القائمة
Reference for generating Orekit cross-validation fixtures. Covers orekit-jpype setup, force model matching, CSSI space weather, and fixture generation patterns.
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Express coordinate reference frames, time scales, and state representations in the type system, and test them with property-based tests — durable design guidance for orts/arika that holds whether you extend the current types or redesign them. Use when implementing, refactoring, or rethinking frame/scale code: adding a frame, scale, or transform; typing vectors, epochs, covariances, or rotations; deciding which time scale a transform takes; isolating EOP dependencies; choosing an interpolation space; or writing tests for rotation and scale-conversion invariants — and also when reviewing or verifying frame/scale code for type-safety. Companion to `coordinate-time-systems`, which covers the domain concerns (which frame/scale/representation, the traps).
Reason about coordinate reference frames and time scales correctly (any astrodynamics work) — which frame/scale/representation a value is actually in, the concerns to resolve before trusting it, and what to look up. Use when interpreting or choosing frames (ECI/ECEF, GCRS/ITRS/CIRS/TIRS, J2000/EME2000, TEME, ICRF, LVLH/RTN/RSW, body-fixed), time scales (TAI/UTC/UT1/TT/TDB/GPS), or state representations (Cartesian/Keplerian/equinoctial); or when reasoning about frame/scale conversions, covariance transforms, interpolation, leap seconds, ERA/GMST/GAST, EOP/ΔUT1, polar motion, frame bias, or realizations — and also when reviewing or verifying frame/time/coordinate work (use it as a checklist of the traps, even for code you could write unaided). The companion skill `coordinate-time-implementation` covers expressing and testing these in orts/arika code.
Run an external AI code review to get independent feedback on code changes. Use this skill when the user asks for a code review, says "コードレビューして", "レビュー", "変更を見て", "code review", or wants external feedback on their recent commits or uncommitted changes.
A knowledgeable neighbor who offers a fresh perspective on architecture, design decisions, and test strategy. Use proactively when a second opinion would improve quality, or when the user says "別の視点が欲しい", "設計を相談したい", "相談", "smart-friend に聞いて", or asks for feedback on their approach.
Guidelines for E2E testing the orts viewer with Playwright. Covers DuckDB query-level data verification, canvas pixel analysis, and common pitfalls.
Check if package names are available on crates.io and npm. Use when naming a new library or crate.
| name | orekit-fixtures |
| description | Reference for generating Orekit cross-validation fixtures. Covers orekit-jpype setup, force model matching, CSSI space weather, and fixture generation patterns. |
Reference for creating Python scripts that generate Orekit reference data for cross-validation with our Rust orbit propagator.
All generators are PEP 723 uv scripts. Run with uv run tools/generate_*.py.
# /// script
# requires-python = ">=3.10"
# dependencies = ["orekit-jpype", "jdk4py"]
# ///
import orekit_jpype as orekit
orekit.initVM()
from orekit_jpype.pyhelpers import download_orekit_data_curdir, setup_orekit_curdir
from pathlib import Path
data_dir = Path("orekit-data")
if not data_dir.exists():
download_orekit_data_curdir()
setup_orekit_curdir()
MU_EARTH_KM3_S2 = 398600.4418 # WGS84
R_EARTH_KM = 6378.137 # WGS84 equatorial
J2_EARTH = 1.08263e-3 # WGS84/EGM96
J3_EARTH = -2.5356e-6
J4_EARTH = -1.6199e-6
MU_SUN_KM3_S2 = 132712440018.0
MU_MOON_KM3_S2 = 4902.800066
OMEGA_EARTH = 7.2921159e-5 # rad/s
SOLAR_RADIATION_PRESSURE = 4.5396e-6 # N/m² at 1 AU
DEFAULT_CR = 1.5
DEFAULT_AREA_TO_MASS = 0.02 # m²/kg
DEFAULT_BALLISTIC_COEFF = 0.01 # m²/kg
Verify at runtime:
from org.orekit.utils import Constants
mu_orekit = Constants.WGS84_EARTH_MU / 1e9 # m³/s² → km³/s²
re_orekit = Constants.WGS84_EARTH_EQUATORIAL_RADIUS / 1e3
from org.hipparchus.ode.nonstiff import DormandPrince853Integrator
from org.orekit.frames import FramesFactory
from org.orekit.orbits import CartesianOrbit, OrbitType
from org.orekit.propagation import SpacecraftState
from org.orekit.propagation.numerical import NumericalPropagator
from org.orekit.utils import PVCoordinates
from org.hipparchus.geometry.euclidean.threed import Vector3D
eci = FramesFactory.getEME2000()
mu_si = MU_EARTH_KM3_S2 * 1e9
pos_m = Vector3D(pos_km[0]*1e3, pos_km[1]*1e3, pos_km[2]*1e3)
vel_m = Vector3D(vel_kms[0]*1e3, vel_kms[1]*1e3, vel_kms[2]*1e3)
pv = PVCoordinates(pos_m, vel_m)
orbit = CartesianOrbit(pv, eci, epoch_date, mu_si)
integrator = DormandPrince853Integrator(0.001, 300.0, 1e-14, 1e-12)
propagator = NumericalPropagator(integrator)
propagator.setOrbitType(OrbitType.CARTESIAN)
propagator.setInitialState(SpacecraftState(orbit, 1.0)) # mass=1 for unit A/m
Important: Use EME2000 as body frame so gravity pole = J2000 Z-axis (matches our Rust code which uses the J2000 Z-axis as Earth's pole).
from org.orekit.forces.gravity import HolmesFeatherstoneAttractionModel
from org.orekit.forces.gravity.potential import GravityFieldFactory
provider = GravityFieldFactory.getNormalizedProvider(degree, 0) # order=0 for zonal
hf = HolmesFeatherstoneAttractionModel(FramesFactory.getEME2000(), provider)
propagator.addForceModel(hf)
from org.orekit.bodies import CelestialBodyFactory
from org.orekit.forces.gravity import ThirdBodyAttraction
propagator.addForceModel(ThirdBodyAttraction(CelestialBodyFactory.getSun()))
propagator.addForceModel(ThirdBodyAttraction(CelestialBodyFactory.getMoon()))
from org.orekit.forces.radiation import IsotropicRadiationSingleCoefficient, SolarRadiationPressure
from org.orekit.bodies import OneAxisEllipsoid
from org.orekit.utils import Constants, IERSConventions
sun = CelestialBodyFactory.getSun()
itrf = FramesFactory.getITRF(IERSConventions.IERS_2010, True)
earth = OneAxisEllipsoid(Constants.WGS84_EARTH_EQUATORIAL_RADIUS,
Constants.WGS84_EARTH_FLATTENING, itrf)
spacecraft = IsotropicRadiationSingleCoefficient(area_to_mass, cr)
srp = SolarRadiationPressure(sun, earth, spacecraft) # earth → cylindrical shadow
propagator.addForceModel(srp)
Our ballistic coefficient B = CdA/(2m). For unit mass (m=1): area = 2B/Cd.
from org.orekit.forces.drag import DragForce, IsotropicDrag
cd = 2.2
area = 2.0 * ballistic_coeff / cd # m²
drag_spacecraft = IsotropicDrag(area, cd)
from org.orekit.models.earth.atmosphere import HarrisPriester
atmosphere = HarrisPriester(sun, earth, n) # n=2 (default exponent)
propagator.addForceModel(DragForce(atmosphere, drag_spacecraft))
import jpype
from org.orekit.models.earth.atmosphere import NRLMSISE00, NRLMSISE00InputParameters
from org.orekit.time import AbsoluteDate
class ConstantSolarActivity:
def getDailyFlux(self, date): return float(f107)
def getAverageFlux(self, date): return float(f107)
def getAp(self, date): return [float(ap)] * 7
def getMinDate(self): return AbsoluteDate.PAST_INFINITY
def getMaxDate(self): return AbsoluteDate.FUTURE_INFINITY
proxy = jpype.JProxy(NRLMSISE00InputParameters, inst=ConstantSolarActivity())
atmosphere = NRLMSISE00(proxy, sun, earth)
Important: Orekit's CssiSpaceWeatherData has internal cache/generator requirements
that make it incompatible with trimmed CSSI files. Use the full SpaceWeather-All-v1.2.txt
from orekit-data instead (same CelesTrak source — F10.7/Ap are identical for overlapping dates).
from org.orekit.models.earth.atmosphere import NRLMSISE00
from org.orekit.models.earth.atmosphere.data import CssiSpaceWeatherData
# Uses the full SpaceWeather-All file from orekit-data.zip
cssi = CssiSpaceWeatherData("SpaceWeather-All-v1.2.txt")
atmosphere = NRLMSISE00(cssi, sun, earth)
Rust equivalent:
let cssi_text = include_str!("fixtures/cssi_test_weather.txt");
let cssi_data = tobari::CssiData::parse(cssi_text).unwrap();
let weather = Box::new(tobari::CssiSpaceWeather::new(cssi_data));
let model = tobari::Nrlmsise00::new(weather);
from org.orekit.time import AbsoluteDate, TimeScalesFactory
utc = TimeScalesFactory.getUTC()
date = AbsoluteDate("2024-03-20T12:00:00", utc)
from org.orekit.bodies import GeodeticPoint
lat_rad = math.radians(lat_deg)
lon_rad = math.radians(lon_deg)
geod = GeodeticPoint(lat_rad, lon_rad, alt_km * 1e3)
pos_ecef = earth.transform(geod)
density = msise_model.getDensity(epoch_date, pos_ecef, itrf) # kg/m³
| Script | Output | Run command |
|---|---|---|
tools/generate_orekit_propagation_fixtures.py | orbits/tests/fixtures/orekit_propagation_reference.json | uv run tools/generate_orekit_propagation_fixtures.py |
tools/generate_orekit_msise_density_fixtures.py | tobari/tests/fixtures/orekit_msise_density_reference.json | uv run tools/generate_orekit_msise_density_fixtures.py |
tools/generate_hp_fixtures.py | tobari/tests/fixtures/hp_orekit_reference.json | uv run tools/generate_hp_fixtures.py |
tools/generate_sgp4_fixtures.py | orbits/tests/fixtures/sgp4_reference.json | uv run tools/generate_sgp4_fixtures.py |
tools/generate_nrlmsise00_fixtures.py | tobari/tests/fixtures/nrlmsise00_reference.json | uv run tools/generate_nrlmsise00_fixtures.py |
tools/generate_iss_decay_fixtures.py | orbits/tests/fixtures/iss_decay_reference.json | uv run tools/generate_iss_decay_fixtures.py |
tools/generate_cssi_test_fixture.py | tobari/tests/fixtures/cssi_test_weather.txt | uv run tools/generate_cssi_test_fixture.py |
| Source | Magnitude | Affects |
|---|---|---|
| Sun position (DE405 vs Meeus) | ~0.35° | SRP, HP bulge, NRLMSISE-00 LST |
| Moon position (DE405 vs analytical) | ~10' | Third-body |
| LST (precise vs UT+lon/15) | ~16 min | NRLMSISE-00 density (1-5%) |
| Gravity (HolmesFeatherstone vs explicit) | J2 diff ~3e-9 | Sub-meter at 10 orbits |
| Geodetic altitude | Both WGS-84 | Matched after geo.rs fix |