

satellite collection object constellation

Creating a Chain object

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. Use a Chain Object to analyze the satellite collection in order of access.

Inserting a new Chain object

Start by inserting a new Chain object.

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

Defining the start and end objects

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

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

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 panel.
  2. Click the From Object ellipsis ().
  3. Select AllSatellites () in the Select Object dialog box.
  4. Click OK to close the Select Object dialog box.
  5. Click the To Object ellipsis ().
  6. Select GroundTerminal () in the Select Object dialog box.
  7. Click OK to close the Select Object dialog box.
  8. Click OK to accept your changes and to close the Properties Browser.

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, the STK software 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.), The STK software also associates these children with the satellite entry.

Generating an Individual Strand Access graph

An Individual Strand Access Individual Strand Access graph displays the time intervals for each strand in a chain that completes the chain. Each strand's intervals are graphed on a separate line.

  1. Right-click on LEO_to_Ground () in the Object Browser.
  2. Select Report & Graph Manager... () in the shortcut menu.
  3. Select the Individual Strand Access () graph in the Installed Styles list.
  4. Click Generate. . ..

    5. individual strand access graph

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

Defining custom availability 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. You can use Availability Intervals to figure out which satellites are relevant during the flight.

  1. Return to the Report & Graph Manager.
  2. Select the Specify Time Properties option in the Time Properties panel.
  3. Open the Select Type drop-down list.
  4. Select Custom Interval List.
  5. Click the ellipsis ().
  6. Select HXRV_X43 () in the object list in the Select Interval List dialog box.
  7. Select AvailabilityIntervals () from the Interval Lists for HXRV_X43 list.
  8. Click OK to close the Select Interval List dialog box.
  9. Select the Individual Strand Access () graph in the Installed Styles list.
  10. 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 (the STK software), changing the necessary systems (transmitters) maintain the required mission metrics (Link Budget - BER).

Saving your work

You can clean up and finish your scenario.

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

Summary

The purpose of this series and this lesson is to evaluate how all the components of the mission work together. In previous sessions, you built detailed models, and in this scenario you determined which satellites in a constellation of satellites can talk to a ground terminal during the flight of the X-43 HXRV.

DME: Events and Time Components

The next lesson in the DME series focuses on 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.