satkit 0.18.1

Satellite Orbital Dynamics Toolkit

satkit

Satellite astrodynamics in Rust, with full Python bindings.

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Satkit is a high-performance orbital mechanics library written in Rust with complete Python bindings via PyO3. It handles coordinate transforms, orbit propagation, time systems, gravity models, atmospheric density, and JPL ephemerides -- everything needed for satellite astrodynamics work.

Documentation and tutorials (Python examples, but the concepts and API apply equally to Rust) | Rust API reference

[!NOTE] Version 0.16.0 introduces several breaking changes: Frame::RIC is renamed to the canonical Frame::RTN (with RIC / RSW remaining as aliases, so existing code still compiles); a new Frame::NTW (velocity-aligned) is added; LVLH is now accepted as a maneuver/thrust frame; the uncertainty API is unified into set_pos_uncertainty(sigma, frame) / set_vel_uncertainty(sigma, frame) (the four old per-frame methods are removed, not deprecated); PropSettings::default() now uses GravityModel::EGM96 instead of JGM3; the Gauss-Jackson 8 fixed-step multistep integrator is available for long-duration propagation; and PropSettings::max_steps is now configurable. See CHANGELOG.md for the full list.

Installation

Rust:

cargo add satkit

Python:

pip install satkit

Pre-built wheels are available for Linux, macOS, and Windows on Python 3.10--3.14.

After installing, download the required data files (gravity models, ephemerides, Earth orientation parameters):

import satkit as sk
sk.utils.update_datafiles()  # one-time download; re-run periodically for fresh EOP/space weather

Quick Examples

SGP4 propagation (Python)

import satkit as sk

tle = sk.TLE.from_lines([
    "ISS (ZARYA)",
    "1 25544U 98067A   24001.50000000  .00016717  00000-0  10270-3 0  9003",
    "2 25544  51.6432 351.4697 0007417 130.5364 329.6482 15.48915330299357"
])

pos, vel = sk.sgp4(tle, sk.time(2024, 1, 2))

High-precision propagation (Python)

import satkit as sk
import numpy as np

r0 = 6378e3 + 500e3  # 500 km altitude
v0 = np.sqrt(sk.consts.mu_earth / r0)

settings = sk.propsettings(
    gravity_model=sk.gravmodel.egm96,  # default; also jgm3, jgm2, itugrace16
    gravity_degree=8,
    integrator=sk.integrator.rkv98,    # default; also rkv87, rkv65, rkts54,
                                       # gauss_jackson8 (fixed-step multistep)
)

result = sk.propagate(
    np.array([r0, 0, 0, 0, v0, 0]),
    sk.time(2024, 1, 1),
    end=sk.time(2024, 1, 1) + sk.duration.from_days(1),
    propsettings=settings,
)

state = result.interp(sk.time(2024, 1, 1) + sk.duration.from_hours(6))

Coordinate transforms (Python)

import satkit as sk

time = sk.time(2024, 1, 1, 12, 0, 0)
coord = sk.itrfcoord(latitude_deg=42.0, longitude_deg=-71.0, altitude=100.0)

q = sk.frametransform.qitrf2gcrf(time)
gcrf_pos = q * coord.vector

Planetary ephemerides (Rust)

use satkit::{Instant, SolarSystem, jplephem};

let time = Instant::from_datetime(2024, 1, 1, 0, 0, 0.0)?;
let (pos, vel) = jplephem::geocentric_state(SolarSystem::Moon, &time)?;

Features

Coordinate Frames

Full IERS 2010 Conventions reduction (IAU 2006/2000A precession-nutation) with Earth orientation parameters:

Frame	Description
ITRF	International Terrestrial Reference Frame (Earth-fixed)
GCRF	Geocentric Celestial Reference Frame (inertial)
TEME	True Equator Mean Equinox (SGP4 output frame)
CIRS	Celestial Intermediate Reference System
TIRS	Terrestrial Intermediate Reference System
Geodetic	Latitude / longitude / altitude (WGS-84)

Plus ENU, NED, and geodesic distance (Vincenty) utilities.

Orbit Propagation

• Numerical -- Selectable adaptive Runge-Kutta integrators (9(8), 8(7), 6(5), 5(4)) plus RODAS4 (stiff) and Gauss-Jackson 8 (fixed-step multistep for high-precision long-duration propagation), with dense output, state transition matrix, and configurable force models
• SGP4 -- Standard TLE/OMM propagator with TLE fitting from precision states
• Keplerian -- Analytical two-body propagation

Orbit Maneuvers

• Impulsive maneuvers -- Instantaneous delta-v applied at a scheduled time during propagation. Supported frames: GCRF (inertial), RTN (radial/tangential/normal — the CCSDS OEM convention, also exposed as RSW and RIC aliases), NTW (velocity-aligned — natural for prograde burns on eccentric orbits, where a pure +T delta-v adds exactly Δv to |v|), and LVLH (Local Vertical / Local Horizontal). Ergonomic helpers add_prograde / add_retrograde / add_radial / add_normal for common scalar-magnitude burns.
• Continuous thrust -- Constant-acceleration thrust arcs over time windows in any of the frames above, integrated directly into the force model
• Automatic segmentation -- Propagation through maneuver sequences is handled transparently, including backward propagation

Force Models

• Earth gravity: JGM2, JGM3, EGM96, ITU GRACE16 (spherical harmonics up to degree/order 360)
• Third-body gravity: Sun and Moon via JPL DE440/441 ephemerides
• Atmospheric drag: NRLMSISE-00 with automatic space weather data
• Solar radiation pressure: Cannonball model with shadow function

Time Systems

Seamless conversion between UTC, TAI, TT, TDB, UT1, and GPS time scales with full leap-second handling.

Solar System

• JPL DE440/DE441 ephemerides for all planets, Sun, Moon, and barycenters
• Fast analytical Sun/Moon models for lower-precision work
• Sunrise/sunset and Moon phase calculations

Linear Algebra

SatKit uses numeris for all linear algebra (vectors, matrices, quaternions, ODE integration). If you also use nalgebra in your project, enable the nalgebra feature on numeris for zero-cost From/Into conversions between types:

numeris = { version = "0.5.7", features = ["nalgebra"] }

Cargo Features

Feature	Default	Description
omm-xml	yes	XML OMM deserialization via quick-xml
chrono	no	TimeLike impl for chrono::DateTime

Data Files

Satkit needs external data for gravity models, ephemerides, and Earth orientation. Call update_datafiles() to download them automatically.

Downloaded once: JPL DE440/441 (~100 MB), gravity model coefficients, IERS nutation tables

Update periodically: Space weather indices (F10.7, Ap) and Earth orientation parameters (polar motion, UT1-UTC) -- both sourced from Celestrak.

Testing and Validation

The library is validated against:

• Vallado test cases for SGP4, coordinate transforms, and Keplerian elements
• JPL test vectors for DE440/441 ephemeris interpolation (10,000+ cases)
• ICGEM reference values for gravity field calculations
• GPS SP3 precise ephemerides for multi-day numerical propagation

157 Rust tests and 81 Python tests run on every commit across Linux, macOS, and Windows.

Running Tests Locally

Tests require two sets of external data: the astro-data files (gravity models, ephemerides, etc.) and the test vectors (reference outputs for validation). Download both before running:

# Install the download helper
pip install requests

# Download test vectors
python python/test/download_testvecs.py

Then run tests with the environment variables pointing to the downloaded directories:

# Rust tests
SATKIT_DATA=astro-data SATKIT_TESTVEC_ROOT=satkit-testvecs cargo test

# Python tests
SATKIT_DATA=astro-data SATKIT_TESTVEC_ROOT=satkit-testvecs pytest python/test/

Documentation

• Rust: docs.rs/satkit
• Python: satkit.dev -- tutorials, Jupyter notebooks, and API reference

References

• D. Vallado, Fundamentals of Astrodynamics and Applications, 4th ed., 2013
• O. Montenbruck & E. Gill, Satellite Orbits: Models, Methods, Applications, 2000
• J. Verner, Runge-Kutta integration coefficients

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.