*[100,000 Stars](https://stars.chromeexperiments.com/) - 100,000 Stars is an interactive visualization of the stellar neighborhood showing the location of 119,617 nearby stars.

*[ANISE](https://github.com/nyx-space/anise) - ANISE provides a toolkit and files for Attitude, Navigation, Instrument, Spacecraft, and Ephemeris data. It's a modern replacement of the NAIF SPICE toolkit.

*[Celestia](https://celestia.space/) - Free real-time 3D visualization of space. (See also[Celestia Motherlode](http://www.celestiamotherlode.net/) for many add-ons.)

*[Cesium.js](https://cesiumjs.org/) - An open-source JavaScript library for world-class 3D globes and maps

*[Gaia Sky](https://zah.uni-heidelberg.de/institutes/ari/gaia/outreach/gaiasky/) - Real-time, 3D, astronomy visualization software developed in the framework of ESA's Gaia mission. Runs on Windows, Linux and macOS.

*[GMAT](https://sourceforge.net/projects/gmat/) - The General Mission Analysis Tool (GMAT) is a space trajectory optimization and mission analysis system (NASA)

*[GO by ienai SPACE](https://go.ienai.space) - A software tool which allows for general design and optimization of missions with electric propulsion systems.

*[NASA Ames Research Center Trajectory Browser](https://trajbrowser.arc.nasa.gov/traj_browser.php) - A tool to find spacecraft trajectories to planets and small-bodies

*[nyx](https://gitlab.com/chrisrabotin/nyx) - Nyx is a high fidelity astrodynamics toolkit for mission design and orbit determinationwrittenin Rust,[validated against GMAT](https://gitlab.com/chrisrabotin/nyx/blob/master/VALIDATION.md).

*[Nyx](https://github.com/nyx-space/nyx) - Nyx is a high fidelity astrodynamics toolkit for mission design and orbit determination in Rust and Python, used on several lunar missions.

*[Open Space Toolkit](https://github.com/open-space-collective/open-space-toolkit) - Collection of versatile software libraries for space engineering applications (e.g., environment modeling, orbit and access computation).

*[poliastro](https://github.com/poliastro/poliastro) - Poliastro is an open source pure Python package dedicated to problems arising in Astrodynamics and Orbital Mechanics. Focuses on interplanetary design.

*[smd](https://github.com/ChristopherRabotin/smd) - A SPICE-enhanced continuous thrust interplanetary mission propagator and visualizer.

*[SPICE](https://naif.jpl.nasa.gov/naif/toolkit.html) - Ephemerides library used by JPL for their missions.[SpiceyPy](https://github.com/AndrewAnnex/SpiceyPy) is a Python wrapper.

*[SpOCK](https://github.com/deflorio/SpOCK/) - The Spacecraft Orbital Computations Kit is an open source tool for spacecraft mission analysis and simulation.

*[Systems Tool Kit (STK)](https://www.agi.com/products/stk) - Simulate missions and create reports, graphs, and 3D animations (paid). From Analytical Graphics, Inc.