Golden Section Search Profile
The Golden Section Search profile uses a golden section search algorithm to find the minimum or maximum value of a given result. This profile is a single-parameter search profile, so it can only modify one control and find the extrema of one result. It modifies the control in order to find the minimum or maximum result value.
The Golden Section Search dialog box comprises of these tabs:
Variables
There are two types of variables in a golden section search profile:
- Control parameters (independent variables)
- Result parameters (dependent variables)
The golden section profile only runs if you select one active control and one active result. You can then choose whether to minimize or maximize the result.
Control parameters (independent variables)
Any element of a nested MCS segment or linked component that you can use as an independent variable is marked by a target icon, 
. To select an element as an independent variable, click its target icon. A check mark appears over the target. Click the target again to clear the selection of that element.
You can select controls in two or more nested segments. In each segment, you can select as many controls as you want. Plugins publish their inputs to Astrogator, so you can also select these inputs as controls. To target an input, you may need to double-click it to open its properties dialog box. The target icon will appear next to any field that you can select. While you can select as many different controls as you want using the target check box, you can only enable one at a time in this profile.
The Restore nominal values as soon as target sequence completes MCS Option isolates changes in value. If the independent variable is an element of a linked component, this option has an important effect. Astrogator will only apply the changed value of the element to subsequent segments within the same target sequence. Segments that are outside the target sequence will use the value of the element at the beginning of the MCS. If you apply corrections after running the MCS, then on the next run all segments in the MCS will use the value produced by the target sequence.
Each control that you select is listed in the Control Parameters section of the Variables tab with the following information, some of which you can modify:
| Control Parameters | |
|---|---|
| Information item | Description |
| Use | Select this option to enable the element as a control parameter. You can only enable exactly one control for this profile. |
| Object | Identifies the segment or component that the element belongs to. |
| Name | This is the name of the element within the object. |
| Current Value | Shows the current value of the element. |
| Lower Bound | Specify the smallest possible value for the control to search over. |
| Upper Bound | Specify the largest possible value for the control to search over. |
| Custom Display Unit | Select this option to use a custom unit for the element in the status window and graphs. |
| Display Unit | Select the unit to be displayed if you have selected Custom Display Unit. |
Graphs cannot display degrees-minutes-seconds (DMS) or hours-minutes-seconds (HMS) angle units and will use the scenario unit instead.
If you have two or more controls, select Hide Inactive to hide the elements that you did not select.
The Tolerance field appears below the control parameters list. This field controls the convergence criterion for the golden section search algorithm. The algorithm terminates when its internal upper and lower bounds are within the specified tolerance. A smaller tolerance leads to longer convergence times, and a larger tolerance leads to shorter convergence times.
Result parameters (dependent variables)
Results are defined in terms of Calculation Objects. To select results for a nested MCS segment, select the segment and then click . In the User-Selected Results dialog box, select the Calculation Objects to use from the Available Components list.
Each result parameter that you select is listed in the Available Results section of the Variables tab with the following information, some of which you can modify:
| Result Parameters | |
|---|---|
| Information item | Description |
| Use | Select this option to enable the element as a variable. You can only enable exactly one result for this profile. |
| Object | Identifies the segment or component that the element belongs to. |
| Name | This is the name of the element within the object. |
| Current Value | This is the element's final value from the last run of the profile. If you have not run the profile yet, this value is the same as the initial value. You can copy the value in this field to the clipboard by right-clicking it and selecting Copy. |
| Desired Operation | Choose whether the profile should minimize or maximize the result. |
| Custom Display Unit | Select this option to use a custom unit for the element in the status window and graphs. |
| Display Unit | Select the unit to be displayed if you have selected Custom Display Unit. |
Graphs cannot display DMS or HMS angle units and will use the scenario unit instead.
If you have two or more results, select Hide Inactive to hide the element that are not selected.
Additional options
The general options that appear above the list of available controls are:
| Option | Description |
|---|---|
| Maximum Iterations | Specify the maximum number of iterations this profile will execute. Each iteration contains two function evaluations. If the internal upper and lower bounds for the extremum are not within the tolerance, it will stop after the last iteration. |
| Display Convergence Status Window | Select this option to have Astrogator display a status window during the targeting run. The window will report the status of the targeting effort as the current value of the result. Click in the status window's title bar to manage its display |
Log
The Log tab contains a log of each iteration for the previous run of the Golden Section Search profile. It contains some general information about the run, including control and result parameters and their corresponding units, the tolerance, upper and lower bounds, and the specified operation. It also contains the control and result values for each iteration.
Graphs
The Graphs tab comprises controls that you can use to create and view graphs of the profile's performance. The upper pane contains a table of the graphs defined for the profile. The Graph Properties pane displays the collection of properties that you can use to define each graph. Select a graph in the table in the upper pane to view and define its properties here.
Graphs table
Using the toolbar, you can create new graphs or cut, copy, paste, or delete them.
| Button | Name | Function |
|---|---|---|
|
New... | Insert a new graph with default properties settings. |
|
Cut | Move the selected graph from the list to the clipboard. |
|
Copy | Copy the selected graph to the clipboard. |
|
Paste | Insert a copy of the graph that is on the clipboard. |
|
Delete | Delete the selected graph. |
The graphs table displays the name and description of each graph. Select Generate on run if you want Astrogator to generate the graph each time that it runs the MCS. You can right-click a graph to select the same commands that are available in the toolbar.
Graph properties
Each graph can display the values of any number of the active Controls and Results defined for the profile against an X axis of the number of iterations performed or any single active Control or Result defined for the profile.
The Independent variable field defines the X axis of the graph. If the X axis is an active Control or Result, select Label Iterations if you want to label the points on the graph by their iteration numbers. If the X axis is one of the active Results and the profile results have a DesiredValue property, you can select Show Desired Value to display its goal. Likewise, if the results have a Tolerance property, you can select Show Tolerance Band to display the tolerance for the Desired Value.
The active Controls defined for the profile are listed in a table. You can customize how they are displayed in the graph by directly clicking the property fields.
| Property Field | Description |
|---|---|
| Name | This is the name of the element within the object. |
| Object | Identifies the segment or component that the element belongs to. |
| Graph Value | Select this option to include the value. |
| Line Color | The color of line that will be used to represent the control's value. |
| Point Style | The style of marker used to represent iteration points along the control's line. |
| Y Axis | Select Y1 or Y2 to display a range of values suitable to the control on the left or right side, respectively, of the graph. |
The active Results defined for the profile are also listed in a table. You can customize how they are displayed in the graph by directly clicking the property fields.
| Property Field | Description |
|---|---|
| Name | This is the name of the Calculation Object selected as a result item. |
| Object | Identifies the segment or component that the result item belongs to. |
| Graph Option | Select this option to include the value. |
| Line Color | The color of line that will be used to represent the control's value. |
| Point Style | The style of marker used to represent iteration points along the control's line. |
| Y Axis | Select Y1 or Y2 to display a range of values suitable to the control on the left or right side, respectively, of the graph. |
| Show Tolerance Band | If the result has a Tolerance property, select this option to display the tolerance for the result's desired value. |
Click to produce the selected graph. To produce a report of the graph data, click .
Scripting
The Scripting tab contains an embedded instance of the Scripting Tool. If you enter a script here, Astrogator will execute it before running the sequence each time Astrogator runs the sequence. You can use parameters that are defined in the Scripting Tool as controls by the profile.
Since the golden section search algorithm has two function evaluations within each iteration, Astrogator will call the scripting tool twice in each iteration.