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Harris A.W.,German Aerospace Center | Barucci M.A.,LESIA Observatoire de Paris | Cano J.L.,Deimos Space | Fitzsimmons A.,Queen's University of Belfast | And 10 more authors.
Acta Astronautica | Year: 2013

Although discussions are underway within the Action Team 14 of the United Nations COPUOS, there is currently no concerted international plan addressing the impact threat from near-Earth objects (NEOs) and how to organize, prepare and implement mitigation measures. We report on a new international project to address impact hazard mitigation issues, being the subject of a proposal submitted to the European Commission in response to the 2011 FP7 Call "Prevention of impacts from near-Earth objects on our planet". Our consortium consists of 13 research institutes, universities, and industrial partners from 6 countries and includes leading US and Russian space organizations. The primary aim of the project, NEOShield, is to investigate in detail the three most promising mitigation techniques: the kinetic impactor, blast deflection, and the gravity tractor, and devise feasible demonstration missions. Furthermore, we will investigate options for an international strategy for implementation when an actual impact threat arises. The NEOShield project was formally accepted by the European Commission on 17 November 2011 and funded with a total of 5.8 million Euros for a period of 3.5 years. The kick-off meeting took place at the DLR Institute of Planetary Research, Berlin, in January 2012. In this paper we present a brief overview of the planned scope of the project. © 2012 IAA. Published by Elsevier Ltd. All rights reserved.

Sicardy B.,University Pierre and Marie Curie | Talbot J.,Occultation Section of the Royal Astronomical Society of New Zealand RASNZ | Meza E.,University Pierre and Marie Curie | Camargo J.I.B.,Observatorio Nacional MCTI | And 72 more authors.
Astrophysical Journal Letters | Year: 2016

We present results from a multi-chord Pluto stellar occultation observed on 2015 June 29 from New Zealand and Australia. This occurred only two weeks before the NASA New Horizons flyby of the Pluto system and serves as a useful comparison between ground-based and space results. We find that Pluto's atmosphere is still expanding, with a significant pressure increase of 5 ± 2% since 2013 and a factor of almost three since 1988. This trend rules out, as of today, an atmospheric collapse associated with Pluto's recession from the Sun. A central flash, a rare occurrence, was observed from several sites in New Zealand. The flash shape and amplitude are compatible with a spherical and transparent atmospheric layer of roughly 3 km in thickness whose base lies at about 4 km above Pluto's surface, and where an average thermal gradient of about 5 K km-1 prevails. We discuss the possibility that small departures between the observed and modeled flash are caused by local topographic features (mountains) along Pluto's limb that block the stellar light. Finally, using two possible temperature profiles, and extrapolating our pressure profile from our deepest accessible level down to the surface, we obtain a possible range of 11.9-13.7 μbar for the surface pressure. © 2016. The American Astronomical Society. All rights reserved.

Benecchi S.D.,Planetary Science Institute | Benecchi S.D.,Carnegie Institution of Washington | Noll K.S.,NASA | Thirouin A.,Institute Astrofisica Of Andalucia Iaa Csic | And 8 more authors.
Icarus | Year: 2014

A superior mutual event of the Kuiper Belt binary system (79360) Sila-Nunam was observed over 15.47. h on UT 7/8 February 2013 by a coordinated effort at four different telescope facilities; it started ~1.5. h earlier than anticipated, the duration was ~9.5. h (about 10% longer than predicted), and was slightly less deep than predicted. It is the first full event observed for a comparably sized binary Kuiper Belt object. We provide predictions for future events refined by this and other partial mutual event observations obtained since the mutual event season began. © 2013 Elsevier Inc.

Baoyin H.,Tsinghua University | Liu X.,Tsinghua University | Beauvalet L.,IMCCE Observatoire de Paris
Monthly Notices of the Royal Astronomical Society | Year: 2013

In this study, the potential locations of asteroidal small satellites (also called moonlets) with quasi-circular mutual orbit are analysed. For the motion of the moonlets, only the solar gravity perturbation and the primary's second degree-and-order gravity field are considered. By eliminating short periodic terms, the dynamical behaviour of the Hamiltonian for the moonlets is investigated. The observational data of some high-size-ratio binary asteroids show that the orbits of the moonlets lie close to the classical Laplace equilibrium points, which reach global minimum values of the Hamiltonian. It is found that tides or Yarkovsky effects alone cannot account for the reason why the orbits of asteroidal moonlets are not exactly at the classical Laplace equilibrium points. The analysis in this study is expected to provide useful information for the potential locations of asteroidal moonlets, and contribute to principles to relate predictions to observations. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Krupp N.,University of California at Los Angeles | Khurana K.K.,University of California at Los Angeles | Iess L.,University of Rome La Sapienza | Lainey V.,IMCCE Observatoire de Paris | And 4 more authors.
Space Science Reviews | Year: 2010

The outer planets of our solar system Jupiter, Saturn, Uranus, and Neptune are fascinating objects on their own. Their intrinsic magnetic fields form magnetic environments (so called magnetospheres) in which charged and neutral particles and dust are produced, lost or being transported through the system. These magnetic environments of the gas giants can be envisaged as huge plasma laboratories in space in which electromagnetic waves, current systems, particle transport mechanisms, acceleration processes and other phenomena act and interact with the large number of moons in orbit around those massive planets. In general it is necessary to describe and study the global environments (magnetospheres) of the gas giants, its global configuration with its large-scale transport processes; and, in combination, to study the local environments of the moons as well, e.g. the interaction processes between the magnetospheric plasma and the exosphere/atmosphere/magnetosphere of the moon acting on time scales of seconds to days. These local exchange processes include also the gravity, shape, rotation, astrometric observations and orbital parameters of the icy moons in those huge systems. It is the purpose of this chapter of the book to describe the variety of the magnetic environments of the outer planets in a broad overview, globally and locally, and to show that those exchange processes can dramatically influence the surfaces and exospheres/atmospheres of the moons and they can also be used as a tool to study the overall physics of systems as a whole. © 2010 Springer Science+Business Media B.V.

Le Fevre C.,French National Center for Space Studies | Fraysse H.,French National Center for Space Studies | Morand V.,French National Center for Space Studies | Lamy A.,French National Center for Space Studies | And 4 more authors.
Proceedings of the International Astronautical Congress, IAC | Year: 2012

Space debris mitigation is one objective of the French Space Operations Act, in line with IADC (Inter-Agency Spacc Debris Coordination Committee) recommendations, through the removal of non-operational objects from populated regions. At the end of their mission, space objects are to be placed on orbits that will minimize future hazards to space objects orbiting in the same region. The French Space Act, which came into force in 2010, ensures that technical risks associated with space activities are properly mitigated. The Act confers CNES a central support role in providing technical expertise to government on regulations dealing with space operations. In order to address the compliance of disposal orbits with the law technical requirements, CNES draws up Good Practices as well as a dedicated tool, STELA (Semi-Analytical Tool for End of Life Analysis). The verification of the criteria of the French Space Act requires long term orbit propagation to evaluate the evolution of the orbital elements over long time scales (up to more than 100 years). The Good Practices define the minimum dynamical model required to compute the orbital evolution with sufficient accuracy, and detail key computation hypotheses such as drag and reflecting areas, drag coefficient, reflectivity coefficient, solar activity, atmospheric density model and so on. They also recommend a methodology adapted to each orbit type (LEO, GEO, GTO) to assess the criteria of the French Space Act. The most recent works have concerned GTO orbits, for which some couplings occur between dynamic perturbations. A small change in the initial conditions or in the estimation of the drag effect will significantly change the entrance conditions in resonance areas and thus the orbital evolution. To cope with this difficulty, a statistical method has been developed. This paper gives an overview of the good practices for orbit propagation in LEO, GEO and GTO orbits as well as a brief description of the STELA tool. It explains the specificities of the GTO orbits and the need for a statistical approach, through a Monte-Carlo campaign of orbital propagations. Then, it raises the question of the statistical convergence and proposes a method to estimate a confidence interval for the results. Finally, we present an example of application of this methodology for some reference cases of GTO orbits. Copyright © (2012) by the International Astronautical Federation.

Daquin J.,Thales Alenia | Deleflie F.,IMCCE Observatoire de Paris | Mercier P.,Thales Alenia | Perez J.,ENSTA ParisTech
Advances in the Astronautical Sciences | Year: 2014

We confront stability results coming from the mean motion theory and the osculating theory in orbital mechanics. The dynamical area studied correspond to the (2:1) tesseral resonance. We present Fast Lyapunov Indicator stability maps, based on the integration of the variational equations, realized in various dynamical configurations and in particular for eccentric orbits. Our main conclusions supports the idea that the tesseral chaos is not sensitive to the averaging process and validate, on a stability point of view, the minimal model implemented in our mean orbit propagator.

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