Radio Frequency Interference

Radio frequency interference is a common issue when scheduling multiple satellite contacts.

Radio Frequency Interference: Exclusion Cones

Interference can result from satellites transmiting on the same or similar frequency too close to one another. A general rule of thumb, as to not encounter this issue, is to constrain your satellites to be at least 5 degrees apart during contact transmissions.

Prerequisites

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

Steps

  1. Open the included STK scenario.
  2. The final STK scenario, RF_Interference_Final.vdf, is also included in C:\Program Files\AGI\STK 11\STKScheduler\Scenarios\Use Cases .

  3. Edit the scenario.
    1. Create Constellations.
      1. From the menu bar, click Insert > New... then, insert a Constellation using the Define Properties method.
      2. In the Basic - Definition page, add all satellites to the Assigned Objects list by clicking the right arrow. Click OK to apply changes.
      3. Repeat steps 2 A i-ii for all facilities.
    2. Create a Chain for every Satellite.
      1. From the menu bar, click Insert > New... then, insert a Chain using the Define Properties method.
      2. In the Basic - Definition page, add the first satellite, facility constellation, and satellite constellation - in that order - to the Assigned Objects list by clicking the right arrow.
      3. Click OK to apply changes.
      4. Repeat steps 2 B i-iii for all satellites.
    3. Save the scenario.
  4. Open STK Scheduler.
  5. 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 location to your edited scenario, RF_Interference.vdf.
    4. Click Open then OK and the STK scenario will be associated with your Scheduler file.
  6. Ingest Resources from STK.
    1. Navigate to Resource > Ingest From STK > All.
    2. In the Select Map Objects for Resource Creation window, select all resources.
    3. Click OK.
  7. Edit ingested Resources.
    1. Create Resource Groups.
      1. Navigate to Resource > Edit Resource... to open the Resource Editor window.
      2. Use [CTRL] + Click to select all facility resources.
      3. In the General tab under Resource Groups, enter "Gnd" in the New Group: field and click Create.
      4. Add "Gnd" to the Included Groups: by selecting it and clicking the right arrow.
      5. Click Update.
    2. Edit Chain Resources.
      1. Select the first Chain resource.
      2. In the General tab, click Browse STK Objects then, in the Select Object Window, click Clear then OK.
      3. Disaffiliating the chain resource with the chain STK Object will prevent STK from incorrectly computing access.

      4. In the Availability tab, ensure the radio button next to Define Blackout Times - Default Available is selected.
      5. In the Discrete Windows sub-tab, click STK Imoprt.
      6. In the STK Report Definitions window, click Add.
      7. In the STK Report Definition window, select the Angle Between report type.
      8. Click the ... button next to STK Object 1: and select "Chain1" then click OK.
      9. Select No Minimum Limit and a value of "5" for From Maximum Value:, then click OK.
      10. Select Chain 1 Angle Between Report and click OK.
      11. In the Resource Editor window click Update.
      12. Repeat steps 6 B i-x for all chain resources.
  8. Create Task definitions.
    1. Go to Task > New Task.
    2. In the Task ID: field, enter "Sat1_Contact".
    3. In the Scheduling tab, select the radio button next to Recurring Task.
    4. In the Duration tab, select the following properties:
      1. Variable Duration = True
      2. Min Total Duration = 000 00:02:00.000
      3. Max Total Duration = Unlimited
      4. Allow Multiple Segments = True
      5. Allow Resource Changes Between Segments = True
      6. Allow Gaps = True
    5. In the Resources tab, Select "Gnd" from the Available Resource Groups: list and click the right arrow.
    6. Click the radio button next to Resource(s) From Group and select 1, then click Create Group/List.
    7. Enter "_1ofGnd" as the resource constraint group name and click OK.
    8. Create the following Resource Constraints string: <"DMSP_5D-3_F18_35951" AND "_1ofGnd" AND "Chain1">.
    9. Click Create Possibilities then Update.
    10. Repeat steps 7 A-I for each respective satellite and corresponding chain resource.
  9. De-conflict the Schedule
    1. Select Schedule > Select Algorithm > Multi Pass then click Schedule > Go!!!

Results

STK Scheduler is not limited to STK's default reports. Custom reports can be made in Scheduler that reflect various constraints and, in turn, limit the timeslot possibilities created by Scheduler.

Ingest Command File

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