adam_core.dynamics.aberrations module

adam_core.dynamics.aberrations.add_light_time(orbits: Array, t0: Array, observer_positions: Array, lt_tol: float = 1e-10, mu: float = 0.00029591220828411956, max_iter: int = 1000, tol: float = 1e-15, max_lt_iter: int = 10) → Tuple[Array, Array][source]

When generating ephemeris, orbits need to be backwards propagated to the time at which the light emitted or relflected from the object towards the observer.

Light time correction must be added to orbits in expressed in an inertial frame (ie, orbits must be barycentric).

Parameters:

  • orbits (~jax.numpy.ndarray (N, 6)) – Barycentric orbits in cartesian elements to correct for light time delay.

  • t0 (~jax.numpy.ndarray (N)) – Epoch at which orbits are defined.

  • observer_positions (~jax.numpy.ndarray (N, 3)) – Location of the observer in barycentric cartesian elements at the time of observation.

  • lt_tol (float, optional) – Calculate aberration to within this value in time (units of days.)

  • mu (float, optional) – Gravitational parameter (GM) of the attracting body in units of AU**3 / d**2.

  • max_iter (int, optional) – Maximum number of iterations over which to converge for propagation.

  • tol (float, optional) – Numerical tolerance to which to compute universal anomaly during propagation using the Newtown-Raphson method.

Returns:

  • corrected_orbits (~jax.numpy.ndarray (N, 6)) – Orbits adjusted for light travel time.

  • lt (~jax.numpy.ndarray (N)) – Light time correction (t0 - corrected_t0).

adam_core.dynamics.aberrations.add_stellar_aberration(orbits: Array, observer_states: Array) → Array[source]

The motion of the observer in an inertial frame will cause an object to appear in a different location than its true geometric location. This aberration is typically applied after light time corrections have been added.

The velocity of the input orbits are unmodified only the position vector is modified with stellar aberration.

Parameters:

  • orbits (~jax.numpy.ndarray (N, 6)) – Orbits in barycentric cartesian elements.

  • observer_states (~jax.numpy.ndarray (N, 6)) – Observer states in barycentric cartesian elements.

Returns:

rho_aberrated – The topocentric position vector for each orbit with added stellar aberration.

Return type:

~jax.numpy.ndarray (N, 3)

References

[1] Urban, S. E; Seidelmann, P. K. (2013) Explanatory Supplement to the Astronomical Almanac. 3rd ed.,

University Science Books. ISBN-13: 978-1891389856