Source code for irfpy.cy1orb.subsolar

''' Module to calculate the subsolar point.
'''

import irfpy.util.utc as utc
from irfpy.cy1orb import lseme
import numpy as np

def subsolar(jd):
    ''' Return a subsolar point position in ME frame.

    >>> import datetime
    >>> print(subsolar(datetime.datetime(2010, 1, 1)))   # doctest: +ELLIPSIS,+NORMALIZE_WHITESPACE
    [1732.257648  -140.8436964   -9.504253 ]
    '''
    Rm = 1738.
    vec = (Rm, 0., 0.)
    return lseme.lse2me(jd, vec)

def subsolar_asdegrees(jd):
    ''' Return a subsolar point position as (longitude, latitude) in ME.

    >>> import datetime
    >>> subsol = subsolar(datetime.datetime(2010, 1, 11))
    >>> print('{0[0]:.3f} {0[1]:.3f} {0[2]:.3f}'.format(subsol))   # doctest: +ELLIPSIS,+NORMALIZE_WHITESPACE
    -1024.471 -1403.960 0.533
    >>> print(subsolar_asdegrees(datetime.datetime(2010, 1, 10)))   # doctest: +ELLIPSIS,+NORMALIZE_WHITESPACE
    (-113.94..., -0.00889...)
    '''
    pos = subsolar(jd)
    dist = np.sqrt((pos * pos).sum())
    lons = np.rad2deg(np.arctan2(pos[1], pos[0]))
    lats = np.rad2deg(np.arcsin(pos[2] / dist))
    return (lons, lats)