Study of high sensitivity GNSS receivers for space applications and lunar missions

Experimentally validating the use of in-orbit Global Navigation Satellite Systems (GNSS) receivers within the Space Service Volume (SSV) has been accomplished at LEO, MEO, and GEO altitudes respectively. Therefore, the most recent missions have revealed the GNSS performance at distances of approximately 150,000 kilometers away from the surface of the Earth. The study of Earth GNSS signals beyond such an altitude is still a matter of research, and it is primarily based on modeling and extrapolation from the experience of using GNSS on both the surface of the Earth and on lower orbits. The Lunar GNSS Receiver Experiment (LuGRE) is a payload that will be carried by the Firefly Blue Ghost Mission 1 and will be a joint effort between NASA and the Italian Space Agency (ASI). Its purpose is to demonstrate GNSS-based positioning, navigation, and timing on the Moon. After its launch in 2024, the LuGRE spacecraft will collect GPS and Galileo measurements while traveling between Earth and the Moon, while in lunar orbit, and on the surface of the Moon. It will also use the data it collects to conduct onboard and ground-based nav- igation experiments using the collected information. These investigations are going to be based on the observation of the data that was collected by a custom development that was carried out by the company Qascom, and it was based on the Qascom QN400-Space GNSS receiver. The QN400’s hardware construction as well as its software implementation are both modular in nature. A Radio Frequency (RF) front-end and a baseband processor that is created using Software Defined Radio (SDR) technologies are the two primary components that make up the receiver. PVT solutions, GNSS raw observables obtained by the real time operation, as well as snapshots of IF digital samples collected by the RF front-end at frequencies L1/E1 and L5/E5 for GPS and Galileo can all be provided by the receiver. Additionally, the receiver is able to provide snapshots of GNSS raw observables obtained in real time. These data will be the input for the various scientific investigations, which will then require the development of appropriate analysis tools in order to serve as the core of the ground segment while the mission is being carried out. The science team of NASA and ASI, which is supported by a research team at Politec- nico di Torino, is currently working on planning the data acquisitions that will take place during the time windows that are dedicated to the LuGRE payload during the checkout, transit, and surface mission phases. The purpose of this thesis is to investigate the different types of processing that can be performed on a snapshot that has been recorded by the Qascom receiver over a spe- cific amount of time. This can be helpful when planning the time windows that will be dedicated to the collection of snapshots as well as designing the duration of those time windows. In order to accomplish this goal, the snapshots were simulated by both our team and Qascom by accurately modeling the space environment. This is an essential step, as this type of analysis has never been conducted and there is no signal available at these distances. The tracking stage, which is more critical than the acquisition stage, is the primary focus of the analysis. The goal is to come up with a snapshot duration that enables at least one tracking lock condition to be reached. Data storage and transmission limitations limit the snapshot duration's value. This thesis's examination is therefore paramount.