GNSS software receiver as navigation sensor in very high orbits

Space navigation in very high Earth orbits and in lunar transfers is based mainly on ground-based tracking. It can be possible to spare the expensive and complex control segment by making the most of Global Navigation Satellite Systems (GNSS). A suitable receiver would be an application-specific sensor, based on software radio architecture and quite different from typical terrestrial devices, meaning that it will lacks the tracking section and will work in the so-called snapshot mode. The knowledge of the orbital dynamics and a moderate quality onboard clock can provide a first solution estimate which is accurate enough for the sensor to meaningfully exploit, with the help of a limited external aiding, the received signals. The receiver therefore becomes a navigation sensor working outside the primary GNSS service volume, where signals are extremely weak and frequently disrupted by outages.