Target Sequence

Use a Target Sequence as a structural element to define maneuvers and propagations in terms of the goals they are intended to achieve.

Setting up a target sequence

Define a target sequence using these three steps:

  1. Add segments to the target sequence.
  2. Define its profiles.
  3. Configure the target sequence.

A target sequence runs the segments nested within it and applies profiles to the run according to its configuration. You can apply the results of a target sequence to the MCS to produce a trajectory that meets the goals you need to achieve.

Adding segments

You can nest any MCS segment within a target sequence, including another target sequence. The segments within a target sequence are defined in the same manner as they are in the MCS itself or in other sequences.

Defining profiles

The actions that the target sequence takes are determined by the profiles that are defined for it. There are three basic types of profiles: search, segment configuration, and Lambert. Search profiles define goals and change variables to achieve them. Segment configuration profiles change segments within the target sequence. Lambert profiles solve one or several instances of Lambert's problem and have the capability to change segments within the target sequence based on those solutions.

It is possible for a segment configuration profile to make a change to the MCS that deactivates a parameter targeted by a search profile.

The following are search profile types:

The following are segment configuration profile types:

There are two types of Lambert profiles:

Finally, there is one profile that you can design to act as either a search or a segment configuration profile:

You can add, copy, delete, and perform other actions on profiles by either right-clicking in the table that lists them or using the following toolbar buttons:

Button Name Function
Properties... This opens the properties window of the currently selected profile. You can also double-click a profile to open its properties window.
New... This opens the component selection window, in which you can select a profile to assign to the segment.
Cut This removes the selected profile from the list and copies it to the clipboard.
Copy This makes a copy of the selected profile to the clipboard.
Paste This inserts a copy of the profile that is on the clipboard.
Delete This deletes the selected profile.
Duplicate This creates a copy of the selected profile and adds it to the list.

The Profiles table in the Target Sequence properties displays the following information for each profile that you have added to the Target Sequence:

  • Name - This is the name you gave to the profile or, if you do not provide one, the default name.
  • Reset - Click to reset the controls of the profile to the segments' values.
  • Apply - Click to apply the current values of the profile's controls, if it is a search profile. If it is a segment configuration profile, this applies the change specified.
  • Mode - This is the profile's mode of operation.
  • Status - This is a profile-specific status indicator.
  • User Comment - This is your description of the profile or, if you do not provide one, a default description.
The sequence invokes the profiles in the order in which they appear in this table. You can click the and arrows to change the order of the profiles.

Configuring the target sequence

You can configure a target sequence to execute in many different ways depending on the solution you are trying to achieve. The following table describes the parameters that define a target sequence.

ActionSelect one of these:
  • Run nominal sequence - runs the mission control sequence
  • Run active profiles ONCE - runs the profile with corrections applied to control parameters
  • Run active profiles - runs the mission control sequence allowing the active profiles to operate
When Profiles ConvergeSelect the action to carry out if targeting converges:
  • Run to RETURN and continue - Astrogator will run to the first Return segment in the sequence, then pass control to the next segment after this target sequence. Often, the only Return is at the end of the target sequence.
  • Run to RETURN and stop - Astrogator will run to the first Return segment and then stop running the MCS altogether.
  • Stop - Astrogator will stop the MCS as soon as the target sequence has converged.
Continue if profiles don't convergeSelect this to have the target sequence continue if a profile fails to converge; otherwise, the MCS will stop upon the failure of a search profile.
Reset inner targeters before each runSelect this to have the profiles of nested target sequences reset at the beginning of each run of the parent target sequence.
Apply Changes Click to apply the current values of search profiles' controls and the changes specified by the segment configuration profiles to the segments within the target sequence.
ResetClick to reset the controls of the search profiles to the segments' values.
Enable LoggingSelect to have the sequence record run history information to a log file. You must enable logging in the MCS Options window before you can enable it for individual target sequences.

Nesting target sequences

If you nest one target sequence into another, you can use the outer targeter to adjust the values of the inner targeter. The values of Equality Constraints that you set for the inner targeter are automatically available as Control Parameters for the outer targeter. However, for the outer targeter to be able to converge, the following conditions must be met:

  • The Action field of the inner targeter must be set to 'Run active profiles'.
  • The Mode for the inner target profile must be set to 'Iterate'.
  • The perturbation for the outer control must be greater than the tolerance of the inner constraint.

For example, suppose that you want to achieve lunar orbit and want to use b-plane parameters as Control Parameters, but would like to have those be the result of targeting from other parameters, such as launch time and coast duration. You can set up an inner target sequence to target the b-plane parameters and an outer one to target the lunar orbit parameters (e.g., radius of periapsis and inclination). If the above conditions on the setup of the inner targeter are met, the outer targeter will vary the Equality Constraints (the b-plane parameters) of the inner targeter to achieve the desired end result.

Target sequence status windows

During the execution of one or more target sequences, target status windows appear and provide valuable information on their progress. You can close these windows individually, or you can clear them all at once by left-clicking the target icon () in the upper-right corner of one of the windows and selecting "Close All Targeting Status Windows."