By Simone D'Amico August 6, 2018
The Distributed multi-GNSS Timing and Localization system (DiGiTaL) is under testing at NASA Goddard's Space Flight Center, Greenbelt, MD. DiGiTaL is being developed by the Stanford's Space Rendezvous Lab (SLAB) under NASA STTP's contract. The lead PhD student, Vince Giralo, is spending a Summer internship at NASA GSFC under the supervision of Neerav Shah and its navigation team to test functionality and performance of DiGiTaL. NASA GSFC offers a unique testbed infrastructure for multi-constellation and multi-frequency Global Navigation Satellite System (GNSS) receivers and antennas, which is routinely used to support a variety of single spacecraft and formation-flying projects such as the recent ground-breaking Magnetospheric Multiscale (MMS) Mission.
The goal of DiGiTaL is to provide nanosatellite formations with unprecedented, centimeter-level navigation accuracy in real-time and nanosecond-level time synchronization ( read recent publication). This is achieved through the integration of a multi-constellation (GNSS) receiver, a Chip-Scale Atomic Clock (CSAC), and a dedicated Inter-Satellite Link (ISL). In comparison, traditional single spacecraft GNSS navigation solutions are accurate only to the meter-level due to the sole usage of coarse pseudorange measurements. To meet the strict requirements of future miniaturized distributed space systems, DiGiTaL uses powerful error-cancelling combinations of raw carrier-phase measurements which are exchanged between the swarming nanosatellites through a decentralized network. A reduced-dynamics estimation architecture on board each individual nanosatellite processes the resulting millimeter-level noise measurements to reconstruct the full formation state with high accuracy.
The test campaign is lead by Vince Giralo with the help of master student Eric Thomas Stoker-Spirt who is a prospective PhD candidate of SLAB. All our wishes of success to them in this delicate and important verification and validation phase!