DGNSS Ranging for CubeSat Rendezvous and Docking Manoeuvres at LEO

In the last decade, the expansion of the Terrestrial Service Volume (TSV) of Global Navigation Satellite Systems (GNSS) toward Medium-Earth Orbits (MEO) is gaining momentum. Low-Earth orbit (LEO) missions have investigated the quality of the GNSS observables, thus demonstrating its availability in near-Earth space. A timely case study is investigated in this work, where a CubeSat is expected to dock a LEO spacecraft while accurately tracking its baseline vector from the object. The mission scenario constitutes a unique chance for the characterization of differential GNSS measurements and the assessment of low-complexity relative GNSS algorithms oriented to collaborative navigation and Positioning, Navigation, and Timing autonomy in space. The paper analyses the simulation results for GNSS-based inter-spacecraft ranging (ISR) measurements leveraging differential, GPS, and Galileo measurements exchanged between the chaser and its mothership. Parametric results analyze the usability of ISRs in rendezvous and docking manoeuvres at LEO altitudes, by comparing their accuracy to pre-defined mission requirements. Output accuracy and precision bounds are eventually provided for the potential integration of ISR into hybrid navigation algorithms.