Galileo: évolution du positionnement

Summary of the evolution of Galileo over the last years. The increase in the number of satellites from 2014 to 2018 impacted the geometry and the positioning quality provided by the Galileo constellation. The Galileo-onyl and GPS-only positioning results are compared in 2018. We concluded that the GPS + Galileo combination improves the quality of the GPS-only and the Galileo-only positioning solutions based on single-frequency SPP, DGPS and RTK results

Discovery of 9-Cyclopropylethynyl-2-((S)-1-[1,4]dioxan-2-ylmethoxy)-6,7-dihydropyrimido[6,1-a]isoquinolin-4-one (GLPG1205), a unique GPR84 negative allosteric modulator undergoing evaluation in a phase II clinical trial

GPR84 is a medium chain free fatty acid-binding G-protein-coupled receptor associated with inflammatory and fibrotic diseases. As the only reported antagonist of GPR84 (PBI-4050) that displays relatively low potency and selectivity, a clear need exists for an improved modulator. Structural optimization of GPR84 antagonist hit 1, identified through high-throughput screening, led to the identification of potent and selective GPR84 inhibitor GLPG1205 (36). Compared with the initial hit, 36 showed improved potency in a guanosine 5′-O-[γ-thio]triphosphate assay, exhibited metabolic stability, and lacked activity against phosphodiesterase-4. This novel pharmacological tool allowed investigation of the therapeutic potential of GPR84 inhibition. At once-daily doses of 3 and 10 mg/kg, GLPG1205 reduced disease activity index score and neutrophil infiltration in a mouse dextran sodium sulfate-induced chronic inflammatory bowel disease model, with efficacy similar to positive-control compound sulfasalazine. The drug discovery steps leading to GLPG1205 identification, currently under phase II clinical investigation, are described herein

Positionnement relatif sur base des mesures de code du signal Galileo E5 AltBOC

Depuis une dizaine d’années, l’Europe développe son propre système de positionnement par satellites (ou Global Navigation Satellites System (GNSS) en anglais), connu sous le nom de Galileo. À la pointe de la technologie, les horloges atomiques embarquées à bord de ses satellites ainsi que les signaux transmis par ces derniers sont extrêmement prometteurs dans beaucoup de domaines. Bien que toujours en phase de test à l’heure actuelle, ce système a déjà conduit à de premières mesures, notamment en matière de positionnement. Parmi ces nouvelles technologies, un signal en particulier semble très prometteur : Galileo E5, aussi appelé Galileo E5a+b ou encore Galileo E5 AltBOC. Ce signal permet d’effectuer des mesures de code et de phase plus précises. Il est également moins sensible au multi-trajet. Grâce à ses caractéristiques innovantes, Galileo E5 devrait permettre d’estimer des positions avec une précision supérieure à tous les autres signaux utilisés aujourd’hui. Une étude comparative des positions estimées avec les systèmes GPS (américain) et Galileo (européen) sur leurs différentes fréquences émises (GPS L1, GPS L2, GPS L5 pour GPS et Galileo E1, Galileo E5a, Galileo E5b et Galileo E5 AltBOC pour Galileo) a été menée dans ce mémoire. Pour ce faire, une combinaison d’observations appelée double différence (DD) est utilisée sous différentes configurations (ligne de base nulle (ZB), courte (SB) et moyenne (MB)) de récepteurs GNSS. Les récepteurs utilisés appartiennent à l’Université de Liège (2 récepteurs Trimble NetR9, 1 récepteur Septentrio XS et un récepteur Septentrio X4). Il ressort de cette étude que Galileo E5 AltBOC présente les observations les plus précises (en ZB, toutes sources d’erreurs éliminées). L’analyse démontre également qu’une précision de l’ordre de quelques décimètres sur la position à déterminer peut être atteinte avec les codes transmis par le signal Galileo E5, et ce jusqu’à 25 kilomètres de distance.Europe has spent the last decade developing its own global satellite-based positioning system known as Galileo. Taking advantage of the latest technologies, the atomic clocks and the signals designed for this constellation are extremely promising. Although this system is still in test phase in 2015, it has already started broadcasting frequencies and allows Galileo-only positioning. Among the new signals provided by this constellation, the Galileo E5a+b, also known as Galileo AltBOC, is demonstrating great multipath mitigation capacities and a measurement noise reduced on the code pseudoranges. These two characteristics turn this signal into the most precise one amongst Galileo and GPS ones. In this master's thesis, we compared positioning results obtained with GPS-only and Galileo-only single-frequency DGPS solutions using GPS L1, L1, L5 and Galileo E1, E5a, E5b, E5a+b signals. We computed zero, short and medium baselines results with Septentrio XS, X4 and Trimble R9 receivers. We concluded that Galileo E5a+b signal presents the more precise observations and that positions may already be acheived at a few decimetres level precision in Galileo-only single-frequency DGPS mode in 2015 over short baselines up to 25 kilometres of distance

Precise positioning in multi-GNSS mode

Presentation to the Department of Geography of the University of Liège of the context of the research undertaken by the PhD Candidate Cécile Deprez. Multi-GNSS positioning improves single-GNSS positioning by many aspects including an increase in the number of satellites available for positioning and a reduction of the geometry impact. In addition, new signals show greater mutlipath mitigation (for instance Galileo E5a+b). Finally, single-frequency low-cost positioning devices could also benfit from multi-GNSS positioning and quantified results are provided to support this observation

GPS, Galileo and BeiDou: Evolution of satellite-based positioning

The modernization of GPS and the development of Galileo and BeiDou constellations improved the quality of the signals available for satellite-based positioning. The RTK solutions in multi-frequency, multl-GNSS mode are improved compared to single-frequency single-GNSS solutions for distances ranging from 20 metres to 20 kilometres

Positionnement relatif sur base des mesures de code du signal Galileo E5 AltBOC

Depuis une dizaine d’années, l’Europe développe son propre système de positionnement par satellites (ou Global Navigation Satellites System (GNSS) en anglais), connu sous le nom de Galileo. À la pointe de la technologie, les horloges atomiques embarquées à bord de ses satellites ainsi que les signaux transmis par ces derniers sont extrêmement prometteurs dans beaucoup de domaines. Bien que toujours en phase de test à l’heure actuelle, ce système a déjà conduit à de premières mesures, notamment en matière de positionnement. Parmi ces nouvelles technologies, un signal en particulier semble très prometteur : Galileo E5, aussi appelé Galileo E5a+b ou encore Galileo E5 AltBOC. Ce signal permet d’effectuer des mesures de code et de phase plus précises. Il est également moins sensible au multi-trajet. Grâce à ses caractéristiques innovantes, Galileo E5 devrait permettre d’estimer des positions avec une précision supérieure à tous les autres signaux utilisés aujourd’hui. Une étude comparative des positions estimées avec les systèmes GPS (américain) et Galileo (européen) sur leurs différentes fréquences émises (GPS L1, GPS L2, GPS L5 pour GPS et Galileo E1, Galileo E5a, Galileo E5b et Galileo E5 AltBOC pour Galileo) a été menée dans ce mémoire. Pour ce faire, une combinaison d’observations appelée double différence (DD) est utilisée sous différentes configurations (ligne de base nulle (ZB), courte (SB) et moyenne (MB)) de récepteurs GNSS. Les récepteurs utilisés appartiennent à l’Université de Liège (2 récepteurs Trimble NetR9, 1 récepteur Septentrio XS et un récepteur Septentrio X4). Il ressort de cette étude que Galileo E5 AltBOC présente les observations les plus précises (en ZB, toutes sources d’erreurs éliminées). L’analyse démontre également qu’une précision de l’ordre de quelques décimètres sur la position à déterminer peut être atteinte avec les codes transmis par le signal Galileo E5, et ce jusqu’à 25 kilomètres de distance.Europe has spent the last decade developing its own global satellite-based positioning system known as Galileo. Taking advantage of the latest technologies, the atomic clocks and the signals designed for this constellation are extremely promising. Although this system is still in test phase in 2015, it has already started broadcasting frequencies and allows Galileo-only positioning. Among the new signals provided by this constellation, the Galileo E5a+b, also known as Galileo AltBOC, is demonstrating great multipath mitigation capacities and a measurement noise reduced on the code pseudoranges. These two characteristics turn this signal into the most precise one amongst Galileo and GPS ones. In this master's thesis, we compared positioning results obtained with GPS-only and Galileo-only single-frequency DGPS solutions using GPS L1, L1, L5 and Galileo E1, E5a, E5b, E5a+b signals. We computed zero, short and medium baselines results with Septentrio XS, X4 and Trimble R9 receivers. We concluded that Galileo E5a+b signal presents the more precise observations and that positions may already be acheived at a few decimetres level precision in Galileo-only single-frequency DGPS mode in 2015 over short baselines up to 25 kilometres of distance

La maladie de Kawasaki (aspects épidémiologiques et physiopathologiques)

LILLE2-BU Santé-Recherche (593502101) / SudocSudocFranceF

Multi-GNSS relative positioning with Galileo, BeiDou and GPS

For several years, the number of Global Navigation Satellite Systems (GNSS) has been increasing, opening new perspectives in the field of precise positioning. Particularly, the European system, Galileo, is experiencing a prompt expansion with the launch, in 2015 and 2016, of 8 satellites belonging to the new Full Operational Capability (FOC) generation. Broadcasting new signals, with new modulations, the first studies addressing this system reveal promising level of precisions on both code and carrier phase observables. Yet, Galileo is far from being the only GNSS undergoing a noteworthy revolution. Alternatively, the Chinese program BeiDou, still in a developing phase, as well as the American GPS, currently undergoing a modernization of its signals, also knew major progress these last two years. Indeed, 7 new satellites have reached the initial BeiDou constellation, bringing to 20 the number of active satellites. Among them, 5 spacecraft inaugurated the Phase III generation, broadcasting the new B1, B2 and B3 signals. Regarding GPS, the block IIF, made of L5 signal broadcasting satellites, kept expanding but at a less steep rate than BeiDou or Galileo. In this study, we first estimated the individual precisions of each signals broadcast by the aforementioned GNSS. For this purpose, we created two short baselines of approximatively 5 meters between similar type receivers. We combined their measurements to form double differences, leaving in the position equations only multipath and receiver noise. The great expectations regarding Galileo’s quality turned into affirmations as long as we studied this system. As a matter of a fact, the code pseudoranges values of the 4 signals of Galileo we have considered (E1, E5a, E5b, E5a+b) presented outstanding precisions (from 5 to 17 centimetres on code pseudoranges with an elevation mask of 10 degrees) when compared to GPS (from 12 to 20 centimetres on codes pseudoranges) and BeiDou (from 26 to 40 centimetres for codes and for phases) in identical conditions. Even though the precision of Galileo observables is noticeable, the influence of the poor geometry of the satellite constellation degrades in a significant way the resulting precision of the position estimated, no matter the recent increase in the number of satellites. Indeed, in this incomplete constellation, the addition of new satellites results in longer visibility period but not in larger number of satellites observed at a single epoch. Combining Galileo with GPS or BeiDou is a way to solve this issue, as the three systems have been designed to be compatible. Therefore, multi-GNSS relative positioning based on overlapping frequencies should entail better accuracy and reliability in position estimations. However, the differences between satellite systems induce inter-system biases (ISBs) inside the multi-GNSS equations of observation. The overlapping frequencies of these GNSS are the L1 and L5 frequencies of GPS with the E1 and E5a signals of Galileo, respectively. As far as BeiDou is concerned, the B2 signal of emitted by the Phase II BeiDou satellites corresponds to the E5b frequency of Galileo. Regarding the new Phase III satellites, the B2 frequencies will correspond to the Galileo E5a+b signal and B1 of BeiDou will be compatible with E1 of Galileo and GPS. The combined use of these overlapping frequencies in zero baseline double differences (ZB DD) based on a unique pivot satellite is employed to resolve ISBs. This model removes all the satellite- and receiver-dependent error sources by differentiating and the zero baseline configuration allows atmospheric and multipath effects elimination. We conducted this study on the L1/E1, L5/E5a, B1(phase II)/E5b overlapping frequencies. Our receivers were not able to receive the phase III signals of BeiDou satellites. An analysis of the long-term stability of ISBs (GPS- Galileo and Galileo - BeiDou) was conducted on various pairs of receivers over large time spans. The possible influence of temperature variations inside the receivers over ISB values was also investigated. Our study is based on the 6 multi-GNSS receivers (2 Septentrio PolaRx4, 1 Septentrio PolaRxS, 1 Septentrio PolaRx5 and 2 Trimble NetR9) installed on the roof of our building in Liege. The estimated ISBs are then used as corrections in the multi- GNSS observation model and the resulting accuracy of multi-GNSS positioning is compared to GPS, Galileo and BeiDou standalone solutions

Operational Envelope and Link Scheduling for Inter-Satellite Links in Next-Generation GNSSs

Future global navigation satellite systems (GNSSs) may implement inter-satellite links (ISLs) enabling one-to-one connections between satellites of the constellation, making available an intra-system communication layer, supporting clock synchronization, and providing precise ranging. We analyse in this work the problem of scheduling inter-satellite links for a number of scenarios in which satellites are equipped with limited numbers of ISL terminals capable of point-to-point connections. Two baseline architectures are addressed. The first is based on an evolution of the current Galileo system, in which two ISL terminals are assumed to be installed on each navigation satellite. The second architecture is an envisioned evolution of the Galileo system, with name Kepler, in which a Galileo-like Medium Earth Orbit (MEO) segment is composed of satellites with two terminals for MEO-to-MEO links and a third terminal for linking to Low Earth Orbit (LEO) satellites. The MEO-to-MEO links between neighboring satellites in the same orbital plane are assumed continuous. The MEO segment is complemented with a constellation of LEO satellites carrying ISL terminals and zenith-pointing antennas for GNSS signal monitoring in space. Different schedulers are proposed for the two scenarios, factoring multiple operational constraints such as number of available ISL terminals on each satellite, terminal’s field-of-regard (azimuth and elevation span), maximum link range, and minimum required duration of each link. Within these boundaries, a link schedule is applied to determine which satellites are paired over time. The pairing criterion aims at establishing dynamically changing closed paths that maintain all the satellites of the constellation connected over time. We analyze the link scheduling strategy devised on the two system architectures proposed, and provide a number of key performance parameters as function of the operational envelope of the ISL terminals and, for the Kepler scenario, for a number of different LEO constellations