adam_core.dynamics.ephemeris module

adam_core.dynamics.ephemeris.generate_ephemeris_2body(propagated_orbits: Orbits, observers: Observers, lt_tol: float = 1e-10, max_iter: int = 1000, tol: float = 1e-15, stellar_aberration: bool = False, predict_magnitudes: bool = True, *, predict_phase_angle: bool = False, max_processes: int | None = 1, chunk_size: int = 100) → Ephemeris[source]

Generate on-sky ephemerides for each propagated orbit as viewed by the observers. This function calculates the light time delay between the propagated orbit and the observer, and then propagates the orbit backward by that amount to when the light from object was actually emitted towards the observer (“astrometric coordinates”).

The motion of the observer in an inertial frame will cause an object to appear in a different location than its true location, this is known as stellar aberration (often referred to in combination with other aberrations as “apparent coordinates”). Stellar aberration can optionally be applied after light time correction has been added but it should not be necessary when comparing to ephemerides of solar system small bodies extracted from astrometric catalogs. The stars to which the catalog is calibrated undergo the same aberration as the moving objects as seen from the observer.

If stellar aberration is applied then the velocity of the input orbits are unmodified, only the position vector is modified with stellar aberration.

For more details on aberrations see:

https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/FORTRAN/req/abcorr.html https://ssd.jpl.nasa.gov/horizons/manual.html#defs

Parameters:

  • propagated_orbits (~adam_core.orbits.orbits.Orbits (N)) – Propagated orbits.

  • observers (~adam_core.observers.observers.Observers (N)) – Observers for which to generate ephemerides. Orbits should already have been propagated to the same times as the observers.

  • 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.

  • stellar_aberration (bool, optional) – Apply stellar aberration to the ephemerides.

Returns:

ephemeris – Topocentric ephemerides for each propagated orbit as observed by the given observers.

Return type:

~adam_core.orbits.ephemeris.Ephemeris (N)