Digital Mission Engineering (DME): Constellation Design and Coverage (Part 1 of 4)

STK Premium (Space) 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.

This lesson requires STK 12.7 or newer to complete.

An external file is needed for this training. You can download the zipped file from theSTK Data Federate (SDF). If you are using STK Cloud, you can browse to the file: Sites > AGI > STK 12 > Starter Tutorials > DME_Session1_Constellation Concept Design and Trade Studies

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.

Capabilities covered

This lesson covers the following STK Capabilities:

  • STK Pro
  • Coverage
  • STK SatPro
  • STK Analyzer
  • STK Analyzer Optimization

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 the concept development phases using STK's Analyzer capability to conduct trade studies on the constellation geometry and optimizing based on system requirements.

Solution

In this section of the DME series, you will focus on satellite constellation design using STK's Analyzer and Coverage capabilities. The goal in this exercise is to understand how to maximize the level of coverage with a global network of satellites. The main components you will analyze are the revisit time, which can be considered gap time, and the number of assets that have visibility to the ground. Using Analyzer's trade study capabilities, you can vary parameters of our system to find the most ideal configuration.

What you will learn

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

  • Build a constellation of satellites using the Satellite Collection object.
  • Build a Coverage analysis.
  • Design relevant Figure of Merit quality metrics.
  • Become familiar with the Analyzer work flow.
  • Understand constellation design configurations.
  • Load in an external results file.

Creating a new scenario

Create a new scenario.

  1. Launch STK ().
  2. Click Create a Scenario in the Welcome to STK dialog.
  3. Enter the following in the STK: New Scenario Wizard:
    4. Option Value
    Name ImagingConstellation
    Start Default
    Stop Default
  4. Click OK when you finish.
  5. Click Save () when the scenario loads.
    STK creates a folder with the same name as your Scenario () object for you.
  6. Verify the scenario name and location in the Save As dialog.
  7. Click Save.

Save () often during this lesson!

Inserting a Satellite Collection object

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.

  1. Select SatelliteCollection () in the Insert STK Objects Tool.
  2. Select Insert Default () as the method.
  3. Click Insert. . ..
  4. Right-click on SatelliteCollection1 () in the Object Browser.
  5. Select Rename in the shortcut menu.
  6. Rename SatelliteCollection1 () to Walker_Collection.

Understanding the Walker type selection

The Walker selection provides a constellation of satellites distributed in a series of altitude shells. Each shell contains evenly spaced orbital planes and Walker populates each orbital plane with evenly spaced satellites. All the satellites in a shell have the same period and inclination. Walker evenly spaces the ascending nodes of the orbital planes over a range (angle spread) of right ascensions (RAAN). This capability is similar to the Walker Tool available from a Satellite () object in STK.

You can generate multiple shells within a single Satellite Collection () object. However, if you access the Walker Tool from a single Satellite () object, it only generates one shell (at that satellite's period and inclination).

Setting the Walker type subset

  1. Right-click on Walker_Collection () in the Object Browser.
  2. Select Properties () in the shortcut menu.
  3. Select the Basic - Definition page when the Properties Browser opens.

    4. You can see that Walker is the default for Type.

  4. Select Shells - Name - 1 in the Walker Properties frame.
  5. Click Edit selected shell () in the Shells toolbar.
  6. Type Walker Group in the Shell Name* field when the Edit Shell dialog opens.
  7. Set the following in the order shown in Shell Properties frame:
    8. Option Value
    Inter Plane Phase Increment 0
    Planes 1
    Satellites in Planes (Slots) 1
  8. Set the following in the Plane 1 : Slot 1 frame:
    9. Option Value
    Semi-Major Axis (a) 6880 km
    Inclination (i) 50 deg
  9. Click Save Changes.
  10. Click Apply to accept your changes and to keep the Properties Browser open.

Setting the subset marker size

You can control the graphical display of a satellite collection. Graphics Attributes covers both the 2D and 3D Graphics window attributes.

  1. Select the Graphics - Attributes page.
  2. Double-click in the AllSatellites - Marker Size cell.
  3. Enter 10 as the Marker Size value.
  4. Click OK to accept your changes and to close the Properties Browser.

Inserting a Coverage Definition object

You are now ready to model a coverage analysis over the Earth. You can start by inserting a Coverage Definition () object and then you can define its properties.

  1. Insert a Coverage Definition () object using the Define Properties () method.
  2. Select the Basic - Grid page in the Properties Browser.
  3. Enter 60 deg in the Max. Latitude field in the Grid Area of Interest frame.
  4. Enter 10 deg in the Lat/Lon field in the Point Granularity frame located in the Grid Definition frame.
  5. Click Apply to accept your changes and to keep the Properties Browser open.

Specifying the coverage assets

Assets properties enable you to specify the STK objects used to provide coverage.

  1. Select the Basic - Assets page.
  2. Expand () Walker_Collection () in the Assets list.
  3. Select AllSatellites ().
  4. Click Assign.
  5. Click Apply to accept your changes and to keep the Properties Browser open.

Clearing Automatically Recompute Accesses

Advanced properties allow you to adjust the manner in which access information is stored and computed.

  1. Select the Basic - Advanced page.
  2. Clear the Automatically Recompute Accesses checkbox.
  3. Click OK to accept your changes and to close the Properties Browser.
  4. Rename CoverageDefinition1 () to CoverageDefinition.

Using the Compute Accesses tool

The ultimate goal of coverage is to analyze accesses to an area by using assigned assets and applying necessary limitations upon those accesses. Compute coverage with the Compute Accesses tool.

  1. Right-click on CoverageDefinition () in the Object Browser.
  2. Select the CoverageDefinition shortcut menu.
  3. Select Compute Accesses in the CoverageDefinition submenu.

Generating a Percent Coverage graph

Now that you have set up and computed the coverage analysis, you can examine the quality of the coverage. But before you do that, take a quick look at the quality of the system you set up. One way to do that is to generate a Percent Coverage graph. This graph tells you how well the satellite in the Walker_Collection () is able to cover the Earth throughout the scenario time period.

  1. Select the Analysis menu.
  2. Select Report & Graph Manager... ().
  3. Open the Object Type dropdown menu.
  4. Select CoverageDefinition.
  5. Select CoverageDefinition () in the Object Type list.
  6. Select the Percent Coverage () graph in the Styles list inside the Styles frame.
  7. Click Generate. . . . Your results may vary based on the default time of your scenario.

    8. Percent Coverage graph

    Take a look at how the current coverage stays low throughout the analysis period, but how the accumulated coverage increases over time. This gives you an idea of how well the single satellite can cover the region. You can understand this further with the Figure of Merit () object.

  8. Close the graph and the Report & Graph Manager.

Designing the coverage definition Figures of Merit

You just set up the problem with the Coverage Definition () object. To evaluate specific types of coverage, you can use a Figure of Merit (FOM). STK enables you to specify the method by which the quality of coverage is measured using a Figure Of Merit () object. FOM entities are a measure of the quality of coverage. In this study, you will focus on two parameters: Number of Assets (N Asset) and Revisit Time. The requirements state you must have at least two (2) assets covering every grid point at all times.

Inserting the N Asset Figure of Merit object

The N Asset FOM determines how many different assets are simultaneously covering each individual grid point at each time in the analysis period.

You can specify that the FOM compute the minimum value from the set of all grid points to make sure all grid points are at or above that threshold.

  1. Insert a Figure of Merit () object using the Define Properties () method.
  2. Select CoverageDefinition () in the Select Object dialog.
  3. Click OK.

Setting the N Asset coverage definition

N Asset Coverage measures the number of assets available simultaneously during coverage. You want to measure if at least two (2) satellites simultaneously cover every single point in the coverage analysis.

  1. Select the Basic - Definition page in the Properties Browser.
  2. Open the Type shortcut menu in the Definition frame.
  3. Select N Asset Coverage.
  4. Open the Compute dropdown menu.
  5. Select Minimum.

    6. Using Minimum calculates the minimum number of assets available over the entire coverage interval.

Selecting the N Asset FOM satisfaction criteria

You can restrict the FOM's behavior so that STK only applies the graphical properties of the FOM when a chosen satisfaction criterion is met.

  1. Select the Enable checkbox in the Satisfaction frame.
  2. Open the Satisfied if dropdown menu.
  3. Select At Least.
  4. Enter two (2) in the Threshold field.

    5. The FOM value is greater than or equal to the Threshold.

  5. Click OK to accept your changes and to close the Properties Browser.
  6. Rename FigureofMerit1 () to NAsset.

Inserting the revisit time Figure of Merit object

Now that the coverage has a threshold of at least two satellites per grid point, you can set up revisit or gap time.

  1. Insert a Figure of Merit () object using the Define Properties () method.
  2. Select CoverageDefinition () in the Select Object dialog.
  3. Click OK.

Defining the revisit time coverage definition

Revisit (gap) time measures the intervals during which coverage is not provided. You want to minimize the gap time so that the maximum value satisfies the requirements in zero (0) second gap time.

  1. Select the Basic - Definition page in the Properties Browser.
  2. Open the Type dropdown menu in the Definition frame.
  3. Select Revisit Time.
  4. Enter two (2) in the Min # Assets field.
    • Min # Assets: specifies the minimum number of simultaneous assets that are required for coverage.
  5. Keep the Compute and End Gaps default selections.

    • Compute: Maximum: the computed value is the duration of the longest gap in coverage over the entire coverage interval.

    • End Gaps: set to Include to have gaps at the ends of the analysis interval included in the revisit time computations.

Selecting the revisit time FOM satisfaction criteria

You will use the At Most Satisfaction Criteria. Using At Most, the FOM value is less than or equal to the Threshold.

  1. Select the Enable checkbox in the Satisfaction frame.
  2. Open the Satisfied if dropdown menu.
  3. Select At Most.
  4. Leave the default Threshold value of 0 sec.
  5. Click OK to accept your changes and to close the Properties Browser.
  6. Rename FigureofMerit2 () to RevisitTime.

At this point, you might be wondering why you're setting up both FOMs to use a minimum of two (2) satellites when you currently have one (1) satellite in your collection. When you use Analyzer, you will set it up so that there are six (6) orbital planes with six (6) satellites per plane.

Downloading precomputed trade study files

You are now ready to dive into some trade study analysis using Analyzer. You can build a simple example and then load the results into a more complex study. The goal is to become familiar with the Analyzer work-flow as well as loading results of previously run analysis.

First, download the precomputed trade study files from the STK Data Federate (SDF). The steps are different if you are on your local machine or using STK Cloud. Choose the appropriate option below to download the files.

Option 1: Downloading the Files Locally

  1. Click the following link: https://sdf.agi.com/share/page/site/AGI/folder-details?nodeRef=workspace://SpacesStore/32ef1e63-66e9-4486-afb1-2a211cfa0920.
  2. Sign in to the SDF.
  3. Click Download as Zip in the Folder Actions menu.
  4. Navigate to the zipped folder DME_Session1_Constellation Concept Design and Trade Studies.zip in your computer's Downloads directory.
  5. Extract the folder if desired.

Option 2: Download the Files on STK Cloud

  1. Open a web browser in your STK Cloud session.
  2. Go to sdf.agi.com.
  3. Sign in to your account.
  4. Go to Sites > AGI > STK 12 > Starter Tutorials.
  5. Place your cursor on the line that contains DME_Session1_Constellation Concept Design and Trade Studies.
  6. Select Download as Zip on the right side.
  7. Click the Gear icon in your STK Cloud browser window.
  8. Select Frame Explorer.
  9. Navigate to the zipped folder DME_Session1_Constellation Concept Design and Trade Studies.zip in Downloads directory.
  10. Extract the folder if desired.

Using Analyzer

Analyzer provides a set of analysis tools that:

  • Enable you to understand the design space of your systems.

  • Enable you to perform analyses in STK easily without involving programming or scripting.

  • Introduce trade study and post-processing capabilities.

  • Can be used with all STK scenarios, including those with STK Astrogator satellites.

Setting up the analysis

You are now ready to dive into some trade study analysis using Analyzer. You can build a simple example and then load the results into a more complex study.

  1. Select the Analysis menu.
  2. Select Analyzer.
  3. Select Analyzer... () in the Analyzer submenu.

Analyzer may open behind the STK application window. Arrange your workspace so you are able to access Analyzer.

Defining the input variables

You need to select input and output variables from the main Analyzer window to pass to the Parametric Study tool. Start by adding the input variables to Analyzer.

  1. Select Walker_Collection () in the STK Variables list.
  2. Select Walker () in the STK Property Variables - General frame.
  3. Move () Walker () to the Analyzer Variables list.

Defining the output variables

Now that the input variables are defined, you can add the output variables. The output variables are the variables you'd like to solve for Minimum N.Asset Overall and Maximum Revisit Time Overall.

  1. Expand CoverageDefinition () in the STK Variables list.
  2. Select NAsset ().
  3. Expand () Overall Value () in the Data Providers () list in the Data Provider Variables frame.
  4. Select Minimum ().
  5. Move () Minimum () to the Analyzer Variables list.
  6. Select RevisitTime () in the STK Variables list.
  7. Expand () Overall Value () in Data Provider Variables frame.
  8. Select Maximum ().
  9. Move () Maximum () to the Analyzer Variables list.

Using the Parametric Study Tool

The Parametric Study Tool runs a model through a sweep of values for some input variable. The resulting data can be plotted to view trends.

The trade study in this example varies the semi-major axis for a network of satellites. You can feed in the setup for the Walker analysis.

  1. Click Parametric Study... () on the Analyzer toolbar to open the Parametric Study Tool.
  2. Press and drag SemiMajorAxis () from the Components list on the left to the Design Variable on the right when the Parametric Study Tool opens.
  3. Set the following options:
    4. Option Value
    starting value: 6880
    ending value: 7680
    step size: 100

    These settings will vary the semi-major axis in 100 kilometer increments. It will take a total of nine (9) runs to complete the trade study.

  4. drag the following to the Responses list:
    • NAsset - Minimum
    • RevisitTime - Maximum

Defining the Walker variables

Define the walker parameters within the parametric study.

  1. Locate the Walker - Shell_Walker_Group list, located in the Components list. To the right of each variable is a value that you can click to change the value.
  2. Set the following for the Walker Constellation:
    3. Option Value
    Planes 6
    SatellitesInPlanes 6

Running the parametric trade study

This parametric trade study will take a few minutes to run.

  1. Click Run. . ..
  2. When the analysis is complete, examine the results.

    3. In each of the runs, you should see the revisit time (gaps) decrease as the semi-major axis increases. Eventually it goes to zero. The average increases to two for the number of assets. The minimum number of assets eventually reaches two.

Generating a scatter plot

There are a few ways to view the data. One interactive way to view the data is in a 3D scatter plot.

  1. Bring the Data Explorer view to the front.
  2. Click Add View in the Data Explorer toolbar.
  3. Select 3D Scatter Plot in the shortcut menu.
  4. Click Dimensions.
  5. Set the following options:
    6. Option Value
    X Maximum
    Y Minimum
    Z SemiMajorAxis
  6. Click the graph to close the Dimensions window.
  7. Examine the matrix.
  8. Click any point to get information about that run.
  9. Note the semi-major axis of the last run (7680 km). This gives you the requirements you are looking for: 2 assets and 0 seconds revisit time.

    10. Analyzer 3D Scatter plot

  10. Close the Data Explorer window.
  11. Click No to save.

Syncing to STK

All of the criteria meet in the final run (semi-major axis 7680 km); however, remember that the semi-major axis values are raised in 100 km increments. There is likely a minimum semi-major axis that enables you to achieve your goals sooner. If you consider cost, which might be tied to a higher orbit, you can find a lower semi-major axis that also reduces cost.

Push the results of a single run to STK and examine the scenario.

  1. Return to the Parametric Study Tool.
  2. Set the SemiMajorAxis () Value to 7680 in the Components list. You do not need to enter units.
  3. Click Sync to STK.

    4. This pushes the results to STK. STK may take a few minutes to insert and configure the satellites.

  4. Close the Parametric Study tool when the coverage analysis is complete.
  5. Minimize Analyzer.
  6. Look at the 2D and 3D Graphics windows.

    7. Walker_Collection () is automatically updated from the last run and the Walker Group now contains six (6) planes, six (6) satellites per plane and all the satellites are at a semi-major axis of 7680 kilometers.

Examining the Data

Now that you have a result loaded in, look at some of the reports and graphs in STK that can shed some light on the scenario.

  1. Right-click NAsset () in the Object Browser.
  2. Select Report & Graph Manager... () in the shortcut menu.
  3. Select the Percent Satisfied () report in the Installed Styles list when the Report & Graph Manager opens.
  4. Click Generate. . ..
  5. Scroll to the bottom of the report and look at the % Satisfied column.

    6. You should have 100% coverage, which means you have a minimum of two (2) satellites with access to a point on the ground. The Percent Satisfied report confirms that information.

  6. Close the Percent Satisfied report.
  7. Select the Grids Stats Over Time () report in the Installed Styles list.
  8. Click Generate. . . .
  9. Scroll through the report.

    10. You can see that you meet the minimum, but you have a few locations that have up to five (5) or six (6) satellites with access (depending on the analysis period). This creates a lot of redundancies, so you can start thinking of optimizing the setup.

    You have two options at this point:

    • Continue to test configurations using parametric scans, carpet studies, and design of experiments.
    • Optimize the scenario to find the optimal semi-major axis.

    You may also consider if you need to change other factors with the study (number of satellites or planes).

  10. Close any reports and the Report & Graph Manager when finished.

In the upcoming procedures, you have the option of loading a pre-computed trade study or setting up and running the trade study yourself. The pre-computed optimization trade study took approximately an hour to run. If you want to use the pre-computed trade study, start at "Loading in an optimization trade study". If you want to set up and run the trade study manually, move to " Setting up an optimization trade study".

Loading in an optimization trade study

The study you are going to load in was run for approximately an hour using the Satellite Collection () object. Older versions of STK required the Walker Tool and individual Satellite () objects and took upwards of 10 hours to analyze.

The goal was to minimize the semi-major axis and the total number of satellites. At the same time, you want to minimize the revisit time (no gaps) and have two satellites maintain access with a point on the ground. Let's load in the data and examine it.

Opening the pre-computed trade study

  1. Select the Analysis menu.
  2. Select Analyzer.
  3. Select the Open Trade Study Result in the Analyzer submenu.
  4. Browse to the DME_Session1_Constellation Concept Design and Trade Studies folder you downloaded from the SDF.
  5. Select DME_OptStudy2.tstudy.
  6. Click Open.

    7. This opens the trade study results table and graph.

Understanding the results

  1. Examine the results of the 3D Scatter plot.

    2. You can see the configurations that met the criteria in blue and those that didn't in gray.

    Analyzer 3D Scatter plot

  2. Click any point in the graph to see more information about a run.
  3. Select the lowest blue point on the graph.

    4. This is the lowest semi-major axis that satisfies all of your criteria (7637.40 km).

  4. Examine the table.

    5. You can scroll to see all the runs that were conducted and each result. You also have the option to export the data into Excel or another tool for post-processing.

  5. Scroll to run 192.

    6. This is the run that met all of the criteria of the trade study.

If you are bypassing "Setting up an optimization trade study", move to "Syncing the results to STK using the pre-computed trade study". If you want to run the trade study yourself, move to "Setting up an optimization trade study".

Setting up an optimization trade study

This is an additional section for users who would like to setup an optimization themselves.

Looking at the data, there is a clear point that meets all the conditions for the study. Build the Optimizer to get an idea of the work-flow. You will load in the best result from the data.

  1. Close the pre-run Data Explorer.
  2. Click No to close.
  3. Select Optimization Tool... () in the Analyzer toolbar.
  4. Click Sync from STK. This loads the current setup in the scenario to the Optimization Tool.

Defining the semi-major axis

  1. Drag SemimajorAxis in the Components list to drop it in the Objective list located in the Objective Definition frame.
  2. Set the Goal to minimize (default).

Defining the NAsset Minimum

  1. Drag the NAsset - Minimum to the Constraint list located in the Objective Definition frame.
  2. Set the Lower Bound to two (2).
  3. Drag the Revisit Time - Maximum to the Constraint list.
  4. Set the Lower and Upper Bounds to zero (0).

Defining the design variables

  1. Drag SemiMajorAxis to the Design Variable list located in the Design Variables frame.
  2. Set the following Lower/Upper bounds:
    3. Option Value
    Lower Bound 7580
    Upper Bound 7680

Defining the number of satellites per plane

  1. Drag SatellitesInPlanes in the Components list to drop it in the Design Variable list.
  2. Set the following options in the dialog:
    3. Option Value
    Start Value 3
    End Value 6
  3. Click OK.

Defining the number of planes

  1. Drag Planes in the Components list to drop it in the Design Variable list.
  2. Set the following options in the dialog:
    3. Option Value
    Start Value 3
    End Value 6
  3. Click OK.

Selecting an algorithm

There are over 30 algorithms to choose from when using the Optimization Tool. An algorithm selection wizard is provided to make it easy to choose algorithms that will work best for the problem at hand. You will use the Darwin Algorithm. Darwin is a genetic search algorithm developed specifically for solving engineering optimization problems. Because Darwin does not require gradient information, it is able to effectively search non-linear and noisy design spaces. Also, Darwin is a genetic optimizer that can solve constrained design problems.

  1. Open the Algorithm dropdown menu.
  2. Select Darwin Algorithm.
  3. Click Run.

    4. Be patient. This will take a long time (potentially an hour or more depending on your PC).

Understanding the results

If you loaded the downloaded trade study, the values may be different due to your analysis period. However, it should be close. The image that follows will probably be different than your results but it should also be close.

  1. When the trade study is finished, bring the Optimization Tool to the front.
  2. Click View Output... located in the lower right corner.
  3. Select the Best Design tab when the Optimization Tool Results window opens.

    4. Best Design

    At the top of the Optimization Tool Results window it will tell you the best design run number. All the values on the right of the dialog shows you the best values.

  4. Bring the Data Explorer to the front.
  5. Scroll to the Best Design Run Number column.

    6. This data will be the same as the values seen in the Optimization Tool Results - Best Design tab.

Syncing the results to STK using the pre-computed trade study

Use the following steps if you used the pre-computed trade study. Out of the runs that met all the criteria of the trade study, run 192 had the lowest semi-major axis (7637.40 km).

  1. Select the Analysis menu.
  2. Select the Analyzer menu.
  3. Select Optimization Tool... () in the Analyzer submenu.
  4. Ensure the following values are set in the Components list:
    OptionValue
    Planes6
    InterPlanePhaseIncrement6
  5. Set the SemiMajorAxis to 7637.40 km in the Components list. You do not need to enter units.
  6. Click Sync to STK. This pushes the results to STK.
  7. Move to the "Examining the Data" section.

Syncing the results to STK using your trade study

Use the following steps if you ran your own trade study.

  1. Bring the Optimization Tool to the front.
  2. The value showing for SemiMajorAxis () should match the best design value. If not, enter the value manually.
  3. Click Sync to STK. This pushes the results to STK.

Examining the Data

Now that you have a result loaded in, let's look at some of the reports and graphs in STK that can shed some light on the scenario.

  1. Bring STK to the front.
  2. Right-click on NAsset () in the Object Browser.
  3. Select Report & Graph Manager... () in the shortcut menu.
  4. Select the Percent Satisfied () report in the Installed Styles list.
  5. ClickGenerate. . ..
  6. Scroll to the bottom of the report.

    7. You know from the results of the trade study that this configuration enables you to have a minimum of two (2) satellites with access to a point on the ground. This report confirms that you have 100% Satisfaction.

  7. Close the report.

Graphing the results

Run a grid stats over time graph.

  1. Return to the Report & Graph Manager.
  2. Select the Specify Time Properties option in the Time Properties frame.
  3. Select the Use step size / time bound option.
  4. Enter 1 sec in the Step size field.

    5. By reducing the step size to one (1) second, the graph will show more information.

  5. Select the Grid Stats Over Time () graph in the Installed Styles list.
  6. Click Generate. . ..

    7. Grid stats over time graph

    From this data, you see that you have full coverage throughout our mission. The minimum criteria of two satellites with simultaneous access to a grid point is met. This is confirmed in the Percent Satisfied Report and the Grid Stats Over Time graph. You can also see that you have a maximum four to six satellites with simultaneous access to a grid point. This redundancy is key in case you lose a satellite in the course of a mission. The objective to create a new satellite constellation that provides persistent, stereo coverage of hypersonic vehicles across the world has been met.

Saving your work

  1. When finished, close all tools, graphs and reports you still have open.
  2. Save () your work.

Summary

You have the results of the optimization run, but there are many parameters that you can vary in the analysis. The flexibility of STK and Analyzer enables you to change an aspect of the mission (like the semi-major axis) while knowing that it carries through and is used in all calculations. If you have access to Model Center, you may link the analysis with Model Center and incorporate cost breakdowns, the total number of satellites, or any other parameters. You can integrate the mission earlier, thus considering all the factors in the environment.

DME Lesson 2

The next lesson in the DME series focuses on Hypersonics and EOIR. You will use a starter scenario and build your own hypersonic vehicle. You will use an EOIR sensor to image it. This leads up to sessions three and four of the DME series where you bring the constellation from this lesson and the flight from session two together to understand how all components for the mission works together.