Source code for irfpy.mars.mars_calendar

""" Martian calendar.

https://en.wikipedia.org/wiki/Timekeeping_on_Mars

See also https://irfpy.irf.se/projects/spice/api/api_irfpy.spice.spicetools.html

.. tip::

    To get the Ls (solar longitude), you can use SPICE function ``lspcn``.

    .. code-block:: python

        import datetime, spiceypy as spice, numpy as np
        ### Kernels should be loaded.
        spice.furnsh('...')   # Needed kernels should be loaded

        ### Or maybe for Mars, it is easier to install ``irfpy.aspera`` and
        # from irfpy.mexpvat import mexspice as ms
        # ms.init()
        t = datetime.datetime(2019, 2, 26, 0, 0, 0)
        et = spice.utc2et(t.strftime('%FT%T'))
        ls = np.rad2deg(spice.lspcn('MARS', et, 'NONE'))
        print('t:', t)
        print('et:', et)
        print('Ls:', kls)
"""

myear_per_sols = 668.5991
sol_per_secs = 88775.244147
myear_per_secs = myear_per_sols * sol_per_secs

def jdtt2msd(jd_tt):
    r""" Convert Julian Day in Terrestrial Time to MSD (Mars Sol Date)

    https://en.wikipedia.org/wiki/Timekeeping_on_Mars#Formulas_to_compute_MSD_and_MTC

    :param jd_tt: Julian day in Terrestrial Time.
        You may get the JD_TT from SPICE.

    .. math::

        MSD = \frac{JD_{TT} - 2405522.0028779}{1.0274912517}

    .. note::

        To convert the UTC to TT, the following SPICE functions are used.

        .. code-block:: python

            > import spiceypy as spice
            > spice.furnsh('NAIF0012.TLS')    # Furnsh the latest TLS.
            > t = datetime.datetime(2019, 2, 24, 15, 9, 12)
            > et = spice.str2et(t.strftime('%FT%T'))
            > jd_tt = spice.unitim(et, 'ET', 'JDTDT')    # TDT is approximately the same as TT
            > print(jd_tt)
            2458539.1321896296

    >>> jd_tt = 2458539.1321896296
    >>> msd = jdtt2msd(jd_tt)
    >>> print('{:.8f}'.format(msd))
    51598.61869774
    """
    msd = jd_tt - 2405522.0028779
    msd = msd / 1.0274912517

    return msd


def msd2jdtt(msd):
    r""" Convert MSD to Juliand Day (Terrestrial Time)

    :param msd: Mars Sol Date (floating point)
    :returns: Julian day (TT)

    >>> msd = 51598.618697737846
    >>> jd_tt = msd2jdtt(msd)
    >>> print('{:.8f}'.format(jd_tt))
    2458539.13218963
    """

    _msd = msd * 1.0274912517
    jd_tt = _msd + 2405522.0028779

    return jd_tt


def jdtt2mtc(jd_tt):
    r""" Convert Julian Day in Terrestrial Time to MSD + MTC.

    :param jd_tt: Julian day in Terrestrial Time.
        You may get the JD_TT from SPICE.
    :returns: A tuple, (MSD, MTC_hr, MTC-min, MTC-sec)

    .. math::

        MSD &= \frac{JD_{TT} - 2405522.0028779}{1.0274912517}  \\
        MTC &= (MSD % 1) \times 24 hr

    .. note::

        Please find :meth:`jdtt2msd` to convert the UTC time to TT time.

    >>> jd_tt = 2458539.1321896296       # UTC 2019-02-24T15:09:12
    >>> msd, hr, mn, se = jdtt2mtc(jd_tt)
    >>> print('{:d} {:d} {:d} {:.6f}'.format(msd, hr, mn, se))
    51598 14 50 55.484550

    """
    msd = jdtt2msd(jd_tt)

    msd_int = int(msd // 1)

    msd_frac = (msd % 1)

    msd_frac *= 24
    mtc_hr = int(msd_frac)
    msd_frac -= mtc_hr
    msd_frac *= 60
    mtc_mn = int(msd_frac)
    msd_frac -= mtc_mn
    msd_frac *= 60
    mtc_se = msd_frac

    return (msd_int, mtc_hr, mtc_mn, mtc_se)