OpenGNC

OpenGNC is a professional-grade, high-fidelity Guidance, Navigation, and Control (GNC) library for spacecraft simulation, orbital mechanics, and mission analysis. Built with SI units and aerospace standards, it provides a comprehensive suite of tools for satellite engineers and researchers.

Explore the Documentation | View Examples | Contributing

Key Highlights

• SI Unit Compliance: All calculations strictly use SI units (meters, kilograms, seconds, radians) unless otherwise explicitly suffixed.
• High-Fidelity Environment: Integrated models for NRLMSISE-00 density, IGRF-13 magnetic fields, and EGM2008 gravity harmonics.
• Validated Algorithms: Implementations of industry-standard filters (MEKF, UKF) and deterministic methods (QUEST, TRIAD).
• Optimization Ready: Built-in support for Optimal Control (LQR) and Model Predictive Control (MPC) using CasADi.
• Modular Architecture: Easily swap integrators, disturbance models, or sensors for customized simulations.

Extensive Features

Environment & Space Weather

• Atmospheric Models: NRLMSISE-00 (high-fidelity), Harris-Priester (diurnal bulge), and Exponential density.
• Geomagnetic Models: IGRF-13 (International Geomagnetic Reference Field) and Tilted Dipole models.
• Solar & Ephemeris: Analytical solar position, shadow models (Umbra/Penumbra), and Planetary ephemeris.
• Gravity Field: Recursive EGM2008 Spherical Harmonics (up to N-degree), J2, and Two-body attraction.

Orbital Mechanics & Propagators

• Propagators: Cowell’s Method, Keplerian elements, and SGP4 for TLE propagation.
• Numerical Integrators: High-order fixed and adaptive steps: RK4, RK45 (Runge-Kutta-Fehlberg), and DOP853.
• Orbital Maneuvers: Hohmann transfer, Bi-elliptic, Phasing, Plane changes, and Lambert Targeting.
• Initial Orbit Determination (IOD): Robust Gauss, Laplace, and universal variable methods.

Attitude Dynamics & Determination

• Kinematics: Quaternion, Euler Angle, and DCM (Direction Cosine Matrix) transformations.
• Dynamics: Euler's equations for rigid body rotation, including variable inertia and disturbances.
• Determination: Deterministic TRIAD and QUEST algortihms for attitude from vector observations.

Guidance, Navigation & Control (GNC)

• State Estimation:
  • MEKF: Multiplicative Extended Kalman Filter for attitude.
  • UKF: Unscented Kalman Filter for non-linear state estimation.
  • EKF/KF: Standard and Extended Kalman Filters for orbital state mapping.
• Control Law Design:
  • Classic: PID controllers and B-Dot detumbling logic.
  • Optimal: LQR (Linear Quadratic Regulator) and LQE (Kalman Filter design).
  • Advanced: Nonlinear MPC (Model Predictive Control) and Sliding Mode Control.
• Sensors: Realistic Star Tracker, Sun Sensor, Magnetometer, and Gyroscope models with bias/noise.
• Actuators: Model Reaction Wheels (saturation/jitter) and Thrusters (Chemical/Electric).

FDIR & Mission Design

• FDIR (Fault Detection): Parity Space methods, Residual Generation, and Safe Mode logic.
• SSA (Space Situational Awareness): Conjunction Assessment (CAT), Maneuver Detection, and TLE interface.
• Mission Design: $\Delta v$ Budgeting, Communication Link Budgets, and Ground Station Coverage tools.

Visualization & Analysis

• 3D Trajectories: Interactive Plotly-based orbital trajectory and attitude visualization.
• Telemetry Dashboards: Web-based GNC dashboards using Dash for real-time like simulation monitoring.
• Coordinate Frames: Visualizers for ECI, ECEF, Hill (RSW), and Body frame transformations.

Installation

From PyPI (Recommended)

pip install opengnc

From Source (Development)

git clone https://github.com/BatuhanAkkova/opengnc.git
cd opengnc
pip install -e ".[dev]"

Quick Start

import numpy as np
from opengnc.environment.mag_field import igrf_field
from opengnc.kalman_filters.mekf import MEKF
from opengnc.utils.quat_utils import quat_rot

# Get Earth's magnetic field at a specific ECI position
B_vec = igrf_field(pos_eci=np.array([7000e3, 0, 0]), time="2024-01-01")

# Initialize a Multiplicative Extended Kalman Filter
mekf = MEKF(q_init=np.array([0, 0, 0, 1]), covariance=1e-3 * np.eye(6))

Example Simulations

Application	Description	Visualization	Script
CubeSat Detumbling	B-Dot magnetic control using noisy magnetometer data.		01_cubesat_detumbling.py
MPC Rendezvous	Optimal multi-burn approach in GEO using NMPC.		04_autonomous_rendezvous.py
MEKF Estimation	High-fidelity orientation tracking fusing star tracker & gyro.		05_attitude_estimation_mekf.py
VLEO Maintenance	Altitude keeping in high-drag orbits using electric propulsion.		02_vleo_orbit_maintenance.py
Gauss IOD	Initial Orbit Determination from 3-LoS vectors.		10_gauss_iod_determination.py

License

Distributed under the MIT License. See LICENSE for more information.

Contributing & Support

Contributions are welcome! Please see CONTRIBUTING.md for guidelines. For support or feedback, please contact Batuhan Akkova.