Papers by Julien LAURENT-VARIN
HAL (Le Centre pour la Communication Scientifique Directe), Jul 9, 2012
HAL (Le Centre pour la Communication Scientifique Directe), Oct 15, 2010
Advances in Space Research, 2018
Numerische Mathematik, Dec 16, 2005
HAL (Le Centre pour la Communication Scientifique Directe), Jul 4, 2011
This paper addresses the topic of damping of the spinning dynamics of a spatial debris orbiting a... more This paper addresses the topic of damping of the spinning dynamics of a spatial debris orbiting around the Earth. Such debris, which can consists of parts of heavy launchers such as the Ariane rocket under consideration in this article, are impacted by torques generated by eddy currents as the conducting nonferromagnetic body orbits through the Earth magnetosphere. Several previous works have focused on describing this induction phenomenon and have proposed analysis of empirical observations of this particular and important phenomenon which has attracted much attention since the number of spatial debris has emerged as a problem for the future of space programs, especially in low orbits. In this paper, we expose a relatively comprehensive modeling of the induction phenomenon, by means of Maxwell equations inside the conducting and non-ferromagnetic body. Through the generalized Ohm's law, we show how one can obtain a Neumann partial differential equations problem that, once solved, e.g. through a considered finite elements method, yields the value of induced currents and braking torques. The case of a spatial debris, being a part of a heavy launcher, having a cylindrical shape and thin walls is particularly studied. We show a methodology to estimate the decay-rate of the spinning velocity, which is proven to satisfy a first-order asymptotically stable linear dynamics. Special cases consisting of orbits of interest are treated.
<p>In the framework of the MMX (Martian Moons Exploration) mission, a geodesy team ... more <p>In the framework of the MMX (Martian Moons Exploration) mission, a geodesy team from CNES has joined Geodesy Sub-Science Team to study the estimation of geodetic parameters of a natural satellite of Mars: Phobos.</p> <p>The MMX mission aims to return a sample of Phobos to Earth, but during the mission, exceptional observations of this natural satellite will be made. What insight into the geodetic parameters of Phobos will be gained from these measurements? The available measurements will be: LIDAR measurements between the probe and the surface of Phobos, 2-way Doppler and range measurements between ground stations on Earth and the probe, as well as optical measurements from photos taken by the probe.</p> <p>The presentation will focus on the results obtained on the restitution of gravity field parameters, Phobos ephemerides, as well as rotation and orientation parameters of the natural satellite, from synthetic measurements simulated on coherent QSO (Quasi Satellite Orbit) of the current mission analysis.</p> <p>The LIDAR measurements correspond to a distance measurement between the surface of the body and the onboard instrument. This very accurate measurement (sigma = 22m @ 100 km) [R1] allows the trajectory to be constrained, but is dependent on the quality of the body shape model.</p> <p>The 2-Way Doppler measurements contain information on the velocity of the probe in the line of sight. These measurements are available during spacecraft observation sessions by ground stations which can be multiple at a rate of one measurement per minute.</p> <p>Optical measurements are angular landmark measurements on the surface of the body. Like LIDAR measurements, these contain information on the relative position of the probe with respect to the natural satellite. These measurements are derived from a pre-processing of the wide angle and narrow angle photos taken by the OROCHI and TENGOO instruments [R2].</p> <p>The combination of these three types of measurements will be used to estimate the various geodetic parameters of Phobos throughout the mission. Indeed, the first and most distant orbits (QSO-H) should allow to estimate the ephemeris of Phobos as well as the low-degree coefficients of the gravity field and rotation parameters including amplitude of libration in longitude. As the mission progresses, the spacecraft will orbit Phobos with closer and closer trajectories (QSO-M, QSO-L) which will allow to refine the first estimates made at QSO-H as well as the coefficients of the higher degree field.</p> <p>This knowledge of the field and the attitude of Phobos will thus allow a precise study of the internal structure of the body.</p> <p>[R1]    Light detection and ranging (LIDAR) laser altimeter for the Martian Moons Exploration (MMX) spacecraft - <em>Senshu et al. (2021)</em> https://doi.org/10.1186/s40623-021-01537-7</p> <p>[R2]    Design of telescopic nadir imager for geomorphology (TENGOO) and observation of surface refectance by optical chromatic imager (OROCHI) for the Martian Moons Exploration (MMX) - <em>Kameda et al. (2021)</em> https://doi.org/10.1186/s40623-021-01462-9</p>
IFAC Proceedings Volumes, Jun 1, 2004
NicoLas.Berend~onera.fr •••• CNES : launcher directorate Rond-point de l'Espace-910~3 Evry Cedex ... more NicoLas.Berend~onera.fr •••• CNES : launcher directorate Rond-point de l'Espace-910~3 Evry Cedex christophe. taLbotlcnes.fr t MaUre de Conferences UMR 66~8-MAPMO B.P. 6759 45067 Orleans cedex ~ mounir.haddou~Labomath.univ-orLeans•fr
56th International Astronautical Congress of the International Astronautical Federation, the International Academy of Astronautics, and the International Institute of Space Law, Oct 17, 2005
Acta Astronautica, 2016
On the 12th of November 2014, The Rosetta Lander Philae became the first spacecraft to softly lan... more On the 12th of November 2014, The Rosetta Lander Philae became the first spacecraft to softly land on a comet nucleus. Due to the double failure of the cold gas hold-down thruster and the anchoring harpoons that should have fixed Philae to the surface, it spent approximately two hours bouncing over the comet surface to finally come at rest one km away from its target site. Nevertheless it was operated during the 57 h of its First Science Sequence. The FSS, performed with the two batteries, should have been followed by the Long Term Science Sequence but Philae was in a place not well illuminated and fell into hibernation. Yet, thanks to reducing distance to the Sun and to seasonal effect, it woke up at end of April and on 13th of June it contacted Rosetta again. To achieve this successful landing, an intense preparation work had been carried out mainly between August and November 2014 to select the targeted landing site and define the final landing trajectory. After the landing, the data collected during on-comet operations have been used to assess the final position and orientation of Philae, and to prepare the wake-up. This paper addresses the Flight Dynamics studies done in the scope of this landing preparation from Lander side, in close cooperation with the team at ESA, responsible for Rosetta, as well as for the reconstruction of the bouncing trajectory and orientation of the Lander after touchdown.
Unité de recherche INRIA Futurs Parc Club Orsay Université, ZAC des Vignes, 4, rue Jacques Monod,... more Unité de recherche INRIA Futurs Parc Club Orsay Université, ZAC des Vignes, 4, rue Jacques Monod, 91893 ORSAY Cedex (France) Téléphone : +33 1 72 92 59 00 Télécopie : +33 1 60 19 66 08 ... Asymptotic expansion of the optimal control under
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Papers by Julien LAURENT-VARIN