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2. Comparing Methods for Gravitational Computation: Studying the Effect of Inhomogeneities

Author

Matthias Noeker, Hermann Meißenhelter, Tom Andert, René Weller, Özgür Karatekin, and Benjamin Haser

Abstract

Introduction Current and future small body missions, such as the ESA Hera mission [1] or the JAXA MMX mission [2] demand good knowledge of the gravitational field of the targeted celestial bodies. This is not only motivated to ensure the precise spacecraft operations around the body, but likewise important for landing manoeuvres, surface (rover) operations, and science, including surface gravimetry [3]. To model the gravitation of irregularly-shaped, non-spherical bodies, different methods exist. Previous work performed a comparison between three different methods [4], considering a homogeneous density distribution inside the body. In this work, the comparison is continued, by introducing a first inhomogeneity inside the body. For this, the same three methods, being the polyhedral method [5] and two different mascon methods [6][7] are compared. We will describe the methods and our test cases in the next Section. Methodology The polyhedral method (PM) provides an analytical solution to the gravitational potential field of any polyhedral body [5]. Intrinsically, the method demands a homogeneous density throughout the body, making it not directly applicable to account for inhomogeneities. Therefore, in this work, we perform a superposition of the gravitational fields of the main body and the inhomogeneities, considering the differential density, which can also be negative. The other two methods are based on mascons, namely MSP (Mascons: Sphere Packing) and MASC (Mascons: Spherical Coordinates). These mascon methods subdivide a body into smaller parts. The mass is then concentrated in the centre of these parts and the gravitational field is the sum of the individual accelerations. MSP uses a sphere packing with non-uniform-sized spheres that do not overlap (see Fig.1). Since the sphere packing does not cover the complete volume, we use additionally a heuristic that tends to assign smaller spheres more mass. To model inhomogeneity, we compute separate sphere packings with different densities assumed. With MASC, the internal mass distribution is modelled by dividing the body in longitude, latitude, and radius, and by assigning individual densities to the resulting set of tesseroids. Test Cases Our two test cases consider two nested ideal spheres that are approximated through a UV-Sphere with 328,328 facets [4]. The outer sphere has a radius r=1,000 m and a density of 1.0g/cm³, and the inner sphere has a radius r=100 m and a density of 0.5g/cm³. In Case I, the inner sphere is placed concentric to the outer sphere, whereas in Case II the sphere’s centre is translated to X=−100 m and Y=−100 m. We compute the gravitational acceleration for points on the ideal sphere and compare it to the analytical solution through a relative error. Clearly, the ratio of computed and analytical solution τ =gcom /gana should always be 100% represent an overshoot. This agreement ratio is presented in the next Section. First Results The overall results and range of τ on the surface of the sphere are summarized in Table 1: For both of our cases, PM delivers the most accurate results (Table 1). The error results from the shape approximation. It is visualized in Figures 1 and 2. We can see the expected shift from an almost equal to an unequal surface gravity. In Figure 1 we can also see that the shape approximation error is larger than the floating-point precision limitation (noisy pattern, Figure 1a). The MSP method creates a noisy overshooting pattern (see Figures 4b and 4c), which results from the spheres near the surface and the heuristic. Large spheres lead to a circular artifact at the surface. Observable at the center of Figures 4b and 1a. It is a similar pattern for Case II. The MASC error results from the subdivision in spherical coordinates. At the poles the number of tesseroids increases, which leads to a circular overshoot at two sides. It is also true for the shifted core (see Figure 4a). The computation time for MSP remained the same as for the homogeneous case [4] while it has doubled for PM and MASC. The three methods presented above for the computation of the gravitational acceleration will be applied to more complex shapes for irregularly shaped bodies. In addition, different inhomogeneous density distributions representing the interior will be studied and the according results presented. Acknowledgements M.N. acknowledges funding from the Foundation of German Business (sdw) and the Royal Observatory of Belgium (ROB) PhD grants. The work by Bundeswehr University was carried out in the frame of project KaNaRiA-NaKoRa which is funded by DLR under grant FKZ50NA1915. The work on the part of University of Bremen presented in this paper was partially funded by DLR under grant 50NA1916. References [1] Michel, Patrick, et al. "The Hera mission: European component of the ESA-NASA AIDA mission to a binary asteroid." 42nd COSPAR Scientific Assembly 42 (2018):B1-1. [2] Campagnola, Stefano, et al. "Mission analysis for the Martian Moons Explorer (MMX) mission." Acta Astronautica 146 (2018):409-417. [3] Noeker, Matthias, et al. "The GRASS Gravimeter Rotation Mechanism for ESA Hera Mission On-Board Juventas Deep Space CubeSat." Proceedings of the 46th Aerospace Mechanisms Symposium, Virtual, May 11-13, (2022):159-172. [4] Meißenhelter, Hermann, et al. "Efficient and Accurate Methods for Computing the Gravitational Field of Irregular-Shaped Bodies." 2022 IEEE Aerospace Conference. IEEE, 2022. [5] Werner and Scheeres. "Exterior gravitation of a polyhedron derived and compared with harmonic and mascon gravitation representations of asteroid 4769 Castalia." Celestial Mechanics and Dynamical Astronomy 65.3 (1996):313-344. [6] A. Srinivas, et. al. “Fast and accurate simulation of gravitational field of irregular-shaped bodies using polydisperse sphere packings.” in ICAT-EGVE, 2017, pp.213–220. [7] M. Pätzold, et. al. “Phobos mass determination from the very close flyby of Mars Express in 2010,” Icarus, vol. 229, pp. 92–98, Feb.2014.

Published
2022

4. A simulated global GM estimate of the asteroid 469219 Kamo‘oalewa for China’s future asteroid mission

Author

Fei Li, Weitong Jin, Jean-Pierre Barriot, Jianguo Yan, Tom Andert, Weifeng Hao, Xuan Yang, and Mao Ye

Subjects
Physics, 0209 industrial biotechnology, Astronomy, Astronomy and Astrophysics, 02 engineering and technology, Ephemeris, 01 natural sciences, Celestial mechanics, Gravitation, 020901 industrial engineering & automation, Space and Planetary Science, Asteroid, 0103 physical sciences, China, 010303 astronomy & astrophysics
Abstract

China will launch in the forthcoming years a sample return mission called ZhengHe, to asteroid 469219 Kamo‘oalewa (provisional designation 2016HO3) and comet 133P/Elst-Pizarro. The mission will consist of an orbiter and a nano-lander. One of ZhengHe’s investigations is the radio science experiment, whose main objective is the asteroid GM estimate. In this paper, we conduct full numerical simulations of the radio science experiment using the wudogs software package, developed by Wuhan University. In addition to two-way Doppler measurements, we also include one-way on-board distance measurements. A list of parameters including the spacecraft initial conditions and the global asteroid GM are solved using a weighted least-squares fit. The simulation results indicate that the GM solution is very sensitive to the ephemeris error. We need an accuracy within 2 km on the ephemeris of the asteroid to achieve a reliable estimate of GM.

Published
2020

5. Solar System Interiors, Atmospheres, and Surfaces Investigations via Radio Links: Goals for the Next Decade

Author

Peter L. Bender, Erwan Mazarico, Frank G. Lemoine, A. P. Jongeling, Anthony J. Mannucci, John W. Armstrong, W. Williamson, K. Matsumoto, Attila Komjathy, A. K. Verma, I. R. Linscott, G. G. Peytaví, O. Karatekin, Paolo Tortora, Alexander S. Konopliv, Takeshi Imamura, E. R. Kursinski, Bruce G. Bills, Michael K. Bird, G. K. Botteon, M.D. Di Benedetto, T. Van Hoolst, David H. Atkinson, R. K. Choudhary, Slava G. Turyshev, Paul G. Steffes, Virginia Notaro, Richard A. Simpson, Daniele Serra, Francesca Ferri, M. M. Kobayashi, Maria T. Zuber, F. M. Flasar, Steve Matousek, Ryan S. Park, D. P. Hinson, C. Dumoulin, Richard G. French, T. M. Bocanegra-Bahamon, Sami W. Asmar, Michael Watkins, Daniele Durante, H. Ando, Dustin Buccino, S. Bruinsma, Chad Edwards, H. M. Elliott, Véronique Dehant, C. O. Ao, Silvia Tellmann, Yohai Kaspi, Jean-Charles Marty, Robert Lillis, Essam A. Marouf, Sander Goossens, Mark Hofstadter, Marzia Parisi, Panagiotis Vergados, Anthony L. Genova, Jean-Pierre Barriot, Nilton O. Renno, Paolo Cappuccio, Ravit Helled, Mark A. Wieczorek, M. P. Pugh, T. J. W. Lazio, Marco Zannoni, Kerri Cahoy, S. Le Maistre, Robert A. Preston, Bernd Häusler, P. Rosenblatt, N. Ashby, D. J. Bell, Nan Yu, Anton I. Ermakov, Paul Withers, David E. Smith, Marie Yseboodt, B. D. Tapley, Martin Pätzold, T. A. Ely, Tom Andert, Luciano Iess, Patricia Beauchamp, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Institut für Raumfahrttechnik, Universität der Bundeswehr München [Neubiberg], Centre des Nouvelles Etudes sur le Pacifique (CNEP), Université de la Nouvelle-Calédonie (UNC), Observatoire Geodesique de Tahiti, Centre National d'Études Spatiales [Toulouse] (CNES), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)

Subjects
Solar System, [SDU]Sciences of the Universe [physics], atmosphere, Environmental science, solar system, radioscience, ComputingMilieux_MISCELLANEOUS, Astrobiology
Abstract

International audience

Published
2021

6. Assessment of Phobos gravity field determination from both near polar and near equatorial orbital flyby data

Author

Mao Ye, Fei Li, Tom Andert, Weitong Jin, Jianguo Yan, Jean-Pierre Barriot, Xuan Yang, Shuanggen Jin, Center for Human Genetics, University of Leuven School of Medicine, SCHOOL of MEDICINE [Louvain], Université Catholique de Louvain = Catholic University of Louvain (UCL)-Université Catholique de Louvain = Catholic University of Louvain (UCL), Institute of Soil Science, Géopôle du Pacifique Sud (GePaSUD), and Université de la Polynésie Française (UPF)

Subjects
Physics, 010504 meteorology & atmospheric sciences, Satellites, Data analysis, Planets, Astronomy and Astrophysics, Geophysics, 01 natural sciences, Gravitation, Gravitational field, Space and Planetary Science, Physics::Space Physics, 0103 physical sciences, Polar, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

International audience; The C20 and C22 coefficients of the Phobos gravity field are key parameters to constrain the internal structure of the Martian moon, but reliable observed values of these parameters are still missing. In this paper, we demonstrate, through a combination of forward and inverse modelling of simulated Doppler spacecraft tracking data collected from the Earth, that a Phobos flyby along a near polar Mars orbit is optimal when determining the C20 coefficient, and further, that a near equatorial flyby Mars orbit is optimal for determination of the C22 coefficient. Therefore, the combination of a near polar and a near equatorial orbit is an effective way to determine the Phobos C20 and C22 gravity field coefficients. This work provides a reference for a future Chinese Mars mission.

Published
2018

7. The second-degree gravity coefficients of Phobos from two Mars Express flybys

Author

Jianguo Yan, Matthias Hahn, Tom Andert, Fei Li, Weitong Jin, Xuan Yang, Jean-Pierre Barriot, Mao Ye, Martin Pätzold, Géopôle du Pacifique Sud (GePaSUD), and Université de la Polynésie Française (UPF)

Subjects
Physics, Gravity (chemistry), 010504 meteorology & atmospheric sciences, Astronomy and Astrophysics, Geophysics, 01 natural sciences, Degree (temperature), Space and Planetary Science, [SDU]Sciences of the Universe [physics], 0103 physical sciences, Mars express, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

Several close spacecraft flybys of Phobos have been performed over the past 40 yr in order to determine the gravity field of this tiny Martian moon. In this work, the second-degree coefficients of the gravity field of Phobos were derived from the radio tracking data of two combined Mars Express flybys (2010 and 2013), by applying a least squares regularized inverse technique, that introduces as an a priori the gravity field retrieved from a shape model based on constant density hypothesis. A gravitational mass estimate of $(7.0765\pm 0.0075)\times 10^5 \, \mathrm{m^3\, s}^{-2}$ and second-degree gravity coefficients C20 = −0.1378 ± 0.0348 and C22 = 0.0166 ± 0.0153(3σ) were derived. The estimated C20 value, in contrast to the value of C20 computed from the shape model under the constant density assumption, supports an inhomogeneous distribution inside Phobos at a confidence interval of 95 per cent (1.96σ). This result indicates a denser mass in the equatorial region or lighter mass in polar areas.

Published
2019

8. A lighter core for Phobos?

Author

Xi Guo, Mao Ye, Fei Li, Martin Pätzold, Jean-Pierre Barriot, Jianguo Yan, Matthias Hahn, Tom Andert, Xuan Yang, and Shanhong Liu

Subjects
Physics, Gravity (chemistry), 010504 meteorology & atmospheric sciences, Accretion (meteorology), Stratification (water), Astronomy and Astrophysics, Context (language use), Astrophysics, 01 natural sciences, Mantle (geology), Gravitation, Core (optical fiber), Moons of Mars, Space and Planetary Science, 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

Context.The origin of the Martian moons Phobos and Deimos is still poorly understood, and is the focus of intense debate.Aims.We demonstrate that a stratified internal structure of Phobos is compatible with the observed gravity coefficients.Methods.We fit previously derivedC20andC22Phobos gravity coefficients derived from the combined MEX Doppler-tracking data from the close flybys in +2010 and 2013 with respect to the corresponding coefficients of a core–mantle stratification model of Phobos, with two opposite cases: a core denser than the mantle, and a core lighter than the mantle.Results.Only the case with a core lighter than the mantle fits at the 3σlevel the previously reported observed second degree and order coefficientC20, but a homogeneous Phobos cannot be strictly ruled out at the 3σlevel.Conclusions.This possible loosening of the core density might be the result of a displacement of material toward the surface, may be caused by centrifugal forces acting on a loosely packed rubble-pile structure, and/or by a hot-then-cold in-orbit accretion process. These two hypotheses are by no means exhaustive.

Published
2021

9. Initial results from the New Horizons exploration of 2014 MU 69 , a small Kuiper Belt object

Author

J. Fischetti, S. Bhaskaran, Matthias Hahn, Karl Whittenburg, Derek S. Nelson, G. A. Griffith, Amanda M. Zangari, B. J. Buratti, James T. Keane, E. J. Lessac-Chenen, Ralph L. McNutt, Tiffany J. Finley, J. Scherrer, M. A. Ritterbush, M. M. Saina, G. Dunn, T. A. Hill, J. Van Eck, T. Stryk, J. M. Albers, D. C. Reuter, C. M. Dalle Ore, H. A. Elliott, D. J. Schultz, J. Andrews, Douglas P. Hamilton, M. H. Versteeg, Orkan M. Umurhan, Matthew E. Hill, Hai Nguyen, M. Simon, L. Gabasova, D. E. Jennings, D. J. Katz, J. E. Riedel, N. Behrooz, M. N. Fosbury, Henry B. Throop, A. J. Verbiscer, E. Bernardoni, Ross A. Beyer, C. Engelbrecht, Francesca Scipioni, H. L. Winters, Thomas H. Zurbuchen, Carey M. Lisse, Veronica J. Bray, M. G. Ryschkewitsch, Stuart J. Robbins, S. E. Jaskulek, M. C. Kochte, Thomas Mehoke, M. S. Lahr, M. J. Salinas, V. A. Mallder, S. P. Williams, B. H. May, D. M. Mages, C. C. Deboy, Simon B. Porter, Gerhard Kruizinga, Marc W. Buie, Jorge I. Nunez, John Hayes, Peter Kollmann, P. Dharmavaram, J. M. Moore, Darrell F. Strobel, John Stansberry, R. P. Binzel, H. M. Hart, Jillian Redfern, E. W. Stahlheber, H. K. Kang, James L. Green, Anthony F. Egan, Carly Howett, Fran Bagenal, Dale Stanbridge, Chris B. Hersman, C. L. Chavez, Debi Rose, J. Y. Pelgrift, Maria E. Banks, D. C. Schurr, Matthew R. Buckley, L. S. Turner, Ivan Linscott, Kaj E. Williams, J. Eisig, Mihaly Horanyi, Matthew Jones, Mark R. Showalter, William B. McKinnon, Leslie A. Young, E. J. Colwell, Daniel T. Britt, Kirby Runyon, David J. McComas, G. Weigle, Bernard Schmitt, Susan D. Benecchi, Alissa M. Earle, M. J. Kinczyk, Tod R. Lauer, M. R. Piquette, Lori S. Glaze, Carver J. Bierson, L. M. Burke, Brian Carcich, O. S. Custodio, A. Harch, Harold A. Weaver, Dale P. Cruikshank, Oliver L. White, L. E. Brown, William M. Grundy, G. K. Oxton, Chelsea L. Ferrell, David E. Kaufmann, Mohamed Ramy El-Maarry, K. A. Harmon, W. R. Schlei, Eric Quirico, Derek C. Richardson, J. M. Freeze, Jennifer Hanley, R. G. Shelton, Andrew J. Steffl, Mike Bird, H. W. Taylor, Harold J. Reitsema, Stamatios M. Krimigis, D. R. Boone, E. D. Fattig, A. L. Regiec, D. J. Rodgers, Jason D. Hofgartner, D. Velez, Catherine B. Olkin, Kelsi N. Singer, Brian Bauer, Carl J. Ercol, Martin Pätzold, Nicole Martin, Stewart Bushman, J. Firer, Allen W. Lunsford, R. W. Webbert, A. L. Chaikin, Alex Parker, C. A. Conrad, M. P. Conner, S. B. Cooper, Chloe B. Beddingfield, William M. Folkner, J. E. Lee, M. B. Tapley, G. R. Gladstone, D. A. Aguilar, Glen H. Fountain, Emma Birath, Rebecca Sepan, Jeremy Bauman, J. Wm. Parker, S. Weidner, J. R. Jensen, Jason C. Cook, Alan D. Howard, William M. Owen, Andrew F. Cheng, B. L. Enke, Sarah A. Hamilton, Tom Andert, K. B. Beisser, K. E. Bechtold, J. R. Wendel, Rajani D. Dhingra, Paul M. Schenk, Michael E. Summers, J. R. Spencer, D. W. Hals, Silvia Protopapa, A. C. Ocampo, Mark E. Holdridge, S. A. Stern, A. Taylor, R. M. Tedford, G. P. Keleher, Gabe Rogers, Frederic Pelletier, Jj Kavelaars, Yanping Guo, Jon Pineau, Steven J. Conard, Alice Bowman, A. Hosadurga, B. G. Williams, Michael Vincent, David Y. Kusnierkiewicz, Paul E. Rosendall, G. B. Lawrence, J. R. Stuart, M. M. Stothoff, Jr. D. S. Mehoke, Southwest Research Institute [Boulder] (SwRI), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), Lowell Observatory [Flagstaff], Space Physics Research Laboratory [Ann Arbor] (SPRL), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, SwRI Planetary Science Directorate [Boulder], Universitat de Lleida, Institut für Raumfahrttechnik, Universität der Bundeswehr München [Neubiberg], Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Department of Space Studies [Boulder], Rheinische Friedrich-Wilhelms-Universität Bonn, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institute of Hydrology, NASA Goddard Space Flight Center (GSFC), Department of Physics, Chemistry and Biology [Linköping] (IFM), Linköping University (LIU), Africa Rice Center [Bénin] (AfricaRice), Africa Rice Center [Côte d'Ivoire] (AfricaRice), Consultative Group on International Agricultural Research [CGIAR] (CGIAR)-Consultative Group on International Agricultural Research [CGIAR] (CGIAR), Yonsei University, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre International de Hautes Etudes Agronomiques Méditerranéennes - Institut Agronomique Méditerranéen de Montpellier (CIHEAM-IAMM), Centre International de Hautes Études Agronomiques Méditerranéennes (CIHEAM), Princeton University, Reed College, Hanoi National University of Education (HNUE), Rhenish Institute for Environmental Research (RIU), University of Cologne, School of Earth, Atmospheric and Environmental Sciences [Manchester] (SEAES), University of Manchester [Manchester], ESA, Southwest Research Institute [San Antonio] (SwRI), NASA Ames Research Center (ARC), Laboratoire pour l'utilisation du rayonnement électromagnétique (LURE), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-MENRT-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, Johns Hopkins University (JHU), Institute of Physics of the Czech Academy of Sciences (FZU / CAS), Czech Academy of Sciences [Prague] (CAS), Laboratoire de Chimie Analytique Bio-Inorganique et Environnement (LCABIE), Université de Pau et des Pays de l'Adour (UPPA)-Centre National de la Recherche Scientifique (CNRS), Department of Biochemistry, Faculty of Biology, University of Warmia and Mazury [Olsztyn], California Institute of Technology (CALTECH)-NASA, Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), University of Warmia and Mazury, Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), inconnu temporaire UPEMLV, Inconnu, INGENIERIE (INGENIERIE), Institut de recherches sur la catalyse et l'environnement de Lyon (IRCELYON), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Génie des Procédés Plasmas et Traitement de Surface (ENSCP), PARIS, Africa Rice Center, Africa Rice Center (AfricaRice), Institut de pharmacologie moléculaire et cellulaire (IPMC), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institute of Physics of Academy of Sciences of Czech Republic, and Czech Academy of Sciences [Prague] (ASCR)

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Solar System, Multidisciplinary, 010504 meteorology & atmospheric sciences, Spacecraft, business.industry, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Astronomy, Coma (optics), Contact binary, Albedo, 01 natural sciences, Object (philosophy), Solar wind, 13. Climate action, 0103 physical sciences, Pebble, business, 010303 astronomy & astrophysics, Geology, ComputingMilieux_MISCELLANEOUS, Astrophysics - Earth and Planetary Astrophysics, 0105 earth and related environmental sciences
Abstract

The Kuiper Belt is a distant region of the Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a Cold Classical Kuiper Belt Object, a class of objects that have never been heated by the Sun and are therefore well preserved since their formation. Here we describe initial results from these encounter observations. MU69 is a bi-lobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color and compositional heterogeneity. No evidence for satellites, ring or dust structures, gas coma, or solar wind interactions was detected. By origin MU69 appears consistent with pebble cloud collapse followed by a low velocity merger of its two lobes., 43 pages, 8 figure

Published
2019

10. Mars Express 10 years at Mars: Observations by the Mars Express Radio Science Experiment (MaRS)

Author

Silvia Tellmann, Daniel Kahan, David P. Hinson, Mikael Beuthe, Richard A. Simpson, S. Remus, Kerstin Peter, G. L. Tyler, Bernd Häusler, Pascal Rosenblatt, Martin Pätzold, Véronique Dehant, S. Le Maistre, Sami W. Asmar, Matthias Hahn, Paul Withers, Janusz Oschlisniok, Tom Andert, A. I. Efimov, Michael K. Bird, and UCL - SST/ELI/ELIC - Earth & Climate

Subjects
Solar conjunction, 010504 meteorology & atmospheric sciences, Mars landing, Astronomy and Astrophysics, Mars Exploration Program, Exploration of Mars, 01 natural sciences, Astrobiology, Space and Planetary Science, Orbit of Mars, Mars Orbiter Laser Altimeter, Physics::Space Physics, 0103 physical sciences, Astrophysics::Earth and Planetary Astrophysics, Ionosphere, 010303 astronomy & astrophysics, Geology, 0105 earth and related environmental sciences, Radio Science
Abstract

The Mars Express spacecraft is operating in Mars orbit since early 2004. The Mars Express Radio Science Experiment (MaRS) employs the spacecraft and ground station radio systems (i) to conduct radio occultations of the atmosphere and ionosphere to obtain vertical profiles of temperature, pressure, neutral number densities and electron density, (ii) to conduct bistatic radar experiments to obtain information on the dielectric and scattering properties of the surface, (iii) to investigate the structure and variation of the crust and lithosphere in selected target areas, (iv) to determine the mass, bulk and internal structure of the moon Phobos, and (v) to track the MEX radio signals during superior solar conjunction to study the morphology of coronal mass ejections (CMEs). Here we report observations, results and discoveries made in the Mars environment between 2004 and 2014 over almost an entire solar cycle. © 2016 Elsevier Ltd.

Published
2016

11. A homogeneous nucleus for comet 67P/Churyumov–Gerasimenko from its gravity field

Author

Laurent Jorda, Frank Scholten, Bernd Häusler, Kerstin Peter, Silvia Tellmann, Jean-Pierre Barriot, Tom Andert, Eberhard Grün, Matthias Hahn, Robert Gaskell, Sami W. Asmar, Holger Sierks, Michael K. Bird, P. R. Weissman, Martin Pätzold, Frank Preusker, Universität zu Köln, Institut für Raumfahrttechnik, Universität der Bundeswehr München [Neubiberg], Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Rhenish Institute for Environmental Research (RIU), University of Cologne, Max-Planck-Institut für Kernphysik (MPIK), Max-Planck-Gesellschaft, Max-Planck-Institut für Sonnensystemforschung (MPS), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Planetary Science Institute [Tucson] (PSI), DLR Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt [Berlin] (DLR), Universität zu Köln = University of Cologne, Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), and Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES)

Subjects
Physics, 67P, Multidisciplinary, 010504 meteorology & atmospheric sciences, nucleus, Comet, Astrophysics, 01 natural sciences, 7. Clean energy, Bulk density, gravity, Gravitation, comet, medicine.anatomical_structure, Volume (thermodynamics), Gravitational field, 13. Climate action, Asteroid, 0103 physical sciences, medicine, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Porosity, 010303 astronomy & astrophysics, Nucleus, 0105 earth and related environmental sciences
Abstract

International audience; Cometary nuclei consist mostly of dust and water ice(1). Previous observations have found nuclei to be low-density and highly porous bodies(2-4), but have only moderately constrained the range of allowed densities because of the measurement uncertainties. Here we report the precise mass, bulk density, porosity and internal structure of the nucleus of comet 67P/Churyumov-Gerasimenko on the basis of its gravity field. The mass and gravity field are derived from measured spacecraft velocity perturbations at fly-by distances between 10 and 100 kilometres. The gravitational point mass is GM = 666.2 +/- 0.2 cubic metres per second squared, giving a mass M = (9,982 +/- 3) x 10(9) kilograms. Together with the current estimate of the volume of the nucleus(5), the average bulk density of the nucleus is 533 +/- 6 kilograms per cubic metre. The nucleus appears to be a low-density, highly porous (72-74 per cent) dusty body, similar to that of comet 9P/Tempel 1(2,3). The most likely composition mix has approximately four times more dust than ice by mass and two times more dust than ice by volume. We conclude that the interior of the nucleus is homogeneous and constant in density on a global scale without large voids. The high porosity seems to be an inherent property of the nucleus material.

Published
2016

12. Phobos: Observed bulk properties

Author

Robert A. Jacobson, Pascal Rosenblatt, Véronique Dehant, Martin Pätzold, and Tom Andert

Subjects
Martian, Physics, Solar System, Spacecraft, business.industry, Astronomy, Astronomy and Astrophysics, Mars Exploration Program, Ephemeris, Orbit, Space and Planetary Science, Asteroid, Orbit of Mars, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, business
Abstract

This work is a review of the mass determinations of the Mars moon Phobos by spacecraft close flybys, by solving for the Martian gravity field and by the analysis of secular orbit perturbations. The absolute value and accuracy is sensitive on the knowledge and accuracy of the Phobos ephemeris, of the spacecraft orbit, other perturbing forces acting on the spacecraft and the resolution of the Martian gravity field besides the measurement accuracy of the radio tracking data. The mass value and its error improved from spacecraft mission to mission or from the modern analysis of “old” tracking data but these solutions depend on the accuracy of the ephemeris at the time of observation. The mass value seems to settle within the range of GMPh=(7.11±0.09)×10−4 km3 s−2 which covers almost all mass values from close flybys and “distant” encounters within its 3−σ error (1.5%). Using the volume value determined from MEX HRSC imaging, the bulk density is (1873±31) kg m−3 (3−σ error or 1.7%), a low value which suggests that Phobos is either highly porous, is composed partially of light material or both. The determination of the gravity coefficients C20 and C22 from the Mars Express 2010 close flyby does not allow to draw conclusion on the internal structure. The large errors do not distinguish whether Phobos is homogeneous or not. In view of theories of the Phobos' origin, one possibility is that Phobos is not a captured asteroid but accreted from a debris disk in Mars orbit as a second generation solar system object.

Published
2014

13. Phobos mass determination from the very close flyby of Mars Express in 2010

Author

G. L. Tyler, Martin Pätzold, Tom Andert, Bernd Häusler, Silvia Tellmann, and Sami W. Asmar

Subjects
Physics, Orbit, Debris disk, Gravitational field, Mass distribution, Space and Planetary Science, Asteroid, Astronomy, Astronomy and Astrophysics, Astrophysics, Mars Exploration Program, Porosity, Bulk density
Abstract

The global geophysical parameters GM Ph = ( 0.7072 ± 0.0013 ) × 10 - 3 km 3 s - 2 , C 20 , C 22 and the bulk density 〈 ρ 〉 = ( 1862 ± 30 ) kg / m 3 have been determined from the closest Mars Express flyby at the Mars moon Phobos on 3rd March 2010 at a distance of 77 km. The second degree gravity field of Phobos ( C 20 , C 22 ) could not be solved for at sufficient accuracy. The low bulk density suggests a high porosity and an inhomogeneous mass distribution but the large errors of C 20 and C 22 are still consistent with a homogeneous as well as an inhomogeneous mass distribution. The modeling of the moon’s interior by a randomly selected mass distribution of given porosity and water ice content but constrained by the observed GM Ph and 〈 ρ 〉 let a simulated C 20 decrease with increasing porosity and water ice content indicating an increasingly inhomogeneous mass distribution. The high porosity together with an inhomogeneous mass distribution would be evidence that Phobos accreted in orbit about Mars from a debris disk and is not a captured asteroid.

Published
2014

14. Microwave absorptivity by sulfuric acid in the Venus atmosphere: First results from the Venus Express Radio Science experiment VeRa

Author

Janusz Oschlisniok, Tom Andert, Bernd Häusler, Silvia Tellmann, Michael K. Bird, S. Remus, G. L. Tyler, and Martin Pätzold

Subjects
biology, Astronomy and Astrophysics, Venus, Molar absorptivity, biology.organism_classification, Atmospheric sciences, Occultation, Atmosphere of Venus, Altitude, Space and Planetary Science, Environmental science, Radio occultation, Radio Science, Radio wave
Abstract

The Venus Express (VEX) Radio Science experiment VeRa utilizes radio occultation techniques to investigate the Venus atmosphere over a wide range of latitudes. Radio attenuation measurements with the VEX 3.6 cm (X-band) signal provide information on the absorptivity distribution within the Venus cloud deck. The combined results from 6 years of occultation measurements reveal a distinct latitudinal variation in absorptivity in the altitude range from 50 to 55 km. Enhanced absorptivity is observed at equatorial and mid-latitudes (0–50°S), exceeding 0.008 dB/km on the dayside and 0.01 dB/km on the nightside of the southern hemisphere. Poleward of 50°S latitude a decrease in the absorptivity is observed, reaching minimal values at polar latitudes (>70°S), where the absorptivity did not exceed 0.005 dB/km on the dayside and 0.004 dB/km on the nightside. The main absorber of radio waves in the Venus atmosphere, gaseous sulfuric acid, can serve as a tracer for atmospheric motions. The inferred absorptivity was used to determine the abundance of gaseous sulfuric acid. Abundances of about 1–2 ppm are found between 0°S and 70°S latitude in the altitude range from 50 to about 52 km, sometimes increasing to values of about 3 ppm on the dayside and 5 ppm on the nightside near 50 km. The abundance at polar latitudes (>70°S) did not exceed 1 ppm within the considered altitude range. The absorptivity and gaseous sulfuric acid height profiles are compared with previous measurements.

Published
2012

15. The Pluto system: Initial results from its exploration by New Horizons

Author

Darrell F. Strobel, James L. Green, Mark R. Showalter, Francis Nimmo, C. Bryan, Richard P. Binzel, M. J. Freeze, Matthew R. Buckley, Matthew E. Hill, Stewart Bushman, Chris B. Hersman, Brian Carcich, Kirby Runyon, Leslie A. Young, Douglas S. Mehoke, Jeremy Bauman, S. Weidner, Nickalaus Pinkine, William M. Grundy, Robert A. Jacobson, V. A. Mallder, Thomas K. Greathouse, H. K. Kang, Ralph L. McNutt, S. Bhaskaran, Dale P. Cruikshank, Marc W. Buie, D. C. Reuter, William M. Owen, Andrew F. Cheng, Peter D. Bedini, C. M. Dalle Ore, Mihaly Horanyi, Alice Bowman, Tiffany J. Finley, David P. Hinson, Harold A. Weaver, David J. McComas, Max Mutchler, Yanping Guo, Oliver L. White, R. W. Webbert, D. E. Jennings, Olivier S. Barnouin, Jennifer Hanley, Harold J. Reitsema, B. Page, K. L. Lindstrom, Catherine B. Olkin, Jorge I. Nunez, M. E. Banks, Carey M. Lisse, A. Hill, John R. Spencer, Coralie D. Jackman, G. R. Gladstone, E. D. Melin, Allen W. Lunsford, M. H. Versteeg, Eric J. Zirnstein, Emma Birath, Thomas Mehoke, Joel Wm. Parker, H. M. Hart, Jane M. Andrews, Zach Dischner, Derek S. Nelson, Amanda M. Zangari, Kurt D. Retherford, Veronica J. Bray, Andrew J. Steffl, M. Piquette, Douglas P. Hamilton, Mike Bird, Stamatios M. Krimigis, Kaj E. Williams, Matthias Hahn, Karl Whittenburg, C. A. Conrad, Kelsi N. Singer, Steven J. Conard, J. E. Lee, Silvia Protopapa, B. G. Williams, Constantine Tsang, Orkan M. Umurhan, Kimberly Ennico, Glen H. Fountain, J. M. Moore, Carolyn M. Ernst, J. Peterson, J. Ercol, Jason C. Cook, Alan D. Howard, H. A. Elliott, Michael Vincent, David Y. Kusnierkiewicz, O. S. Custodio, M. G. Ryschkewitsch, Sarah A. Hamilton, D. J. Bogan, Eric Schindhelm, M. Brozovic, K. B. Beisser, Mark E. Holdridge, James H. Roberts, S. A. Stern, M. B. Tapley, Simon B. Porter, A. Harch, W. W. Woods, B. Bauer, Debi Rose, S. P. Williams, Alex Parker, Philip J. Dumont, Sarah H. Flanigan, Gabe Rogers, Dale Stanbridge, Ivan Linscott, Frederic Pelletier, B. Sepan, Andrew B. Calloway, Jamey Szalay, Tod R. Lauer, Jillian Redfern, Martin Paetzold, Tom Andert, A. J. Verbiscer, Paul M. Schenk, Nicole Martin, Michael E. Summers, Stuart J. Robbins, H. W. Taylor, A. C. Ocampo, Bonnie J. Buratti, A. Taylor, William B. McKinnon, G. Weigle, Alissa M. Earle, David E. Kaufmann, M. Soluri, T. Stryk, Henry B. Throop, Fran Bagenal, G. L. Tyler, Ross A. Beyer, C. C. Deboy, Peter Kollmann, Carly Howett, and Joshua A. Kammer

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), geography, Multidisciplinary, geography.geographical_feature_category, Haze, Landform, FOS: Physical sciences, Terrain, Crust, Astrobiology, Atmosphere, Pluto, Tectonics, Planet, Geology, Astrophysics - Earth and Planetary Astrophysics
Abstract

The Pluto system was recently explored by NASA's New Horizons spacecraft, making closest approach on 14 July 2015. Pluto's surface displays diverse landforms, terrain ages, albedos, colors, and composition gradients. Evidence is found for a water-ice crust, geologically young surface units, surface ice convection, wind streaks, volatile transport, and glacial flow. Pluto's atmosphere is highly extended, with trace hydrocarbons, a global haze layer, and a surface pressure near 10 microbars. Pluto's diverse surface geology and long-term activity raise fundamental questions about how small planets remain active many billions of years after formation. Pluto's large moon Charon displays tectonics and evidence for a heterogeneous crustal composition, its north pole displays puzzling dark terrain. Small satellites Hydra and Nix have higher albedos than expected., 8 pages - Initial Science paper from NASA's New Horizons Pluto Encounter

Published
2015

16. Mars Express Investigations of Phobos and Deimos

Author

V. Companys, A. Chicarro, Martin Pätzold, T. Morley, Olivier Witasse, S. Barabash, M. Mueller, P. Martin, J. Oberst, Tanja Zegers, Harald Hoffmann, M. Denis, Jean-Loup Bertaux, Klaus-Dieter Matz, Roberto Orosei, G. Neukum, R. Pischel, Yoshifumi Futaana, J. J. Plaut, Mats Holmström, J. P. Bibring, Nico Schmedemann, Franck Montmessin, Marco Giuranna, B. Gondet, David Heather, A. Cichetti, Giovanni Picardi, A. Aronica, P. Pardo Voss, Alejandro Cardesín-Moinelo, S. Remus, Pascal Rosenblatt, N. Manaud, T. Roatsch, Konrad Willner, Aurélie Reberac, Nicolas Altobelli, Véronique Dehant, Tom Andert, Thomas C. Duxbury, Vittorio Formisano, European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), Department of Physics and Astronomy [Fairfax], George Mason University [Fairfax], European Space Astronomy Centre (ESAC), Institut für Raumfahrttechnik, Universität der Bundeswehr München [Neubiberg], Istituto di Astrofisica e Planetologia Spaziali - INAF (IAPS), Istituto Nazionale di Astrofisica (INAF), Swedish Institute of Space Physics [Kiruna] (IRF), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), European Space Operations Center (ESOC), Royal Observatory of Belgium [Brussels] (ROB), German Aerospace Center (DLR), Freie Universität Berlin, Rhenish Institute for Environmental Research (RIU), University of Cologne, Dipartimento di Ingegneria dell'Informazione, Elettronica e Telecomunicazioni (DIET), Università 15 ' Sapienza', Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Agence Spatiale Européenne = European Space Agency (ESA), and Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES)

Subjects
[PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Mars landing, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Mars, Astronomy and Astrophysics, Mars Exploration Program, Exploration of Mars, Planetary Data System, Astrobiology, Moons of Mars, Phobos, Orbit, Planetary science, Deimos, Space and Planetary Science, Asteroid, Moons, Mars Express, Flyby, Geology
Abstract

International audience; The Mars Express mission was launched in June 2003 and was inserted into orbit around Mars in December 2003. Its main objective is to study the Mars' subsurface, surface, atmosphere and interaction with the solar wind. A secondary objective is to study the martian moons, in particular the largest one Phobos, thanks to a near polar and elliptical orbit which allows the spacecraft to perform close flybys about every five months. The Mars Express data not only consist of high-resolution 3D color images, but also astrometric images, spectra from 0.18 to 20 μm, radar echoes, Doppler signals from gravity experiments, and ion data. A new view of the moons has emerged from this data set, favoring now the idea that they are not captured asteroids, but rather the result of a re-accretion following a major impact on Mars. This unique set of data is available in the ESA Planetary Science Archive (PSA) and mirror imaged in the NASA Planetary Data System (PDS). This paper presents an overview of the Mars Express Phobos flybys, the specificities of their operations and the scientific achievements.

Published
2014

17. Asteroid 21 Lutetia: Low Mass, High Density

Author

Bernd Häusler, Jean-Pierre Barriot, Benjamin P. Weiss, John D. Anderson, Sami W. Asmar, Silvia Tellmann, P. L. Lamy, Holger Sierks, Michael K. Bird, Tom Andert, Matthias Hahn, Martin Pätzold, Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences, and Weiss, Benjamin P.

Subjects
Physics, Multidisciplinary, 010504 meteorology & atmospheric sciences, Spacecraft, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], business.industry, Infrared, Gravitational perturbation, Astronomy, High density, Astrophysics, 7. Clean energy, 01 natural sciences, symbols.namesake, 13. Climate action, Asteroid, 0103 physical sciences, Trajectory, symbols, business, Low Mass, 010303 astronomy & astrophysics, Doppler effect, 0105 earth and related environmental sciences
Abstract

Asteroid 21 Lutetia was approached by the Rosetta spacecraft on 10 July 2010. The additional Doppler shift of the spacecraft radio signals imposed by 21 Lutetia’s gravitational perturbation on the flyby trajectory were used to determine the mass of the asteroid. Calibrating and correcting for all Doppler contributions not associated with Lutetia, a least-squares fit to the residual frequency observations from 4 hours before to 6 hours after closest approach yields a mass of (1.700 ± 0.017) × 1018 kilograms. Using the volume model of Lutetia determined by the Rosetta Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) camera, the bulk density, an important parameter for clues to its composition and interior, is (3.4 ± 0.3) × 103 kilograms per cubic meter., German Aerospace Center (DLR) (grant 50QM1002), German Aerospace Center (DLR) (grant 50QM1004), United States. National Aeronautics and Space Administration

Published
2011

18. Precise mass determination and the nature of Phobos

Author

Véronique Dehant, Tom Andert, G. L. Tyler, Bernd Häusler, Pascal Rosenblatt, Martin Pätzold, and Jean-Charles Marty

Subjects
Physics, Spacecraft, business.industry, Mars Exploration Program, Astrophysics, Astrobiology, Gravitation, Geophysics, Radio tracking, Standard gravitational parameter, Asteroid, Mars express, General Earth and Planetary Sciences, business, Radio Science
Abstract

[1] We report independent results from two subgroups of the Mars Express Radio Science (MaRS) team who independently analyzed Mars Express (MEX) radio tracking data for the purpose of determining consistently the gravitational attraction of the moon Phobos on the MEX spacecraft, and hence the mass of Phobos. New values for the gravitational parameter (GM = 0.7127 ± 0.0021 × 10 -3 km 3 /s 2 ) and density of Phobos (1876 ± 20 kg/m 3 ) provide meaningful new constraints on the corresponding range of the body's porosity (30% ± 5%), provide a basis for improved interpretation of the internal structure. We conclude that the interior of Phobos likely contains large voids. When applied to various hypotheses bearing on the origin of Phobos, these results are inconsistent with the proposition that Phobos is a captured asteroid.

Published
2010

19. Pre-flyby estimates of the precision of the mass determination of asteroid (21) Lutetia from Rosetta radio tracking

Author

Sami W. Asmar, Silvia Tellmann, Michael K. Bird, Bernd Häusler, Jean-Pierre Barriot, Tom Andert, John D. Anderson, and Martin Pätzold

Subjects
Physics, Radio tracking, Spacecraft, Space and Planetary Science, Planet, business.industry, Asteroid, Astronomy, Astronomy and Astrophysics, Astrophysics, Tracking (particle physics), business
Abstract

The Rosetta spacecraft will fly by its second target asteroid (21) Lutetia on 10 July 2010. Simulations based on the currently known size of Lutetia and assumptions on the bulk density show that tracking of two radio-carrier frequencies at X-band (8.4 GHz) and S-band (2.3 GHz) during the flyby will determine the mass at less than 1% accuracy. Derivation of the asteroid volume by camera observation will drive the uncertainty in derivation of the bulk density. Mass and bulk density provide valuable clues that might help resolve the difficulties in determining the taxonomic class of the asteroid.

Published
2010

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