Analysis of 3GM Callisto Gravity Experiment of the JUICE Mission

The ESA's JUICE mission will provide a thorough investigation of the Jupiter system and the Galilean moons during its nominal tour, comprising flybys of Europa and Callisto, and an orbital phase about Ganymede at the end of the mission. The 3GM experiment will exploit accurate Doppler and range measurements to determine the moons' orbits and gravity fields (both static and tidal) and infer their interior structure. This paper presents the attainable accuracies of the Callisto geodesy experiment and addresses the effect of different flybys mean anomaly distribution and geometry on the estimation of the tidal Love number k2.Comment: 2020 AAS/AIAA Astrodynamics Specialist Conference, Virtual Lake Taho

Time transfer and orbit determination for a Martian navigation system based on smallsats

We present a novel mission concept that can be used to support a near-autonomous navigation of different kind of users, such as rovers or landers in EDL (entry, descent and landing) phase, operating in the martian environment. We propose a constellation of 5 small satellites in polar orbits able to acquire their position in a Mars-fixed reference frame with minimal support from Earth thanks to a high accuracy Doppler system enabled by a novel inter-satellite link (ISL) communication architecture. The high quality of range rate measurements relies on radio link architectures able to suppress the adverse effects of on-board clock instabilities. Periodic synchronisation of the main spacecraft (mothercraft) with Earth UTC/TAI is enabled through a direct link to Earth, while the synchronization within the constellation is performed individually between each mothercraft-daughtercraft pair through the ISL, using a novel approach based on two-way coherent ranging measurements. The current orbital configuration provides mainly a regional coverage, but the navigation service could be easily expanded to cover the entire planet. In this work, we describe the overall system architecture and the time synchronization techniques, resulting from a tradeoff conducted both by analysis and numerical simulations, in terms of positional accuracy, reuse of the existing ground infrastructure, TRL of the onboard RF instrumentation and cost. We show that this navigation system, based on a simple and low-cost architecture, can autonomously reconstruct the trajectories of its nodes with ∼10 meters accuracy (3a, worst case) and can achieve a time synchronization accuracy at ns level, being on target to provide meter-level positioning service to a variety of end users

Active Fault Systems in the Inner Northwest Apennines, Italy: A Reappraisal One Century after the 1920 Mw ~6.5 Fivizzano Earthquake

International audienceBased on the review of the available stratigraphic, tectonic, morphological, geodetic, and seismological data, along with new structural observations, we present a reappraisal of the potential seismogenic faults and fault systems in the inner northwest Apennines, Italy, which was the site, one century ago, of the devastating Mw ~6.5, 1920 Fivizzano earthquake. Our updated fault catalog provides the fault locations, as well as the description of their architecture, large-scale segmentation, cumulative displacements, evidence for recent to present activity, and long-term slip rates. Our work documents that a dense network of active faults, and thus potential earthquake fault sources, exists in the region. We discuss the seismogenic potential of these faults, and propose a general tectonic scenario that might account for their development