Synthetic Aperture Radar (SAR) Analysis with STK Problem Statement You are conducting an exercise testing a Spotlight Synthetic Aperture Radar (SAR) system over a ground site. An experimental satellite containing a radar package is flying at around 800 km over the ground site. Furthermore, you are testing whether or not the radar jammer on-board the ground station can jam the SAR radar. Solution Use Orbit Wizard to create an orbit. Build a monostatic SAR radar and create a custom graph to determine if you can image the ground area. Build an attached radar jam system on the ground site. Using a custom graph, determine if the ground radar can jam the SAR radar. Create a New Scenario Create a new scenario using the default analysis time period. 1. Launch STK ( ). 2. Create a scenario (). 3. Name the scenario SAR_Jamming. 4. Choose default Start and Stop Time. SAVE OFTEN! Radar Cross Section (RCS) Prior to setting up and constraining a radar system, STK Radar allows you to specify an important property of a potential radar target - its Radar Cross Section (RCS) Since you'll only have one object that uses an RCS, you can set the properties at the scenario level. If you had multiple objects requiring an RCS that were different, you would insert the RCS at the individual object level. 1. Browse to the RF - Radar Cross Section page. 2. Examine the default RCS properties. 3. Click OK.
RCS Values can be expressed in decibels referenced to a square meter (dbsm). STK can use External Radar Files Since you don't have an external RCS file, use a constant value of 0 dbsm. Target Ground Site The target is located in a central location of the training area. 1. Insert a Place () object using the Define Properties method. 2. Make the following changes: Option Latitude: 33.334 Longitude: 44.3978 Value 3. Click OK. 4. Rename the Place object "Enemy".
Create SARSat 1. Bring up the Orbit Wizard 2. When the Orbit Wizard appears, select the following: Type Satellite Name Option Circular SARSat Value 2. Set the Inclination to 53 degrees. 3. Set the Altitude to 800 km. Servomotor The Radar object's antenna can be bore-sited. However, in STK, if you have an antenna that can track another object, use a Sensor object as the servomotor. 1. Insert a Sensor () object using the Insert Default method and attach it to SARSat. 2. Rename the Sensor object SARServo. 3. Open the SARServo's () properties (). 4. On the Basic - Definition page, change Sensor Type to Rectangular. 5. Set the Vertical Half Angle to 0.75 deg. 6. Set the Horizontal Half Angle to 7.5 deg. Target the Ground Site The Sensor object is acting as a servomotor. Target the sensor which in turn will target the antenna later in the lesson. 1. Return to SARServo's properties. 2. Browse to the Basic - Pointing page. 3. Change the Pointing Type to Targeted and move Enemy to the Assigned Targets list. Model the Radar
For this analysis, you will use a single beam. The Radar object will be a child of the Sensor object. Since the Sensor object is bore sighted towards the place object, the Radar object, which is pointing along the parent's Z body, will also point at the place object. (Orientation Methods) 1. Insert a Radar ( ) object using the Insert Default method, and attach the Radar object to Servo. 2. Open the Radar's ( ) properties (). 3. On the Basic - Definition page, ensure the Type: is Monostatic. 4. Change the Mode Type to SAR. Radar Mode 1. In the Pulse Definition tab, change the Unambiguous Range to 800 km. 2. Change the Range Resolution to 8 meters. Set Antenna Specifications Select the antenna and change its design to specifications. 1. Click the Antenna tab. 2. In the Model Specs tab, change the type to Uniform Aperture Rectangular (Uniform Rectangular Aperture Antenna) 3. Set the X dimension to 1.5 meters. 4. Set the Y dimension to 15 meters. Build the Transmitter 1. Click the Transmitter tab. 2. Enable Frequency and change the value to 5.3 GHz. Analyze the Radar The first step is to determine how well your radar can image the ground area. 1. In the Object Browser, right click on the Radar object ( ) and open the Access ( ) tool. 2. In the Associated Objects List, select Enemy and click the Compute button. 3. Click the Report & Graph Manager... button.
Create a Custom Graph For your analysis, you are interested in two report contents, SAR SNR (Signal-To-Noise-Ratio) and Range Resolution. By creating a custom graph that contains these contents, you can quickly determine the effectiveness of your radar. 1. Select the My Styles folder and click the Create new graph style button. 2. Give the graph a name such as "Range Resolution and SNR" and click the Enter key on your keyboard. This will take you to the custom graph's properties. 3. In the Data Provider window, expand Radar SAR. 4. Move SAR Range Resolution to the Y Axis window. 6. Move SAR SNR to the Y2 Axis. 7. Click OK. 8. Generate the graph. SNR Range Resolution Graph You are looking for an SNR of greater than zero. It's a given that as distance increases, your SNR will decrease. Using the Toggle animation time line button, right clicking on the graph, and selecting Set Animation Time, enables you to jump back to the 3D Graphics window to visualize what is occurring. Overall, the radar system is able to image the region. It's time to see if you can jam the radar. 9. Close the graph, the Report & Graph Manager, and the Access Tool.
Radar Jamming You will simulate the ground site jamming the SAR Radar with its own Radar. Servomotor The Radar object's antenna can be bore-sited. However, in STK, if you have an antenna that can track another object, use a Sensor object as the servomotor. 1. Insert a Sensor () object using the Insert Default method and attach it to Enemy. 2. Rename the Sensor object GroundServo. 3. Open the GroundServo's () properties (). 4. On the Basic - Definition page, in the Simple Conic field, change Sensor Cone Angle to 1 degree. Target the Satellite The Sensor object is acting as a servomotor. Target the sensor which in turn will target the antenna later in the lesson. 5. Return to Servo's properties. 6. Browse to the Basic - Pointing page. 7. Change the Pointing Type to Targeted and move SARSat to the Assigned Targets list. 8. Click OK. Model the Radar For this analysis, you will use a single beam. The Radar object will be a child of the Sensor object. Since the Sensor object is bore sighted towards the place object, the Radar object, which is pointing along the parent's Z body, will also point at the place object. (Orientation Methods) 5. Insert a Radar ( ) object using the Insert Default method, and attach the Radar object to Servo. 6. Open the Radar's ( ) properties (). 7. On the Basic - Definition page, ensure the Type: is Monostatic. Build the Jammer 1. Click the Transmitter tab. 2. Enable Frequency and change the value to 5.3 GHz. 3. Change Power to 10 dbw.
Jam the Radar The next step is to tell the surveillance radar that it's being jammed. 1. Open the SAR Radar ( ) properties (). 2. On the Basic - Definition page, select the Jamming tab. 3. Enable Use and move the jamming Radar object to the Assigned Jammers field. You are now ready to analyze Jammer's effectiveness against the surveillance radar. Jam Effectiveness Create a custom graph that shows only those contents you are interested in for your analysis. You are interested in SAR SNR (Signal-To-Noise-Ratio) and SAR S/(N+J) (Signal-To- Noise+Jamming-Ratio). 1. In the Object Browser, right click on the SAR Radar ( ) and open the Access ( ) tool. 2. In the Associated Objects List, select Enemy. 3. Click the Report & Graph Manager... button. 4. Select the My Styles folder and click the Create new graph style button. 5. Give the graph a name such as SAR Jamming then click the Enter key on your keyboard. 6. In the Data Provider window, expand Radar Search Track. 7. Move ( ) SAR SNR to the Y Axis window. 8. Move ( ) the SAR S/(N+J) to the Y Axis window. 9. Click OK. 10. Generate the graph. By placing the SAR SNR and SAR S/(N+J) on the same axis, it's easier to read the graph. As you can see by looking at the graph the jammer attached to the ground site is effectively jamming the SAR radar.