orbix

A JAX library of functions for exoplanet simulations: differentiable Keplerian orbit propagation and Kepler-equation solvers, plus solar-system geometry (observatory position, keepout) for the Habitable Worlds Observatory direct imaging simulation suite. Scene composition (planet catalogs, EXOSIMS integration, zodiacal photometry) lives in other libraries; see below.

Install

pip install orbix

Quickstart

import jax.numpy as jnp
from orbix.orbit import KeplerianOrbit
from orbix.kepler.shortcuts.grid import get_grid_solver

orbit = KeplerianOrbit(
    a_AU=1.0,
    e=0.0167,
    W_rad=0.0,
    i_rad=0.0,
    w_rad=0.0,
    M0_rad=0.0,
    t0_d=0.0,
)
trig_solver = get_grid_solver(level="scalar", E=False, trig=True)
t_jd = jnp.linspace(2451545.0, 2451545.0 + 365.25, 5)
r_AU, phase_angle_rad, dist_AU = orbit.propagate(trig_solver, t_jd, Ms_kg=1.989e30)
print(r_AU.shape)  # (1, 3, 5): (K orbits, xyz, T times)

get_grid_solver builds a cached grid-interpolation Kepler solver with the contract trig_solver(M, e) -> (sinE, cosE); KeplerianOrbit.propagate uses it to convert orbital elements and times into position vectors, phase angle, and star-planet distance.

For an alternative without interpolation tables, use from orbix.kepler import markley_solve_trig and pass markley_solve_trig as the orbit's trig_solver. This Markley-based solver supports scalar inputs, broadcasting, and both forward and reverse derivatives. Enable jax.config.update("jax_enable_x64", True) for double-precision accuracy. The RPP/orvara solver remains available in orbix.kepler.core.

Scope

orbix provides Keplerian orbit geometry and Kepler-equation solvers; scene composition lives in skyscapes.

Citation

If you use orbix, please cite it as described in CITATION.cff.