Medium Earth Orbit Relay Scheduling

Multiple satellites can be used as components of a communication system to relay signals indirectly from one point of interest to another.

Ground Contact Scheduling via MEO Relay Constellation.

Often times, contact between a LEO satellite and a ground station cannot be directly established. In these instances it is possible to indirectly establish contact through a MEO constellation. The following steps will familiarize you with the procedure for scheduling the appropriate scenario.

Prerequisites

File: Meos.vdf Path: C:\Program Files\AGI\STK 11\STKScheduler\Scenarios\Use Cases

Steps

  1. Open STK Scheduler.
  2. Load the associated STK Scenario.
    1. Navigate to Schedule > STK > Load Scenario....
    2. In the Schedule Properties window, click Change Scenario.
    3. Select the file path to Meos.vdf.
    4. Click Open then OK and the STK scenario will be associated with your Scheduler file.
  3. Ingest Resources from STK.
    1. Navigate to Resource > Ingest From STK > All.
    2. In the Select Map Objects for Resource Creation window, click Select All then OK.
  4. Edit the ingested Resources.
    1. Adjust MEO relay satellites attributes.
      1. Navigate to Resource > Edit Resource.
      2. On the left side of the Resource Editor window use Ctrl + click to select all GPS satellite resources.
      3. In the General tab, locate the New Group field and enter "MEO".
      4. Click the Create button next to New Group.
      5. Select the MEO resource group under Available Groups.
      6. Click the right arrow button to add MEO to the Included Groups.
      7. In the Accommodation tab, set the Accommodation value equal to 2.
      8. Click Update.
    2. Adjust Ground Station attributes.
      1. Select Ground in the Resource Editor window.
      2. In the General tab, set Setup equal to 2 minutes.
      3. In the Accommodation tab, set Unlimited Accommodation to Checked.
      4. Click Update.
  5. Set Task definitions.
    1. Go to Task > New Task.
    2. In the Task ID: field, enter "Kompsat1_Contact".
    3. In the Duration tab, select the radio button next to Variable Duration.
    4. Set the Minimum Duration to 1 minute and the Maximum Duration to Unlimited.
    5. Check the boxes next to Allow Multiple Segments and Allow Resource Changes Between Segments.
    6. Ensure the radio button next to Allow Gaps is selected.
    7. Create a resource constraint group.
      1. In the Resources tab, select MEO under Avail Resource Group and click the blue right arrow to move all MEO resources to the Constraint Group/Template List Builder on the right.
      2. Under Constraint Group, select the Resources From Group option and set the number to 1.
      3. Click the Create Group/List button.
      4. Name the new resource constraint group "_1ofMeos" then click OK.
    8. Create the following Resource Constraints string: <"Kompsat1_26032" AND (("Ground" AND "_1ofMeos") OR "Ground")>.
    9. Click Create Possibilities, then view the Timeslot Definitions tab.
    10. For each possibility in the Possibility list, click STK Import and delete the <Kompsat1_26032, Ground Access Report>. Click OK after each delete.
    11. Click Update then Close.
  6. Run the Sequential Algorithm.
    1. Navigate to Schedule > Select Algorithm > and select the Sequential algorithm.
    2. Click Schedule > Go!!! to run the selected algorithm.
    3. Click OK when Done Scheduling to exit the Scheduling Progress window. A Summary Report window will open.

Results

In this instance there are multiple metrics useful for the analysis of the schedule. The Gantt and Table views can be used to quickly determine the timeslot of the assigned contact scheduling task. As always, one can also review the various reports offered by STK Scheduler.

Ingest Command File

A sample ingest command file named MEO_Relay_Scheduling.txt is available in the Examples/Use Cases folder. Ingesting that file will replicate the schedule described here.