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Goddard Engineering and Technology Directorate

Goddard Enhanced Onboard Navigation System (GEONS) 

Global Positioning System (GPS) Satellite Illustration Credit: NASA
Global Positioning System (GPS) Satellite Illustration Credit: NASA

Flight Software Engineered to Satisfy Cost and Resource Constraints

The Goddard Enhanced Onboard Navigation System (GEONS) is an enterprise, multi-mission, flight software library with associated tools that provides high-accuracy orbit, time, and attitude (future capability) solutions. GEONS can be used for onboard autonomous navigation, ground-based operational navigation, and ground-based simulation and analysis of navigation systems. For flight applications, the GEONS flight software can be integrated either within a GPS receiver, a communications receiver, or a spacecraft onboard computer. GEONS processes data from GPS receivers, ground stations, spacecraft crosslinks, cameras, accelerometers, and attitude sensors to produce accurate absolute and relative navigation solutions in real time. Additional capabilities include fault detection, time and coordinate transformations, and onboard maneuver planning for absolute and relative orbits. GEONS is written in ANSI standard C with object-oriented techniques, and it uses a UD-factorized Extended Kalman filter (EKF) architecture. The software includes high-fidelity dynamics models, including non-spherical gravity, third body gravitational perturbations, solar radiation pressure, atmospheric drag, process noise models, and clock error models. GEONS is highly configurable, which allows it to support a wide variety of applications.

The core GEONS algorithms and software have 20+ years of flight heritage. GEONS was integrated with the Navigator GPS receiver for NASA’s Magnetospheric MultiScale (MMS) and Global Precipitation Measurement (GPM) missions and continues to provide onboard navigation for these missions. GEONS is also flying on the International Space Station (ISS) providing navigation using pulsar X-ray measurements as part of the Station Explorer for X-ray Timing and Navigation Technology (SEXTANT) experiment on the Neutron Star Interior Composition Explorer Mission (NICER) mission. GEONS was going to provide onboard navigation for the On-orbit Servicing, Assembly, and Manufacturing 1 (OSAM-1) mission before its cancellation. Additionally, GEONS is a key component of the autonomous Navigation Guidance and Control (autoNGC) flight software currently under development at NASA Goddard. Although GEONS has only flown for Earth orbiting missions to date, it can support a wide range of orbit regimes including cislunar/lunar space and beyond.

The mathematical specifications for GEONS 3.0 are publicly available at https://ntrs.nasa.gov/citations/20240004259. GEONS 3.0 may be made available to government entities and government contractors through a Government Purposes license. For additional information, please contact Nathan Stacey at nathan.i.stacey@nasa.gov.

The Goddard Enhanced Onboard Navigation System (GEONS) is managed by ETD’s Mission Engineering & System Analysis Division (MESA). Contact MESA for more information.