Global Positioning System Navigation Above 76,000 KM for NASA'S Magnetospheric Multiscale Mission

NASAs Magnetospheric Multiscale (MMS) mission, launched in March of 2015, consists of a controlled formation of four spin‐stabilized spacecraft in similar highly elliptic orbits reaching apogee distances of 12 and 25 Earth radii (RE) in the first and second phases of the mission. Navigation for MMS is achieved independently on‐board each spacecraft by processing Global Positioning System (GPS) observables using NASA Goddard Space Flight Center (GSFC)'s Navigator GPS receiver and Goddard Enhanced Onboard Navigation System (GEONS) extended Kalman filter software. To our knowledge, MMS constitutes, by far, the highest‐altitude operational use of GPS to date. In this paper, we highlight past and ongoing high‐altitude GPS research in and outside of GSFC, describe the MMS GPS navigation system, and present on‐orbit performance data from the first phase of the mission. We extrapolate these results to predict performance in the second phase orbit, and conclude with a discussion of the implications for future high‐altitude GPS navigation. Copyright © 2017 Institute of Navigation.