Multiple applications for this type of particle filter software package exist in the broader spaceflight community and outside of the aerospace industry entirely. The proposed particle filter based navigation system can serve any entity developing or operating space vehicles by providing positioning and timing estimates. This could be as a ground based analysis tool, an onboard flight software element, or both. In fact, the proposed software package could also easily support any other application where dynamic states must be estimated and is not limited to spaceflight dynamics problems. These potential applications for the navigator include providing solutions for ground-based GPS applications or for coupled rotation/translation filters on an unmanned aerial vehicle. Although this product will be developed primarily with the aerospace user in mind, the elements of PEP could be utilized in any application requiring particle filter capabilities. Particle filters are currently applied in many fields where the response of a highly complex system must be estimated from a wide variety of inputs. Such problems commonly arise in fields as diverse as economics, sociology, ecology and even epidemiology. This tool could be implemented by analysts at a variety of research institutions to enhance their capabilities with state-of-the-art particle filtering methods. This project has the capability to be an enabling technology for a wide range of technical estimation problems. The navigation system offered will be available as a "plugin" for several simulation analysis platforms including GMAT, GIPSY, and GEONS (potentially others), to provide users of these existing NASA tools with its advanced filtering capabilities. By providing this function to designers in an easily integrated package, users can benefit from the expanded capability provided during all phases of vehicle design, analysis, test and flight. This will be particularly useful during the early design stage when major decisions and trades are being made whose impacts are historically difficult to assess. The system can also be utilized during verification and assessment of designs brought forward by commercial providers to reliably ascertain the performance expected from a given hardware configuration and identify areas of weakness early in the design when they are most easily addressed. The product can also be utilized by those currently operating an on-orbit spacecraft or analyzing flight data to expand the capabilities of their navigation system. The proposed filtering package can be used to provide improved estimates of difficult to measure real-time effects like the gravitational potential of a small body or ionospheric error in a GPS measurement. The system can also be used as an inline analysis tool to provide a vehicle's position based on observation data or as a ground-analysis tool to verify the function of onboard algorithms and solutions.