Modeling Near-real-time Relays in STK

STK Pro, STK Premium (Air), STK Premium (Space), or STK Enterprise
You can obtain the necessary licenses for this training by contacting AGI Support at support@agi.com or 1-800-924-7244.

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 an internet connection and STK 12.8 or newer to complete in its entirety. If you have an earlier version of STK, you can complete a legacy version of this lesson.

Capabilities covered

This lesson covers the following STK Capabilities:

  • STK Pro

Problem Statement

Engineers and operators require a quick and simple way to simulate multi-hop relays of information (e.g. communications, images, data) between satellites and ground sites. With the increased global seismic activity, the Italian government wants you to collect visual imagery on one of the greatest tourist attractions; the Roman Colosseum. They want you to monitor the geography of the area around the Colosseum and its structural integrity.

To do this, you must take as many pictures of the Colosseum as possible and return them to White Sands or Guam during a three (3) week analysis period.

Solution

With STK, you can determine when you can take images of the Colosseum, in daylight, over a 3-week analysis period. You will use cameras attached to two operational Landsat satellites to take the pictures. After you take the pictures, you will uplink them to an operational TDRS satellite and then downlink them to White Sands or Guam in near-real-time. Processing delays and link distance will be taken into account in the analysis.

What you will learn

Upon completion of this tutorial, you will have an understanding of the following:

  • Inserting Keyhole Markup Language (.kml or .kmz) files into STK for visualization
  • Promoting a .kmz file to an analytical STK object
  • Building Constellation objects
  • Building Chain objects

Creating a new scenario

First, you must 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 Image_Relay
    Description Default
    Location Default
    Start 1 Nov 2023 16:00:00.000 UTCG
    Stop + 21 days
  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 dialog box.
  7. Click Save.

Save () often during this lesson!

Disabling Terrain Server

The Terrain Server adds geographic features to the 3D Graphics Window that you do not need for this scenario's calculations.

  1. Right-click on Image_Relay () in the Object Browser.
  2. Select Properties () in the shortcut menu.
  3. Select the Basic - Terrain page when the Properties Browser opens.
  4. Clear the Use terrain server for analysis check box in the Terrain Server frame.
  5. Click OK to accept your change and to close the Properties Browser.

Simulating the Roman Colosseum

Since you will determine when a satellite can see the Roman Colosseum during the day time, you need to add the Colosseum itself. You will use a .kmz file to model the Roman Colosseum in your scenario.

Globe Manager - KML window

You can use the KML window to add Keyhole Markup Language (KML) files (.kml/.kmz) to a 3D Graphics window. This enhances the visuals in the 3D Graphics window for movie making, briefings and situational awareness. Use a local .kmz file to visualize the Roman Colosseum in the 3D Graphics window.

  1. Bring the 3D Graphics window to the front.
  2. Click Globe Manager () in the Globe Manager toolbar.
  3. Select the KML tab when Globe Manager opens.
  4. Click Open KML Content ().
  5. Browse to the location of your KML file. The default location is <STK install folder>\Data\Resources\stktraining\KML.
  6. Select romecolosseum.kmz.
  7. Click Open.

Viewing the Roman Colosseum in the 3D Graphics Window

Once loaded, you can view the KML model in the 3D Graphics window.

  1. Right-click on model () in the KML browser.
  2. Select Zoom To () in the shortcut menu.
  3. Close the informational dialog. The message informs you that the model was created using Google Sketchup.
  4. Mouse around in the 3D Graphics window until you can clearly see the Roman Colosseum. You may need to left-click then drag to pan around the Colosseum or you may need to scroll out with the mouse wheel to zoom out.

3D Graphics View of the Roman Colosseum

Promoting the KML Model to an STK Object

You can use the Colosseum model for analysis in STK by promoting it into an STK object. Since the Colosseum is the target of your imaging satellites, promote it to an STK Target () object.

  1. Return to Globe Manager.
  2. Expand () model.
  3. Right-click on Model ().
  4. Select Import as Target in the shortcut menu.
  5. Right-click on Model () in he Object Browser.
  6. Select Rename in the shortcut menu.
  7. Rename Model () to Colosseum.

Viewing the Colosseum in the 2D Graphics Window

You can view Colosseum () in the 2D Graphics window.

  1. Bring the 2D Graphics window to the front.
  2. Click Zoom In () in the 2D Window Defaults toolbar.
  3. Hold down your left mouse button and drag a box around Colosseum () and then let the button go.
  4. Do this as many times as you need to until you can clearly see the Colosseum.

    5. 2D Graphics View of the Roman Colosseum

Modeling both TDRSS ground sites

Two ground sites will receive the images of the Colosseum. You will use the Standard Object Database to model selected U.S. Tracking and Data Relay Satellite System (TDRSS) ground sites. Specifically, you will add the White Sands and Guam Remote Ground Terminals to the scenario.

  1. Select Facility () in the Insert STK Objects tool.
  2. Select the From Standard Object Database () method.
  3. Click Insert... .
  4. Type White Sands in the Name: field when the Search Standard Object Data dialog box opens.
  5. Open the Role: shortcut menu.
  6. Select Ground Station.
  7. Select the Active Status: checkbox.
  8. Click Search.
  9. Select White Sands STDN WH3K in the Facility Name column of the Results: list.
  10. Click Insert.

Inserting a Guam Remote Ground Terminal

  1. Return to the Search Standard Object Data dialog box.
  2. Type Guam in the Name: field.
  3. Click Search.
  4. Select GRGT STDN GWMJ in the Facility Name column of the Results: list.
  5. Click Insert.
  6. Click Close to close the Search Standard Object Data dialog box.

White_Sands_STDN_WH3K's and GRGT_STDN_GWMJ's properties

You are not using terrain in your analysis. You can place White_Sands_STDN_WH3K () and GRGT_STDN_GWMJ () on the surface of the WGS84 and turn off the Mask File.

  1. Select White_Sands_STDN_WH3K () and GRGT_STDN_GWMJ () in the Object Browser.
  2. Click Properties () in the Object Browser toolbar.
  3. Select the Basic - Position page when the Properties Browser opens.
  4. Select the Use terrain data check box.
  5. Click Apply to accept your change and to keep the Properties Browser open.
  6. Select the Basic - AzElMask page.
  7. Open the Use: shortcut menu.
  8. Select None.
  9. Clear the Use Mask for Access Constraint check box.
  10. Click OK to accept your changes and to close the Properties Browser.

Group the TDRSS ground sites

In your scenario, you have the two ground stations used by the TDRSS network. You can group them together with a Constellation () object. You want either of these facilities to collect the data whenever either one can complete an access chain.

  1. Insert a Constellation () object using the Insert Default () method.
  2. Rename Constellation1 () to TDRSS_Ground.
  3. Open TDRSS_Ground's () properties ().
  4. Select the Basic - Definition page when the Properties Browser opens.
  5. Select the Facility () check box in the Selection filter: frame.
  6. Move () the Facility () objects from the Available Objects list to the Assigned Objects list.
  7. Click OKto accept your changes and to close the Properties Browser.

Landsat satellites

You can take pictures of the Colosseum with two Landsat satellites and uplink the images to selected TDRS satellites.

  1. Insert a Satellite () object using the From Standard Object Database () method.
  2. Type Landsat in the Name or ID: field when the Search Standard Object Data dialog box opens.
  3. Open the Operational Status: shortcut menu.
  4. Select Operational.
  5. Click Search.
  6. Select Landsat 8 and LANDSAT 9 in the Common Name column of the Results: list.
  7. Select the Create Constellation from Selected check box in the Insert Options frame.
  8. Type Landsat_Sats in the Name: field.
  9. Click Insert.
  10. Click Close to close the Search Standard Object Data dialog box once the satellites have been propagated.

Satellite cameras using Sensor objects

The Sensor () objects simulate a camera's field of view on a satellite. Landsat8_39084 () propagated into your scenario with attached Sensor () objects. You'll delete one of them then copy the other one and attach it to LANDSAT_9_49260 ().

  1. Select Landsat8_Tirs_Ir_FixedPt_FieldOfView () in the Object Browser.
  2. Click Delete () in the Object Browser toolbar.
  3. Click Delete in the Delete Object dialog box.
  4. Select Landsat8_Oli_Vis_Ir_FixedPt_FieldOfView () in the Object Browser.
  5. Click Copy () in the Object Browser toolbar.
  6. Select LANDSAT_9_49260 () in the Object Browser.
  7. Click Paste () in the Object Browser toolbar.
  8. Rename Landsat8_Oli_Vis_Ir_FixedPt_FieldOfView1 () to Landsat9_Oli_Vis_Ir_FixedPt_FieldOfView ().

Viewing LANDSAT_9_49260 () in the 3D Graphics window

  1. Bring the 3D Graphics window to the front.
  2. Right-click on LANDSAT_9_49260 () in the Object Browser.
  3. Select Zoom To in the shortcut menu.

LANDSAT_9_49260 Sensor Field of View

Grouping the sensors

You can insert a Constellation () object that groups your sensors for analysis.

  1. Insert a Constellation () object using the Insert Default () method.
  2. Rename Constellation2 () to CamerasFOV.
  3. Open CamerasFOV's () properties ().
  4. Select the Basic - Definition page when the Properties Browser opens.
  5. Select the Sensor () check box in the Selection filter: frame.
  6. Move () Landsat8_Oli_Vis_Ir_FixedPt_FieldOfView () and Landsat9_Oli_Vis_Ir_FixedPt_FieldOfView () from the Available Objects list to the Assigned Objects list.
  7. Click OK to accept your changes and to close the Properties Browser.

Inserting TDRS satellites

You will insert the TDRS satellites and group them in a Constellation () object.

  1. Insert a Satellite () object using the From Standard Object Database () method.
  2. Type TDRS in the Name or ID: field when the Search Standard Object Data dialog box opens.
  3. Open the Operational Status: shortcut menu.
  4. Select Operational.
  5. Click Search.
  6. Select the following TDRS Satellites using the Common Name column in the Results: list:

    • TDRS 12

    • TDRS 3

    • TDRS 6

    • TDRS 7

  7. Set the following in the Insert Options frame:
    8. Option Value
    Create Constellation from Selected Selected
    Name: TDRS_Sats
  8. Click Insert.
  9. Click Close to close the Search Standard Object Data dialog box when the satellites have been propagated.

Removing unneeded objects

The TDRS satellites propagated with attached Antenna (), Receiver () and Transmitter () objects. They won't be used in your analysis. Take your time when deleting multiple objects. You don't want to accidentally delete a Satellite () object.

  1. Delete () all the Antenna (), Receiver () and Transmitter () objects from Tdrs3_19548.
  2. Delete () all the Antenna (), Receiver () and Transmitter () objects from Tdrs6_22314.
  3. Delete () all the Antenna (), Receiver () and Transmitter () objects from Tdrs7_23613.
  4. Save () your scenario.

Creating a Chain Object

A chain is a list of objects (either individual or grouped into constellations) in order of access. Assign objects to the chain and define the order in which objects are accessed. In this analysis, you need to analyze a chain of events from Colosseum () to CameraFOV (), then to a Landsat_Sats (), then to TDRS_Sats () and then to TDRSS_Ground (). All objects grouped in a Constellation () object might be used or only one.

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

Define the start and end objects

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

  1. Open Colosseum_To_TDRSS's () properties ().
  2. Select the Basic - Definition page when the Properties Browser opens.
  3. Click the Start Object: ellipses ().
  4. Select Colosseum () in the Select Object dialog box.
  5. Click OK to close the Select Object dialog box.
  6. Click the End Object: ellipses ().
  7. Select TDRSS_Ground () 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.

Create the Chain Object's connections

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

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

    8. Colosseum () must pass through either Landsat8_Oli_Vis_Ir_FixedPt_FieldOfView's () or Landsat9_Oli_Vis_Ir_FixedPt_FieldOfView's () field of view to complete an access.

Create the Chain Object's second connection

When either Landsat8_Oli_Vis_Ir_FixedPt_FieldOfView () or Landsat9_Oli_Vis_Ir_FixedPt_FieldOfView () accesses Colosseum (), it passes the image to its parent object.

  1. Click Extend in the Connections frame.
  2. Click the To Object: ellipses ().
  3. Select Landsat_Sats () in the Select Object dialog box.
  4. Click OK to close the Select Object dialog box.

Create the Chain Object's third connection

The Landsat satellite will then pass the image to a TDRS satellite.

  1. Click Extend in the Connections frame.
  2. Click the To Object: ellipses ().
  3. Select TDRS_Sats () in the Select Object dialog box.
  4. Click OK to close the Select Object dialog box.

Create the Chain Object's final connection

The TDRS satellite then passes the image to a TDRSS ground station.

  1. Click Extend in the Connections frame.
  2. Click the To Object: ellipses ().
  3. Select TDRSS_Ground () in the Select Object dialog box.
  4. Click OK to close the Select Object dialog box.
  5. Click OK to accept your changes and to close the Properties Browser.

Constrain Access to Rome

The Landsat cameras will take pictures of the Colosseum during daylight hours. To model this, you need to impose a constraint based on the position of the Sun.

  1. Open Colosseum's () properties ().
  2. Select the Constraints - Sun page when the Properties Browser opens.
  3. Select the Lighting: check box.
  4. Open the Lighting: shortcut menu.
  5. Select Penumbra or Direct Sun.
  6. Click OK to accept your changes and to close the Properties Browser.

Cleaning up the scenario

You will have an easier time seeing your chain accesses if you turn off the satellite ground tracks and orbits.

  1. Bring the 3D Graphics window to the front.
  2. Click Home View () in the 3D Graphics toolbar.
  3. Zoom out until you see all the satellite orbits.
  4. Open Image_Relay's () properties ().
  5. Select the 2D Graphics - Global Attributes page when the Properties Browser opens.
  6. Clear the following check boxes in the Vehicles frame:

    • Show Ground Tracks/ Routes

    • Show Orbits/ Trajectories

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

    8. You can still see the satellites, but the orbits and ground tracks have been removed.

Making labels visible at long distances

To obtain improved situational awareness, you can make your satellite and ground site labels visible at greater distances in the 3D Graphics window.

Satellite Objects

  1. Select all the Satellite () objects in the Object Browser. You can hold the Ctrl key on your keyboard while clicking to select multiple satellites.
  2. Click Properties () in the Object Browser toolbar.
  3. Select the 3D Graphics - Model page when the Properties Browser opens.
  4. Slide the Simple Model, Label slider in the Detail Thresholds frame all the way to the right.
  5. Click OK to accept your change and to close the Properties Browser.

Facility Objects

  1. Select all the Facility () objects in the Object Browser. You can hold the Ctrl key on your keyboard while clicking to select multiple satellites.
  2. Click Properties () in the Object Browser toolbar.
  3. Select the 3D Graphics - Model page when the Properties Browser opens.
  4. Slide the Simple Model, Label slider in the Detail Thresholds frame all the way to the right.
  5. Click OK to accept your change and to close the Properties Browser.

Target Object

  1. Open Colosseum's () properties ().
  2. Select 3D Graphics - Model page when the Properties Browser opens.
  3. Slide the All slider in the Detail Thresholds frame all the way to the right.
  4. Click OK to accept your change and to close the Properties Browser.
  5. Save () your scenario.

Generating a Complete Chain Access report

Generate a Complete Chain Access report to analyze whether or not you have accesses during your scenario analysis period. A complete chain access reports the time intervals for which the chain is completed. These intervals are computed by overlapping all the strand accesses. You're analyzing when will you have the opportunity to take pictures of the Roman Colosseum and relay them to White Sands or Guam in near-real-time.

  1. Select Colosseum_To_TDRSS () in the Object Browser.
  2. Open the Chain menu item.
  3. Select Compute Accesses.
  4. Right-click Colosseum_To_TDRSS () in the Object Browser.
  5. Select Report & Graph Manager... () in the shortcut menu.
  6. Select the Complete Chain Access () report in the Installed Styles () folder in the Styles frame.
  7. Click Generate....

Visual analysis

You can look at a complete chain access in the 2D or 3D Graphics windows. Use the 3D Graphics window.

  1. Right-click the first access Start Time in the complete chain access report.
  2. Select Start Time in the first shortcut menu.
  3. Select Set Animation Time in the second shortcut menu.
  4. Bring the 3D Graphics window to the front.

Complete Chain Access View

Now, you can view the complete chain access in the 3D Graphics window.

  1. Right click on LANDSAT_9_49260 () in the Object Browser.
  2. Select Zoom To in the shortcut menu.
  3. Use your mouse so that you can see down to the ground.

    4. Colosseum to Landsat9 access

    In this view, you can see the access from Colosseum () passing through Landsat9_Oli_Vis_Ir_FixedPt_FieldOfView's () field of view to LANDSAT_9_49260 ().

  4. Click Home View () in the 3D Graphics toolbar.
  5. Zoom out until you can see the complete chain access.

    6. Complete Chain Access

Analyzing the complete chain access

This is an interesting complete chain access.

  • LANDSAT_9_49260 () has access to Tdrs3_19548 (), Tdrs6_22314 () and TDRS_12_39504 ().

    • All three satellites have access to White_Sands_STDN_WH3K ().

  • LANDSAT_9_49260 () has access to Tdrs7_23613 () which has access to GRGT_STDN_GWMJ ().

Engineers have a choice of which TDRS satellite and which TDRSS ground site to use at this particular time.

Recording the scenario time for later

  1. When finished, close the Complete Chain Access report.
  2. Make sure to keep this current scenario time. You will use it later.

Individual Strand Access

An individual strand access represents one possible access pathway through the chain. For a chain that consists of a series of individual objects, only a single strand is possible. If a chain contains one or more constellations, multiple strands are possible, but constellation constraints (ANY OF, ALL OF, AT LEAST N, EXACTLY N) can affect the possible number of strands.

  1. Return to the Report & Graph Manager.
  2. Select the Individual Strand Access () report in the Installed Styles () folder in the Styles frame.
  3. Click Generate....

    4. You can use the Individual Strand Access report to balance time lines against accuracy of assets. For example, using this report (or graph) would help you determine the impact on your mission should any of the satellites or ground stations become inoperable.

  4. Close the Individual Strand Access report.

Adding a new connection

You saw in the Complete Chain Access report that their were multiple connections to choose from. Some operators need to pass the image between satellites in the same constellation of satellites. In this instance, you want to be able to pass the image between TDRS satellites in the TDRS_Sats () constellation.

  1. Open Colosseum_To_TDRSS's () properties ().
  2. Select the Basic - Definition page when the Properties Browser opens.
  3. Click Add in the Connections frame.
  4. Click the From Object: ellipses ().
  5. Select TDRS_Sats () in the Select Object dialog box.
  6. Click OK to close the Select Object dialog box.
  7. Click the To Object: ellipses ().
  8. Select TDRS_Sats () in the Select Object dialog box.
  9. Click OK to close the Select Object dialog box.
  10. Click Apply to accept your changes and to keep the Properties Browser open.

Viewing the accesses in the 3D Graphics window

Your accesses will change dramatically since all possibilities of a TDRS satellite accesses another TDRS satellite have now been calculated.

  1. Bring the 3D Graphics window to the front.
  2. Click Home View () in the 3D Graphics toolbar.
  3. Zoom out until you can see the complete chain access.

    4. Updated Complete Chain Access

You can compare this view with the original complete chain access view. Now you are seeing all possibilities of the image being passed between TDRS satellites before it is passed to a TDRSS ground site.

Valid Paths

An important Chain () object data provider can provide valuable information to your analysis. The data provider Definition reports the settings used by the Chain () object when computing available strands.

  1. Bring the Report & Graph manager to the front.
  2. Select the Valid Paths () report in the Installed Styles list.
  3. Click Generate... .

    4. This report is showing you the valid paths being used to send the image to a TDRSS ground site.

Number of strands

The Strand Names data provider and associated Strand Names element lists the names of the object in all valid strands for a computed chain. The Number of Strands element lists the number of strands with valid access intervals.

  1. Select the Computed Strands () report in the Installed Styles list.
  2. Click Generate... .
  3. Look at the Number of Strands (e.g. 32) at the top of the report. There's a lot of information in the report detailing each possible strand.
  4. Return to Colosseum_To_TDRSS's () properties ().
  5. Select the Basic - Definition page.
  6. Look at Maximum # of Uses: in the Connections frame.

The current value defaults to 1. This specifies the maximum number of times a connection may be used in a strand. When you generated the Computed Strands () report, it reported how many strands there were based on all of your possible connections being used once.

Increasing the maximum strands

You can increase the maximum number of strands. In this case, you will increase strands per node to 2 in the TDRS satellite constellation.

  1. Select the TDRS_Sats to TDRS_Sats connection in the Connections list.
  2. Enter 2 in the Maximum # of Uses: field.
  3. Click Apply to accept your changes and to keep the Properties Browser open.
  4. Bring the Computed Strands () report back to the front.
  5. Click Refresh (F5) () in the report toolbar.
  6. Look at the Number of Strands value.

You created more possibilities (e.g. 80) by increasing the number of strands allowed in this connection.

Optimal Strands

The Chain () object Optimal Strand properties allows you to determine the best strands for a computed Chain based on a specified metric. Currently, you have approximately 80 strands to choose from. You can narrow this down to choose the time and strand that meets your operational needs.

Determining the shortest strand

You will find the shortest possible strand.

  1. Return to Colosseum_To_TDRSS's () properties ().
  2. Select the Basic - Optimal Strand page.
  3. Select the Compute check box.
  4. Select the Metric: Distance option.
  5. Look at the Strand Comparison selection. The default setting is Min (minimum).
  6. Click Apply to accept your changes and to keep the Properties Browser open.
  7. Bring the 2D Graphics window to the front.

    8. You can see a highlighted strand. This is the strand containing the shortest distance between nodes in which to transfer the image to a TDRSS ground station.

    Optimal strand minimum distance

Determining the longest strand

You will find the longest possible strand.

  1. Return to Colosseum_To_TDRSS's () properties ().
  2. Open the Strand Comparison: shortcut menu.
  3. Select Max.
  4. Click Apply to accept your change and to keep the Properties Browser open.
  5. Bring the 2D Graphics window to the front.

    6. You can see a highlighted strand. This is the strand containing the longest distance between nodes in which to transfer the image to a TDRSS ground station.

    optimal strand maximum distance

Optimal Strand reports

There are two reports you can use to determine your optimal strand: Optimal Strands by Time and Optimal Strand at Time. These aren't the only reports you can use, but for the purposes of your analysis, these will suffice.

Generating a Optimal Strand at Time report

The Optimal Strand at Time report reports the best optimal strand by name and metric value for the sampled times when optimal strands exist based on computed Chain accesses.

  1. Return to Colosseum_To_TDRSS's () properties ().
  2. Open the Strand Comparison: shortcut menu.
  3. Select Min.
  4. Click Apply to accept your changes and to keep the Properties Browser open.
  5. Bring the Report & Graph manager to the front.
  6. Select the Optimal Strand at Time () report in the Installed Styles list.
  7. Click Generate... .
  8. Look at the data contained in the report.

    9. The report is based on minimal distance at time.

Generating a Optimal Strand by Time report

The Optimal Strands by Time report reports the optimal strands by name and metric value for the sampled times when optimal strands exist based on computed Chain accesses.

  1. Bring the Report & Graph manager to the front.
  2. Select the Optimal Strands by Time () report in the Installed Styles list.
  3. Click Generate... .
  4. Look at the data contained in the report.

    5. The report is similar to the optimal strand at time report but it's breaking down the data by each individual access.

Processing Delay

Processing delay is a noticeable latency due to the speed of light when sending data to and from satellites and the distance between the satellites. Speed of light is constant, but other delays could be caused by hardware and software in every device that the signal must pass through. The default processing delay for your objects in this scenario defaults to 0 (zero) seconds. You will change the processing delay for one object to see how this works in STK.

  1. Open to LANDSAT_9_49260's () properties ().
  2. Select the Basic - Processing Delay page when the Properties Browser opens.
  3. Enter 5 sec in the Processing Delay Time: field.
  4. Click OK to accept your change and to close the Properties Browser.
  5. Open Colosseum_To_TDRSS's () properties ().
  6. Select the Basic - Optimal Strand page when the Properties Browser opens.
  7. Select the Processing Delay option.
  8. Click OK to accept your changes and to close the Properties Browser.

Accounting for processing delay in reports

The Optimal Strand at Time report is showing the optimal strand based on maximum distance. Refreshing the report will change it to optimal strand based on maximum processing delay.

  1. Bring the Optimal Strand at Time report to the front.
  2. Click Refresh (F5) () in the report toolbar.
  3. Look at the data in the report.

When LANDSAT_9_49260 () is sending an image, it is showing the added five (5) second delay. The Optimal Strands at Time report will take the light time delay into account too.

Saving your work

You can clean up and finish your scenario.

  1. Close any open reports, properties, and the Report & Graph Manager.
  2. Save () your work.

Summary

The overall purpose of this scenario was to determine when you can take pictures of the Colosseum, in daylight, over a three (3) week analysis period and send them to a selected TDRSS ground site in near-real-time to include processing delay. You learned how to load a .kmz file into STK and then promote it to an STK object. Next, you loaded 2 Facility objects that are TDRSS ground sites (Guam and White Sands). You grouped them into a Constellation object. You inserted 2 operational Landsat satellites, grouped them into a Constellation object and used Sensor objects to simulate the fields of view of cameras on the satellites. You grouped the Sensor objects into Constellation object. You inserted multiple operational TDRS satellites and grouped them into a Constellation object. You constrained the Colosseum so that any Sensor object accessing it could only do so in penumbra or direct sunlight. Finally, you inserted a Chain object which allowed you to determine when near-real-time accesses were possible during your three (3) week analysis period. A Landsat camera had to pass over the Colosseum, the Landsat satellite had to have access to a TDRS satellite and the TDRS Satellite had to have access to a TDRSS ground site. You allowed image transfers between TDRS satellites and added a processing delay to your analysis.