Distributed multi‐GNSS timing and localization for nanosatellites

Abstract

Recent advances in distribution and miniaturization among spacecraft and expansion of global navigation satellite systems (GNSS) motivate the Distributed Multi-GNSS Timing and Localization system. The DiGiTaL system is intended to provide nanosatellite swarms with unprecedented centimeter-level relative navigation accuracy in real time and nanosecond-level time synchronization through the integration of a multiconstellation GNSS receiver, a chipscale atomic clock, and an intersatellite link. This paper describes DiGiTaL's hardware and software design, architecture, and navigation software in detail. The swarming spacecraft are grouped into subsets, where differential GNSS is performed by a precise orbit determination module with integer ambiguity resolution in real time. The resulting precise orbits are then exchanged and fused by a swarm determination module, creating full-swarm knowledge. Finally, the DiGiTaL architecture is integrated into CubeSat avionics and tested with key hardware in the loop using Stanford's GNSS navigation testbed. For the first time, this paper shows the capability to perform centimeter-level precise relative navigation using commercial-off-the-shelf CubeSat hardware for spacecraft swarms.