.. _issue_yaw_steering:

====================
Yaw steerling impact
====================

After the selection of PEP, an issue on the possible yaw-steering operation
of JUICE spacecraft popped up.  (March 2013).


Background
==========

Not very clear to me, but possible sun-illumination of the spacecraft
may impact on power issues, so that a possible yaw-steering discussion has been
initiated by ESA.

No matter what has been thought by ESA, we PI team is requested to
investigate the possible impact on our science.

Frankly speaking, two possible impacts can be thought.
JNA field of view and the pitch angle.


Impact on JNA field of view
===========================

The JNA field of view analysis is done in ``../../../src/scripts/apps120816_flyover/flyover_mini.py``,
:mod:`apps120816_flyover.flyover` module.

On 130325, I have started to implement a new "yaw-steered" version of flyover, namely,
:mod:`apps120816_flyover.flyover_yaw`.

Here the assumption of continuous steering with proportional to the latitude is made.
Also, constant version is also added to get an idea.

A sample output is

.. image:: ../../../src/scripts/apps120816_flyover/flyover_yaw_70steer.png
   :width: 90%

A keynote summary is also made, but it is too big size. Therefore you can only
ask to YF with referencing the file name as follows.
``130324-YawSteeling/pyana.pep/src/scripts/apps120816_flyover/flyover_yaw_v1.key``


Yaw-steering attitude
=====================

The attitude is calculated from self-developed module.  See :ref:`definition_of_frames`.
The :class:`pyana.pep.pep_attitude.NadirLookingSc` provides the nominal **nadir looking
spacecraft coordinates**.
A new class, :class:`pyana.pep.pep_attitude.NadirLookingYawSteeringSc` is implemented.
This provides the **yaw-steering nadir looking spacecraft**.