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Spoto F.,University of Pisa | Spoto F.,SpaceDyS srl | Milani A.,University of Pisa | Knezevic Z.,Astronomical Observatory
Icarus | Year: 2015

A new family classification, based on a catalog of proper elements with ~384,000 numbered asteroids and on new methods is available. For the 45 dynamical families with >250 members identified in this classification, we present an attempt to obtain statistically significant ages: we succeeded in computing ages for 37 collisional families.We used a rigorous method, including a least squares fit of the two sides of a V-shape plot in the proper semimajor axis, inverse diameter plane to determine the corresponding slopes, an advanced error model for the uncertainties of asteroid diameters, an iterative outlier rejection scheme and quality control. The best available Yarkovsky measurement was used to estimate a calibration of the Yarkovsky effect for each family. The results are presented separately for the families originated in fragmentation or cratering events, for the young, compact families and for the truncated, one-sided families. For all the computed ages the corresponding uncertainties are provided, and the results are discussed and compared with the literature. The ages of several families have been estimated for the first time, in other cases the accuracy has been improved. We have been quite successful in computing ages for old families, we have significant results for both young and ancient, while we have little, if any, evidence for primordial families. We found 2 cases where two separate dynamical families form together a single V-shape with compatible slopes, thus indicating a single collisional event. We have also found 3 examples of dynamical families containing multiple collisional families, plus a dubious case: for these we have obtained discordant slopes for the two sides of the V-shape, resulting in distinct ages. We have found 2 cases of families containing a conspicuous subfamily, such that it is possible to measure the slope of a distinct V-shape, thus the age of the secondary collision. We also provide data on the central gaps appearing in some families. The ages computed in this paper are obtained with a single and uniform methodology, thus the ages of different families can be compared, providing a first example of collisional chronology of the asteroid main belt. © 2015 Elsevier Inc.


Milani A.,University of Pisa | Spoto F.,University of Pisa | Spoto F.,SpaceDyS S.r.l. | Knezevic Z.,Astronomical Observatory | And 2 more authors.
Proceedings of the International Astronomical Union | Year: 2016

In this paper we present the results of our new classification of asteroid families, upgraded by using catalog with > 500,000 asteroids. We discuss the outcome of the most recent update of the family list and of their membership. We found enough evidence to perform 9 mergers of the previously independent families. By introducing an improved method of estimation of the expected family growth in the less populous regions (e.g. at high inclination) we were able to reliably decide on rejection of one tiny group as a probable statistical fluke. Thus we reduced our current list to 115 families. We also present newly determined ages for 6 families, including complex 135 and 221, improving also our understanding of the dynamical vs. collisional families relationship. We conclude with some recommendations for the future work and for the family name problem. Copyright © 2016 International Astronomical Union.


Micheli M.,Serco | Koschny D.,European Space Agency | Drolshagen G.,European Space Agency | Hainaut O.,European Southern Observatory | Bernardi F.,SpaceDyS S.r.l.
Earth, Moon and Planets | Year: 2014

In this work we summarize the initial results of a targeted effort of the ESA NEO Coordination Centre to obtain additional observational data in order to eliminate or reduce the impact probability estimate of a subset of the known near-Earth objects representing the highest fraction of the total known impact risk, as measured by the Palermo Scale. © 2014, Springer Science+Business Media Dordrecht.


Schettino G.,University of Pisa | Cicalo S.,SpaceDyS S.r.l. | Di Ruzza S.,SpaceDyS S.r.l. | Tommei G.,University of Pisa
2nd IEEE International Workshop on Metrology for Aerospace, MetroAeroSpace 2015 - Proceedings | Year: 2015

BepiColombo is a joint ESA/JAXA mission to Mercury with challenging objectives regarding geophysics, geodesy and fundamental physics. In particular, the Mercury Orbiter Radio science Experiment (MORE) intends, as one of its goals, to perform a test of General Relativity. This can be done by measuring and constraining the parametrized post-Newtonian (PPN) parameters to an accuracy significantly better than current one. In this work we perform a global numerical full-cycle simulation of the BepiColombo Radio Science Experiments (RSE) in a realistic scenario, focussing on the relativity experiment, solving simultaneously for all the parameters of interest for RSE in a global least squares fit within a constrained multiarc strategy. The results on the achievable accuracy for each PPN parameter will be presented and discussed, confirming the significant improvement to the actual knowledge of gravitation theory expected for the MORE relativity experiment. In particular, we will show that, including realistic systematic effects in the range observables, an accuracy of the order of 10-6 can still be achieved in the Eddington parameter β and in the parameter α1, which accounts for preferred frame effects, while the only poorly determined parameter turns out to be ζ, which describes the temporal variations of the gravitational constant and the Sun mass. © 2015 IEEE.


Tornmei G.,University of Pisa | Dimare L.,SpaceDyS srl | Milani A.,University of Pisa | Serra D.,University of Pisa
Proceedings of the International Astronautical Congress, IAC | Year: 2012

Juno is a NASA New Frontiers mission to the planet Jupiter, launched from Cape Canaveral on August 5, 2011. The spacecraft will arrive to Jupiter in 2016 and will be placed for one year in a polar high-eccentric orbit to study the composition of the planet, the gravity and the magnetic field, and the magnetosphere. The Italian Space Agency (ASI) contributed to the mission providing the radio science instrument KaT (Ka-Band Translator, developed by the University of Rome "La Sapienza" and Thales Alenia Space) used for the gravity experiment, which has the goal of studying the Jupiter's deep structure by mapping the planet's gravity. Such instrument takes advantage of synergies with a similar tool in development for BepiColombo, the ESA cornerstone mission to Mercury. The Celestial Mechanics Group of the University of Pisa and SpaceDyS s.r.l. are responsible, under an ASI contract, for the development of an orbit determination and parameters estimation software for processing the real data independently from NASA software ODP. We shall present the state of the art of such software highlighting the theoretical models used, the problems addressed and first results about the scientific goals obtained with simulated data. Copyright © (2012) by the International Astronautical Federation.


Tommei G.,University of Pisa | Dimare L.,SpaceDyS srl | Serra D.,University of Pisa | Milani A.,University of Pisa
Monthly Notices of the Royal Astronomical Society | Year: 2014

Juno is a NASA mission launched in 2011 with the goal of studying Jupiter. The probe will arrive to the planet in 2016 and will be placed for one year in a polar high-eccentric orbit to study the composition of the planet, the gravity and the magnetic field. The Italian Space Agency (ASI) provided the radio science instrument KaT (Ka-Band Translator) used for the gravity experiment, which has the goal of studying the Jupiter's deep structure by mapping the planet's gravity: such instrument takes advantage of synergies with a similar tool in development for BepiColombo, the ESA cornerstone mission to Mercury. The Celestial Mechanics Group of the University of Pisa, being part of the Juno Italian team, is developing an orbit determination and parameters estimation software for processing the real data independently from NASA software ODP. This paper has a twofold goal: first, to tell about the development of this software highlighting the models used, secondly, to perform a sensitivity analysis on the parameters of interest to the mission. © 2014 The Authors.


Farnocchia D.,SpaceDyS s.r.l. | Cioci D.B.,SpaceDyS s.r.l. | Milani A.,University of Pisa
Celestial Mechanics and Dynamical Astronomy | Year: 2013

In this paper we discuss the resolution of Kepler's equation in all eccentricity regimes. To avoid rounding off problems we find a suitable starting point for Newton's method in the hyperbolic case. Then, we analytically prove that Kepler's equation undergoes a smooth transition around parabolic orbits. This regularity allows us to fix known numerical issues in the near parabolic region and results in a non-singular iterative technique to solve Kepler's equation for any kind of orbit. We measure the performance and the robustness of this technique by comprehensive numerical tests. © 2013 Springer Science+Business Media Dordrecht.


D'Abramo G.,SpaceDyS S.r.l. | D'Abramo G.,Iaps Instituto Nazionale Of Astrofisica
Studies in History and Philosophy of Science Part B - Studies in History and Philosophy of Modern Physics | Year: 2012

Even though the second law of thermodynamics holds the supreme position among the laws of nature, as stated by many distinguished scientists, notably Eddington and Einstein, its position appears to be also quite peculiar. Given the atomic nature of matter, whose behavior is well described by statistical physics, the second law could not hold unconditionally, but only statistically. It is not an absolute law. As a result of this, in the present paper we try to argue that we have not yet any truly cogent argument (known fundamental physical laws) to exclude its possible macroscopic violation. Even Landauer's information-theoretic principle seems to fall short of the initial expectations of being the fundamental 'physical' reason of all Maxwell's demons failure. Here we propose a modified Szilard engine which operates without any steps in the process resembling the creation or destruction of information. We argue that the information-based exorcisms must be wrong, or at the very least superfluous, and that the real physical reason why such engines cannot work lies in the ubiquity of thermal fluctuations (and friction).We see in the above peculiar features the main motivation and rationale for pursuing exploratory research to challenge the second law, which is still ongoing and probably richer than ever. A quite thorough (and critical) description of some of these challenges is also given. © 2012 Elsevier Ltd.


Farnocchia D.,Jet Propulsion Laboratory | Chesley S.R.,Jet Propulsion Laboratory | Micheli M.,Coordination Center | Micheli M.,SpaceDyS s.r.l. | And 7 more authors.
Icarus | Year: 2015

The Mars flyby of C/2013 A1 (Siding Spring) represented a unique opportunity for imaging a long-period comet and resolving its nucleus and rotation state. Because of the small encounter distance and the high relative velocity, the goal of successfully observing C/2013 A1 from the Mars orbiting spacecraft posed strict accuracy requirements on the comet's ephemeris. These requirements were hard to meet, as comets are known for being highly unpredictable: astrometric observations can be significantly biased and nongravitational perturbations affect comet trajectories. Therefore, even prior to the encounter, we remeasured a couple of hundred astrometric images obtained with ground-based and Earth-orbiting telescopes. We also observed the comet with the Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE) camera on 2014 October 7. In particular, these HiRISE observations were decisive in securing the trajectory and revealed that out-of-plane nongravitational perturbations were larger than previously assumed. Though the resulting ephemeris predictions for the Mars encounter allowed observations of the comet from the Mars orbiting spacecraft, post-encounter observations show a discrepancy with the pre-encounter trajectory. We reconcile this discrepancy by employing the Rotating Jet Model, which is a higher fidelity model for cometary nongravitational perturbations and provides an estimate of C/2013 A1's spin pole (RA,DEC)=(63°,14°). © 2015 Elsevier Inc.


Farnocchia D.,Jet Propulsion Laboratory | Chesley S.R.,Jet Propulsion Laboratory | Micheli M.,Coordination Center | Micheli M.,SpaceDyS s.r.l. | Micheli M.,National institute for astrophysics
Icarus | Year: 2015

We describe systematic ranging, an orbit determination technique suitable to assess the near-term Earth impact hazard posed by newly discovered asteroids. For these late warning cases, the time interval covered by the observations is generally short, perhaps a few hours or even less, which leads to severe degeneracies in the orbit estimation process. The systematic ranging approach gets around these degeneracies by performing a raster scan in the poorly-constrained space of topocentric range and range rate, while the plane of sky position and motion are directly tied to the recorded observations. This scan allows us to identify regions corresponding to collision solutions, as well as potential impact times and locations. From the probability distribution of the observation errors, we obtain a probability distribution in the orbital space and then estimate the probability of an Earth impact. We show how this technique is effective for a number of examples, including 2008 TC3 and 2014 AA, the only two asteroids to date discovered prior to impact. © 2015 Elsevier Inc.

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