Part 16: Ground-based SSA with EOIR

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 EOIR installation package is included with the STK Premium installation package. However, you must install EOIR on your computer separately from the STK application. See the EOIR capability help for more information.

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.

Capabilities covered

This lesson covers the following STK Capabilities:

  • STK Pro
  • Electro-Optical Infrared Sensor Performance (EOIR)
  • STK SatPro

Video guidance

Watch the following video. Then follow the steps below, which incorporate the systems and missions you work on (sample inputs provided).

Define the scenario's assets

You will be using the MSSC 1.6m telescope at the AMOS observatory in Maui, Hawaii, to track a polar satellite in LEO. To create a scenario and define its assets:

  1. Click the Create a Scenario () button.
  2. Enter the following in the New Scenario Wizard:
    3. Option Value
    Name STK_EOIR
    Location C:\Users\<username>\Documents\STK 12\
    Start 1 Jan 2018 16:00:00 UTCG
    Stop + 10 min
  3. When you finish, click OK .
  4. When the scenario loads, click Save (). A folder with the same name as your scenario is created for you in the location specified above.
  5. Verify the scenario name and location and click Save .

Insert a Facility object

Use the Insert STK Objects tool to add the MSSC_1_6m facility from the Standard Object Database.

  1. Bring the Insert STK Objects tool to the front.
  2. Insert a Facility () object using the From Standard Object Database () method.
  3. Click Insert... .
  4. Enter MSSC in the Name field and click Search .
  5. Select 'MSSC 1.6m' and click Insert .
  6. Click Close to return to the Insert STK Objects tool.

Verifying that EOIR is installed

Ensure that EOIR is installed on your computer.

  1. If you do not see the EOIR toolbar (), extend the View menu.
  2. Select the Toolbars option
  3. Select EOIR.

Adding a sensor to the MSSC_1_6m facility

Add a sensor to the facility you just added to the scenario.

  1. Insert a Sensor () object using the Insert Default () method.
  2. Select MSSC_1_6m () and click OK .
  3. Attach a sensor to the MSSC_1_6m facility.

Setting the EOIR properties for the sensor

You can set up this sensor to model the large AEOS telescope at AMOS.

Setting the Spatial Properties

  1. Open the sensor's properties.
  2. Set the sensor type to EOIR on the sensor's Basic - Definition page.

    You will set up this sensor to model the large AEOS telescope at AMOS. The first tab contains the spatial information of the sensor. This is where you define the total field-of-view angles and the number of pixels on the sensor detector.

    3. For a more detailed explanation of the EOIR property windows, click the Help button on the bottom of the properties page.

  3. Set the following parameters:
    4. Option Value
    Field of View Horizontal Half Angle 7.5 deg
    Field of View Vertical Half Angle 7.5 deg

    Since you left the default setting for Input, which is "Field-of-View and Number of Pixels", the Related Detector Parameters and Instantaneous Field of View values are then based on the Spatial and Optical properties and are updated when you click Apply . These are read-only fields.

Setting the Spectral Properties

  1. Select the Spectral tab.

    This tab is where you define the spectral range of your sensor. The sensor model samples your spectral band using the number of intervals you define. The more intervals you have, the higher the accuracy of the analysis. However, more intervals mean longer computation time.

  2. Set the following Spectral Parameters:
    OptionValue
    Spectral Band Edge Wavelengths - Low 0.4 um
    Spectral Band Edge Wavelength- High 0.7 um

    The telescope observes the long infrared waveband. If you would like to do your analysis with those parameters, then set the Spectral Band Edge Wavelengths Low to 0.7 um and High to 1.0 um.

Setting the Optical Properties

  1. Select the Optical tab.
  2. In the Input field, select F-Number and Entrance Pupil Diameter.
    3. Option Value
    F/# 200
    Entrance Pupil Diameter 367.00 cm
    Image Quality Negligible Aberrations

    The Image Quality property models wave front error through the optics. The Negligible Aberrations setting introduces 7% wave front error.

Setting the Radiometric Properties

  1. Select the Radiometric tab.

    2. This is where you define the noise floor and the saturation ceiling. You can define a set of points that relate Integration (Exposure) Time to NEI/SEI. STK linearly interpolates between the points to get correct NEI/SEI for the integration time you set at the bottom of the window.

  2. Set the following Sensitivity parameters:
    OptionValue
    Sensitivity - Integration Time 100
    Sensitivity - Equivalent Value 1e-16
  3. Set the Processing Level to Sensor Output. The processing levels enable you to visualize the geometric information in the sensor scene or the sensor output image. The Radiometric Input simulates the light entering the sensor lens before hitting the sensor detector when generating the EOIR sensor scene.
  4. Set the Line of Sight Jitter to 1 mrad to introduce a Gaussian vibration along the sensor boresight.
  5. Click OK to apply and save your changes.
  6. Open the Target Configuration () window. This window defines the objects used in the EO/IR analysis.
  7. Verify that Facility/MSSC_1_6m is in the Selected Targets list.

Generate EOIR sensor scenes

Now you are ready to generate sensor scenes. These scenes accurately portray sensor images for the processing level selected.

  1. Select the sensor in the Object Browser and click EOIR Sensor Scene () to generate an image that represents the radiometric input to the sensor. You will see some white dots and gray dots against a black background.

  2. Right-click the sensor scene and select Details.... Here you can set the color map, determine the resolution of the Earth map using the scene detail box, adjust the brightness and contrast, change the file output settings, and return back information on the pixel clicked inside of the sensor scene. Set the Color Map to BGRY and click Apply .
  3. For the Sensor Output processing level, the raw sensor data and image can be saved out at every animation step.

    4. You can save the data in each sensor click to a file by selecting Pixel Spectral Data on the EOIR Scene Visual Details page. You can then compound these images to create a movie or run through external image processing software for further analysis.

  4. Click around the scene to display information on the EOIR Scene Visual Details window for each pixel. Click one of the stars to get more details on this object.
  5. Close the EOIR Scene Visual Details properties page and the EOIR Sensor Scene window.

Creating a satellite that flies over the facility

Using the Orbit Wizard, create a satellite that flies over the MSSC_1_6m.

  1. Insert a Satellite () object using the Orbit Wizard () method.
  2. Set the following values in the Orbit Wizard:
    3. Option Value
    Type Circular (default)
    Inclination 98 deg
    Altitude 500 km (default)
    RAAN 189 deg
  3. Click OK to insert the new satellite.

Zoom to the satellite

  1. Zoom To the satellite in the 3D Graphics window. Pan and zoom around so that you can view both the satellite and the facility.
  2. Set the Animation Time Step to one (1) second and animate the scenario.

    3. When the target satellite passes over the AMOS facility, AMOS is in darkness while the satellite is illuminated. This scenario gives good lighting conditions for imaging.

    Although this tutorial is a ground-to-space example, it is possible to host an EOIR sensor on air and space vehicles. The work flow of setting up an EOIR sensor model is similar for all supported STK objects.

Examine the satellite's basic EOIR Shape

Examine the material and shape properties of your satellite.

  1. Open the Satellite's properties.
  2. Open the Basic - EOIR Shape properties page.
  3. Examine the following options:
    4. Option Value
    Shape Sphere (default)
    Radius 1 m
    Body Temperature Static (default)
    Temperature 273 K (default)
    Material Gray Body (default)

    This temperature is steady and uniform over the body and corresponds to its external temperature in sunlight.

  4. Open the Target Configuration () box and add Satellite/Satellite1 to the Selected Targets list.

    5. Available objects include central bodies, satellites, facilities, missiles, and aircraft. Both targets and sensor parent objects must be included as Selected Targets.

  5. Click OK to close the EOIR Configuration window.

Run an Access report

Run an access report between the sensor and the satellite.

  1. Right-click the sensor object and select Access... from the Sensor menu.
  2. Select Satellite1 from the list.
  3. Click Advanced... button and disable Use Light Time Delay. Light time delay is not used in EOIR analysis.
  4. Click OK .
  5. Click Access... in the Reports section.

    6. The Access report shows one access interval at or near the following times:

    • 1 Jan 2018 16:05:19.723
    • 1 Jan 2018 16:05:37.186
  6. Right-click the start time in the Access report and extend the Start Time menu.
  7. Select the Set Animation Time option. This sets the animation time to the access time, which will be reflected in the animation field.

    8. Keep the access report open.

Regenerating the EOIR Sensor Scene

  1. Select the sensor in the Object Browser and click EOIR Sensor Scene () to generate an image that represents the sensor output.
    2. You will see colorful dots against a dark background.
  2. Set the Animation Time Step to 0.5 seconds and animate the scenario until you see the satellite come into the scene. The dot that represents the satellite moves across the scene while the stars stay relatively still.
  3. Right-click the sensor scene and select Details....
  4. Click around the scene to view information on each pixel. Click one of the stars and the target satellite to get more details on those objects.
  5. Close the EOIR Scene Visual Details properties page and the EOIR Sensor Scene window.

Create custom graphs for EO/IR Sensors

EOIR does more than simulate scenes created by an EO/IR sensor. It can also calculate metrics a sensor would receive from a target's signal. The following will familiarize you with some of the available EOIR data providers.

  1. Open the Report & Graph Manager for the sensor on the facility.
  2. Click the Create a New Graph () button to create a custom graph for the sensor.
  3. Name the new graph EOIR Sensor-to-TargetMetrics.
  4. Open up the graph's Content properties.
  5. In the EOIR Sensor to Target Metrics data provider, select the following data elements:
    • Y Axis: Effective target irradiance
    • Y2 Axis: Signal to noise ratio
  6. Set the following titles:
    7. Option Name
    Time Axis Title Time
    Y Axis Title Effective Target Irradiance
    Y2 Axis Title Signal to Noise Ratio (SNR)
  7. Select EOIR Sensor to Target Metrics-Effective target irradiance under Y Axis and click Units... below the Y2 Axis box.
  8. Clear the Use Defaults check box
  9. Select Power.
  10. Select Watts (W) as the new unit value.
  11. Click OK to close the Units window.
  12. Click OK to finalize your custom graph and return to the Report & Graph Manager.

Setting the Time properties

  1. Select Specify Time Properties under the Time Properties section.
  2. In the Select type field, select Specify Times.
  3. Click the button to the right of the Start and Stop times and select Interval Component....
  4. In the Select Time Interval window, select the Access object ().
  5. Under Installed Components, expand Access Intervals.
  6. Select First (since there is only one access interval) and click OK to return to the Report & Graph Manager.
  7. Enable the Use step size/time bound option.
  8. Set the Step Size to 4 seconds.

Generating the custom graph

  1. Generate the graph.
  2. Take a look at the graph. You should see a graph similar to the one below.

    3. EOIR calculations are computationally expensive. It is recommended that you confine your report and graph times to access intervals and choose your time steps wisely.

    This graph shows the signal is large relative to the noise by up to a factor of 373 to 1 which is why you are able to see the target clearly in the scene. Keep the graph open.

Defining more EOIR properties

  1. Open the Target Configuration () box.
  2. Click Atmosphere and Textures to display the EOIR Atmosphere Model properties.
  3. Take a minute to view the different atmosphere models available with EOIR, Simple Atmosphere and MODTRAN Atmosphere
    • The Simple Atmosphere calculates the atmospheric properties at the wavelengths corresponding to the Spectral Band Edges, and at a spectral resolution specified by the Number of Intervals set on the Sensor's Spectral Properties page.
    • The MODTRAN-based atmosphere model is one of the highest fidelity, community standard, atmospheric models available in EOIR. As such, it takes longer to compute.
  4. Select Simple Atmosphere and set the following parameters:
    OptionValue
    Aerosol ModelsMaritime
    Visibility40 km
    Humidity 70 %
  5. Click OK to close the EOIR Atmosphere Model; then click OK to close the EOIR Configuration window.
  6. Select the sensor in the Object Browser and click EOIR Sensor Scene () to generate an image that represents the sensor output. Take a moment to view the new sensor scene.

Refreshing the custom graph

  1. Refresh the graph. You will see a graph similar to the one below:

    2. This graph shows the signal large relative to the noise by up to a factor of 210 to 1. The degradation is due to the atmosphere effects. Keep the graph open.

Regenerating the EOIR sensor scene

  1. Select the sensor in the Object Browser.
  2. Click EOIR Sensor Scene () to generate an image that represents the sensor output.
  3. Right-click the sensor scene and select Details....
  4. Set the Animation Time Step to 0.5 and animate the scenario. You will see only one bright dot that represents the satellite moving against a dark background. After the satellite moves out of the scene, the stars will return to the image.
  5. Close the EOIR Scene Visual Details properties page and the EOIR Sensor Scene window.

Turning off the Simple Atmosphere model

Now that you have seen the effects the atmosphere has on your data, turn the atmosphere off.

  1. Open the Target Configuration () box.
  2. Click Atmosphere and Textures to reopen the EOIR Atmosphere properties
  3. Set the Atmosphere Mode back to Atmosphere Off for the remainder of this tutorial and return to the EOIR Configuration window.
  4. Click OK to close the EOIR Configuration window

Redefining the EOIR Properties

Define the material and shape properties of your satellite and the properties of your EO/IR sensor.

Define the Satellite's Basic EOIR Shape

  1. Open the Satellite's properties.
  2. Select the Basic - EOIR Shape page.
  3. Set the following options:
    4. Option Value
    Shape LEOComm
    Body Temperature Static (default)
    Temperature 400 K
    Material Aluminum MLI

    This temperature is steady and uniform over the body and corresponds to its external temperature in sunlight.

  4. Click OK .

Regenerating the EOIR Sensor Scene

  1. Select the sensor in the Object Browser and click EOIR Sensor Scene () to generate an image that represents the sensor output.
  2. Right-click on the sensor scene and select Details....
  3. In general, a satellite will be dimmer than the brightest stars in the FOV. To make that satellite easier to see, slide the Brightness slider all of the way to the right.
  4. Click Apply , more objects in the scene will be visible, but which one is the satellite?
  5. Set the Animation Time Step to 0.5 and animate the scenario.
  6. Click around the scene to view information on each pixel. Click one of the stars and the target satellite to get more details on those objects.
  7. Close the EOIR Scene Visual Details properties page and the EOIR Sensor Scene window.

Refreshing the custom graph

  1. Bring the Graph window to the front.
  2. Set the Step value to 0.5 seconds.
  3. Refresh the graph.
    4. You will see a graph similar to the one below:

    The curve is smooth, showing a single minimum rate in effective target irradiance and SNR that coincides with the satellite passing near the facility's zenith. In this analysis, the satellite is holding a nadir-pointing attitude profile. Because of this, the sensor sees a near-constant satellite cross-section during the overhead pass.

Analyzing the Light Signature

Now you will analyze the light signature of a tumbling satellite to compare to the nadir pointing satellite.

  1. Open the Satellite's properties.
  2. Select the Basic - Attitude page.
  3. Set the following options:
    4. Option Value
    Type PrecessingSpin
    Body Spin Axis Type: Cartesian

    (X,Y,Z) = 0,1,0
    Precession - Rate 30 revs/min
    Spin - Rate 30 revs/min
  4. Click OK .
  5. Zoom To the satellite.
  6. Set the Animation Time Step to 0.1 seconds.
  7. Animate the scenario to view the satellite's spinning orbit in the 3D Graphics window.

Refreshing the graph

  1. Bring the Graph window to the front.
  2. Change the scaling of the Y axis:
    1. Double-click the Effective Target Irradiance title.
    2. Select the Axis tab.
    3. Select Min/Max in the Y-Axis (default).
    4. Enter the following values:
      5. Option Value
      Min 0
      Max 3e-010
    5. Click OK .
  3. Set the Step to 0.1 sec.
  4. Refresh the custom Irradiance and SNR graph. You will see a graph similar to the one below; your graph does not need to match exactly:

The plot is jagged, thus confirming that the spacecraft is tumbling. As the spacecraft rotates, various panels reflect varying amounts of light and create an unsmooth plot.

Further study

To become more familiar with all the capabilities of EOIR, continue to experiment with changing EOIR properties and creating scene settings.

For example, use the ModTran Atmosphere Model to define the atmosphere. To access the model, go to the Target Configuration () box and click Atmosphere and Textures.