astrodyn_planet 0.2.0

Planet definitions and presets (Earth, Moon, Sun, Mars) for the astrodyn orbital-dynamics pipeline
Documentation

astrodyn_planet

Reference-ellipsoid parameters and standard preset bodies for the astrodyn_bevy workspace.

Ports models/environment/planet/ from NASA JEOD v5.4.0 — the per-body shape parameters (gravitational parameter, equatorial and polar radii, flattening) consumed by gravity, geodetic, atmospheric, and frame-rotation code.

When to use

  • Building a gravity source — every astrodyn_gravity source needs mu; PlanetShape::mu is the canonical accessor.
  • Geodetic conversions — astrodyn_math::geodetic needs r_eq, r_pol, and the flattening for the ellipsoidal latitude / longitude / altitude solver.
  • Atmosphere models — MET and the exponential fallback both need the reference radius to compute altitude above the ellipsoid.
  • Reusing canonical bodies — presets::EARTH / MOON / SUN / MARS give the JEOD-matched parameter blocks so cross-validation tests don't drift from JEOD numerics.

Most mission code reaches the preset constants via the recipe layer in astrodyn::recipes::earth / moon / mars; this crate is the pure parameter source those recipes wrap.

Key concepts

PlanetShape is a value type — name, mu (m³/s²), r_eq (m), r_pol (m), flat_coeff — plus a small handful of derived helpers (flat_inv, e_ellipsoid). It carries no state and no allocations, so it is freely Copy-passable through the physics pipeline. There is no separate "live planet" struct: the gravity source, the geodetic solver, and the frame-rotation models all read from PlanetShape and combine it with their own model-specific data (gravity coefficients, nutation tables) downstream.

presets::EARTH follows the GGM05C mu = 3.986004415e14 m³/s² rather than IERS 2010, which differs by ~3e6 m³/s² — we follow JEOD's choice so Tier 3 cross-validation against JEOD trajectories doesn't chase a 7-ppm mu offset for hundreds of orbits. The other presets similarly track the JEOD source data files (planet/data/src/<body>.cc) verbatim.

Layered architecture

astrodyn_bevy        (Bevy ECS adapter, mission code)
   ↓
astrodyn         (orchestration, recipes, single API surface)
   ↓
astrodyn_planet      ←  this crate (pure Rust, zero Bevy)
   ↓
astrodyn_quantities  (typed length / GravParam quantities)

astrodyn_planet is part of the astrodyn_* physics layer — pure Rust with no Bevy dependency. See the project Strategy wiki page for the layered architecture.

Public surface

  • PlanetShape — reference-ellipsoid parameter block (mu, r_eq, r_pol, flat_coeff) with derived helpers and typed accessors.
  • presets::EARTH / MOON / SUN / MARS — canonical constants matching the JEOD planet/data/src/<body>.cc files plus the corresponding gravity-model mu (Earth uses GGM05C, Moon GRAIL150, Mars MRO110B2, Sun spherical).

Earth's mu follows the GGM05C value 3.986004415e14 m³/s² rather than IERS 2010, to keep cross-validation faithful to JEOD source.

See also