IO.Astrodynamics 7.0.3

IO.Astrodynamics

A modern .NET astrodynamics toolkit powered by NASA/JPL NAIF SPICE. IO.Astrodynamics delivers SPICE accuracy with a productive .NET API; a thin, stable C++ layer provides fast interop with CSPICE.

Important: The C++ layer is feature-frozen and exists only for communication with SPICE. All new features and APIs will land in the .NET projects.

What you can do

• Work with SPICE kernels and star catalogs
• Export simulations to Cosmographia
• Manage PDS archives (generate, materialize objects, validate against XML schemas)
• Ephemerides and propagation
  • Spacecraft propagator: geopotential models, simplified atmospheres (Earth, Mars), solar radiation pressure, n-body perturbations, impulsive maneuvers, fuel balance
  • Small-body propagator: geopotential (Earth), simplified atmospheres (Earth, Mars), SRP, n-body
• Orbital parameters: compute/convert State Vector, TLE, Equinoctial, Keplerian
• Frames and coordinates: ICRF/J2000, Ecliptic (J2000/B1950), TEME, Galactic, FK4, body-fixed/ITRF93, Equatorial/Horizontal/Planetodetic/Planetographic
• Spacecraft configuration: clocks, fuel tanks, engines, instruments
• Impulsive maneuvers: Lambert transfers, apogee/perigee height changes, plane/apsidal alignment, phasing, combined maneuvers
• Attitudes: instrument pointing, nadir/zenith, prograde/retrograde
• Time systems: Calendar, Julian, TDB, UTC, local; conversions included
• Event finding: distance, occultation, coordinate, illumination constraints; instrument field-of-view windows
• Kernel management utilities
• Math helpers: vectors, matrices, planes, quaternions, Jacobians, interpolation (Lagrange), Legendre polynomials, SLERP/LERP
• Use via CLI for common tasks (props, conversions, info queries)

How it works

• SPICE data: You supply NAIF kernels (ephemerides, planetary constants, leap seconds, mission data)
• Native bridge: A small C++ interop library talks to CSPICE for performance-critical calls (frozen API)
• .NET SDK: Rich, evolving API surface for scenarios, modeling, and utilities
• CLI: Command-line tools built on the .NET SDK for quick analyses

Links:

• SPICE concept: https://naif.jpl.nasa.gov/naif/spiceconcept.html
• SPICE data: https://naif.jpl.nasa.gov/naif/data.html

Install (.NET)

This package is on NuGet: https://www.nuget.org/packages/IO.Astrodynamics/

Install into your project:

 dotnet add package IO.Astrodynamics

Requirements:

• Supported OS: Windows and Linux x64 (native CSPICE interop is bundled)
• SPICE kernels: you must load the kernels required for your computations

Quick start (C#)

Load kernels once at startup, then query ephemerides, frames, and more.

// Load required kernels (recursively) from your data directory
API.Instance.LoadKernels(new DirectoryInfo("<your path containing data>"));

// Example: Moon ephemeris at 2000-01-01T12:00Z in ICRF with Earth as center
var earth = new CelestialBody(PlanetsAndMoons.EARTH);
var moon  = new CelestialBody(PlanetsAndMoons.MOON);
var epoch = new TimeSystem.Time(new DateTime(2000, 1, 1, 12, 0, 0), TimeFrame.UTCFrame);
var eph   = moon.GetEphemeris(epoch, earth, Frames.Frame.ICRF, Aberration.None);

More examples: https://github.com/IO-Aerospace-software-engineering/Astrodynamics.Net/wiki/Examples

Using the CLI

A CLI is included in the repository for quick tasks (propagation, conversions, info queries, event finding).

• Build and show help:

 dotnet run --project IO.Astrodynamics.Net/IO.Astrodynamics.CLI -- --help

• Typical commands include: sub-observer point, angular separation, orientation, orbital/frame/time conversions, event window finding (distance, occultation, FoV, illumination).

Getting SPICE data

You need to provide the kernels relevant to your scenario. Common sets:

• Leap seconds (e.g., naif0012.tls)
• Planetary constants (e.g., pck files)
• Ephemerides (e.g., de430.bsp, planetary/spacecraft SPKs)
• Frames and spacecraft clocks as needed

Organize them in a directory and load them recursively:

API.Instance.LoadKernels(new DirectoryInfo("Data/SolarSystem"));

Native C++ interop (frozen)

The native C++ library exists only as a high-performance bridge to CSPICE. It won’t receive new features. If you need to link it directly:

• Download prebuilt binaries from Releases: https://github.com/IO-Aerospace-software-engineering/Astrodynamics/releases
• Linux: install headers to /usr/local/include/IO and libIO.Astrodynamics.so to /usr/local/lib
• Windows: place IO.Astrodynamics.dll/.lib alongside your app and include headers

Note: Prefer the .NET SDK for all new work.

Build status and coverage

Sponsoring

Building and sustaining a .NET-first astrodynamics toolkit on top of SPICE takes significant effort across:

• Keeping pace with SPICE releases and kernel updates
• Evolving the .NET API, CLI, and documentation
• Cross-platform packaging and CI (Windows/Linux)
• Extensive tests, validation against reference data, and performance work
• New features and scenarios (propagators, event finders, attitudes, PDS tooling, Cosmographia export)
• Community support, triage, and example curation

How you can help:

• Sponsor the project via GitHub Sponsors to fund ongoing development and maintenance
• Company sponsorships to prioritize features, integrations, or support
• Back specific issues or improvements; contribute kernel sets, scenarios, or docs
• Provide infrastructure (CI minutes/compute) or test hardware when relevant

Where funds go:

• .NET SDK and CLI development (the native C++ bridge is feature-frozen)
• Documentation, tutorials, and examples
• Validation datasets and automated QA
• Release engineering, packaging, and platform support

Sponsor: https://github.com/sponsors/IO-Aerospace-software-engineering

Contributing

• We welcome contributions to the .NET SDK, CLI, docs, and tests. The native layer accepts only fixes and perf/stability improvements.
• Please read CONTRIBUTING.md and follow the code of conduct.

License and acknowledgments

• License: See LICENSE
• Security: See SECURITY.md
• Built on NASA/JPL NAIF SPICE. SPICE is developed by the Navigation and Ancillary Information Facility (NAIF) at JPL.