.. default-domain:: py
.. highlight:: py
.. currentmodule:: SpaceCenter

Closest Approach
================


.. class:: ClosestApproach

   A close approach between an orbit and a target orbit. Obtained by calling
   :meth:`Orbit.next_closest_approach` or :meth:`Orbit.closest_approaches`.

   .. note::

      A close approach is a snapshot: the time of closest approach is estimated once
      when the object is created, and every member describes the state at that time.
      Relative quantities are the target relative to the orbiting object (target minus
      self).

   .. attribute:: ut

      The universal time of the closest approach, in seconds.

      :Attribute: Read-only, cannot be set
      :rtype: float
   

   .. attribute:: time_to

      The time until the closest approach, in seconds.

      :Attribute: Read-only, cannot be set
      :rtype: float
   

   .. attribute:: distance

      The distance between the objects at the closest approach, in meters.

      :Attribute: Read-only, cannot be set
      :rtype: float
   

   .. attribute:: relative_speed

      The relative speed of the objects at the closest approach, in meters per
      second. This is the magnitude of :meth:`ClosestApproach.relative_velocity`, and does
      not depend on the choice of reference frame.

      :Attribute: Read-only, cannot be set
      :rtype: float
   

   .. attribute:: vessel

      The vessel doing the approaching, or ``None`` if it is not a vessel.

      :Attribute: Read-only, cannot be set
      :rtype: :class:`Vessel`
   

   .. attribute:: body

      The celestial body doing the approaching, or ``None`` if it is not a
      celestial body.

      :Attribute: Read-only, cannot be set
      :rtype: :class:`CelestialBody`
   

   .. attribute:: target_vessel

      The vessel being approached, or ``None`` if the target is not a vessel.

      :Attribute: Read-only, cannot be set
      :rtype: :class:`Vessel`
   

   .. attribute:: target_body

      The celestial body being approached, or ``None`` if the target is not a
      celestial body.

      :Attribute: Read-only, cannot be set
      :rtype: :class:`CelestialBody`
   

   .. method:: position([reference_frame = None])

      The position of the orbiting object at the closest approach.

      :param ReferenceFrame reference_frame: The reference frame that the returned position vector is in. Defaults to the orbital reference frame of the object the orbit belongs to.
      :returns: The position as a vector.
      :rtype: tuple(float, float, float)
   

   .. method:: target_position([reference_frame = None])

      The position of the target object at the closest approach.

      :param ReferenceFrame reference_frame: The reference frame that the returned position vector is in. Defaults to the orbital reference frame of the object the orbit belongs to.
      :returns: The position as a vector.
      :rtype: tuple(float, float, float)
   

   .. method:: velocity([reference_frame = None])

      The velocity of the orbiting object at the closest approach.

      :param ReferenceFrame reference_frame: The reference frame that the returned velocity vector is in. Defaults to the orbital reference frame of the object the orbit belongs to.
      :returns: The velocity as a vector.
      :rtype: tuple(float, float, float)
   

   .. method:: target_velocity([reference_frame = None])

      The velocity of the target object at the closest approach.

      :param ReferenceFrame reference_frame: The reference frame that the returned velocity vector is in. Defaults to the orbital reference frame of the object the orbit belongs to.
      :returns: The velocity as a vector.
      :rtype: tuple(float, float, float)
   

   .. method:: relative_position([reference_frame = None])

      The position of the target relative to the orbiting object at the closest
      approach.

      :param ReferenceFrame reference_frame: The reference frame whose axes the returned vector is expressed in. Defaults to the orbital reference frame of the object the orbit belongs to.
      :returns: The relative position as a vector.
      :rtype: tuple(float, float, float)
   

   .. method:: relative_velocity([reference_frame = None])

      The velocity of the target relative to the orbiting object at the closest
      approach.

      :param ReferenceFrame reference_frame: The reference frame whose axes the returned vector is expressed in. Defaults to the orbital reference frame of the object the orbit belongs to.
      :returns: The relative velocity as a vector.
      :rtype: tuple(float, float, float)