======
Frames
======

There are several frames used for Chandrayaan-1 SARA data analysis.

.. note::

        Apart from other mission's packages, Chandrayaan-1/SARA package does not rely on SPICE (18-09-13).
        This is because the SPICE has not been organized well by the project at the beginning,
        and the SARA team decided not to rely on not to hinder the data analysis.

        Therefore, the frame conversions need a bit of deep knowledge.


Definition
==========

- Spacecraft frame (SC): Fixed at spacecraft.
- CENA frame: Fixed at CENA. Fixed conversion to Spacecraft.
- CENA angles: Fixed at CENA, with azimuth and elevation angles.
- SWIM frame: Fixed at SWIM. Fixed conversion to Spacecraft.
- LSO: Lunar-Solar-Orbiting.
        - x-axis: From Moon to Sun
        - y-axis: :math:`\vec{z}\times\vec{x}`
        - z-axis: In the ecliptic plane
- ME: Moon-fixed frame. Longitude, latitude system equivalent to the Earth. Vector expression is also available (right-hand system).
        - (0, 0) for the average sub-earth point
        - Longitude eastward increasing.
        - Latitude northward increasing.


Conversion in between
=====================

========== ========== ======================================= ============================================
From       To         Convert                                        Matrix
---------- ---------- --------------------------------------- --------------------------------------------
SC         CENA       :func:`irfpy.cena.frame.sc2cena`        :func:`irfpy.cena.frame.get_sc2cena_matrix`
CENA       SC         :func:`irfpy.cena.frame.cena2sc`        :func:`irfpy.cena.frame.get_cena2sc_matrix`
CENA_Angle CENA       :func:`irfpy.cena.frame.angles2cena`    N/A
CENA       CENA_Angle :func:`irfpy.cena.frame.cena2angles`    N/A
                      :func:`irfpy.cena.frame.cena2angles2`
SC         LSE        :func:`irfpy.cy1orb.pvat2.getlsevec`    :func:`irfpy.cy1orb.pvat2.get_sc2lse_matrix`
LSE        SC         :func:`irfpy.cy1orb.pvat2.getscvec`     :func:`irfpy.cy1orb.pvat2.get_lse2sc_matrix`
LSE        ME         :func:`irfpy.cy1orb.lseme.lse2me`       :func:`irfpy.cy1orb.lseme.lse2me_matrix`
ME         LSE        :func:`irfpy.cy1orb.lseme.me2lse`       :func:`irfpy.cy1orb.lseme.me2lse_matrix`
========== ========== ======================================= ============================================


.. digraph:: frame_conversion

        SC -> CENA [label="irfpy.cena.frame.sc2cena"]
        CENA -> SC [label="irfpy.cena.frame.cena2sc"]
        CENA_Angle -> CENA [label="irfpy.cena.frame.angles2cena"]
        CENA -> CENA_Angle [label="irfpy.cena.frame.cena2angles\nirfpy.cena.frame.cena2angles2"]
        SC -> LSE [label="irfpy.cy1orb.pvat2.getlsevec"]
        LSE -> SC [label="irfpy.cy1orb.pvat2.getscvec"]
        LSE -> ME [label="irfpy.cy1orb.lseme.lse2me"]
        ME -> LSE [label="irfpy.cy1orb.lseme.me2lse"]
        SC -> SWIM [label="TO BE CHECKED"]
        SWIM -> SC [label="TO BE CHECKED"]
        SWIM -> SWIM_Angle [label="TO BE CHECKED"]
        SWIM_Angle -> SWIM [label="TO BE CHECKED"]

.. todo::

        Update the information with SWIM frame