SpaceDyS srl

Cascina, Italy

SpaceDyS srl

Cascina, Italy
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Farnocchia D.,Jet Propulsion Laboratory | Jenniskens P.,Search for Extraterrestrial Intelligence Institute | Robertson D.K.,NASA | Chesley S.R.,Jet Propulsion Laboratory | And 2 more authors.
Icarus | Year: 2017

The impact of asteroid 2008 TC3 was an unprecedented event-the first ever predicted impact of a near-Earth object. When it was first detected about 20 h before impact, 2008 TC3 was still farther away than the Moon. Once it was recognized as an impactor and announced as such, 2008 TC3 began to receive considerable attention from astronomical observers. Using the unprecedented dataset of nearly 900 astrometric observations and the latest observation debiasing and weighting techniques, we estimate the precise trajectory of 2008 TC3 and its impact ground track. At the entry point into the atmosphere, the 3-σ formal uncertainty in predicted position is an ellipse only 1.4 km × 0.15 km in size. The locations of the many meteorites recovered from the desert floor mark the asteroid's actual ground track and provide a unique opportunity to validate trajectory models. We find that the second-order zonal harmonics of the Earth gravity field moves the ground track by more than 1 km and the location along the ground track by more than 2 km, while non-zonal and higher order harmonics change the impact prediction by less than 20 m. The contribution of atmospheric drag to the trajectory of 2008 TC3 is similar to the numerical integration error level, a few meters, down to an altitude of 50 km. Integrating forward to lower altitudes and ignoring the break-up of 2008 TC3, atmospheric drag causes an along-track deviation that can be as large as a few kilometers at sea level. © 2017.

Schettino G.,University of Pisa | Di Ruzza S.,SpaceDys S.r.l. | De Marchi F.,University of Pisa | Cicalo S.,SpaceDys S.r.l. | And 2 more authors.
Memorie della Societa Astronomica Italiana - Journal of the Italian Astronomical Society | Year: 2016

BepiColombo is a joint ESA/JAXA mission to Mercury with challenging objectives regarding geophysics, geodesy and fundamental physics. The Mercury Orbiter Radio science Experiment (MORE) is one of the on-board experiments, including three different but linked experiments: gravimetry, rotation and relativity. Using radio observables (range and range-rate) performed with very accurate tracking from ground stations, together with optical observations from the on-board high resolution camera (SIMBIO-SYS) and accelerometer readings from the on-board accelerometer (ISA), MORE will be able to measure with unprecedented accuracy the global gravity field of Mercury and the rotation state of the planet. In this work we present the results of a numerical full-cycle simulation of the gravimetry and rotation experiments of MORE: we discuss the accuracies which can be achieved, focussing in particular on the possible benefits from the use of optical observations in support to the tracking measurements. © 2016 SAIt.

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.

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. | 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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