Part 2: Objects and Properties

STK Pro, STK Premium (Air), 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.

Capabilities covered

This lesson covers the following STK Capabilities:

  • STK Pro

Problem statement

Engineers and operators need to quickly add realistic analytical and visual properties to objects in STK. They may need a realistic satellite attitude, analysis of an enclosed area in a deep canyon, a mission plan for an aircraft flight route, a sensor footprint, or a briefing with detailed visuals and analysis.

Solution

Use STK to insert STK objects into your scenario. Then update the object's properties to define its characteristics relevant to your scenario.

What you will learn

Upon completion of this tutorial, you will be able to:

  • Update STK's Databases
  • Insert objects into your STK scenario
  • Modify properties
  • Understand why you are using different objects in your analysis

There are many objects and properties used in STK. Not all objects or properties are covered in this lesson. Other tutorials cover some objects or properties not discussed in this tutorial.

Video guidance

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

Data Update Utility

If you have an internet connection, you can use the Data Update Utility to update astro datasets (such as EOP, Space Weather, Leap Second, time.ker, Solar Flux, satellite databases, GPS, etc). You can manually update one or more data sets or you can you can schedule a time and frequency for automatic updates.

If you work with satellites, update your databases prior to opening a new scenario.

  1. Launch STK ().
  2. Extend the Utilities menu.
  3. Select the Data Update... option.

    The color of the data set indicates its current status: red data sets have updates available, black are up to date, and purple are not currently available on AGI servers (these are rarely seen). If you select the Enable Automatic Updates check box, you can set your preferred options. Your PC needs to be on and connected to the Internet for the auto updates to occur.

  4. Select all the data set check boxes that have updates available (Red) in the Update Column. Ignore black and purple data sets.
  5. Click Update Now.
  6. Click Yes when the warning appears.
  7. Wait for the progress bar in the lower right-hand corner of the tool to complete and for all the data sets to turn black.
  8. Click OK when the update is complete to close the Data Update Utility.
  9. Click Exit STK in the Welcome to STK dialog box.

Create the new scenario

Create a new scenario using the following properties. For a step-by-step guide to creating a new scenario, see Lesson One: Build Scenarios.

  1. Launch STK ().
  2. Click Create a Scenario in the Welcome to STK dialog box.
  3. Enter the following in the STK: New Scenario Wizard:
    4. Option Value
    Name: STK_Objects_Properties
    Location: Default
    Start: Default
    Stop: Default
  4. Click OK when you finish.
  5. Click Save () when the scenario loads. STK 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.

Modifying the Scenario object's properties

The Scenario () object defines the context that influences the properties and behavior of other objects.

  1. Right-click on the Scenario () object in the Object Browser.
  2. Select Properties ().

When the Scenario () object's properties open, there is a branching list on the left containing pages of properties. The main category that you will need to know is the Basic category, which holds properties such as Time, Units, Database, and many others.

Basic Time

In the Basic - Time page, the Analysis Period defines the epoch and the start/stop times for your scenario. Animation properties control the animation cycle, step duration, and the intervals between refresh updates in the graphics windows.

Throughout the various STK tutorials, you are instructed to browse to a properties page. Just click the specified page on the left.

Basic Units

Scenario Units establish the default settings for all units of measure used in a scenario.

  1. Select the Basic - Units page.
  2. Change the unit of any dimension listed in the table, click the CurrentUnit (e.g., Kilometers (km)) and select the appropriate value from the shortcut menu.

Basic Database

Database properties enable you to set the defaults for the city, facility, satellite, and star databases. You can specify a stock STK database or one of your own that meets STK's format requirements.

Basic Earth Data

Use this page to update the Earth Orientation Parameters (EOP).

Basic Terrain

You can use the Terrain properties page of a scenario to enable streaming terrain that enables you to view terrain features in the 3D Graphics window.

To use analytical terrain in your scenario requires STK PRO.

  1. Select the Basic - Terrain page.
  2. Take a look around the Terrain page.

In the Terrain page, you should see the "Use terrain server for analysis" option. You can toggle the Terrain Server on and off with this option. "Advanced Analysis Operations" and "Custom Analysis Terrain Sources" require an STK Professional license.

Basic 3D Tiles

STK 12 adds the ability to include 3DTileset geometry (e.g., massive city models, photogrammetry, etc) computationally in your analysis. The constraint 3DTiles Mask is available for Facility, Target, and Place objects, as well as all vehicle types. This allows for 3D Tileset geometry to obstruct visibility when computing access. You can use a 3D Titleset hosted in GCS, Cesium ion, or from the local file system for analysis with this constraint.

Basic Global Attributes

Use the Basic - Global Attributes page to configure the display of warning messages for satellite and missile objects. By selecting the Basic - Global Attributes page, you should see options to suppress warnings for Satellites and Missiles.

Description

The Description page for an object is a handy place to record miscellaneous information about the object and its role in your analytical or operational task. By selecting this property, you should see a text box for a "Short Description," a larger text box for a "Long Description," and an area to add "Metadata."

Global Attributes

Global Attributes can (or, in some cases, must) be set at the scenario level for all objects.

2D Graphics Global Attributes

2D Graphics Global Attributes answer three basic questions about an STK object:

  • What do you want to show?
  • How do you want it to look?
  • When do you want it to be seen?
  1. Select the 2D Graphics - Global Attributes page.
  2. Take a look at the Global Attributes page, where you can decide what to display in the Graphics Windows.

There are a couple of things to keep in mind when using this page. Any changes you make on the Global Attributes page are applied to ALL objects that fall into the category (e.g. Vehicles). Any changes made on this page are also applied to 3D Graphics. For instance, if you disable the Show Labels option, object labels in both the 2D Graphics and 3D Graphics windows will be removed.

3D Graphics Global Attributes

The 3D Graphics - Global Attributes properties page of a scenario can be used to define 3D visualization options that affect the entire scenario.

  1. Select the 3D Graphics - Global Attributes page.
  2. Make note of the fields and what they do.
Option Description
Surface Reference of Earth Globes Use either Mean Sea Level or WGS84 Ellipsoid (default).
3D Object Editing Allows you to pull great arc vehicles, facilities, and targets below the globe's surface reference - thus assigning them negative altitude values - while using 3D object editing.
Image Cache Temporarily stores imagery for the globe. You may need to increase the size of the cache if all of the images that you are trying to display cannot be loaded at the same time or if an image appears blurry.
Terrain Cache Temporarily stores terrain data for the globe. You may need to increase the size of the cache if all of the terrain that you are trying to display cannot be loaded at the same time or if the globe surface at the terrain level appears blurry.
Surface Lines Allows you to select an option for displaying lines on the surface of the central body when terrain data is available. Select When Terrain Server is on to display surface lines on terrain only when you are connected to a terrain server, On to display surface lines on terrain data whenever it is available from any source, or Off to never display surface lines on terrain.

2D and 3D Graphics Fonts

  1. Select the 2D Graphics - Fonts page.

    2. 2D Graphics Fonts allows you to configure the display of small, medium, and large fonts in your 2D Graphics window and apply an outline to the text to improve readability on changing map colors.

  2. Select the 3D Graphics - Fonts page.

    3. 3D Graphics Fonts allows you to configure the display of small, medium, and large fonts in your 3D Graphics window and apply an outline to the text to improve readability on changing globe colors.

  3. Click OK to close STK_Objects_Properties () properties ().

Insert STK Objects tool

The Insert STK Objects tool provides an easy, convenient way to populate a scenario. The Insert STK Objects tool, by default, displays the most commonly-used scenario objects. You can customize the tool to display all the scenario objects or a user-defined subset of objects.

  1. Click Close on the Insert STK Objects tool.

    2. There are two ways to reopen the Insert STK Objects tool:

    • Click Insert Object () located in the Default toolbar.
    • Expand the Insert menu and select New.
  2. Reopen the Insert STK Objects tool by using one of the aforementioned methods.

New object preferences

You can set preferences for the Insert STK Objects tool and setting default methods for inserting objects.

  1. Click Edit Preferences... in the Insert STK Objects tool.
  2. To choose the objects you want to appear Insert STK Objects tool, select the Show check box for them in the Object list.

    3. For the purposes of this tutorial, you won't make changes to the Object list. Later, you can enable all available objects and practice with them.

  3. Click Cancel.

Objects and Methods

In the Insert STK Objects tool, you will see Scenario Objects, Attached Objects, and Methods. Scenario objects are children of the larger Scenario () (e.g. STK_Objects_Properties). Attached objects are the children of scenario objects. You must add scenario objects before you can add attached objects.

To insert an object, you must choose a particular method. These methods determine the starting properties of each object and you can change these properties later. For instance, when this training says to "Insert a Default Object," that means insert an object using the default method. You should pick the method for the demands of your scenario, as we will show later in this training.

For instance, you could insert an Aircraft () object (a Scenario object) using the Insert Default () method. Then, you could insert a Sensor () object (an Attached object) onto that aircraft.

Scenario-level objects

The following Scenario Level objects will be discussed:

We won't cover every insert method for every object, but will cover different insert methods for different objects to give you an idea what they do. Furthermore, we won't cover all properties. For instance, some properties will be discussed for the Aircraft () object that can be applied to other objects.

Satellite object

The Satellite object models the properties and behavior of a vehicle in orbit around a central body.

From Standard Object Database

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

    3. Both the satellite database file and the corresponding TLE file evolve over time and need to be updated as needed.

    The U.S. Strategic Command (USSTRATCOM) currently keeps track of thousands of space objects. These objects constitute the space object catalog. While most of the catalog is made available to the public, some information is restricted. AGI provides the publicly released information for use with STK in the form of satellite database files and two-line mean element files (TLEs).

  3. Click Insert....
  4. In the Name or ID: field, enter 25544 (the SSC number or Satellite Catalog Number)
  5. Click Search.
  6. In the Results: field, select ISS (Zarya).
  7. Click Insert.

    8. The ISS (Zarya) is downloaded from AGI's Standard Object Data Service. If you were to choose ISS or Zarya using Local Database, you would need to ensure you've updated your satellite database.

  8. Click Close to close the Search Standard Object Data window.

View in 2D

  1. Bring the 2D Graphics window to the front.
  2. Zoom Out () if needed to see the entire earth and the current orbit track of ISS_ZARYA_25544 ().

    3. International Space Station Orbit in 2D

  3. Using the Animation Toolbar, make any adjustments to the time step.
  4. Click Start () to animate the scenario.
  5. When finished, click Reset ().

View in 3D

  1. Bring the 3D Graphics window to the front.
  2. Click Home View ().

    3. International Space Station Orbit in 3D

    In this view, you can see both a ground track representing the ISS's current orbit and the actual orbit track. Not all Satellite () objects are represented by both a ground track and an orbit track.

  3. Right-click on ISS_ZARYA_25544 () in the Object Browser.
  4. Select Zoom To.
  5. Using the Animation Toolbar, make any adjustments to the time step.
  6. Click Start () to animate the scenario.
  7. When finished, click Reset ().

Real-time Animation Mode

The scenario animates in real time in accordance with your computer's internal clock. In order for you to be able to visualize ISS_ZARYA_25544 () using real-time animation mode, your scenario analysis period must fall within your current time. For instance, if the analysis period is set at 1 Jun 2020 18:00:00.000 UTCG - 2 Jun 2020 18:00:00.000 UTCG, and the actual local time is 1 Jun 2020 11:00 Mountain Time (11:00 am), ISS_ZARYA_25544 () is not be visible. 1 Jun 2020 18:00:00.000 UTCG is 1 Jun 2020 12:00 local time. You'll have to adjust your scenario times if you experience this problem. If you do adjust your times, other moving objects such as the Aircraft () object need to be readjusted too.

  1. Ensure your scenario analysis period falls within your local time period.
  2. In the Animation Toolbar, select Real-time Animation Mode ().
  3. Click Start (). You're now visualizing ISS_ZARYA_25544 () at its actual location based on the TLE from which it was propagated.
  4. When finished, click Reset ().
  5. In the Animation Toolbar, select Normal Animation Mode ().
  6. Click Reset ().

ISS_ZARYA_25544's Properties

  1. Right-click on ISS_ZARYA_25544's () in the Object Browser.
  2. Select properties ().
  3. Note that the Propagator is set to the SGP4 Propagator. The Simplified General Perturbations (SGP4) propagator is used with two-line mean element (TLE) sets.
  4. In the TLE Source frame, click Preview.... Here, you can preview or modify the two-line element (TLE) information that is used to propagate the SGP4 satellite.
  5. Close the TLE Preview window.
  6. Click OK to close ISS_ZARYA_25544's () properties ().

Orbit Wizard

The Orbit Wizard is a satellite-level tool designed to assist you in creating any one of several standard orbits, or designing your own satellite orbit. The configurable options available depends on the orbit type selected.

  1. Select Satellite () in the Insert STK Objects tool.
  2. Select the Orbit Wizard () method.
  3. Click Insert....

    4. Orbit Wizard

  4. When the Orbit Wizard opens, set the following:
    5. Option Value
    Type: Repeating Ground Trace
    Satellite Name: RGT_Sat
    Approximate Altitude: 600 km

    The Analysis Time Period / Interval: defaults to your scenario analysis period. The satellite is propagated for that period.

  5. Click OK.
  6. Just like you did with ISS_ZARYA_25544 (), view RGT_Sat () in the 2D Graphics and 3D Graphics windows.
  7. Click Start () to animate the scenario if desired.
  8. When finished, click Reset ().

RGT_Sat's Properties.

  1. Right-click on RGT_Sat () in the Object Browser.
  2. Select properties ().
  3. Note that the propagator is set to J2 Perturbation.

    4. Unlike a Satellite () object propagated using TLEs, a Satellite () object propagated using the Orbit Wizard can be edited using your own data.

Satellite Vectors and Attitude

Sometimes you need to understand your attitude.

  1. Return to RGT_Sat's () properties ().
  2. Select the 3D Graphics - Vector page.
  3. Select the Axes tab.
  4. Enable Body Axes Show option.
  5. Change the Body Axes color if desired.

    6. If you double-click on the Color cell, you can change the color of Angles, Axes, Points, Vectors, or Planes. This presents a shortcut menu which, when clicked, shows a color palette. Simply click the color you want to apply to your geometric element.

  6. Click Apply.

View in 3D

  1. Right-click on RGT_Sat () in the Object Browser.
  2. Select Zoom To.
  3. Bring the 3D Graphics window to the front.

    4. Nadir alignment with ECI velocity constraint

    The Satellite () object defaults to a Nadir alignment with ECI velocity constraint attitude. In this vehicle body frame definition, the vehicle's Z axis is aligned with the nadir direction and its X axis is constrained in the direction of the ECI velocity vector.

    Satellite, Missile, Aircraft, Ship, and Ground Vehicle objects have one thing in common. The Body X is aligned with the direction of travel unless you change the attitude.

Attitude Profiles

Vehicle body frame definitions are based on Attitude profiles.

  1. Return to RGT_Sat's () properties ().
  2. Select the Basic - Attitude page.
  3. Change the Basic Type: to ECF Velocity Alignment with Radial Constraint.
  4. Click Apply.
  5. Bring the 3D Graphics window to the front.

    6. ECF Velocity Alignment with Radial Constraint

    The vehicle's X axis is aligned with the Earth-fixed velocity vector direction and the Z axis is constrained in the radial direction (the direction along the position vector and opposite to geocentric nadir).

Set the Nadir alignment back to ECI velocity constraint

  1. Return to RGT_Sat's () properties () Basic - Attitude page.
  2. Change the Basic Type: back to Nadir alignment with ECI velocity constraint
  3. Click OK.

Update the Local Satellite Database

You must connect to the internet to update your satellite database.

There are times when you need to look at older data or you want to use local files such as your own TLE file. In this section, we'll use an archived database. You must be connected to the Internet to utilize this source.

  1. Open the STK_Objects_Properties's () properties ().
  2. Select the Basic - Database page.
  3. Ensure Database Type: is set to Satellite.
  4. Click Update Database Files...

Updating the Satellite Database

You can update satellite database information using Update Database Files.

Option Description
Update Database Obtains the latest satellite database information from the AGI satellite database server
Obtain Archived Database Obtains an older version of the database from the date specified in the Archive Date field. If an archive is not available from the specified date, the archive for the next newest date is used instead.
  1. Select the Obtain Archived Database option.
  2. Select Specific Database: and ensure it's set to stkAllTLE (the entire database of satellites).
  3. Click the Database ellipsis ().
  4. Select the scenario folder or place the file in a folder of your choice.

    5. Your default save location may be in C:/ProgramData/... and this folder may be hidden. To unhide it, you must select the option in your File Explorer to show all hidden folders. Consult the help for Microsoft Windows to select that option.

  5. Specify the Archive Date by entering it in the text field or using the drop-down menu. In the case, change the year to the previous year (e.g. if it's 2023, change it to 2022).
  6. Click Update. If an archive is not available for the specified date, the archive for the next newest data is used instead.
  7. When the Information window appears, click OK.
  8. Click Close to exit the Update Satellite Database dialog box.
  9. Click OK to accept your changes and to close the Properties Browser.

Insert a Satellite from the Local Satellite Database

Use the Insert From Satellite Database tool to query a locally installed Spacecraft database.

  1. Insert a Satellite () object using the From TLE File () method.
  2. Navigate to the archived satellite database file (e.g. C:\Users\username\Documents\STK 12\STK_Objects_Properties).
  3. Select stkAllTLE.tce.
  4. Click Open.
  5. Click Yes when the Question window appears. Be patient, this can take a few minutes.

Satellite Database TLE Source

The Satellite Database TLE Source window specifies the satellite database TLE source.

  1. Click Modify... on the Insert From Satellite Database dialog box.
  2. Clear the On propagation, automatically retrieve elements check box in the Satellite Database: TLE Source dialog box. Disabling this option keeps the satellite's designated TLEs from being automatically updated next time you open the scenario.
  3. Click OK to close the Satellite Database: TLE Source dialog box.
  4. Click Yes when the Question window appears. Be patient, this can take a few minutes.
  5. Enter 25544 in the SSC Number field.
  6. Click Search.
  7. Select Zarya.
  8. Click Insert.
  9. Click Close to close the Insert From Satellite Database dialog box.

New Versus Old TLEs

Earlier you inserted ISS_ZARYA_25544 using the most current TLE. Now you've inserted the same satellite using an archived TLE that is a year old. STK propagated the TLE from a year ago. Any changes to the orbit during that period are not reflected. You should be able to see the difference in both the 2D and 3D Graphics windows.

  1. Bring the 3D Graphics window to the front.
  2. Click Home View () on the 3D Graphics window toolbar.
  3. Rearrange your view so that you can see both satellites.

    4. New Versus Old TLE Data

    You should see a difference between using old data and new data. This is a great example why you need to use current data or data that matches your analysis period.

  4. When finished, clear the ZARYA_25544 check box in the Object Browser. This turns object off visually in both the 2D and 3D Graphics windows, but the object is still available analytically if needed.

Aircraft object

The Aircraft () object models the properties and behavior of a vehicle that travels in a great arc route, generally above the surface of the earth.

  1. Insert an Aircraft () object using the Insert Default () method.

Renaming objects

It's usual to rename objects in STK. If you choose not to rename your objects, STK will name them giving each object a number. For instance, the first Aircraft () object that you insert will be named Aircraft1. The next Aircraft () object you insert will be named Aircraft2 and so on.

  1. Right-click on Aircraft1 () in the Object Browser.
  2. Select Rename in the shortcut menu.
  3. Rename Aircraft1 () to My_Plane.

Aircraft Object's Properties

  1. Open My_Plane's () properties ().
  2. Select the Basic - Route page.

Great Arc Propagator

At the top of the page, notice that the propagator is set to GreatArc. The Great Arc Propagator defines the route of a vehicle that follows a point-by-point path along, over, or below the surface of the Earth at a given altitude or depth. A great arc path, which lies in a plane that intersects the center of the Earth, connects the waypoints. The following Great Arc Propagator settings work with Aircraft () , Ground Vehicle (), and Ship () objects.

Start Time

The Start Time defaults to the scenario start time and you can reset it. The Stop Time field is read-only and is defined by the last waypoint for the vehicle.

  1. Click the down arrow or right-click on the start or stop times to interact with the object time options.
  2. Hover over Start Time.

The shortcut gives you an idea of other selections, such as: Set to Today or Set to Tomorrow. When you enter waypoints for the object, this window enables the Replace With Time option. If you change the Start Time after you enter waypoints, all time entries in the waypoint table are updated automatically.

Route Calculation Method

You can use the Route Calculation Method shortcut menu to select the manner in which the route is calculated between each waypoint. For this training, use the default Smooth Rate method.

Option Description
Specify Rate/Acc Uses the Speed and Acceleration properties of each waypoint
Specify Time Uses the Time properties of each waypoint. This is useful if you want an object to stay in one spot for a period of time without moving
Smooth Rate Uses the Speed property of each waypoint

Altitude Reference

Ground vehicles, aircraft, and ships can reference their altitude from mean sea level, terrain data, or WGS84. The World Geodetic System 1984 (WGS 84) is a 3-dimensional coordinate reference frame for establishing latitude, longitude and heights for navigation, positioning and targeting for the DoD, IC, NATO, International Hydrographic Office and the International Civil Aviation Organization.

Since you're currently using Terrain Server, a good rule of thumb when creating an aircraft flight route using the Great Arc Propagator, is to set the altitude reference to Mean Sea Level. In the United States, mean sea level is defined as the mean height of the surface of the sea for all stages of the tide over a 19-year period.

  1. Open the Reference: shortcut menu in the Altitude Reference frame.
  2. Select MSL.

Waypoints

The waypoints that comprise the great arc route are contained in a table that displays each point, along with all of its properties, in sequence. The table can be used to directly edit those properties. One row of values describes a single waypoint in the route of the vehicle.

There are two ways to enter waypoints:

  • Clicking Insert Point and manually entering values.
  • Clicking on the 2D Graphics window when the Basic - Route page is open.

Check out more information about the Great Arc Waypoint Properties by looking at the table with the same name on the Great Arc Waypoint Properties help page. It describes all the major position, movement, and time properties, along with the calculation method.

Clicking on Map

  1. Leave My_Plane's () properties () open.
  2. Bring the 2D Graphics window to the front by clicking on the 2D Graphic tab below the Properties Browser.
  3. Click somewhere in the Atlantic Ocean near the African coast and then click somewhere in the Indian Ocean near the Indian coast.

    4. Make sure you only click where you want a waypoint!

  4. Bring My_Plane's () properties () back to the front.

    5. Notice that the Altitude, Speed, and Turn Radius values are copied for each waypoint.

Modify a Waypoint Location

  1. Select the first waypoint.
  2. Select the Clicking on map changes current point check box.
  3. Bring the 2D Graphics window back to the front.
  4. Click somewhere in the Pacific Ocean near the United States coast.

    5. Wherever you click, the waypoint will be moved to that location. Also, the Great Arc Propagator will automatically reroute the aircraft using the shortest distance between the waypoints. If you want to fly in a specific direction, you will need to add more waypoints.

  5. Bring My_Plane's () properties () back to the front.
  6. Click Delete Point until all waypoints are deleted.
  7. Clear the Clicking on map changes current point check box.
  8. Click Apply.

Insert Point

You can insert waypoints manually. This is more precise than clicking on the map.

  1. Click Insert Point.
  2. Enter the following by clicking in the associated cell. Press the Enter key on the keyboard after each entry:
    3. Option Value
    Latitude 38.00 deg
    Longitude -120.00 deg
  3. Click Insert Point.
  4. Enter the following for the second waypoint:
    5. Option Value
    Latitude 30.00 deg
    Longitude -99.00 deg
  5. Click Insert Point.
  6. Enter the following for the third waypoint:
    7. Option Value
    Latitude 40.00 deg
    Longitude -77.00 deg
  7. Click Apply.

View the waypoints in the 2D and 3D Graphics windows

My_Plane's () flight route is located in the Continental United States.

  1. Bring the 2D Graphics window to the front to view the flight route.
  2. Bring the 3D Graphics window to the front to view the flight route.
  3. Return to My_Plane's () properties ().

Modify a Waypoint's Altitude

When modifying one waypoint, you need to know proper units. For instance, look at the first waypoint:

  • The Altitude unit uses km (kilometers).
  • The Speed unit uses km/sec (kilometers per second).
  • The Turn Radius unit uses km.

    Modify the first waypoint's altitude to 20000 ft (feet).

  1. Select the first waypoint.
  2. Click inside the Altitude cell.
  3. Enter 20000 ft.
  4. Press Enter on the keyboard.

    5. Notice the unit reverts back to the default km. My_Plane () is flying at an altitude of 6.09600000 km (20000 ft) at the first waypoint. It slowly ascends until it reaches the second waypoint.

Modify a Waypoint's Speed

Modify the first waypoint's speed to 450 mi/hr (miles per hour).

  1. Click inside the Speed cell.
  2. Enter 450 mi/hr.
  3. Press Enter on the keyboard.

    4. My_Plane slowly decelerates between the first and second waypoints. You can see this in the Accel cell.

Modify a Waypoint's Turn Radius

Modify the first waypoint's turn radius to two (2) km.

  1. Click inside the Turn Radius cell.
  2. Enter 2 km.
  3. Press Enter on the keyboard.
  4. Click Apply.

    5. The great arc path will never reach the given waypoint unless the change in heading The direction that the aircraft is pointing. is negligible. Instead, the turn will be inscribed between the lines connecting the previous procedure to the given waypoint and the waypoint to the next procedure. The position will arrive along the line from the previous procedure toward the given waypoint and leave along the line from the given waypoint toward the next procedure. The radius of the inscribed turn will be contained to the vehicle's radius. See the figure below for a visual representation of this.

    Keep this in mind when creating a movie. If your aircraft isn't flying over the location you clicked on the map or entered as a latitude and longitude, you should either decrease the turn radius or modify the waypoint location.

Turn Radius

Set All Grid Values tool

With the Set All Grid Values tool, you can modify the Altitude, Speed, Acceleration, and Turn Radius properties for all waypoints that are currently defined in the table. The properties that can be modified using this tool will be constrained with respect to the currently selected Route Calculation Method.

  1. Click Set All....
  2. Select Altitude, Speed, and Turn Radius in the Set All Grid Values dialog box.

    3. To the right of each value is a shortcut menu. These appear throughout STK. By clicking on them here, you can set units for Altitude, Speed, Acceleration, or Turn Radius. This comes in handy when you can't find or don't know the acronym for the unit you are looking for.

  3. Extend the shortcut menu for Speed.
  4. Select nm (nautical mile).
  5. In the second shortcut menu, select hr (hour).
  6. Set the value to 500. The aircraft flies from the first to the last waypoints at a speed of 500 nautical miles per hour.
  7. Set the following for altitude and Turn Radius:
    8. Option Value
    Altitude: 45000 ft
    Turn Radius: 3 km
  8. Click OK to close the Set All Grid Values dialog box.
  9. Click Apply.

Set the animation time

You can jump to a waypoint in the 2D and 3D Graphics windows.

  1. Select the second waypoint.
  2. Click inside the Time cell.
  3. Copy (Ctrl + C) the Time of the second waypoint.
  4. Right-click in the Current Scenario Time field in the Animation Toolbar.
  5. Select Paste.
  6. Click the Enter key on your keyboard.

View in 3D

  1. Bring the 3D Graphics window to the front.
  2. Right-click on My_Plane () in the Object Browser.
  3. Select Zoom To.
  4. Using the left mouse button, create a head on view of My_Plane ().

    5. All three waypoints are using the same values. The units converted back to the default units. The aircraft is flying the entire route at an altitude of 45000 feet MSL, at a speed of 500 nautical miles per hour and will require a turn radius of 3 kilometers at waypoint two. My_Plane () is in the middle of the turn. Notice that there is no roll (banking) associated with the attitude.

No Roll in Turn

Attitude Profiles

STK is set at the Standard attitude option which allows you define a vehicle's attitude profile using the following:

Attitude changes can be applied to all moving objects in STK (e.g. Aircraft, Ground Vehicles, Missiles, Satellites, Ships).

  1. Leave the view in the 3D Graphics window.
  2. Return to My_Plane's () properties ().
  3. Select the Basic - Attitude page.

Coordinated Turn Attitude

This profile computes the roll (banking) of an aircraft based on a balancing of the forces acting on the aircraft, assuming a zero angle of attack The angle between the body X axis and the projection of the velocity vector onto the body XZ plane. The velocity vector is the velocity of the object as observed in the object's central body fixed coordinate system. and no slip condition. There are many reasons why you would use a coordinated turn. For instance, you are modeling an aircraft with a fixed Sensor () object which is acting as a camera's field-of-view. Maybe you're making a movie and you want the Aircraft () object to roll like a real aircraft.

  1. Open the Type: shortcut menu in the Basic frame.
  2. Select Coordinated Turn.
  3. Leave the Time Offset at 10 sec.
  4. Click Apply.

View in 3D

  1. Bring the 3D Graphics window back to the front.

    2. Coordinated Turn

    The aircraft is now banking (roll). The severity of the roll is determined by the speed and turn radius of the plane.

  2. Click Reset () in the Animation Toolbar.

2D Graphics properties

2D Graphics Attributes answer three basic questions about an STK object:

  1. Return to My_Plane's () properties ().
  2. Select the 2D Graphics - Attributes page.

    3. 2D Graphics Attributes Properties

  3. Change Color, Line Style, and Line Width to whatever selections you want.
  4. Click Apply.

View in the Graphics windows

  1. Bring the 2D Graphics window to the front.
  2. Zoom in or out in order to get a good view of MyPlane's () flight route.
  3. When finished, bring the 3D Graphics window to the front.
  4. If needed, zoom to My_Plane ().

Changes made in the 2D Graphics Properties are applied to both the 2D Graphics and 3D Graphics windows.

3D Graphics properties

Unlike 2D Graphics properties which are seen in both the 2D and 3D Graphics windows, 3D Graphics properties can only be seen in the 3D Graphics window.

3D Graphics Properties - Vector is used to do the following:

  • Control the display of vectors and other geometric elements, such as axes and angles, related to the Earth or other central body in the selected 3D Graphics window.
  • Control the display of vectors and other geometric elements related to the selected object.
  1. Return to My_Plane's () properties ().
  2. Select the 3D Graphics - Vector page.
  3. Ensure the Vectors tab is selected.
  4. Select the Show check box for Sun Vector.
  5. Select the Axes tab.
  6. Select the Show check box for Body Axes.
  7. Click Apply.

View in 3D

  1. Bring the 3D Graphics window to the front.
  2. If needed, Zoom To My_Plane ().

Body Axes and Sun Vector

Animate the scenario

The body axes remain fixed throughout the flight. Even when the Sun drops below the horizon, the sun vector continuously stays locked on the Sun.

  1. Decrease Time Step () to five (5.00) seconds in the Animation Toolbar.
  2. Click Start () to animate the scenario.
  3. Click Reset () when finished.

3D Graphics Model

The 3D Graphics - Model page is used to specify a model to represent a given vehicle, facility, place, or target in the 3D Graphics window. You can scale the model and adjust the position of any model articulations. You can use models that install with STK, download modelsfrom the AGI Website, or build your own models and use them in STK. The models are simply visual representations of your objects. Analysis is typically done from the center point of your object unless otherwise specified. You may want to change the model for a more realistic briefing or movie.

Supported model file types are:

  1. Return to My_Plane's () properties ().
  2. Select the 3D Graphics - Model page. The current model you see in the 3D Graphics window is the aircraft.glb.
  3. Click the Model File: ellipses () in the Model frame. All the models shown in the File dialog box come with the STK install.
  4. Select any model (DAE File or Simulink Model) you'd like to use in the scenario.
  5. Click Open.
  6. Click OK.
  7. Bring the 3D Graphics window to the front. You have a new model type representing the Aircraft () object.

RC-135 Rivet Joint Model

Area Target object

The Area Target object () models a region on the surface of the central body.

Select Countries And US States Method

This insert method available on the Insert STK Objects tool enables you to add single or multiple US states or countries as area targets. By default, the list displays both countries and US states.

  1. Insert an Area Target () object using the Countries and US States () method.
  2. Select United_States_of_America when the Select Countries And US States dialog box opens. Notice that the Insert field becomes active.

    3. Area targets are created from shapefiles, which contain one or more polygons. Each polygon is converted into one area target. If the shapefile for the selected area contains multiple polygons, you can choose whether to add only the largest polygon (Primary Area Only) or all polygons (All Areas) in the shapefile.

  3. Keep the default selection of Primary Area Only.
  4. Click Insert.
  5. Click Close.

View in 2D

  1. Bring the 2D Graphics window to the front.
  2. Zoom out far enough so you can see the Area Target, Hawaii, and Alaska.

    3. This is a good example of Primary Area Only and All Areas. Had you selected All Areas, you'd see all of Alaska and all the Hawaiian Islands enclosed in area targets.

United States Area Target Primary Area Only

Area Target Wizard Method

The Area Target Wizard is used to add an area target, define its perimeter, and set its graphic properties. There are two types of Area Targets: ellipse and pattern. Using the Area Target Wizard, create an ellipse.

  1. Insert an Area Target () object using the Area Target Wizard () method.
  2. Set the following in the Area Target Wizard:
    3. Option Value
    Name: AT_Ellipse
    Area Type: Ellipse
    Semi-Major Axis: 2 km
    Semi-Minor Axis: 1 km
    Bearing: 132.353 deg
    Centroid: Latitude 38.4613 deg / Longitude -105.3256 deg
  3. Click OK.

View in 3D

  1. Bring the 3D Graphics window to the front.
  2. Right-click on AT_Ellipse () in the Object Browser.
  3. Select Zoom To.
  4. Use your mouse to zoom out until you can see the entire area target.
  5. Using your left mouse button, move your view around in circles. Note how the label gets "lost" in the terrain.

3D Graphics window properties - Label Declutter

Label Declutter raises labels above from the central body and towards the viewer, keeping the labels from being obscured by the terrain. This is especially helpful if you label is at the bottom of a valley or canyon.

  1. Click Properties () on the 3D Graphics window toolbar.
  2. Select the Details page.
  3. Select the Enable check box in the Label Declutter frame.
  4. Click OK.

    5. Notice how the label appears above the surface of the terrain.

Area Target Ellipse Using Label Declutter

Insert Default Method

Insert Default adds the selected object and applies the default settings to the newly added object.

  1. Insert an Area Target () object using the Insert Default () method.
  2. Rename AreaTarget3 () to Local_Airfield.

Define the Area Target

Define the Area Target.

  1. Open Local_Airfield's () properties ().

    2. The Basic - Boundary page is similar to the Area Target Wizard except you don't get a small 2D Graphic view. Now you'll outline a local airfield. Maybe you're trying to determine when a Satellite () object or an Aircraft () object sees the airfield.

  2. Select the Basic - Boundary page.
  3. Click Add four (4) times.
  4. Set the following Latitude and Longitude values for the Points in the order shown (simply copy and paste from the tutorial):
    5. Latitude Longitude
    38.4345 deg -105.116 deg
    38.4267 deg -105.0999 deg
    38.4256 deg -105.1008 deg
    38.4333 deg -105.117 deg
  5. Click OK.

View in 3D

  1. Bring the 3D Graphics window to the front.
  2. Zoom To Local_Airfield ().
  3. Use your mouse to get a good view of the area target outlining the airfield.

Area Target Local Airfield

Facility Object

The Facility object () models a ground station or other facility on the surface of the central body. Similar to Place () and Target () objects property wise, what makes a Facility () object stand out is when you insert one using the standard object database.

  1. Insert a Facility () object using the From Standard Object Database () method.
  2. Enter Castle Rock in the Name: field on the Search Standard Object Data dialog box.
  3. Click Search.
  4. Take a look at the Results.

    5. Notice that the first result gives you information such as role, country and status. If you insert the first selection it is downloaded from the online source: AGI's Standard Object Data Service. The other two results were part of the STK install and come from the install area on your hard drive.

  5. Change Name: to White Sands.
  6. Click Search.

    7. White sands has many more selections to include ground stations, launch pads and launch sites.

  7. Delete White Sands from the Name: field.

Insert Intelsat

  1. Scroll down to the Network: field.
  2. Open the Network: shortcut menu.
  3. Select INTELSAT.
  4. Click Search.

    5. This allows you to quickly add all the Facility () objects associated with that network.

Enter White Sands - SULF

  1. Change Network: back to no selection (-).
  2. Enter White Sands in the Name: field.
  3. Click Search.
  4. In the Results: list, select White - Sands - SULF.
  5. Click Insert.
  6. Click Close to close the Search Standard Object Data dialog box.

Edit SULF's Properties

  1. Open White - Sands SULF's () properties ().
  2. Select the Basic - Position page.
  3. Select the Use terrain data check box.

    4. The Use terrain data option overrides the altitude used by the Facility () object and it now uses Terrain Server's terrain as an altitude reference. This is unique to the Facility () object. The default altitude was most likely based on a terrain file other than the terrain used by Terrain Server. If Terrain Server is disabled, then the Facility () object references the surface of the WGS84 Ellipsoid.

  4. Click Apply.

View in 3D

  1. Bring the 3D Graphics window to the front.
  2. Zoom To White - Sands SULF ().

    3. The Facility () object is located at the launch pad at White Sands.

    White Sands SULF

Azimuth-elevation Mask

Looking at White - Sands SULF () you can see a visual representation of an azimuth-elevation mask. You can use an azimuth-elevation mask to constrain access to the object. The mask can come from terrain or a custom az-el mask. Turn off the mask file.

  1. Select the Basic - AzElMask page.
  2. Open the Use: shortcut menu.
  3. Select None.
  4. Clear the Use Mask for Access Constraint check box.
  5. Click OK.

Ground Vehicle object

The Ground Vehicle () object models the properties and behavior of a vehicle that travels in a great arc route on the surface of the earth. The great arc propagator works exactly the same for a ground vehicle as it does for an Aircraft () object.

  1. Insert a Ground Vehicle () object using the Insert Default () method.
  2. Rename GroundVehicle1 () to ATV.
  3. Open ATV's () properties ().

Reference Terrain

Unlike the Aircraft () object, the Ground Vehicle () object is on the surface of the terrain. You need to take that into account.

Great Arc Referencing Terrain

  1. Select the Basic - Route page.
  2. Set the following in the Altitude Reference frame:
    3. Option Value
    Reference: Terrain
    Granularity: 1 m
    Interp Method: Terrain Height

Create Waypoints

ATV () is driving down the road to the launch pad at White_Sands-SULF ().

  1. Click Insert Point.
  2. Set the following (you can copy and paste to save time if desired):
    3. Option Value
    Latitude 33.71868 deg
    Longitude -106.73949 deg
  3. Click Insert Point.
  4. Set the following:
    5. Option Value
    Latitude 33.72085 deg
    Longitude -106.73928 deg
  5. Click Insert Point.
  6. Set the following:
    7. Option Value
    Latitude 33.72085 deg
    Longitude -106.73731 deg

Speed and Altitude

Keep in mind that the center point of the ground vehicle is right on top of the terrain. You might want to raise it a foot or so depending on your analysis. The object center point, unless changed, is where analysis for the object takes place. Also, terrain undulation could be a factor. The ground vehicle could appear, visually, to dart into and out of terrain, especially when modeling in an area containing rugged terrain. Terrain resolution can be a factor too.

All ground object center points start on the WGS84 or terrain surface.

Ground Vehicle Center Point

  1. Click Set All...
  2. Select the Altitude and Speed check boxes in the Set All Grid Values dialog box.
  3. Set the following:
    4. Option Value
    Altitude: 1 ft
    Speed: 15 mi/hr
  4. Click OK to close the Set All Grid Values dialog box.
  5. Click OK to apply all changes and close the properties window.

View in 3D

  1. Bring the 3D Graphics window to the front.
  2. Zoom To ATV ().

    3. ATV Driving At White Sands

  3. Select X Real-time Animation Mode () in the Animation Toolbar.
  4. Click Start () to animate the scenario.
  5. Click Reset () when finished.

Target object

The Target object () models a point of interest on the surface of the central body. The properties are identical to the Place () and Facility () objects.

  1. Insert a Target () object using the Define Properties () method.
  2. Select the Basic - Position page.
  3. Set the following:
    4. Option Value
    Latitude: 32.9 deg
    Longitude: -106.3 deg
  4. Click OK.
  5. Rename Target1 () to Missile_Tgt.

View in 3D

  1. Bring the 3D Graphics window to the front.
  2. Zoom To Missile_Tgt ().

    3. Missile Tgt in the White Sands SULF Area Target

  3. Zoom out so you can see both White_Sands-SULF () and Missile_Tgt ().

    4. You are going to launch a sounding rocket from White_Sands-SULF () and it impacts Missile_Tgt ().

Missile object

The Missile () object models the properties and behavior of a vehicle following an elliptical path that begins and ends at the surface of the central body.

  1. Insert a Missile () object using the Insert Default () method.
  2. Rename Missile1 () to Sounding_Rocket.
  3. Open Sounding_Rocket's () properties ().
  4. Select the Basic - Trajectory page.
  5. Notice the Propagator is Ballistic.

Ballistic Propagator

The Ballistic Propagator defines an elliptical path that begins and ends at the Earth's surface. Specifying a fixed flight time, initial velocity or altitude can further refine the shape of the trajectory. Start by launching the missile from White_Sands-SULF () and impacting Missile_Tgt ().

  1. Clear the check box next to White_Sands_SULF () in the Object Browser.

    2. The Facility () object is still there and can be used analytically. Disabling the option disables it visually.

  2. Return to Sounding_Rocket's () properties () Basic - Trajectory page.
  3. Set the following:
    4. Option Value
    Launch Latitude - Geodetic 33.7212 deg
    Launch Longitude -106.7364 deg
    Launch Altitude 4750 ft (compensate for terrain)
    Change Fixed Delta-V to Fixed Apogee Alt 100 km
    Impact Latitude - Geodetic 32.9 deg
    Impact Longitude -106.3 deg
    Impact Altitude 3910 ft (compensate for terrain)
  4. Click OK.

View in 3D

  1. Bring the 3D Graphics window to the front.
  2. Zoom To Sounding_Rocket ().

    3. Sounding Rocket and Target

  3. Click Increase () Time Step in the Animation Toolbar to set the X Real Time Multiplier to 8.00.
  4. Click Start () to animate the scenario.
  5. Click Reset () when finished.

Place object

The Place () object models a point of interest on the surface of the central body.

Search by Address Method

  1. Insert a Place () object using the Search by Address () method.

    2. The Insert by Address option requires an internet connection. If you do not have an internet connection you can select the Define Properties option and set the lat/lon manually to 38.8409, - 105.0423.

  2. Type Pikes Peak in the Enter an address or other search criteria below: field when the STK: Insert by Address dialog box opens.
  3. Select Pikes Peak, CO in the Results: list.
  4. Click Insert. Place(s).
  5. Click Close to close the STK: Insert by Address dialog box.
  6. Zoom To Pikes_Peak_CO().
  7. Bring the 3D Graphics window to the front.

Search by Address / Pikes Peak Colorado

Insert Default Method

  1. Insert a Place () object using the Insert Default () method.
  2. Zoom To Place1 ().

    3. The Place () object may have a different number than the one in this tutorial. If you have entered other Place () objects prior to this, it may be something like Place2, Place3, etc.

  3. Bring the 3D Graphics to the front.

    4. A Place () object or a Facility () object will default to AGI Headquarters.

    Place Object Insert Default / AGI Headquarters

From City Database Method

  1. Insert a Place () object using the From City Database () method.
  2. Type Exton in the Name: field when the Search Standard Object Data dialog box opens.
  3. Click Search.
  4. Right-click on Exton/Pennsylvania in the Results: list.
  5. Select Insert Selected Item. This is another way to insert an item from the database.
  6. Click Close to close the Search Standard Object Data dialog box.

View in 3D

  1. Bring the 3D Graphics window to the front.
  2. Using your right mouse button or the mouse scroll wheel, zoom out from Place1 () until you see Place1 () and Exton ().

    3. Exton and Place1

    The From City Database method inserts the city using a centroid for the city area. If you need an exact location, use the Search by Address method or the following procedure.

Move Place1 by Clicking on the 2D Graphics Window

When you have a Facilty (), Place () or Target () object's properties open and you are on the Basic - Position page, you can move the object to a desired location by clicking on the 2D Graphics window. Move Place 1 () to the top let corner of the building where a sensor is located.

  1. Bring the 2D Graphics window to the front.
  2. Zoom to Place1 (). Remember, in the 2D Graphics window, you have to use your mouse to center and zoom to an object!
  3. Open Place1's () properties ().
  4. Return to the 2D Graphics window.
  5. Click the upper left corner of the building.

    6. Move Place1 on 2D Graphics Window

Set the height above ground of the facility

Set Place1 () 30 feet above the ground to model the sensor on the roof of the building.

  1. Return to Place1's () properties ().
  2. Enter 30 ft in the Height Above Ground: field.
  3. Click OK.

    4. All these steps were purposeful. You moved Place1 () to the upper left corner of the building because there is a sensor located at that spot. Furthermore, the building's roof is 30 feet above the ground. These steps were used to put the Place1 () in the correct location for future analysis in STK.

3D Object Editor

Use the 3D Object Editor to define and modify the position of an area target, facility, place, aircraft, ground vehicle, ship, or target in the 3D Graphics window.

  1. Bring the 3D Graphics window to the front.
  2. Click Orient from Top () in the 3D Graphics window toolbar.
  3. Zoom To Place1 ().
  4. Open the 3D Editing Object shortcut menu.
  5. Select Place/Place1.
  6. Click Object Edit Start/Accept () to start the editing process.
  7. Press the Shift key on your keyboard.
  8. Left-click in the center of the building.

    9. This is an easy way to add or move a place object. However, that's not where we want this object to go this time.

  9. Click Object Edit Cancel () because that is not where you want to object to go.

Fix the location

  1. Click Object Edit Start/Accept () to start the editing process.
  2. Press the Shift key on your keyboard.
  3. Left-click in the upper right hand corner of the building.
  4. Click Object Edit Start/Accept () to accept the change.

Move Place1 with the 3D Object Editor

Ship object

The Ship () object models the properties and behavior of a ship. Like the Aircraft () object and the Ground Vehicle () object, the Ship () object uses the Great Arc propagator. You can use the 3D Object Editor to create waypoints for the Ship () object.

  1. Insert a Ship () object using the Insert Default () method.
  2. Rename Ship1 () to MyShip.

View in 3D

  1. Bring the 3D Graphics window to the front.
  2. In the 3D Graphics window toolbar, click Home View ().
  3. In the 3D Graphics window toolbar, use Zoom In () to recenter your view off the east coast of the United States.

    4. East Coast of the United States Centered

3D Object Editing of Ship

  1. Open the 3D Editing Object shortcut menu.
  2. Select Ship/MyShip.
  3. Click Object Edit Start/Accept () to start the editing process.
  4. Press the Shift key on your keyboard.
  5. Left-click somewhere in the Atlantic Ocean off the north east coast of the United States.
  6. Press the Shift key on your keyboard.
  7. Left-click somewhere in the Atlantic Ocean off the south east coast of the United States. MyShip () will move north to south.
  8. Click Object Edit Start/Accept () to accept the change.

My Ship Properties

Since you're using streaming terrain (Terrain Server), its a good idea to reference Mean Sea Level for the ship.

  1. Open MyShip's () properties ().
  2. Select the Basic - Route page when the Properties Browser opens.
  3. Open the Reference: shortcut menu in the Altitude Reference frame.
  4. Select MSL.

    5. You can make any other changes such as speed as required.

  5. Click OK.

Modify a Waypoint

You want to modify a waypoint. You can use the 3D Object Editor.

  1. Bring the 3D Graphics window to the front.
  2. Zoom To MyShip ().
  3. Click Orient from Top () in the 3D Graphics window toolbar.
  4. Ensure Ship/MyShip is still showing in the 3D Object Editing shortcut menu.
  5. Click Object Edit Start/Accept () to start the editing process.

    6. MyShip Waypoint

  6. Place your cursor on MyShip's () waypoint.
  7. Hold down your left mouse button to drag MyShip's () waypoint to a different location.
  8. Click Object Edit Start/Accept () to accept the change.

View in 3D

Just like you did with the Ground Vehicle () object and the Aircraft () object, you can watch your scenario animate in real time:

  1. Click Start () in the Animation Toolbar to animate your scenario.
  2. Click Reset () when finished.

Sensor object

The Sensor () object models the field-of-view and other properties of a sensing device attached to another STK object.

  1. Insert a Sensor () object using the Insert Default () method.
  2. Select White_Sands-SULF () in the Select Object dialog box.
  3. Click OK.
  4. Rename Sensor1 () to WS_Sensor.

View in 3D

  1. Bring the 3D Graphics window to the front.
  2. Zoom To White_Sands-SULF ().
  3. Select the check box next to White_Sands-SULF () in the Object Browser. This will turn it back on visually.

White Sands Situational Awareness

If you're going to use the Sensor () object analytically to include a report containing an azimuth, remember the following: A report such as an Azimuth, Elevation, Range (AER) report is calculated with respect to the parent object. You will learn more about AER reports in Lesson Three: Access Reports and Graphs.

  1. Open White_Sands-SULF's () properties ().
  2. Select the 3D Graphics - Vector page.
  3. Select the Axes tab.
  4. Click Add...

    5. This opens the Vector Geometry Tool (VGT) which is part of the STK's Analysis Workbench capability. VGT contains components that define location, pointing, and orientation in 3D space.

  5. Select White_Sands-SULF () in the Object List on the left.
  6. Select Body () in the Installed Components folder in the Components for: White_Sands-SULF list on the right.
  7. Click OK.
  8. Click OK to accept your changes and to close White_Sands-SULF's () properties ().

View in 3D

  1. Return to the 3D Graphics window.
  2. Use your mouse to zoom in on White_Sands-SULF () to view the body axes.

Facility Object Body Axes

Sensor Orientation

The Sensor () object can see out to the stars. Using the body axes on the parent object, you can visualize where the sensor is looking. Set up WS_Sensor () so that it covers a field-of-view of 180 degrees and has a limited range of 1000 kilometers (km).

  1. Open WS_Sensor's () properties ().

    2. A Simple Conic sensor pattern (default type) is defined by a simple cone angle. In this case it defaults to a cone half angle of 45 degrees which means you have a 90 degree field-of-view.

    Cone Half Angle

  2. Select the Basic - Definition page.
  3. In the Simple Conic frame, enter 90 deg in the Cone Half Angle: field.
  4. Click Apply.

Sensor Pointing

The Pointing page enables you to set parameters to determine how a sensor is aimed. The Fixed pointing type allows you to specify the orientation of the sensor with respect to the body frame of your parent object. While the sensor remains fixed relative to the parent object, motion of the parent object changes the direction in which the sensor is pointing.

  1. Select the Basic - Pointing page.
  2. Notice that the Pointing Type: defaults to Fixed.

Understanding the Fixed Type

Facility, place, and target objects have body-fixed coordinate axes, which align the x-axis along local horizontal North direction, the y-axis along local horizontal East direction, and the z-axis along local Nadir direction (i.e., opposite to local surface normal). Therefore:

The Sensor () object defines azimuth based off the Facility () object's x axis and elevation as an angle measured from the x-y plane toward the negative z-axis; i.e., in a manner that makes positive elevation look up from the local horizontal plane.

About Boresight - Rotate:

  • z axis is aligned with the boresight.
  • y axis runs along the intersection of the sub-component reference xy plane and the parent body XY plane.
  • xy plane is perpendicular to the sensor or antenna boresight so that it forms an azimuth angle with the parent reference Y axis

Basic Constraints

Basic Constraints enable you to impose standard access constraints on an object.

  1. Select the Constraints - Basic page.
  2. Note the currently used constraints.
    • Line of Sight: Access to the object is limited to lines of sight not obstructed by the ground. In this instance, the central body.
    • Field-of-View (Sensors only): Access is denied if the associated object is not within the field-of-view as defined by the angle settings for the sensor.
  3. Select the Max: check box in the Range frame.
  4. Enter 1000 km Max: field.

    5. Range is measured as the distance between the two objects.

  5. Click OK.

View in 3D

  1. Bring the 3D Graphics window to the front.
  2. Zoom out until you can see WS_Sensor's () field-of-view.

    3. Sensor Object field-of-view

    WS_Sensor () only sees other objects when they are inside of or passing through its field-of-view.

Rectangular Sensor Object

Rectangular sensor types are typically used with satellites or aircraft for modeling the field-of-view of instruments such as push broom sensors and star trackers.

  1. Insert a Sensor () object using the Insert Default () method.
  2. Select RGT_Sat () in the Select Object dialog box.
  3. Click OK.
  4. Rename the Sensor () Sat_Sensor.
  5. Bring the 3D Graphics window to the front.
  6. Zoom To RGT_Sat ().
  7. Use your mouse to zoom out until you can see Sat_Sensor's () field of view.

    8. Unlike the Sensor () object attached to a Facility () object which points up, a Sensor () object attached to an airborne object (e.g. Satellite () object) points down.

Define the Sensor's properties

  1. Open Sat_Sensor's () properties ().
  2. Select the Basic - Definition page:
  3. Set the following:
    4. Option Value
    Sensor Type: Rectangular
    Vertical Half Angle: 20 deg
    Horizontal Half Angle: 10 deg
  4. Click Apply.
  5. Bring the 3D Graphics window to the front.
  6. Change the view so that the sensor is visible between the satellite and the surface of the Earth.

Rectangular Sensor

Redirect the Sensor

The sensor is pointing straight down with its boresite directed along the satellite's body Z. By default, when you attach an object onto a satellite, the object points in the body +Z direction. Here, you will point the sensor in a different direction.

  1. Return to Sat_Sensor's () properties ().
  2. Select the Basic - Pointing page.
  3. Set the following:
    4. Option Value
    Azimuth: 270 deg
    Elevation: 60 deg
  4. Click Apply.

    5. The first thing you may notice when you click Apply is that the Azimuth setting went from 270 deg to -90 deg. You see this throughout STK. The original Azimuth of zero (0) deg placed the sensor's boresite along the body X. The original Elevation setting of 90 deg swung that boresite so that it was pointing down along the body Z. So, if you set both the Azimuth and Elevation settings to zero (0) deg, the sensor's boresite would be pointing along the satellite's orbital path.

  5. Click OK.

View in 3D

  1. Bring the 3D Graphics window to the front.

    2. Redirected Boresite

    The boresite is now pointing along the negative body Y (Azimuth: 270 deg OR -90 deg) and the boresite is elevated 30 degrees (Elevation: 60 deg) from the satellite's body Z.

  2. Select Normal Animation Mode () in the Animation Toolbar.
  3. Click Decrease Time Step () to set the Time Step: to one (1) sec.
  4. Click Start () to animate the scenario. Any objects that pass through the sensor's field-of-view will be seen by the sensor.
  5. Click Reset () when finished.
  6. Save () your work.

Summary

This tutorial began with understanding the purpose of the Insert STK Objects tool. Next, the Scenario () object and its properties were discussed. This was followed by an in depth discussion of commonly used object in the Insert STK Objects tool, how to insert objects into the scenario, and which method to use during that insertion.

Continue to Lesson Three: Access Reports and Graphs.

On your own

Open the Insert STK Objects tool and select Edit Preferences. Enable the following objects:

  • Launch Vehicle: The Launch Vehicle () object models the properties and behavior of a vehicle that follows an ascent trajectory from a launch point to an orbit insertion point.
  • Line Target: The Line Target () object models a linear region of interest on the surface of the central body.
  • Planet: The Planet () object models orbital and other properties of a planet, a moon, an asteroid or the sun.
  • Star: The Star object models position, proper motion, annual parallax, visual magnitude and other properties of a star.

Explore the capabilities of these additional objects.