Part 17: Ground-based SSA with EOIR

STK Premium (Space) or STK Enterprise
You can obtain the necessary licenses for this tutorial by contacting AGI Support at support@agi.com or 1-800-924-7244.

Required Capability Install: This lesson requires an additional capability installation for the STK software's EOIR capability. The EOIR install is included in the STK Premium software download, but requires a separate install process. Read the Readme.htm found in the STK software install folder for installation instructions. You can obtain the necessary install by visiting https://support.agi.com/downloads or calling AGI support.

This tutorial requires version 12.9 of the STK software or newer to complete in its entirety. If you have an earlier version of the STK software, you can view a legacy version of this lesson.

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 Ansys Systems Tool Kit (STK®) digital mission engineering software capabilities:

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

Problem statement

Engineers and operators require a fast and easy way to model and simulate detection, tracking, and imaging performance of electro-optical and infrared sensors. You want to simulate tracking a polar satellite that is in a low Earth orbit (LEO) from an observatory located in Hawaii. You need to model the telescope specifications and take cloud cover, temperature, emissivity, and radiance into consideration for your analysis.

Solution

Use the STK application and the Electro-Optical Infrared Sensor Performance (EOIR) capability to model, simulate, and analyze a Maui Space Surveillance Complex (MSSC) 1.6-meter (m) telescope at the Air Force Maui Optical Station (AMOS) observatory in Maui, Hawaii, that tracks a polar satellite in LEO.

What you will learn

Upon completion of this tutorial, you will understand:

  • How to configure Sensor objects to use the EOIR type

  • How to create an EOIR sensor scene

  • How to view data in the EOIR Scene Visual Details dialog

  • How to create a custom EOIR signal-to-noise (SNR) graph

Video guidance

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

Creating a new scenario

First, you must create a new STK scenario, and then build from there.

  1. Launch the STK application ().
  2. Click Create a Scenario in the Welcome to STK dialog.
  3. Enter the following in the STK: New Scenario Wizard:
    4. Option Value
    Name STK_EOIR
    Location Default
    Start 1 Aug 2024 15:00:00.000 UTCG
    Stop + 10 min
  4. Click OK when you finish
  5. Click Save () when the scenario loads. The STK application creates a folder with the same name as your scenario for you.
  6. Verify the scenario name and location in the Save As window.
  7. Click Save.

Save () often during this lesson!

Inserting MSSC as a Facility object

Add MSSC as a Facility object to your scenario.

Inserting Facility object

Use the Insert STK Objects tool to insert a Facility object from the Standard Object Database.

  1. Select Facility () in the Insert STK Objects tool.
  2. Select the From Standard Object Database () method.
  3. Click Insert....

Selecting an MSSC Facility object

Add the MSSC_1_6m Facility object to your scenario.

  1. Type MSSC in the Name field in the Search Standard Object Data dialog.
  2. Click Search.
  3. Select MSSC 1.6m in the Results list that uses the Local Database Data Source.
  4. Click Insert.
  5. Click Closeto close the Search Standard Object Data dialog.

Opening the EOIR toolbar

Open the EOIR toolbar.

  1. Extend the View menu.
  2. Select Toolbars in the shortcut menu.
  3. Select EOIR in the second shortcut menu.

Eoir toolbar

Inserting a Sensor object

Add a sensor to MSSC_1_6m.

  1. Insert a Sensor () object using the Insert Default () method.
  2. Select MSSC_1_6m () in the Select Object dialog.
  3. Click OK.
  4. Right-click on Sensor1 () in the Object Browser.
  5. Select Rename in the shortcut menu.
  6. Rename Sensor1 () to Telescope.

Using the EOIR sensor type

Start by setting sensor type to EOIR.

  1. Right-click on Telescope () in the Object Browser.
  2. Select Properties () in the shortcut menu.
  3. Select the Basic - Definition page when the Properties Browser opens.
  4. Select EOIR for the Sensor Type.
  5. Click Apply to accept your change and to keep the Properties Browser open.

Setting the spatial properties

You are modeling the Advanced Electro-Optical System (AEOS) telescope. Start by setting the Spatial properties of the Sensor object. Use the spatial properties to define the total field-of-view angles and the number of pixels on the sensor detector. The default input setting 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 apply your changes. These are read-only fields.

  1. Ensure the Spatial tab is selected on the Basic - Definition page.
  2. Set the following parameters in the Field of View frame:
    3. Option Value
    Horizontal Half Angle 7.5 deg
    Vertical Half Angle 7.5 deg
  3. Click Apply.

Setting the Spectral Properties

Define the spectral range of the Sensor object. 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.

  1. Select the Spectral tab on the Basic - Definition page.
  2. Set the following parameters in the Spectral Band Edge Wavelengths frame (you have to set High first):
    OptionValue
    High1.0 um
    Low0.7 um

    3. The telescope observes the long infrared waveband.

  3. Click Apply.

Setting the Optical Properties

Next, set the Optical properties. The Image Quality property models wave front error through the optics. The Negligible Aberrations setting introduces 7% wave front error.

  1. Select the Optical tab on the Basic - Definition page.
  2. Select F-Number and Entrance Pupil Diameter for the Input.
  3. Set the following parameters:
    4. Option Value
    F/# 200
    Entrance Pupil Diameter 367.00 cm
  4. Select Negligible Aberrations for the Image Quality.
  5. Click Apply.

Setting the Radiometric Properties

Radiometric properties define the noise floor and the saturation ceiling. You can define a set of points that relate Integration (Exposure) Time to NEI/SEI (noise equivalent irradiance / saturation equivalent irradiance). The STK software linearly interpolates between the points to get correct NEI/SEI for the integration time you set.

  1. Select the Radiometric tab on the Basic - Definition page.
  2. Set the following in the Sensitivity frame:
    OptionValue
    Integration Time 100
    Equivalent Value 1e-16
  3. Notice that Processing Level defaults to Sensor Output.

    4. 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. Enter 1 (mrad) in the Line of Sight Jitter field in the Jitter frame.

    5. This introduces a Gaussian vibration along the sensor boresight.

  5. Click OK to apply your changes and to close the Properties Browser

Setting the EOIR Configuration

The EOIR Line of Sight and Field of View are synchronized to the STK Sensor object.

  1. Click EOIR Configuration... () in the EOIR toolbar.

    2. This displays the sensor's EOIR Configuration dialog. All central bodies and objects, except for the source sensor, that are part of the EOIR Configuration are listed in the available target list.

  2. Click OK to close the EOIR Configuration dialog.

Generating EOIR sensor scenes

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

  1. Select Telescope () in the Object Browser.
  2. Click EOIR Sensor Scene... () in the EOIR toolbar.

    3. This generates an image that represents the radiometric input to the sensor. You will see some white dots and gray dots against a black background.

    Gray Scale color map

  3. Right-click the sensor scene.
  4. Select Details.... in the shortcut menu.
  5. Move the EOIR Scene Visual Details dialog so that it's not sitting on top of the sensor scene.

    6. Use the EOIR Scene Visual Details dialog to 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.

  6. Select the BGRY option in the Color Map frame.
  7. Click Apply.

    8. For the Sensor Output processing level, the raw sensor data and image can be saved out at every animation step. 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.

    BGRY color map

  8. Click around the scene to display information on the EOIR Scene Visual Details window for each pixel.
  9. Click one of the stars to get more details on this object.
  10. Cclose the EOIR Scene Visual Details dialog and the EOIR Sensor Scene window when finished.

Inserting a Satellite object

Insert a Satellite object using the Orbit Wizard.

  1. Insert a Satellite () object using the Orbit Wizard () method.
  2. Set the following in the Orbit Wizard:
    3. Option Value
    Type Circular
    Satellite Name LEO_Sat
    Inclination 98 deg
    Altitude 700 km
    RAAN 24 deg
  3. Click OK to accept your changes and to close the Orbit Wizard.

Viewing the LEO satellite and the ground site

View the LEO satellite and the Facility in the 3D Graphics Window.

  1. Bring the 3D Graphics window to the front.
  2. Right-click on LEO_Sat () in the Object Browser.
  3. Select Zoom To.
  4. Pan and zoom around so that you can view both LEO_Sat () and MSSC_1_6m ().
  5. Click Decrease Time Step () in the Animation toolbar until the Time Step is set to 1 sec.
  6. Click Start () to animate the scenario.

    7. 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.

  7. Click Reset () when finished.

    8. 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.

Examining the LEO satellite's basic EOIR shape

Examine the material and shape properties of LEO_Sat.

  1. Open LEO_Sat's () properties ().
  2. Select the Basic - EOIR Shape page when the Properties Browser opens.
  3. Examine the following options:

    • Shape

    • Radius

    • Body Temperature

    • Temperature

    • Material

  4. Keep the default settings.
  5. Click Cancel to close the Properties Browser.

Adding LEO_Sat to the EOIR Configuration

Add the satellite to the EOIR Configuration.

  1. Click EOIR Configuration... () in the EOIR toolbar to open the EOIR Configuration dialog.
  2. Double click on Satellite/LEO_Sat () in the Available STK Objects list to move it to the Selected Targets list.
  3. Click OK to close the EOIR Configuration dialog.

Creating an Access report

Create an access report between Telescope and LEO_Sat.

  1. Right-click on Telescope () in the Object Browser.
  2. Select Access... ().
  3. Select LEO_Sat () in the Associated Objects list.
  4. Click .
  5. Click Advanced... to open the Advanced Options dialog.
  6. Clear Use Light Time Delay in the Light Time Delay frame.

    7. Light time delay is not used in EOIR analysis.

  7. Click OK to close the Advanced Options dialog.

Generating an Access Report

Generate an Access report.

  1. Click Access... in the Reports frame.
  2. Right-click on the first access start time in the Access report.
  3. Select Start Time in the shortcut menu.
  4. Select Set Animation Time in the second shortcut menu.

    5. This sets the Current Scenario Time in the Animation toolbar to the first access time.

  5. Close () the access report.
  6. Close () the Access tool.

Creating the EOIR Sensor Scene

Create the EOIR scenario scene.

  1. Select Telescope () in the Object Browser.
  2. Click EOIR Sensor Scene... () in the EOIR toolbar.
  3. Right-click on the sensor scene.
  4. Select Details... in the shortcut menu to open the EOIR Scene Visual Details dialog.
  5. Select the Gray Scale option in the Color Map frame.
  6. Click Apply.

Performing EOIR sensor scene analysis

You can view the EOIR sensor scene details.

  1. Move the slider bar to the right in the Brightness frame to help see LEO_Sat () against the background stars.
  2. Click around the scene to view information on each pixel.
  3. Click one of the stars and the target satellite to get more details on those objects.
  4. Decrease () the animation Time Step to 0.5 seconds.
  5. Animate () the scenario until you see the satellite come into the scene.
  6. Click Pause () to stop the scenario animation.

    7. The dot that represents the satellite moves across the scene while the stars stay relatively still.

  7. Click Close to close the EOIR Scene Visual Details dialog when finished.
  8. Close () the EOIR sensor scene.

Creating custom graphs for EOIR Sensors

EOIR does more than simulate scenes created by an EOIR 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.

Creating a new graph

First, create a new graph called Target Metrics.

  1. Right-click on Telescope () in the Object Browser.
  2. Select Report & Graph Manager... () to open the Report & Graph Manager.
  3. Select My Styles () in the Styles frame.
  4. Click Create new graph style () in the Styles toolbar.
  5. Type Sensor to Target Metrics.
  6. Select the Enter key to rename the graph and to open the graph's properties.

Setting the graph's data providers

You will use the EOIR Sensor To Target Metrics data provider and the In-band target irradiance and Signal to noise ratio elements.

    • EOIR Sensor To Target Metrics: are time dependent metrics for a unique EOIR Sensor-Band / Target pairing.

    • In-band target irradiance: the irradiance at the sensor aperture from a target object whose angular extent is smaller than the effective instantaneous field of view, i.e. a point source target.

    • Signal to noise ratio: is the ratio of the difference in sensor response between target-containing pixel(s) and the local surrounding pixels to the total noise. For point source targets the background is assumed to be uniform (spatial clutter is neglected) and the target is assumed to be exactly centered on a pixel

  1. Expand () EOIR Sensor To Target Metrics in the Data Provider list.
  2. Move () In-band target irradiance to the Y Axis list.
  3. Move () Signal to noise ratio to the Y2 Axis list.
  4. Set the following parameters:
    5. Option Name
    Time Axis Title Time
    Y Axis - Axis In-band target irradiance
    Y2 Axis - Axis Signal to Noise Ratio (SNR)
  5. Select EOIR Sensor to Target Metrics-In-band target irradiance in the Y Axis list
  6. Click Units... below the Y2 Axis box to open the Units dialog.
  7. Clear Use Defaults.
  8. Select Power in the Dimension column.
  9. Select Watts (W) in the New Unit Value list.
  10. Click OK to close the Units dialog.

Setting the step size

Set the graph's step size.

  1. Enter 1.0 sec in the Step Size field.
  2. Click OK to accept your changes and to close the Properties Browser.

Setting the Time properties

Set the time properties so the data is reported over the first Access interval.

  1. Return to the Report & Graph Manager.
  2. Select Specify Time Properties in the Time Properties frame.
  3. Open the Start and Stop times dropdown menu.
  4. Select Interval Component... to open the Select Time Interval dialog.
  5. Select Facility-MSSC_1_6m-Sensor-Telescope-To-Satellite-LEO_Sat () in the Objects list.
  6. Expand () AccessIntervals () in the Intervals for list.
  7. Select First ().
  8. Click OK to close the Select Time Interval dialog.

Generating the custom graph

Now, generate the custom graph over the first Access interval.

  1. Select the Sensor to Target Metrics () in the Styles list.
  2. Click Generate... .
  3. Look at the graph.

In-band target irradiance versus SNR

This graph shows the signal is small relative to the noise, however using gray scale you are able to see the target in the scene. Keep the graph open.

Defining the EOIR atmosphere model

Set the EOIR atmosphere model.

  1. Click EOIR Configuration... () in the EOIR toolbar to open the EOIR Configuration dialog.
  2. Click Atmosphere and Textures... to open the EOIR Atmosphere, Clouds, and Texture Maps dialog.
  3. Take a minute to view the different atmosphere models:
    • 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.
    • MODTRAN Atmosphere: MODTRAN is a community standard, and the MODTRAN-derived atmosphere model is one of the highest-fidelity atmospheric models available in EOIR.
  4. Select the Simple Atmosphere option.
  5. Set the following parameters:
    OptionValue
    Aerosol ModelsMaritime
    Visibility40 (km)
    Humidity 70 (%)
  6. Click OK to close the EOIR Atmosphere, Clouds, and Texture Maps dialog.
  7. Click OK to close the EOIR Configuration dialog.

Refreshing the custom graph

Refresh the open graph to see the changes.

  1. Return to the custom graph.
  2. Click Click Refresh (F5) () in the graph toolbar.

MODTRAN atmosphere graph

Degradation is due to the atmosphere effects. Keep the graph open.

Turning off the Simple Atmosphere model

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

  1. Click EOIR Configuration... () in the EOIR toolbar to open the EOIR Configuration dialog.
  2. Click Atmosphere and Textures... to open the EOIR Atmosphere, Clouds, and Texture Maps dialog.
  3. Select the Atmosphere Off option in the Modes frame.
  4. Click OK to close the EOIR Atmosphere, Clouds, and Texture Maps dialog.
  5. Click OK to close the EOIR Configuration dialog.

Redefining the EOIR Properties

Define the material and shape properties of your satellite and the properties of your EOIR sensor.

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

      Notes:

    • LeoComm: based on the 3D model iridium.glb.

    • Static: STK applies this temperature to the entire shape. This then applies for the entire EOIR scene time period.

    • Aluminum MLI: multi-layer insulation.

  4. Click OK.

Regenerating the EOIR Sensor Scene

Regenerate the EOIR scenario scene with the updated properties.

  1. Right-click at the beginning of the custom graph.
  2. Select Set Animation Time.
  3. Select Telescope () in the Object Browser.
  4. Click EOIR Sensor Scene... () in the EOIR toolbar.
  5. Right-click on the sensor scene.
  6. Select Details... in the shortcut menu to open the EOIR Scene Visual Details dialog.
  7. Select the BGRY option in the Color Map frame.
  8. Click Apply.

Performing EOIR sensor scene analysis

You can view the EOIR sensor scene details.

  1. Move the slider bar to the right in the Brightness frame to help see LEO_Sat () against the background stars.
  2. Click around the scene to view information on each pixel.
  3. Click one of the stars and the target satellite to get more details on those objects.
  4. Animate () the scenario until you see the satellite come into the scene.
  5. Click Pause () to stop the scenario animation.
  6. Click Close to close the EOIR Scene Visual Details dialog when finished.

Refreshing the custom graph

Refresh the custom graph to see how the updated properties affect it.

  1. Return to the custom graph.
  2. Click Click Refresh (F5) () in the graph toolbar.

    3. EOIR shape changes

    The curve is showing a single minimum rate in in-band 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 LEO_Sat's () properties ().
  2. Select the Basic - Attitude page.
  3. Set the following options:
    4. Option Value
    Type Precessing Spin
    Body Spin Axis Type: Cartesian

    X: 0

    Y: 1

    Z: 0
    Precession - Rate 30 revs/min
    Spin - Rate 30 revs/min
  4. Click OKto accept your changes and to close the Properties Browser.

Viewing LEO_Sat in the 3D Graphics window

View the LEO_Sat spinning in the 3D Graphics window.

  1. Bring the 3D Graphics window to the front.
  2. Zoom To LEO_Sat ().
  3. Decrease () the animation Time Step to 0.1 seconds.
  4. Click Start () to animate the scenario.
  5. Click Pause () to stop the scenario animation when finished.

Changing the scaling of the Y axis

Change the Y axis scale for In-band target irradiance.

  1. Return to the custom graph.
  2. Double-click the In-band target irradiance title to open the Sensor Telescope dialog.
  3. Select the Axis tab.
  4. Enter the following in the Y Axis frame:
    5. Option Value
    Min 0
    Max 3e-010
  5. Click OK to close the Sensor Telescope dialog.
  6. Click Click Refresh (F5) () in the graph toolbar.
  7. Enter 0.1 sec in the Step field.
  8. Select the Enter key. Be patient.

    9. tumbling satellite

    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 jagged plot.

Saving your work

Clean up your workspace and save your scenario.

  1. Close any open reports, properties and tools which are still open.
  2. Save () your work.

Summary

This was an introduction to the STK software's EOIR capability. You modeled, simulated, and analyzed a Maui Space Surveillance Complex (MSSC) 1.6 meter (m) telescope at the Air Force Maui Optical Station (AMOS) observatory in Maui, Hawaii, that tracked a polar satellite in LEO. You set your Sensor object attached to the ground site to use the EOIR capability. You set spatial, spectral, optical, and radiometric properties. Using the EOIR sensor scene you obtained data on stars and the LEO satellite. You became familiar with satellite EOIR shape configurations and attitude issues. Using EOIR configuration, you applied MODTRAN atmospheric changes to your analysis. You created a custom graph and graphed the various changes to your analysis.