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 STK 12.9 or newer to complete.

Capabilities covered

This lesson covers the following STK Capabilities:

  • 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 lesson will look at event-based operations for mission or test and evaluation planning. You will be building on the previous scenarios to evaluate the series of events within a mission and how their dependencies on each other influence the overall mission effectiveness.

Solution

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

What you will learn

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

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

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 file here:https://support.agi.com/download/?type=training&dir=sdf/help&file=DME_Session3_Starter_Comms.vdf

    (missing or bad snippet)

  2. Navigate to the downloaded VDF.
  3. Note the location of the VDF.

Opening the starter scenario

Open the downloaded scenario.

  1. Launch STK ().
  2. Click Open a Scenario () in the Welcome to STK dialog.
  3. Open DME_Session3_Starter_Comms.vdf from the downloaded location.

Saving a VDF file as a Scenario file

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

  1. Open the File menu.
  2. Select Save As...
  3. Select the STK User folder in the navigation pane when the Save As dialog opens.
  4. Click the New Folder option in the selector bar.
  5. Name the New folder DME_Session3_Starter_Comms.
  6. Select the DME_Session3_Starter_Comms.
  7. Click Open.
  8. Select Scenario Files (*.sc) as the Save as type.
  9. Enter X43_Mission_Comms.sc as the File name.
  10. Click Save.

Save Often!

Downloading required files

This lesson uses antenna pattern model files that you will need to download following the steps below.

  1. Download the zipped folder here: https://support.agi.com/download/?type=training&dir=sdf/help&file=DME_CommAnalysis_Part3.zip

    If you are not already logged in, you will be prompted to log into 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_CommAnalysis_Part3.zip.
  4. Select Extract All...
  5. Set the Files will be extracted to this folder: path to be within your scenario folder (e.g. C:\Users\username\Documents\STK  12\DME_Session3_Starter_Comms\DME_CommAnalysis_Part3).
  6. Click Extract .
  7. Go to your scenario folder.
  8. The following files will be in the DME_CommAnalysis_Part3 folder:
    1. SatCom_Omni_2p2G_Installed.pattern - This is a simple antenna pattern model file to be loaded into the scenario.
    2. 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

Creating a communications system

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

The 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 Part 4 of the DME series.

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 location

  1. Set the following in the Position frame:
    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 () to GroundTerminal.

Viewing the ground terminal in the 3D Graphics window

  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: GroundTerminal

    This location is on Laguna Peak, near Naval Base Ventura County - Point Mugu.

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.
  3. Click OK.
  4. Rename Receiver1 () to Receiver.

Inserting a Satellite object

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

  1. Insert a Satellite () object using the Orbit Wizard () method.
  2. Set the following in the Orbit Wizard:
    3. Option Value
    Type Circular
    Satellite Name LEO_Sat
    Inclination 50 deg
    Altitude 1734 km
  3. Click the 3D Model ellipsis () in the Graphics frame.
  4. Select stss.glb in the File dialog.
  5. Click Open.
  6. Click OK to close the Orbit Wizard.

    7. The orbital values were found from another optimization of the satellite constellation. After the initial study in DME: Constellation Design and Coverage (Part 1 of 4), 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 ().

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

Adding a transmitter to model access

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 () to 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.
  4. Select Receiver ().
  5. Click .
  6. Click Link Budget. . . in the Reports frame.

    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.

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.

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

  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.
  4. Click OK to close the Select Component dialog .
  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.
  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

Within STK's Communications csapability 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.

  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. SatCom_Omni_2p2G_Isolation Pattern File

    The SatCom_Omni_2p2G_Isolation 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. STK 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. To turn these files into an antenna gain patterns for STK, use a text editor and ensure the headers are in the data.

    STK supports a wide variety of industry antenna gain formats. Contact support@agi.com if you have questions about other formats.

  7. Close your text editor when you are finished viewing the data.
  8. Close 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.

  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 checkbox.
  3. Clear the Relative to Maximum checkbox.
  4. Set the following dB values in the Level Adding frame:
    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 checkbox in the Contour Graphics frame.
  3. Select the Show Volume checkbox in the Volume Graphics frame.
  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 frame.
  6. Open the Min Color dropdown menu in the Gain Coloring frame.
  7. Select red.
  8. Open the Max Color dropdown menu.
  9. Select blue.
  10. Click OK to accept your changes and to close the Properties Browser.
  11. Rename Antenna1 () to OmniIsolated.

Viewing the OmniIsolated antenna pattern in the 3D Graphics window

View the 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 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.

  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.
  5. Click OK to close the Select Component dialog.

Using the Model Specs tab

  1. Select the Model Specs tab.
  2. Enter 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.

Using the Antenna tab

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 dropdown menu.
  3. Select Link.

    4. 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.

  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

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

    3. 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 can 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. SBR+ 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 source of the antenna behavior data could come from a multitude of sources: you can create your own data in STK, load external models, and load results from system tests.

Reusing the OmniIsolated antenna

You can reuse objects in STK.

  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 () to OmniInstalled.
  6. Clear the OmniIsolated () checkbox in the Object Browser.

Updating OmniInstalled's properties

  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.
  5. Select SatCom_Omni_2p2G_Installed.pattern.
  6. Click Open.

    7. 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

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

Viewing the OmniInstalled 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 new antenna pattern.

    5. 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.

    OmniInstalled antenna pattern

Switching to 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 dropdown menu.
  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

  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 this in more detail with a bit error rate graph.

Refreshing the Link Budget report

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

    3. Examine the data. 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

  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 dropdown menu.
  4. Select Satellite-LEO_Sat-Transmitter-Transmitter-To-Facility-GroundTerminal-Receiver-Receiver () in the Object Type list.
  5. Expand () Installed Styles () in the Styles frame 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 () checkbox 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 those in STK's Coverage and Communications capabilities, the Deck Access tool, and the Advanced CAT tool.

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

Displaying the satellite constellation labels in the 3D Graphics window

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.

  1. Open LEO_Sats () Properties ().
  2. Select the Graphics - Attributes page in the Properties Browser.
  3. Select the AllSatellites Label checkbox.
  4. Click OK to accept your change and to close the Properties Browser.
  5. Bring the 3D Graphics window to the front.
  6. Move around in the 3D Graphics window to 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.

  1. Insert a Chain () object using the Insert Default () method.
  2. Rename Chain1 () to 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.
  5. Click OK to close the Select Object dialog.
  6. Click the End Object ellipsis ().
  7. Select GroundTerminal () in the Select Object dialog.
  8. Click OK to close the Select Object dialog.

Creating the Chain object's connections

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

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

    9. 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.

Generating an Individual Strand Access graph

An 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 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.

  1. Return to the Report & Graph Manager.
  2. Select the Specify Time Properties option in the Time Properties frame.
  3. Open the Select Type dropdown menu.
  4. Select Custom Interval List.
  5. Click the ellipsis ().
  6. Select HXRV_X43 () in the object list in the Select Interval List dialog.
  7. Select AvailabilityIntervals () from the Interval Lists for HXRV_X43 list.
  8. Click OK to close the Select Interval List dialog.
  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 work flow. 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.

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

Summary

The purpose of this series and of 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.

DME Lesson 4

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.