Van Valkenburg (Ph.D., Stanford University, 1952) was Grainger Professor of Electrical Engineering at the University of Illinois from 1982 until his retirement in 1988. He was a member of the Dean's Advisory Board at Purdue University, the Advisory Board at the University of California at Santa Barbara, and the Board of Directors of. View Notes - Chapter 3 from MAC 2311 at University of North Florida. Section 3.1 - The Derivative and the Tangent Line Problem Consider the following picture: The slope of the secant line.
GMAT offers multiple ways to design and execute your mission. The two primary interfaces are the graphical user interface (GUI) and the script interface. These interfaces are interchangeable and each supports most of the functionality available in GMAT. When you work in the script interface, you are working in GMAT’s custom script language. To avoid issues such as circular dependencies, there are some basic rules you must follow. Below, we discuss these interfaces and then discuss the basic rules and best practices for working in each interface.
When you start a session, the GMAT desktop is displayed with a default mission already loaded. The GMAT desktop has a native look and feel on each platform and most desktop components are supported on all platforms.
When you open GMAT on Windows and click Run in the Toolbar, GMAT executes the default mission as shown in the figure below. The tools listed below the figure are available in the GMAT desktop.
Figure 3.1. GMAT Desktop (Windows)
The menu bar contains File, Edit, Window and Help functionality.
On Windows, the File menu contains standard Open, Save, Save As, and Exit functionality as well as Open Recent. The Edit menu contains functionality for script editing when the script editor is active. The Window menu contains tools for organizing graphics windows and the script editor within the GMAT desktop. Examples include the ability to Tile windows, Cascade windows and Close windows. The Help menu contains links to Online Help, Tutorials, Forums, and the Report An Issue option links to GMAT’s defect reporting system, the Welcome Page, and a Provide Feedback link.
The toolbar provides easy access to frequently used controls such as file controls, Run, Pause, and Stop for mission execution, and controls for graphics animation. On Windows and Linux, the toolbar is located at the top of the GMAT window; on the Mac, it is located on the left of the GMAT frame. Because the toolbar is vertical on the Mac, some toolbar options are abbreviated.
GMAT allows you to simultaneously edit the raw script file representation of your mission and the GUI representation of your mission. It is possible to make inconsistent changes in these mission representations. The GUI/Script Sync Status indicator located in the toolbar shows you the state of the two mission representations. See the the section called “GUI/Script Interactions and Synchronization” section for further discussion.
The Resources tab brings the Resources tree to the foreground of the desktop.
The Resources tree displays all configured GMAT resources and organizes them into logical groups. All objects created in a GMAT script using a Create command are found in the Resources tree in the GMAT desktop.
The Mission tab brings the Mission Tree to the foreground of the desktop.
The Mission tree displays GMAT commands that control the time-ordered sequence of events in a mission. The Mission tree contains all script lines that occur after the
Figure 3.2. Undocked Mission Tree
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The Output tab brings the Output Tree to the foreground of the desktop.
The Output tree contains GMAT output such as report files and graphical displays.
When you run a mission in GMAT, information including warnings, errors, and progress are written to the message window. For example, if there is a syntax error in a script file, a detailed error message is written to the message window.
The status bar contains various informational messages about the state of the GUI. When a mission is running, a Busy indicator will appear in the left pane. The center pane displays the latitude and logitude of the mouse cursor as it moves over a ground track window.
The GMAT script editor is a textual interface that lets you directly edit your mission in GMAT's built-in scripting language. In Figure 3.3, “GMAT Script Editor” below, the script editor is shown maximized in the GMAT desktop and the items relevant to script editing are labeled.
Figure 3.3. GMAT Script Editor
The GMAT desktop allows you to have multiple script files open simultaneously. Open script files are displayed in the Scripts folder in the Resources tree. Double click on a script in the Scripts folder to open it in the script editor. The GMAT desktop displays each script in a separate script editor. GMAT indicates the script currently represented in the GUI with a boldface name. Only one script can be loaded into the GUI at a time.
Script Status Box
The Script Status box indicates whether or not the script being edited is loaded in the GUI. The box says Active Script for the script currently represented in the GUI and Inactive Script for all others.
The Save,Sync button saves any script file changes to disk, makes the script active, and synchronizes the GUI with the script.
The Save,Sync,Run button saves any script file changes to disk, makes the script active, synchronizes the GUI with the script, and executes the script.
Save As Button
When you click Save As, GMAT displays the Choose A File dialog box and allows you to save the script using a new file name. After saving, GMAT loads the script into the GUI, making the new file the active script.
The Close button closes the script editor.
The GMAT desktop supports both a script interface and a GUI interface and these interfaces are designed to be consistent with each other. You can think of the script and GUI as different 'views' of the same data: the resources and the mission command sequence. GMAT allows you to switch between views (script and GUI) and have the same view open in an editable state simultaneously. Below we describe the behavior, interactions, and rules of the script and GUI interfaces so you can avoid confusion and potential loss of data.
GMAT allows you to simultaneously edit both the script file representation and the GUI representation of your mission. It is possible to make inconsistent changes in these representations. The GUI/Script Sync Status window located in the toolbar indicates the state of the two representations. On the Mac, the status is indicated in abbreviated form in the left-hand toolbar. Synchronized (green) indicates that the script and GUI contain the same information. GUI Modified (yellow) indicates that there are changes in the GUI that have not been saved to the script. Script Modified (yellow) indicates that there are changes in the script that have not been loaded into the GUI. Unsynchronized (red) indicates that there are changes in both the script and the GUI.
GMAT will not attempt to merge or resolve simultaneous changes in the Script and GUI and you must choose which representation to save if you have made changes in both interfaces.
The Save button in the toolbar saves the GUI representation over the script. The button on the script editor saves the script representation and loads it into the GUI.
Clicking the Save button in the toolbar saves the GUI representation to the script file; this is the same file you edit when working in the script editor. GUI items that appear in the Resources tree appear before the
BeginMissionSequence command in a script file and are written in a predefined order. GUI items that appear in the Mission Tree appear after the
BeginMissionSequence command in a script file in the same order as they appear in the GUI.
If you have a script file that has custom formatting such as spacing and data organization, you should work exclusively in the script. If you load your script into the GUI, then click Save in the toolbar, you will lose the formatting of your script. (You will not, however, lose the data.)
Clicking the Save,Sync button on the script editor saves the script representation and loads it into the GUI. When you work in a GMAT script, you work in the raw file that GMAT reads and writes. Each script file must contain a command called
BeginMissionSequence. Script lines that appear before the
BeginMissionSequence command create and configure models and this data will appear in the Resources tree in the GUI. Script lines that appear after the
BeginMissionSequence command define your mission sequence and appear in the Mission tree in the GUI. Here is a brief script example to illustrate:
Sat.X = 3000 sets the x-component of the Cartesian state to 3000; this value will appear on the Orbit tab of the Spacecraft dialog box. However, because the line
Sat.X = 1000 appears after the
BeginMissionSequence command, the line
Sat.X = 1000 will appear as an assignment command in the Mission tree in the GUI.
Each script file must contain one and only one
GMAT commands are not allowed before the
You cannot use inline math statements (equations) before the
BeginMissionSequence command in a script file. (GMAT considers in-line math statements to be an assignment command. You cannot use equations in the Resources tree, so you also cannot use equations before the
In the GUI, you can only use in-line math statements in an assignment command. So, you cannot type
3000 + 4000 or
Sat.Y - 8 in the text box for setting a spacecraft’s dry mass.
GMAT’s script language is case-sensitive.
For a more complete discussion of GMAT's script language, see the Script Language documentation.