Satellite Collection Object: How to Use External Files

STK Pro, STK Premium (Air), 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 12.9 or newer to complete in its entirety. If you have an earlier version of STK, you can complete a legacy version of this lesson.

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

Problem

You require a fast, easy way to set up and analyze a group of satellites as a single object. Your Satellite Collection object must support metadata for additional descriptive information and support categorization into subsets.

Solution

Use STK to model large constellations of satellites using the Satellite Collection object and associated external files.

What you will learn

Upon completion of this tutorial, you will understand:

  • How to implement the Satellite Collection object.
  • How to create custom orbit definition files.
  • How to use reference objects.
  • How to use the Deck Access Tool.
  • How to use routing files.

Creating a new scenario

First, you will create a new STK scenario and then build from there.

  1. Launch STK ().
  2. Click Create a Scenario in the Welcome to STK dialog box.
  3. Enter the following in the STK: New Scenario Wizard:
    4. Option Value
    Name: SatelliteCollection
    Location: Default
    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 for you.
  6. Verify the scenario name and location in the Save As window.
  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.

Using the Walker Tool

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).

Creating Walker Type Group 1

  1. Right-click on Walker_Collection () in the Object Browser.
  2. Select Properties () in the shortcut menu.
  3. Select the Basic - Definition page.
  4. Select Shells Name 1 in the Walker Properties frame.
  5. Click Edit selected shell () in the Shells toolbar.
  6. Enter Group 1 in the Shell Name* field when the Edit Shell dialog box opens.
  7. Set the following in Shell Properties frame:
    8. Option Value
    Planes 72
    Satellites in Planes (Slots) 22
  8. Set the following in the Plane 1 : Slot 1 frame:
    9. Option Value
    Semi-Major Axis (a) 6928.14 km
    Inclination (i) 53 deg
  9. Click Save Changes.
  10. Click Apply to accept your changes and to keep the Properties Browser open.

    11. You can see the new satellites have been added to the Subsets list.

Creating Walker Type Group 2

  1. Click Add a new shell () in the Shells toolbar.
  2. Enter Group 2 in the Shell Name* field when the New Shell dialog box opens.
  3. Set the following in Shell Properties frame:
    4. Option Value
    Planes 36
    Satellites in Planes (Slots) 20
  4. Set the following in the Plane 1 : Slot 1 frame:
    5. Option Value
    Semi-Major Axis (a) 6948.14 km
  5. Click Save Changes.
  6. Click Apply to accept your changes and keep the Properties Browser open.

    7. You can see the new satellites have been added to the Subsets list.

Subsets

STK automatically generates a subset called AllSatellites for each selected type. If the type is Walker, a subset is created for each plane and each shell in the collection. Take a moment to scroll down through the list to view your satellites in the Subsets frame.

Setting graphics attributes

Each subset has its own graphical properties. Subsets are used when performing calculations (e.g., as assets in the Coverage analysis). You want to visualize Group 1 and Group 2 in the 3D Graphics window, separating them by using different colors.

  1. Select the Graphics - Attributes page.
  2. Clear the AllSatellites Show checkbox.
  3. Select the Show check box for Shell_Group 1.
  4. If you desire to change the color of the satellites in this group, double-click on the color cell.
  5. Open the Color shortcut menu.
  6. Select a new color.
  7. Select the Show check box for Shell_Group 2.
  8. Change the color if desired.
  9. Click OK to accept your changes and to close the Properties Browser.

Viewing the satellites in the 3D Graphics window.

You will need to turn on the Satellite Collection () object in the Object Browser.

  1. Bring the 3D Graphics window to the front.
  2. Ensure that the Walker_Collection () check box is selected in the Object Browser.
  3. Use your mouse to zoom out until you can see the constellation of satellites.

    4. Group 1 and Group 2

  4. Click Start () in the Animation toolbar to animate your scenario.
  5. Click Reset () in the animation toolbar once you finish viewing your constellation of satellites.
  6. Clear the Walker_Collection () check box.

    7. The satellites do not need to be visible in the 3D Graphics window during analysis.

Updating the satellite database

The Scenario object database properties enable you to set the defaults for the city, facility, satellite, and star databases. You can specify a stock STK database or one of your own that meets STK's format requirements. You will update the satellite database based on your scenario's analysis time period. An Internet connection is required for this step.

  1. Open SatelliteCollection's () properties().
  2. Select the Basic - Database page.
  3. Click Update Database Files...
  4. Click Update when the Update Satellite Database dialog box opens. The typical path to the satellite database is C:\ProgramData\AGI\STK 12\Databases\Satellite.
  5. Click OK to close the Information dialog box.
  6. Click Close to close the Update Satellite Database dialog box.
  7. Click OK to accept your changes and to close the Properties Browser.

Creating a collection of Geosynchronous (GEO) satellites

You will create a new collection of satellites showing the GEO belt.

  1. Insert a SatelliteCollection () object using the Insert Default () method.
  2. Rename SatelliteCollection2 () to Database_GEO.

Setting Database Type

For this option, you provide search parameters for STK to apply in extracting satellites for the collection from a satellite database.

  1. Open Database_GEO's () properties ().
  2. Select the Basic - Definition page.
  3. Open the Type: shortcut menu.
  4. Select Database.

Searching the Database

When you click Define Search Parameters, a dialog box appears, with a panel on the left for parameter specification, and one on the right to display results.

  1. Click Define Search Parameters in the Database Search frame.
  2. Resize the Database Search dialog box so that you can see all of the selections in the Define Parameters frame.
  3. Clear the Min: check box for Periapsis Altitude.
  4. Clear the Max: check box for Inclination.
  5. Select all the check-boxes (Active, Inactive, Unknown) for Operational Status.
  6. Click Search.
  7. Click Apply Parameters.
  8. Click Apply to accept your changes and to keep the Properties Browser open.

Viewing the satellites in the 3D Graphics window

Turn on Database_GEO () in the Object Browser.

  1. Bring the 3D Graphics window to the front.
  2. Ensure that the Database_GEO () check box is selected in the Object Browser.
  3. Use your mouse to zoom out until you can see the constellation of satellites.

    4. GEO Belt Satellites

  4. Click Start () in the Animation toolbar to animate your scenario.
  5. Click Reset () in the animation toolbar once you finish viewing your constellation of satellites.
  6. Clear the Database_GEO () check box.

Orbit Definition File

A custom orbit definition file is an ASCII text file that is formatted for compatibility with STK and ends in a .csv extension. The Header defines file content and Data provides orbit information and / or Metadata.

ORBIT DEFINITION FILE REQUIREMENTS

Creating a new folder

Create a new folder where you will save the satellite collection files.

  1. Create a New Folder on your Desktop.
  2. Rename the New Folder to Satellite Collection Files.

Creating OrbitElements file

You will start by creating an OrbitElements file. Use Notepad, Notepad++, MS WordPad or a text editor that does not add hidden characters to your document.

  1. Open your text editor.
  2. Copy and paste the following text into a blank page in your text editor.

    3. VERSION 1.0

    ContentType OrbitElements

    Begin Columns
    Name, SemiMajorAxis, Eccentricity, Inclination, RAAN, ArgumentOfperiapse, TrueAnomaly
    S1_P1_S1,8000,0.1,10,80,0,0
    S1_P2_S1,8000,0.1,20,70,0,0
    S1_P3_S1,8000,0.1,30,60,0,0
    S1_P4_S1,8000,0.1,40,50,0,0
    S1_P5_S1,8000,0.1,50,40,0,0
    S1_P6_S1,8000,0.1,60,30,0,0
    S1_P7_S1,8000,0.1,70,20,0,0
    S1_P8_S1,8000,0.1,80,10,0,0
    End Columns

  3. Open the File menu.
  4. Select Save As...
  5. Browse to the Satellite Collection Files folder on your Desktop.
  6. Open the Satellite Collection Files folder.
  7. Change the File name: to OrbitElementsCollection.csv.
  8. Click Save.

Creating a collection of custom satellites using orbital parameters

You will create a new collection of custom satellites.

  1. Return to STK.
  2. Insert a SatelliteCollection () object using the Insert Default () method.
  3. Rename SatelliteCollection3 () to Custom_OrbitElems.

Setting Custom Type

For this option, you provide an orbit definition file that defines the members, orbital parameters, and metadata.

  1. Open Custom_OrbitElems's () properties ().
  2. Select the Basic - Definition page.
  3. Open the Type: shortcut menu.
  4. Select Custom.

Loading the OrbitElementsCollection file

Load the OrbitElementsCollection.csv file that you created.

  1. Click Select a file () for the Orbit Definition File in the Custom Properties frame.
  2. Click Desktop in the Select a File dialog box.
  3. Select Satellite Collection Files.
  4. Click Open.
  5. Select the OrbitElementsCollection.csv file.
  6. Click Open.
  7. Click Apply to accept your changes and to keep the Properties Browser open.

Setting graphics attributes

  1. Select the Graphics - Attributes page.
  2. Ensure that the Show check box is selected for AllSatellites.
  3. Double-click the Marker Size cell.
  4. Enter the value 7.
  5. Change the color if desired.
  6. Click OK to accept your changes and to close the Properties Browser.

Viewing the satellites in the 3D Graphics window

View the satellites in the 3D Graphics window.

  1. Bring the 3D Graphics window to the front.
  2. Use your mouse to move the Earth and to zoom out until you can see the constellation of satellites.

    3. Custom Orbital Elements Satellites

  3. Click Start () in the Animation toolbar to animate your scenario.
  4. Click Reset () in the animation toolbar once you finish viewing your constellation of satellites.
  5. Clear the Custom_OrbitElems () check box.

Adding Metadata

The CustomColumns section defines metadata that are associated with each satellite collection entry in the content of the Columns section. The first nonblank, noncomment line is the header row, which contains the keywords to be read, separated by commas. You can place Keywords in any order, though typically the ColumnName column appears first and DataType appears second. Each nonblank, noncomment line that follows the header line contains comma-separated content defining a metadata value. The values correspond to the order defined by the header row. You may leave values for optional columns blank.

Creating SSC file

STK uses the SSC identifier to obtain the orbit definition from a file specified by the Satellite Collection.

  1. Return to your text editor.
  2. Copy and paste the following text into a blank page in your text editor.

    3. Version 1.0
    ContentType SSC

    BEGIN CustomColumns
    ColumnName, DataType, Required, EnumValues, CreateSubsets
    OrbitRegime, Enum, Yes, GEO | LEO, Yes
    Payload, String, No, , No
    END CustomColumns

    BEGIN Columns
    Name, SSC ID, OrbitRegime, Payload
    EDRS-C, 44475, GEO, Comm
    ARTEMIS, 26863, GEO, Comm
    AEOLUS, 43600, LEO, Science
    SENTINEL-1A, 39634, LEO, Science
    SENTINEL-2A, 40697, LEO, Science
    SENTINEL-3A, 41335, LEO, Science
    SENTINEL-1B, 41456, LEO, Science
    SENTINEL-2B, 42063, LEO, Science
    SENTINEL-5P, 42969, LEO, Science
    SENTINEL-3B, 43437, LEO, Science C
    SENTINEL-6, 46984, LEO, Science
    END Columns

  3. Open the File menu.
  4. Select Save As...
  5. Browse to the Satellite Collection Files folder on your Desktop.
  6. Open the Satellite Collection Files folder.
  7. Change the File name: to Custom_SSC.csv.
  8. Click Save.

Creating a collection of custom satellites using SSC parameters

Create a new collection of custom satellites.

  1. Return to STK.
  2. Insert a SatelliteCollection () object using the Insert Default () method.
  3. Rename SatelliteCollection4 () to Custom_SSC.

Setting Custom Type

Set the Type to Custom.

  1. Open Custom_SSC's () properties ().
  2. Select the Basic - Definition page.
  3. Open the Type: shortcut menu.
  4. Select Custom.

Loading the Custom_SSC file

Load the Custom_SSC.csv file that you created.

  1. Click Select a file () for the Orbit Definition File in the Custom Properties frame.
  2. Click Desktop in the Select a File dialog box.
  3. Select Satellite Collection Files.
  4. Click Open.
  5. Select the Custom_SSC.csv file.
  6. Click Open.
  7. Click Apply to accept your changes and to keep the Properties Browser open.

Viewing Subsets

There are now three subsets:

  • AllSatellites
  • OrbitRegime_GEO
  • OrbitRegime_LEO

You can view them together or separate them by subset.

  1. Select OrbitRegime_GEO in the Subsets section.
  2. Click View entries in subset () in the Subsets toolbar.

    3. ORBIT REGIME GEO SUBSET

  3. Click Close when finished viewing the information.
  4. Select OrbitRegime_LEO.
  5. Click View entries in subset ().
  6. Click Close when finished viewing the information.
  7. Select AllSatellites.
  8. Click View entries in subset ().
  9. Click Close when finished viewing the information.

Setting graphics attributes

Display only the satellites in the OrbitRegime_GEO and OrbitRegime_LEO subsets.

  1. Select the Graphics - Attributes page.
  2. Clear the AllSatellites - Show checkbox.
  3. Select the Show and Label check-boxes for OrbitRegime_GEO.
  4. Select the Show and Label check-boxes for OrbitRegime_LEO.
  5. Change the color for each if desired.
  6. Click OK to accept your changes and to close the Properties Browser.

Viewing the satellites in the 3D Graphics window

You will need to turn on the Satellite Collection () object in the Object Browser.

  1. Bring the 3D Graphics window to the front.
  2. Use your mouse to zoom out until you can see both the LEO and GEO satellite collections.
  3. Click Start () in the Animation toolbar to animate your scenario.
  4. Click Reset () in the animation toolbar once you finish viewing your constellation of satellites.
  5. Double-click on ARTEMIS (the small dot) in the 3D Graphics window to view the metadata.

    6. ARTEMIS METADATA

  6. Clear the Custom_SSC () check box once you are done.

Adding Additional Metadata

You can assign metadata to satellite entries already defined by a satellite collection.

Creating Metadata file

Use this ContentType to designate the file as supplemental data. It does not define an orbit.

  1. Return to your text editor.
  2. Copy and paste the following into a blank page in the text editor.

    3. Version 1.0

    ContentType MetaData

    BEGIN CustomColumns
    ColumnName, DataType, Required, CreateSubsets
    Band1, String, No, Yes
    Band2, String, No, Yes
    Band3, String, No, Yes
    END CustomColumns

    BEGIN Columns
    Name, Band1, Band2, Band3
    S1_P1_S1, S, Ka
    S1_P2_S1, S, , Ku
    S1_P3_S1, S, Ka, Ku
    S1_P4_S1, S, , Ku
    S1_P5_S1, S, Ka
    S1_P6_S1, S, Ka, Ku
    S1_P7_S1, S, , Ku
    S1_P8_S1, S, Ka, Ku
    END Columns

  3. Open the File menu.
  4. Select Save As...
  5. Browse to the Satellite Collection Files folder on your Desktop.
  6. Open the Satellite Collection Files folder.
  7. Change the File name: to SupplementalMetadata.csv.
  8. Click Save.

Loading the custom SupplementalMetadata file

Load the SupplementalMetadata.csv file that you created.

  1. Return to STK.
  2. Select the Custom_OrbitElems () check box in the Object Browser.
  3. Open Custom_OrbitElems's () properties ().
  4. Select the Basic - Definition page.
  5. Click Select a file () in the File (optional) field in the Supplemental Metadata frame.
  6. Click Desktop in the Select a File dialog box.
  7. Select Satellite Collection Files.
  8. Click Open.
  9. Select the SupplementalMetadata.csv file.
  10. Click Open.
  11. Click Apply to accept your changes and to keep the Properties Browser open.

Viewing Subsets

You now have four subsets. You can view all the satellites at once or choose a specific subset. For instance, you are interested in seeing only those satellites using Band3/Ku.

  1. Select Band3_Ku in the Subsets section.
  2. Click View entries in subset () in the Subsets toolbar.

    3. SATELLITES USING BAND3/KU

  3. Click Close when finished viewing the information.
  4. Click OK to close the Properties Browser.

Creating Reference Objects

You will use reference objects as a template for a specific subset of a Satellite Collection object. 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. You can then use these children in the analysis tools. For example, your satellite constellation subset might have the same sensor type which is needed for analysis by all the satellites. By creating a reference object with the required attached object, in this case a sensor, you can use the reference object as a template and apply the sensor to all the satellites in the Satellite Collection () object subset.

  1. Insert a Satellite () object using the Insert Default () method.
  2. Rename Satellite1 () to KaBandTemplate.

Setting Ka Band Transmitter Field of View

Insert a Sensor () object that represents the Ka Band transmitter antenna's field of view.

  1. Insert a Sensor () object using the Insert Default () method.
  2. Select KaBandTemplate () in the Select Object dialog box.
  3. Click OK to close the Select Object dialog box.
  4. Rename Sensor1 () to KaFoV. FoV stands for field-of-view.

Setting Sensor Properties

Use a nominal value for the Ka Band transmitter antenna's field of view.

  1. Open KaFoV's () properties ().
  2. Select the Basic - Definition page.
  3. Enter 35 deg in the Cone Half Angle: field within the Simple Conic frame.
  4. Click OK to accept your change and to close the Properties Browser.

Using the Reference object template

You can associate KaFoV's () field of view to Custom_OrbitElems () Band2_Ka subset.

  1. Open Custom_OrbitElems () properties ().
  2. Select the Basic - Definition page.
  3. Select Band2_Ka in the Subsets list.
  4. Click Edit selected subset () in the Subsets toolbar.
  5. Select KaBandTemplate () in the Select Object dialog box.
  6. Click OK to close the Select Object dialog box.
  7. Click Apply to accept your changes and to keep the Properties Browser open.
  8. Look in the Subsets list. You now have a subset named AllSensors.
  9. Click OK to accept your changes and to close the Properties Browser.

Applicable Analytics

Besides displaying your Satellite Collection object subsets in the 3D Graphics window, you can use elements in the collection for different computational processes (e.g. Coverage, Deck Access, Advanced CAT, Communications, Chains). Start with a Coverage Definition object.

Inserting a Coverage Definition object

Insert a Coverage Definition object with 4 deg point granularity.

  1. Insert a Coverage Definition () object using the Insert Default () method.
  2. Open CoverageDefinition1's () properties ().
  3. Select the Basic - Grid page.
  4. Enter 4 deg in the Point Granularity - Lat/Lon field in the Grid Definition frame.
  5. Click Apply to accept your change and to keep the Properties Browser open.

Choosing your assets

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

  1. Select the Basic - Assets page.
  2. Expand () Custom_OrbitElems () in the Assets list.
  3. Select AllSensors, which uses the reference object template.
  4. Click Assign.
  5. Click OK to accept your changes and to close the Properties Browser.

Computing Coverage

The ultimate goal of coverage is to analyze accesses to an area using assigned assets and applying necessary limitations (e.g. Sensor object field of view) upon those accesses.

  1. Right-click on CoverageDefinition1 () in the Object Browser.
  2. Select CoverageDefintion in the shortcut menu.
  3. Select Compute Accesses in the second shortcut menu.

Inserting a Figure Of Merit

You can evaluate the quality of coverage for an area by creating one or several Figure Of Merit () objects attached to the Coverage Definition () object of interest.

  1. Insert a Figure Of Merit () object using the Insert Default () method.
  2. Select CoverageDefinition1 () in the Select Object dialog box.
  3. Click OK to close the Select Object dialog box.

Viewing the coverage in the 2D graphics window

You can view the KaBandTemplate coverage in both the 2D and 3D Graphics windows. You will use the 2D Graphics window.

  1. Bring the 2D Graphics window to the front.
  2. Click Start () in the Animation toolbar.
  3. Click Reset () in the Animation toolbar once you are done.
  4. Clear the CoverageDefinition1 () check box in the Object Browser.
  5. Clear the KaBandTemplate () check box in the Object Browser.

    6. You can also create applicable reports and graphs using the Figure Of Merit and the Report & Graph Manager.

Inserting a tracking station

The tracking station will track your satellites.

  1. Insert a Place () object using the Insert Default () method.
  2. Rename Place1 () to TrackingStation.

Inserting Tracking Station Sensor

The tracking station uses a sensor to track satellites.

  1. Insert a Sensor () object using the Insert Default () method.
  2. Select TrackingStation () in the Select Object dialog box.
  3. Click OK to close the Select Object dialog box.
  4. Rename Sensor2 () to SensorFoR. FoR stands for field-of-regard.

Modeling Complex Conic Sensor Patterns

Complex Conic sensor patterns are defined by the inner and outer half angles and minimum and maximum clock angles of the sensor's cone.

  1. Open SensorFoR's () properties ().
  2. Select the Basic - Definition page.
  3. Open the Sensor Type: shortcut menu.
  4. Select Complex Conic.
  5. Enter 180 deg in the Half Angles - Outer: field in the Complex Conic frame.
  6. Click Apply to accept your changes and to keep the Properties Browser open.

Defining the field-of-regard

Basic Constraints enable you to impose standard access constraints on an object. In this instance, your tracking sensor can see out to a maximum range of 2500 kilometers.

  1. Select the Constraints - Active page.
  2. Click Add new constraints () in the Active Constraints toolbar.
  3. Select Range in the Constraint Name list in the Select Constraints to Add dialog box.
  4. Click Add.
  5. Click Close to close the Select Constraints to Add dialog box.
  6. Select the Max: check box in the Range frame.
  7. Enter 2500 km in the Max: field.
  8. Click Apply to accept your changes and to keep the Properties Browser open.

Setting 2D Graphics Attributes

2D Graphics Attributes answer three basic questions about an STK object:

  • What do you want to show?
  • How do you want it to look?
  • When do you want it to be seen?
  1. Select the 2D Graphics - Attributes page.
  2. Open the Color: shortcut menu.
  3. Select Gray (the first color on the bottom row).
  4. Click Apply to accept your changes and to keep the Properties Browser open.

Setting 3D Graphics Attributes

Use this page to control the display of a sensor in the 3D graphics window.

  1. Select the 3D Graphics - Attributes page.
  2. Enter the value 70 in the % Translucency: field in the Projection frame.
  3. Click OK to accept your changes and to close the Properties Browser.

Opening Deck Access Tool

The Deck Access tool enables you to compute access to a set of objects, not currently defined within the STK scenario, from a single object within the scenario. Deck access operations are useful when you have a large number of objects that no longer need to be in the STK scenario but for which you would like visibility information. Using deck access can greatly reduce load and save time for such scenarios and minimize graphical clutter.

  1. Right-click on SensorFoR () in the Object Browser.
  2. Select Deck Access... () in the shortcut menu.

Selecting the target deck

Indicate the type of object that is defined by the data in the specified file.

  1. Open the Type: shortcut menu in the Select Target Deck frame once the Deck Access tool opens.
  2. Select Collection Subset.
  3. Open the Name: shortcut menu. All of the subsets from the Satellite Collection () objects are located here.
  4. Select Custom_OrbitElems.AllSatellites.
  5. Click Compute Accesses...

    6. The report shows you accesses to each satellite from the tracking station sensor over your analysis period.

  6. Close the report and the Deck Access tool once you are done.

Routing Files

Use a routing file to specify the rules for links in a chain associated with objects in a constellation or entries in a satellite collection subset. It is an ASCII text file with a *.routing extension that STK reads every time it computes a chain with the constellation or subset.

  1. Return to your text editor.
  2. Copy and paste the following into a blank page in the text editor.

    3. Begin MultihopRules
    DefaultRule Never

    Begin Rules
    Access "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P1_S1" "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P2_S1" reciprocal
    Access "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P2_S1" "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P3_S1" reciprocal
    Access "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P3_S1" "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P4_S1" reciprocal
    Access "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P4_S1" "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P5_S1" reciprocal
    Access "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P5_S1" "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P6_S1" reciprocal
    Access "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P6_S1" "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P7_S1" reciprocal
    Access "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P7_S1" "CollectionSubsetEntry SatelliteCollection/Custom_OrbitElems/Subset/AllSatellites S1_P8_S1" reciprocal
    End Rules
    End MultihopRules

  3. Open the File menu.
  4. Select Save As...
  5. Browse to the Satellite Collection Files folder on your Desktop.
  6. Open the Satellite Collection Files folder.
  7. Change the File name: to Rules.routing.
  8. Click Save.

    9. This routing file example uses MultihopRules which is a new feature added in STK 12.5. MultihopRules govern the links between two or more objects within the constellation or between two or more entries within a subset. MultihopRules do not apply to objects outside of the constellation or subset. In this example, looking at the first access line, the satellite in orbital plane 1 can only talk to the adjacent satellite in orbital plane 2. The next access, the satellite in orbit plane 2 can only talk to the satellite in orbit plane 3 etc. At the end of each access is reciprocal which simply means the data can flow in both directions.

  9. Close your text editor.

Inserting Receiving Station

Insert a Place () object in West Africa which will act as a receiving station.

  1. Insert a Place () object using the Insert Default () method.
  2. Rename Place2 () to ReceivingSatation.
  3. Open ReceivingStations's () properties ().
  4. Select the Basic - Position page.
  5. Set the following in the Position frame:
    6. Option Value
    Latitude 21.5353 deg
    Longitude -16.4078 deg
  6. Click OK to accept your changes and to close the Properties Browser.

Applying the MultihopRules to a Satellite Collection object

Use the Rules.routing file to define the satellite collection's routing.

  1. Open Custom_OrbitElems's () properties ().
  2. Select the Basic - Routing page.
  3. Select the Use routing file: check box.
  4. Click the Use routing file: ellipsis ().
  5. Click Desktop in the Select a File dialog box.
  6. Select Satellite Collection Files.
  7. Click Open.
  8. Select Rules.routing.
  9. Click Open.
  10. Click OK to accept your changes and to close the Properties Browser.

Creating a Chain object

A chain is a list of objects (either individual or grouped into constellations or satellite collection subsets) in order of access. You want to route data from the tracking station's field of regard to the satellites in the Custom_OrbitElems () collection, and then reroute data to any other satellites in the collection and then to the receiving station.

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

Defining the start and end objects

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

  1. Open RoutedChain's () properties ().
  2. Select the Basic - Definition page when the Properties Browser opens.
  3. Click the Start Object: ellipses ().
  4. Select SensorFoR () in the Select Object dialog box.
  5. Click OK to close the Select Object dialog box.
  6. Click the End Object: ellipses ().
  7. Select ReceivingStation () in the Select Object dialog box.
  8. Click OK to close the Select Object dialog box.
  9. Click Apply to accept your changes and to keep the Properties Browser open.

Creating the Chain object's first connection

After you choose the start and end objects in your chain, you need to build the chain's connections. The first connection is from the tracking station's field of regard to the satellites in the Custom_OrbitElems () collection.

  1. Click Add in the Connections frame.
  2. Click the From Object: ellipses ().
  3. Select SensorFoR () in the Select Object dialog box.
  4. Click OK to close the Select Object dialog box.
  5. Click the To Object: ellipses ().
  6. Select Custom_OrbitElems () - AllSatellites () in the Select Object dialog box.
  7. Click OK to close the Select Object dialog box.

Creating the Chain Object's second connection

Next, build the second connection from the Custom_OrbitElems () collection to any other satellites in the collection.

  1. Click Add in the Connections frame.
  2. Click the From Object: ellipses ().
  3. Select Custom_OrbitElems () - AllSatellites () in the Select Object dialog box.
  4. Click OK to close the Select Object dialog box.
  5. Click the To Object: ellipses ().
  6. Select Custom_OrbitElems () - AllSatellites () in the Select Object dialog box.
  7. Click OK to close the Select Object dialog box.

Creating the Chain Object's final connection

Now build the third connection from the Custom_OrbitElems () collection to the receiving station.

  1. Click Add in the Connections frame.
  2. Click the From Object: ellipses ().
  3. Select Custom_OrbitElems () - AllSatellites () in the Select Object dialog box.
  4. Click OK to close the Select Object dialog box.
  5. Click the To Object: ellipses ().
  6. Select ReceivingStation () 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.

Computing the Chain object's accesses

  1. Select RoutedChain () in the Object Browser.
  2. Open the Chain menu shortcut.
  3. Select Compute Accesses.

Generating Complete Chain Access Report

A complete chain access reports the time intervals for which the chain is completed. These intervals are computed by overlapping all the strand accesses.

  1. Right-click on RoutedChain () in the Object Browser.
  2. Select Report & Graph Manager... () in the shortcut menu.
  3. Select the Complete Chain Access () report in the Installed Styles list once the Report & Graph Manager opens.
  4. Click Generate...
  5. View the data in the report to determine when complete chain accesses occur during your scenario.
  6. Close the report and the Report & Graph Manager once you are done.

Displaying accesses in the Timeline View

With the Timeline View, you can visualize a variety of time intervals within your scenario.

  1. Click Add Time Components () in the Timeline toolbar.
  2. Select RoutedChain () in the Objects list once the Select Timeline Component dialog box opens.
  3. Select CompleteChainAccessIntervals () in the Components for: RoutedChain list.
  4. Click OK to accept your changes and to close the Select Timeline Component dialog box.
  5. Look at the Timeline View. You can see when complete chain accesses are taking place during your scenario.

Viewing the complete chain access intervals in the 3D Graphics window

You can visualize the exact moment when Chain object's accesses take place in the 3D Graphics window.

  1. Bring the 3D Graphics window to the front.
  2. Move the gray pointer () in the Timeline View until it's over the first access.

    3. COMPLETE CHAIN ACCESS INTERVAL

    In this example, one satellite in the Satellite Collection Object passes through the tracking station sensor's field of regard. There is an access between the sensor and that satellite. That satellite then passes data to the satellite in the adjacent orbital plane which can access the receiving station and passes data to the receiving station.

  3. Continue moving the gray pointer () to view additional accesses.
  4. Click Reset () in the Animation toolbar once you are done.

Summary

This was a comprehensive scenario that covered multiple ways to use the Satellite Collection () object. You learned the following:

  • Using the Walker Tool to create groups
  • Using a database search to select satellites used in your Satellite Collection object
  • Custom orbit definition files
  • How to create a collection of satellites using OrbitElements
  • How to create a collection of satellites using ContentType SSC and adding metadata
  • How to add additional metadata using ContentType Metadata
  • How to build and use a Reference object
  • How to use the Deck Access Tool to track satellites in a Satellite Collect object
  • How to create a routing file and use it in a Chain object