Topology of the Relative Motion: Circular and Eccentric Reference Orbit Cases

This paper deals with the topology of the relative trajectories in flight formations. The purpose is to study the different types of relative trajectories, their degrees of freedom, and to give an adapted parameterization. The paper also deals with the research of local circular motions. Even if they exist only when the reference orbit is circular, we extrapolate initial conditions to the eccentric reference orbit case.This alternative approach is complementary with traditional approaches in terms of cartesian coordinates or differences of orbital elements

GENESIS: Co-location of Geodetic Techniques in Space

Improving and homogenizing time and space reference systems on Earth and, more directly, realizing the Terrestrial Reference Frame (TRF) with an accuracy of 1mm and a long-term stability of 0.1mm/year are relevant for many scientific and societal endeavors. The knowledge of the TRF is fundamental for Earth and navigation sciences. For instance, quantifying sea level change strongly depends on an accurate determination of the geocenter motion but also of the positions of continental and island reference stations, as well as the ground stations of tracking networks. Also, numerous applications in geophysics require absolute millimeter precision from the reference frame, as for example monitoring tectonic motion or crustal deformation for predicting natural hazards. The TRF accuracy to be achieved represents the consensus of various authorities which has enunciated geodesy requirements for Earth sciences. Today we are still far from these ambitious accuracy and stability goals for the realization of the TRF. However, a combination and co-location of all four space geodetic techniques on one satellite platform can significantly contribute to achieving these goals. This is the purpose of the GENESIS mission, proposed as a component of the FutureNAV program of the European Space Agency. The GENESIS platform will be a dynamic space geodetic observatory carrying all the geodetic instruments referenced to one another through carefully calibrated space ties. The co-location of the techniques in space will solve the inconsistencies and biases between the different geodetic techniques in order to reach the TRF accuracy and stability goals endorsed by the various international authorities and the scientific community. The purpose of this white paper is to review the state-of-the-art and explain the benefits of the GENESIS mission in Earth sciences, navigation sciences and metrology.Comment: 31 pages, 9 figures, submitted to Earth, Planets and Space (EPS

Altimetry for the future: Building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ‘‘Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion

Altimetry for the future: building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the “Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion

Orbitographie des satellites artificiels sur de grandes périodes de temps

Long term prediction of artificial satellites motionDepuis le lancement des premiers satellites artificiels, l'intégration numérique des équations différentielles régissant leur mouvement de révolution est venue très vite compenser le manque de précision des différentes théories analytiques compte tenu de la complexité croissante des fonctions de forces à intégrer. La méthode que nous avons développée, pour l'étude des systèmes dynamiques sur de grandes périodes de temps, s'attache à la détermination précise d'un mouvement moyen, autour du mouvement réel instantané. Sa force résulte de l'utilisation conjointe des méthodes de la mécanique céleste, pour transformer le système différentiel classique des équations du mouvement et de méthodes numériques récentes pour une intégration rapide, à grands pas. Les possibilités d'application sont d'abord liées à une détermination des constantes géophysiques, qui sont à l'origine des perturbations a longues périodes dans le mouvement de révolution des satellites artificiels. Plus généralement, la méthode de centrage s'applique à l'étude du comportement à long terme de systèmes dynamiques a plusieurs corps

Long-Term Behavior of the DORIS Oscillator Under Radiation: The Jason-2 Case

International audienc

Semi-analytical theory of the mean orbital motion

International audienc

Experimental and theoretical analysis of the inertial sensor prototype for the MICROSCOPE in-orbit test of the equivalence principle

L'objectif de la mission MICROSCOPE est la vérification en orbite du principe d'équivalence, avec une précision de 10^-15. Ce test sera réalisé avec deux masses d'épreuve de matériaux différents maintenues sur la même trajectoire par des forces électrostatiques dans un accéléromètre différentiel. L'instrument optimisé pour l'usage en orbite ne fonctionnant pas sur Terre, une série de modèles de développement est nécessaire. Le premier modèle fonctionnel est le sujet de cette thèse. Les équations de la capacité entre la masse et ses électrodes de contrôle sont développées, et une simulation numérique dynamique du capteur est créée pour définir les lois de commande de la masse. La précision de l'intégration du capteur est vérifiée avant de commencer l'expérimentation qui mène à la première lévitation d'une masse cylindrique. Les mesures obtenues avec ce modèle, une fois la configuration optimisée, constituent la première confirmation des prévisions théoriques de la performance du capteur.The MICROSCOPE mission is a space based test of the equivalence principle, to a precision of 10^-15. The test will be performed by a differential accelerometer in which two proof masses of different materials are held on the same trajectory by means of electrostatic forces. Because the instrument optimized for use in orbit can not function on ground, a series of development models are necessary. The first functional model, the prototype, is the subject of this thesis. The work begins with the development of equations for the capacitance between the proof mass and its control electrodes and the creation of a computer simulation required to define the mass control laws. The precision of the sensor integration is verified before beginning the experimentation which leads to the first complete levitation of a cylindrical proof mass. Measurements from the prototype, once in an optimal configuration, provide the first confirmation of the theoretical predictions of the sensor performance.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF