SpaceObject

class sorts.space_object.SpaceObject(propagator, propagator_options={}, propagator_args={}, parameters={}, epoch=<Time object: scale='utc' format='mjd' value=57125.7729>, oid=1, **kwargs)[source]

Bases: object

Encapsulates a object in space who’s dynamics is governed in time by a propagator.

The relation between the Cartesian and Kepler states are a direct transformation according to the below orientation rules. If the Kepler elements are given in a Inertial system, to reference the Cartesian to a Earth-fixed system a earth rotation transformation must be applied externally of the method.

#TODO: THIS DOC MUST BE UPDATED TOO

Orientation of the ellipse in the coordinate system:

  • For zero inclination \(i\): the ellipse is located in the x-y plane.

  • The direction of motion as True anoamly \(\nu\): increases for a zero inclination \(i\): orbit is anti-coockwise, i.e. from +x towards +y.

  • If the eccentricity \(e\): is increased, the periapsis will lie in +x direction.

  • If the inclination \(i\): is increased, the ellipse will rotate around the x-axis, so that +y is rotated toward +z.

  • An increase in Longitude of ascending node \(\Omega\): corresponds to a rotation around the z-axis so that +x is rotated toward +y.

  • Changing argument of perihelion \(\omega\): will not change the plane of the orbit, it will rotate the orbit in the plane.

  • The periapsis is shifted in the direction of motion.

  • True anomaly measures from the +x axis, i.e \(\nu = 0\) is located at periapsis and \(\nu = \pi\) at apoapsis.

  • All anomalies and orientation angles reach between 0 and \(2\pi\)

Reference: “Orbital Motion” by A.E. Roy.

Variables:

  • \(a\): Semi-major axis

  • \(e\): Eccentricity

  • \(i\): Inclination

  • \(\omega\): Argument of perihelion

  • \(\Omega\): Longitude of ascending node

  • \(\nu\): True anoamly

Variables

  • orbit (pyorb.Orbit) – Orbit instance

  • oid (int) – Identifying object ID

  • C_D (float) – Drag coefficient

  • C_R (float) – Radiation pressure coefficient

  • A (float) – Area [\(m^2\)]

  • m (float) – Mass [kg]

  • d (float) – Diameter [m]

  • mjd0 (float) – Epoch for state [BC-relative JD]

  • prop (float) – Propagator instance, child of PropagatorBase

  • propagator_options (dict) – Propagator initialization keyword arguments

  • propagator_args (dict) – Propagator call keyword arguments

The constructor creates a space object using Kepler elements.

Parameters

  • A (float) – Area in square meters

  • m (float) – Mass in kg

  • C_D (float) – Drag coefficient

  • C_R (float) – Radiation pressure coefficient

  • mjd0 (float) – Epoch for state

  • oid (int) – Identifying object ID

  • d (float) – Diameter in meters

  • propagator (PropagatorBase) – Propagator class pointer

  • propagator_options (dict) – Propagator initialization keyword arguments

  • propagator_args (dict) – Keyword arguments to be passed to the propagator call

  • kwargs (dict) – All additional keywords are used to initialize the orbit

Keyword arguments

  • a (float) – Semi-major axis in meters

  • e (float) – Eccentricity

  • i (float) – Inclination in degrees

  • aop (float) – Argument of perigee in degrees

  • raan (float) – Right ascension of the ascending node in degrees

  • mu0 (float) – Mean anomaly in degrees

  • x (float) – X-position

  • y (float) – Y-position

  • z (float) – Z-position

  • vx (float) – X-velocity

  • vy (float) – Y-velocity

  • vz (float) – Z-velocity

Methods

__init__(propagator[, propagator_options, …])

Initialize self.

copy()

Returns a copy of the SpaceObject instance.

get_position(t)

Gets position at specified times using propagator instance.

get_state(t)

Gets ECEF state at specified times using propagator instance.

get_velocity(t)

Gets velocity at specified times using propagator instance.

propagate(dt)

Propagate and change the epoch of this space object if the state is a pyorb.Orbit.

update(**kwargs)

If a pyorb.Orbit is present, updates the orbital elements and Cartesian state vector of the space object.

Attributes

d

default_parameters

in_frame

m

Object mass, if changed the Kepler elements stays constant

orbit

out_frame