boinor.earth.util
=================

.. py:module:: boinor.earth.util

.. autoapi-nested-parse::

   utility functions in module util of sub-package earth



Functions
---------

.. autoapisummary::

   boinor.earth.util.raan_from_ltan
   boinor.earth.util.get_local_sidereal_time


Module Contents
---------------

.. py:function:: raan_from_ltan(epoch, ltan=12.0)

   RAAN angle from LTAN for SSO around the earth.

   :param epoch: Value of time to calculate the RAAN for
   :type epoch: ~astropy.time.Time
   :param ltan: Decimal hour between 0 and 24
   :type ltan: ~astropy.units.Quantity

   :returns: **RAAN** -- Right ascension of the ascending node angle in GCRS
   :rtype: ~astropy.units.Quantity

   .. rubric:: Notes

   Calculations of the sun mean longitude and equation of time
   follow "Fundamentals of Astrodynamics and Applications"
   Fourth edition by :cite:t:`Vallado2013`.


.. py:function:: get_local_sidereal_time(lon, time)

   Gets the local sideral time from input location.

   :param lon: East longitude of a point on a body.
   :type lon: astropy.units.Quantity
   :param time: Time at which to calculate the local sidereal time.
   :type time: astropy.time.Time

   :returns: **theta** -- Local Sidereal Time (LST).
   :rtype: astropy.units.Quantity