Keywords: STK, sceneless

Summary

This demo shows how to ingest mission planning reports produced by Systems Toolkit (STK). Specifically, how the DIRSIG FlexMotion model can directly read STK ephemeris (.e) and attitude (.a) reports. This demo is also "scene-less", in that it doesn’t use a conventional DIRSIG scene and utilizes the EarthGrid plugin exclusively for the scene.

Related Materials

The following demos, manuals and tutorials can provide additional information about the topics at the focus of this demo:

  • Related Demos

    • N/A

  • Related Manuals

  • Related Tutorials

    • N/A

Details

The orbit of the WorldView-2 satellite was modeled in STK using the Two-Line Element (TLE) for the vehicle in 2012. A 2 minute long portion of the orbit where the vehicle passed over Ontario Canada, Western NY, PA, etc. was selected and exported as standard STK ephemeris and attitude reports. A screenshot of the selected orbital path in STK is shown below:

WORLDVIEW 2 35946
Figure 1. Screenshot of the WorldView-2 vehicle path in STK.

Important Files

This section highlights key files important to the simulation.

The FlexMotion STK Import Setup

The STK ephemeris and attitude reports are used directly by the BasicPlatform plugin directly via the STK import options available in the FlexMotion waypoint and quanternion engines. The WORLDVIEW-2_35946.e and WORLDVIEW-2_35946.a are the respective ephemeris and attitude report files generated for the previously described orbital pass in STK.

The demo.motion file featuring the direct STK import method.
<motion type="flexible">
  <locationengine type="waypoints">
    <data source="stk_report">
      <filename>WORLDVIEW-2_35946.e</filename>
    </data>
  </locationengine>
  <orientationengine type="quaternions">
    <data source="stk_report">
      <filename>WORLDVIEW-2_35946.a</filename>
    </data>
  </orientationengine>
</motion>

The video.tasks (and demo.tasks) file mirrors the collection start (21 May 2012 16:36 UTC) and 2 minute duration of the orbital pass modeled and exported from STK:

The video.tasks file.
<tasklist>
  <reference>
    <datetime type="absolute">2012-05-21T16:36:00.0000-00:00</datetime>
  </reference>
  <task>
    <metadata>
      <entry>
        <name>Description</name>
        <value><![CDATA[(none)]]></value>
      </entry>
      <entry>
        <name>Name</name>
        <value><![CDATA[Task #1]]></value>
      </entry>
    </metadata>
    <start>
      <datetime type="relative">0</datetime>
    </start>
    <stop>
      <datetime type="relative">120</datetime>
    </stop>
  </task>
</tasklist>
Note
 The demo.tasks file captures a single frame halfway through the 2 minute pass modeled in STK.

Although the satellite orbit at the heart of this simulation is for WorldView-2 (a multi-spectral pushbroom sensor), the sensor used in this demonstration is a 640 x 480 2D framing array sensor with RGB channels (see demo.platform for more information).

The demo.platform, demo.motion and demo.tasks (or video.tasks) are supplied to the BasicPlatform plugin instance in the simulation:

The BasicPlatform setup in the demo.jsim file.
    {
       "name" : "BasicPlatform",
       "inputs" : {
           "platform_filename" : "demo.platform", 
           "motion_filename" : "demo.motion", 
           "tasks_filename" : "demo.tasks"
       }
    }

The Scene-less EarthGrid Setup

The 2nd major component of this simulation is that it demonstrates a "scene-less" scenario. There is not a conventional DIRSIG scene in the simulation (the JSIM scene_list is empty), instead it utilizes the EarthGrid plugin to provide the primary geometry for the scene. In this case, the plugin is configured with a image using NASA Blue Marble imagery and the major_lines and minor_lines are setup so that they are not displayed (the half width is set to 0).

The "scene-less" setup using the EarthGrid plugin in the demo.jsim file.
[{
  "scene_list": [
  ],
  "plugin_list": [
    {
      "name" : "EarthGrid",
      "inputs" : {
        "background_filename" : "./maps/bluemarble.jpg",
        "major_lines" : [180,0.0,255,255,255],
        "minor_lines" : [ 10,0.0,255,255,255]
      }
    },
    ...
  ]
  ...
}]

Simulations and Results

The Single-Frame Simulation

Run the single-frame demo.sim file using DIRSIG5:

$ dirsig5 demo.jsim

Load the resulting demo-t0000-c000.img radiance file in the DIRSIG image viewer and display the RGB bands using one of the high dynamic range scaling options (e.g., "two sigma" or "two percent" scaling). Alternatively, the image_tool provides the non-linear "gamma" scaling option, which can be used to directly produce a PNG with the following syntax:

$ image_tool convert --autoscale=gamma --gamma=3.0 --format=png demo-t0000-c0000.img
demo
Figure 2. The single-frame simulation.

The Multi-Frame Simulation

Run the multi-frame video.jsim file using DIRSIG5:

$ dirsig5 video.sim

All the frames produced by the multi-frame simulation can be scaled in a single execution of the image_tool by using the appropriate wildcards for the image filename and then encoded into a video file with the FFmpeg video encoder:

$ image_tool convert --autoscale=gamma --gamma=3.0 --format=png demo-t0000-c*.img
$ ffmpeg -framerate 30 -i demo-t0000-c%04d.img.png -codec:v libx264 -profile:v high -pix_fmt yuv420p video.mp4
An animatation of the multi-frame simulation.