High-Fidelity Propagation¶

Pro

RK78Integrator, CentralBodyPropagatorBuilder, albedo radiation pressure, and thermal radiation pressure are Pro features.

The CentralBodyPropagatorBuilder fluent API assembles a propagator with the full suite of community and Pro force models in a single declarative setup.

Full Force Model Assembly¶

// Central body with geopotential, atmosphere, albedo, and thermal properties
var earth = new CelestialBody(PlanetsAndMoons.EARTH,
    new GeopotentialModelParameters("Data/SolarSystem/EGM2008_to70_TideFree", 10),
    new Nrlmsise00Model(SpaceWeather.Nominal),
    albedo: 0.306, thermalEffectiveTemperature: 254.0, thermalEmissivity: 0.95);

// Adaptive integrator
var integrator = new RK78Integrator(
    absoluteTolerance: 1e-10,
    relativeTolerance: 1e-10,
    initialStepSize: 30.0);

// Assemble propagator with all perturbations
using var propagator = new CentralBodyPropagatorBuilder(window, spacecraft, integrator, deltaT)
    .WithPerturbingBody(Stars.SUN_BODY)
    .WithPerturbingBody(PlanetsAndMoons.MOON_BODY)
    .IncludeAtmosphericDrag()
    .IncludeSolarRadiationPressure()
    .IncludeAlbedo(earth)
    .IncludeThermalRadiation(earth)
    .Build();

var solution = propagator.Propagate();

Force Models¶

The builder supports the following perturbations:

Method	Force Model	Source
(automatic)	Central-body gravity	Community
`WithPerturbingBody(body)`	Third-body perturbation	Community
`IncludeAtmosphericDrag()`	Atmospheric drag	Community
`IncludeSolarRadiationPressure()`	Direct solar radiation pressure	Community
`IncludeAlbedo(body)`	Reflected sunlight (Lambertian sphere)	Pro
`IncludeThermalRadiation(body)`	Infrared emission (isotropic emitter)	Pro

Geopotential Degree Guidance¶

Degree	Use Case
`2`	Fast J2-only preliminary analysis
`10`	Good LEO production baseline
`20-30`	Higher-fidelity geodesy and mission analysis
`70`	Maximum supported EGM2008 fidelity

Performance trade-off

Higher geopotential degree increases computation time significantly. Degree 10 is sufficient for most LEO missions. Reserve degree 70 for geodetic satellites or when matching external high-fidelity references.

Typical Acceleration Magnitudes (LEO)¶

For context, approximate acceleration magnitudes at 400 km altitude:

Direct SRP: ~4.5e-8 m/s^2 (reference)
Albedo: ~10-20x smaller than direct SRP
Thermal (IR): ~15% of direct SRP, always present regardless of eclipse