.. _scenarioFormationMeanOEFeedback:

scenarioFormationMeanOEFeedback
===============================

Overview
--------

This script sets up a formation flying scenario with two spacecraft. The deputy spacecraft keeps a given
mean orbital element difference based on Lyapunov control theory.

This script is found in the folder ``xmera/examples`` and executed by using::

      python3 scenarioFormationMeanOEFeedback.py

The simulation layout is shown in the following illustration. Two spacecraft are orbiting the earth at
close distance. Only :math:`J_2` gravity perturbation is included. Each spacecraft sends a :ref:`simpleNav`
output message of type :ref:`NavAttMsgPayload` message at a certain period
to :ref:`meanOEFeedback`, where mean orbital element difference is calculated and necessary control force is output to
extForceTorque module.

.. image:: /_images/static/test_scenarioFormationMeanOEFeedback.svg
   :align: center


Illustration of Simulation Results
----------------------------------

::

    show_plots = True, useClassicElem = True

In this case, target orbital element difference is set based on classical orbital element.
This resulting feedback control error is shown below.


.. image:: /_images/Scenarios/scenarioFormationMeanOEFeedback11.svg
   :align: center

::

    show_plots = True, useClassicElem = False

In this case, target orbital element difference is set based on equinoctial orbital element.
This resulting feedback control error is shown below.

.. image:: /_images/Scenarios/scenarioFormationMeanOEFeedback20.svg
   :align: center