========================================
How to load the JUICE orbit and attitude
========================================

.. toctree::

        spice_kernel_locations

Loading orbit
=============


1. Setup the SpiceyPy.

.. code-block:: sh

        pip install "git+https://github.com/AndrewAnnex/SpiceyPy.git"


2. Prepare kernels.

Needed kernels are

	- 'de421.bsp'
	- 'jse_111130.tf'
	- 'jup230l.bsp'
	- 'mantra_juice_jup_a5d_141a_lau_c5e_016.bsp'
	- 'naif0009.tls'
	- 'pck00010.tpc'

3. Newly create a file by text editor as follows, and save it as "juice.mk".

::

        KPL/MK
        \begindata
          PATH_VALUES = ( '.' )
          PATH_SYMBOLS = ( 'KERNELS' )
          KERNELS_TO_LOAD = (
	        '$KERNELS/de421.bsp'
	        '$KERNELS/jse_111130.tf'
	        '$KERNELS/jup230l.bsp'
	        '$KERNELS/mantra_juice_jup_a5d_141a_lau_c5e_016.bsp'
	        '$KERNELS/naif0009.tls'
	        '$KERNELS/pck00010.tpc'
          )


4. Start python!

.. code-block:: sh

        ipython


5. Initialize the JUICE spice kernels.

.. code-block:: python

        >>> from irfpy.juice import jspice as js
        >>> js.init(mkkernel='./juice.mk')


6. To get the spacecraft position seen from some body in a specific frame can be retrieved by
:func:`irfpy.juice.jspice.get_position` function.

.. code-block:: python

        >>> import datetime
        >>> t = datetime.datetime(2031, 5, 10, 1, 20, 0)    # 2031-05-10T01:20:00
        >>> js.get_position(t, target='JUICE', origin='JUPITER', frame='JSE')
        array([ 753430.83362161, -790039.59240909,   17587.96798178])

7. To get the spacecraft velocity vector seen from some body, use :func:`irfpy.juice.jspice.get_velocity` function.

.. code-block:: python

        >>> js.get_velocity(t, target='JUICE', origin='JUPITER', frame='JSE')
        array([  4.98295226,  11.23419393,   3.6634433 ])

8. To get the conversion matrix, use :func:`irfpy.juice.jspice.get_conversion_matrix` function.

.. code-block:: python

        >>> js.get_conversion_matrix(t, from_frame='JSE', to_frame='IAU_JUPITER')
        array([[ 0.26772223,  0.96334943, -0.01681298],
               [-0.96242748,  0.26656293, -0.05174498],
               [-0.04536678,  0.03003456,  0.99851879]])