Interplanetary Scheduling

Mars Pathfinder Contact

This use case will provide steps to schedule contact between the Mars Pathfinder Probe and an Earth ground station. Once the probe completes its interplanetary transfer and enters a Martian orbit, a 30 minute contact task via MEO relay will be scheduled.

Prerequisites

File: Interplanetary.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 Interplanetary.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, use Ctrl + click to select all resources except Earth and Mars.
    3. Click OK.
  4. Edit schedule period
    1. Navigate to Schedule > Define Start/Stop... and the Schedule Properties window will open.
    2. Adjust the Start Time and Stop Time parameters respectively to the following: <1997/07/03 17:00:00.000><1997/07/05 00:00:00.000>.
    3. Click OK.
  5. 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.
  6. Create Task definitions.
    1. Go to Task > New Task.
    2. In the Task ID: field, enter "Contact".
    3. In the Duration tab, select the radio button next to Variable Duration.
    4. Set the Min Total Duration to 1 minute and the Max Total Duration to 30 minutes.
    5. Click the check box next to Allow Multiple Segments.
    6. Adjust the Min Segment Duration to 1 minute.
    7. Click the check box next to Allow Resource Change Between Segements and select the Allow Gaps radio button.
    8. Construct "_1ofMEOs' Constraint Group
      1. In the Resources tab, select "MEO" under Available Resource Groups: and click the right arrow button.
      2. Selcet the radio buttion next to Resources From Group and change the field to 1 resource from group.
      3. Click Create Group/List and enter "_1ofMEOs".
      4. Click OK and _1ofMEOs will appear under Available Resources.
    9. Create the following Resource Constraints string: <"GroundStation" AND "MarsProbe" AND "_1ofMEOs">.
    10. Click Create Possibilities, then Update and Close.
  7. Run the One-Pass Algorithm.
    1. Navigate to Schedule > Select Algorithm > and select the One-Pass 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

Reviewing the summary report confirms the Contact task has been scheduled for the complete 30 minute duration. The Gantt view illustrates the Contact task occurring throughout the earliest possible windows after a 2 minute setup time offset. For this use case it may be useful to view the STK animation for clarification purposes.

Ingest Command File

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