Search

Hyperselective neurectomy (HSN) procedures in the spastic upper limb aim to reduce tone by excising some branches of the involved peripheral motor nerves, at the point of entry of each motor ramus into the target muscle. In this prospective study, 42 patients with upper limb spasticity were treated by HSN for the muscles of elbow flexion, forearm pronation and wrist flexion and evaluated for their short-term results (average 6 months) and long-term outcomes (average 31 months). Results at both time points showed an effective reduction of the spastic tone, with no decrease of muscle strength in the operated spastic muscles. Comparison of results between the two time points showed durability of the improvement, which remained statistically significant despite a slight relapse in spasticity. The results of HSN compare favourably with the other techniques of partial neurectomy; however, the technique requires a detailed knowledge of upper limb motor anatomy. Level of evidence: II

Context. Near-earth objects (NEOs), thanks to their proximity, provide a unique opportunity to investigate asteroids with diameters down to dozens of meters. The study of NEOs is also important because of their potential hazard to the Earth. The investigation of small NEOs is challenging from Earth as they are observable only for a short time following their discovery and can sometimes only be reached again years or decades later. Aims. We aim to derive the visible colors of NEOs and perform an initial taxonomic classification with a main focus on smaller objects and recent discoveries. Methods. Photometric observations were performed using the 1.2 m telescope at the Haute-Provence observatory and the 1.0 m telescope at the Pic du Midi observatory in broadband Johnson-Cousins and Sloan photometric systems. Results. We present new photometric observations for 55 NEOs. Our taxonomic classification shows that almost half (43%) of the objects in our sample are classified as S+Q-complex members, 19% as X-complex, 16% as C-complex, 12% as D-types, and finally 6% and 4% as A- and V-types, respectively. The distribution of the observed objects with H > 19 and H ≤ 19 remains almost the same. However, the majority of the objects in our dataset with D < 500 m belong to the “silicate” group, which is probably a result of an observational bias towards brighter and more accessible objects. “Carbonaceous” objects are predominant among those with a Jovian Tisserand parameter of Tj < 3. These bodies could be dormant or extinct comets. The median values of the absolute magnitude for “carbonaceous” and “silicate” groups are H = 18.10 ± 0.95 and H = 19.50 ± 1.20, whereas the estimated median diameters are D = 1219 ± 729 m and D = 344 ± 226 m, respectively. “Silicate” objects have a much lower median Earth’s minimum orbit intersection distance (MOID) and a somewhat lower orbital inclination in comparison to “carbonaceous” objects. About half of the observed objects are potentially hazardous asteroids and are mostly (almost 65%) represented by “silicate” objects.

Using data acquired by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission, we investigate spectral properties of craters on the near-Earth asteroid (101955) Bennu. We compare Bennu's craters with its global average by means of four spectral parameters: (a) minimum position of the band at 2.7 μm, (b) depth of the hydrated phyllosilicate absorption band at 2.7 μm, (c) normalized spectral slope from 0.55 to 2.0 μm, and (d) reflectance factor at 0.55 μm. We examine 45 craters using spectral data obtained under various observing conditions. For 20 craters, we find a shortward shift of the 2.7-μm band minimum relative to the global 2.7-μm band minimum, which we attribute to the presence of relatively fresh (less space-weathered) material excavated from the sub-surface by crater-forming impacts. For three craters, we find an anti-correlation between spectral slopes and reflectance factor for a series of spectra acquired during a specific scan, where we observe that spectra become redder and darker towards the center of the crater. We attribute this to the presence of fine-particulate regolith. Localized spectral heterogeneities are apparent inside a prominent equatorial crater on Bennu, which is one of the asteroid's oldest geological features. We propose that such local spectral heterogeneities could be used as a tracer of mass movement on Bennu. We show that younger craters are redder, brighter, and have deeper 2.7-μm bands. Comparing global average spectral values of Bennu and crater frequency distributions as a function of the chosen spectral parameters, we find that craters evolve to assume the global average spectral properties of Bennu. A positive correlation identified between the reflectance factor and 2.7-μm band depth suggests that brighter craters tend to be more hydrated. Finally, we put into context, the results from the Small Carry-on Impactor experiment by the Hayabusa2 spacecraft, which created an artificial crater on the near-Earth asteroid (162173) Ryugu.

Trojans, Centaurs and Trans-Neptunian objects are small dark objects orbiting in the outer Solar System. These objects, still very poorly known, can be considered as fossils of our Solar System, and, as such, they can still contain information about some primordial processes which governed the evolution of the early Solar System. In the next decade, GAIA with its large sky surveys, can allow the discovery of many new objects belonging to these outer solar system populations. In addition, it will provide very precise orbits and visible broad-band colours for many of them.

International audience

Contact.The NASA New Frontiers asteroid sample return mission Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) has provided a large amount of data on the asteroid (101955) Bennu, including high-quality spectra obtained by the OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS).Aims.To better constrain the surface properties and compositional variations of Bennu, we studied the visible and near-infrared spectral behavior across the asteroid surface by means of a statistical analysis aiming to distinguish spectrally distinct groups, if present.Methods.We applied theG-mode multivariate statistical analysis to the near-infrared OVIRS spectra to obtain an automatic statistical clustering at different confidence levels.Results.The statistical analysis highlights spectral variations on the surface of Bennu. Five distinct spectral groups are identified at a 2σconfidence level. At a higher confidence level of 3σ, no grouping is observed.Conclusions.The results at a 2σconfidence level distinguish a dominant spectral behavior group (group 1, background) and four small groups showing spectral slope variations, associated with areas with different surface properties. The background group contains most of the analyzed data, which implies a globally homogeneous surface at the spectral and spatial resolution of the data. The small groups with redder spectra are concentrated around the equatorial ridge and are associated with morphological surface features such as specific craters and boulders. No significant variation is detected in the band area or depth of the 2.74μm band, which is associated with hydrated phyllosilicate content. The spectral slope variations are interpreted as a consequence of different regolith particle sizes, and/or porosity, and/or space weathering, that is, the presence of more or less fresh material. The OSIRIS-REx mission primary sampling site, Nightingale, and a boulder known as the Roc, are redder than the background surface.

International audience; Asteroids were likely a major source of volatiles and water to early Earth. Quantifying the hydration of asteroids is necessary to constrain models of the formation and evolution of the Solar System and the origin of Life on Earth. The OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) mission showed that near-Earth asteroid (101955) Bennu contains widespread, abundant hydrated phyllosilicates, indicated by a ubiquitous absorption at ~ 2.7 μm. The objective of this work is to quantify the hydration-that is, the hydrogen content-of phyllosilicates on Bennu's surface and investigate how this hydration varies spatially. We analyse spectral parameters (normalized optical path length, NOPL; effective single-scattering albedo, ESPAT; and Gaussian modeling) computed from the hydrated phyllosilicate absorption band of spatially resolved visible-near-infrared spectra acquired by OVIRS (the OSIRIS-REx Visible and InfraRed Spectrometer). We also computed the same spectral parameters using laboratory-measured spectra of meteorites including CMs, CIs, and the ungrouped C2 Tagish Lake. We estimate the mean hydrogen content of water and hydroxyl groups in hydrated phyllosilicates on Bennu's surface to be 0.71 ± 0.16 wt%. This value is consistent with the hydration range of some aqueously altered meteorites (CMs, C2 Tagish Lake), but not the most aqueously altered group (CIs). The sample collection site of the OSIRIS-REx mission has slightly higher hydrogen content than average. Spatial variations in hydrogen content on Bennu's surface are linked to geomorphology, and may have been partially inherited from its parent body.

ESA's Rosetta Mission has followed Comet 67P/Churyumov-Gerasimenko from 3.6 au inbound to 3.6 au outbound. Many results are largely unexpected, as compared to previous models based on in situ and ground-based observations of Jupiter-family comets. The main topics discussed in this review are (1) the importance of the large concavities characterizing the 67P nucleus, that, (2) coupled to the nucleus obliquity, make seasons an unexpectedly important source of many phenomena observed in this and probably in most comets; (3) the mostly uniform distribution of ices over the nucleus surface; (4) the high dust-to-water mass ratio, which implies that much of the nucleus mass is in the form of minerals partly coming from the inner proto-solar nebula, thus making 67P very porous and less hydrated than primitive CI chondrites. 67P nucleus may have never experienced any collision at speeds larger than 1 m s-1.

Besides being of great scientific interest, near-Earth objects represent a well-founded threat to life on our planet. Nonetheless, up to now there has been no concerted international plan on how to deal with the impact threat, and how to prepare and implement mitigation measures. The NEOShield project is funded by the European Commission to address such issues, to investigate the feasibility of techniques to prevent a potentially catastrophic impact on Earth by an asteroid or a comet, and to develop detailed designs of appropriate space missions to test deflection techniques. In this work we present and discuss the scientific and strategic aspects of the asteroid impact threat, highlighting the necessary steps so as to be ready to react to future hazardous objects.

International audience; We investigate the possible presence of heterogeneous surface features on asteroid (2867) Steins, using the G-mode multivariate statistical method (Coradini et al., 1977) applied to Rosetta/OSIRIS images. We analyze both NAC and WAC images obtained near around the closest approach that occurred on September 5th, 2008, through different filters centered on wavelengths ranging from 295 to 986 nm. The shape of Steins is modeled as a polyhedron of almost 58 000 facets. Photometric corrections were performed using Hapke's (2002) model to compensate for the variable illuminations conditions at the surface. The G-mode classification method was performed on all visible and illuminated facets, i.e. in a region limited to [-50 degrees,+60 degrees] in latitude and [-40 degrees,+90 degrees] in longitude, that represents almost 30% of the total surface. The analyzed set of facets does not show any significant difference in the reflected light content, suggesting no surface inhomogeneities larger than 4% at the 95% confidence level. (C) 2010 Elsevier Ltd. All rights reserved.

International audience; Context: Asteroid 2867 Steins is the first target of the Rosetta space mission with a flyby scheduled in September 2008. Aims: An early characterization is needed to optimize the flyby parameters and the science operations, and to maximize the scientific return. Methods: We used the infrared spectrograph (IRS) of the Spitzer Space Telescope (SST) to obtain 14 spectra ranging from 5.2 to 38.0 mum, and to sample the rotational period of the asteroid. The observations were performed on 22 November 2005, when the asteroid was 2.13 AU from the Sun, 1.60 AU from the SST, and at a phase angle of 27.2°. They were interpreted using a standard thermal model incorporating the thermal inertia. Results: The solution for a spherical shape leads to an effective radius rn = 2.46 ± 0.20 km and a thermal inertia I = 150 ± 60 J K-1 m-2 s-1/2, for a beaming factor between 0.8 and 1.0. The geometric albedo is then constrained by visible photometry to pR = 0.31 ± 0.05 and pV = 0.27 ± 0.04 when using a linear phase function. The H-G phase law, which includes an opposition effect, leads to larger values of the albedo, p_R(H-G) = 0.40 ± 0.07 and p_V(H-G) = 0.34 ± 0.06. The solution for our 3-dimensional shape model has overall dimensions of 5.73 ± 0.52 × 4.95 ± 0.45 × 4.58 ± 0.41 km.

International audience; We have calculated the condensation and evaporation of ternary CH 4-N 2-C 2H 6 liquid drops and solid CH 4 hail as they fall through Titan's lower atmosphere to determine the likelihood that precipitation reaches the ground. Assuming the humidity profile determined by the Huygens probe, binary liquid CH 4/N 2 condensate grows in the region from ˜8 to 15 km in Titan's atmosphere because the combined humidity of CH 4 and N 2 exceeds saturation. These drops evaporate below ˜8 km. We determine the fate of 10 mum seeds composed of ethane, which is expected to provide condensation sites. In addition, we study the fate of already formed raindrops with radii of 1-4.75 mm falling out of the growth region. High (50%) and low (0%) ethane relative humidities (RH) are considered in the calculation. We find that drops with radii ˜3 mm and smaller dropping from 8 km reach the ground in compositional equilibrium with the atmosphere in the high ethane RH case as a result of the stabilizing influence of the ethane, and evaporate in the atmosphere in the low ethane RH case. Large drops (>˜3 mm) reach the surface large and cold because the latent heat loss due to the evaporation of methane cools the drop and slows the evaporation rate. Pure methane hail hits the ground if its radius is initially more than 4 mm at 16 km above the surface and sublimates in the atmosphere if its radius is smaller.

In this paper we present the observational campaign carried out at ESO NTT and VLT in April and May 2006 to investigate the nature and the structure of the Near Earth Object (144898) 2004 VD17. In spite of a great quantity of dynamical information, according to which it will have a close approach with the Earth in the next century, the physical properties of this asteroid are largely unknown. We performed visible and near--infrared photometry and spectroscopy, as well as polarimetric observations. Polarimetric and spectroscopic data allowed us to classify 2004 VD17 as an E-type asteroid. A good agreement was also found with the spectrum of the aubrite meteorite Mayo Belwa. On the basis of the polarimetric albedo (p_v=0.45) and of photometric data, we estimated a diameter of about 320 m and a rotational period of about 2 hours. The analysis of the results obtained by our complete survey have shown that (144898) 2004 VD17 is a peculiar NEO, since it is close to the breakup limits for fast rotator asteroids, as defined by Pravec and Harris (2000). These results suggest that a more robust structure must be expected, as a fractured monolith or a rubble pile in a "strength regime" (Holsapple 2002)., Comment: 32 pages, 7 figure, paper accepted for publication in Icarus

The principal component (PC) and G-mode multivariate statistics have been used in analysing the set of the 34 Edgeworth—Kuiper objects (EKOs) — 23 Trans Neptunian Objects (TNO) and 11 Centaurs — for which B, V, R, I,J homogeneous photometry were available. The results obtained show that V-I and V-Js are the key parameters in structuring the sample in homogeneous groups. The PC1 axis (which contains ~93% of the sample total variance) spans five times more than the PC2 (which contains ~6% of the sample total variance). The extremes of the PC1 axis contain the objects having a flat spectrum (low PC1 values) and a very red spectrum respectively. Independently, the G-mode analysis allows us to distinguish six homogeneous groups of objects which confirm and extend the results obtained with the PC analysis. In addition to these groups, a few objects remain not included in any group (i.e., does not have significant similitude with other objects) and yet give an indication of a more complex compositional structure of the sample. These preliminary results will have to be confirmed and completed when a larger sample is available, but they provide some interesting hints for understanding the — mainly collisional — evolution of the EKOs.

Observations of emissivity features of 10 Hygiea have been made for the first time in the relatively unexplored thermal-infrared wavelength region with the ISO (Infrared Space Observatory) satellite. Spectrophotomer (PHT-S) and short wavelength spectrometer (SWS) spectra of 10 Hygiea, obtained at 5.8–11.6 and 7–45 μm, respectively, are presented. In order to remove the thermal emission continuum, an advanced thermo–physical model has been applied to the observational data. To better interpret the spectral features above the thermal emission continuum, we compared the ISO observations with laboratory spectra available in the literature. Several laboratory experiments on minerals and meteorites have been performed to complete the analysis and to study the spectral behavior at various grain sizes. A possible spectral similarity with CO carbonaceous chondrites at small grain size is demonstrated.

In the framework of the Cassini-Huygens mission towards the Saturnian system, the Huygens Atmospheric Structure Instrument (HASI) is a multisensor package which has been designed to measure the physical quantities characterizing the atmosphere of Titan, Saturn's largest satellite. HASI sensors are devoted to the study of Titan's atmospheric structure and electric properties, and also to provide information on the surface, whatever its phase, solid or liquid. A description of the experiment, its subsystems and sensors package is reported together with their performances.

Orbiting asteroid (4) Vesta from July 2011 to August 2012, the Framing Camera on board the Dawn spacecraft has acquired several tens of thousand images of the asteroid surface, revealing a complex landscape. The topography is dominated by craters of all sizes and shapes, from fresh, simple, bowl-shaped craters to giant basins, as seen in the southern hemisphere. Craters of different ages or states of degradation can be seen all over the surface; some have very sharp rims and simple morphology, whereas others are highly eroded and have sometimes been filled by landslides and ejecta from nearby craters. The general depth/Diameter (d/D) distribution on Vesta is similar to what has been observed on other small rocky objects in the Solar System with a distribution peaking at 0.168±0.01 in the range 0.05–0.35. However, the global map of d/D reveals important geographic variations across the surface, unlike any other asteroid. The northern most regions of Vesta show d/D values comparable to other asteroid surfaces, with a mean d/D of 0.15±0.01, and a steep cumulative distribution. Craters in the regions affected by the giant southern impacts are deeper (mean d/D=0.19±0.01) and show less erosion. It can be interpreted as the southern surface being younger than the rest of the asteroid, or made of a material which either allows the formation of deeper features or prevents their erosion. This picture is consistent with the idea of a southern Vestan hemisphere resurfaced relatively recently by the giant impact that created the Rheasilvia basin. The analysis of depth-to-Diameter variations over the whole surface also brings some insight into the transition regions between different cratering regimes: about 20 km for the strength-to-gravity dominated regime, and 38 km for the beginning of the simple-to-complex transition.

We report the results of the rst statistical analysis of colours (B V , V R, V I ,a ndV J) of the Trans-Neptunian and Centaur populations. Using the same statistical techniques applied to dene the current asteroid taxonomy, we nd a continuous spread of the objects between neutral colour to very red. Pushing further the analysis, the TNOs may be split into four groups. The dierences in colour content are interpreted as a consequence of the TNOs evolution (i.e. collisional history, space weathering, ...)

Barucci et al. (1987. Icarus 72 , 304–324) developed their asteroid taxonomy based on the G-mode statistical method, applied to a sample of 438 asteroids, where each asteroid was described by eight variables (seven ECAS colors and the IRAS albedo). They found that the asteroid population separates into nine major taxonomic classes (C, S, M, D, B, G, E, A, V) and that three of these (S, D, B) can be further subdivided into subclasses. Birlan et al. (1996b. Icarus 124 , 352–354) found that the values of the corrected IRAS albedos do not influence the bulk structure of this taxonomy. The aim of this paper is to define an algorithm that allows us to extend this classification system to any asteroid for which the ECAS reflectances and the albedos become available through new observations. The algorithm which allows us to extend the G-mode method is presented, along with a test of the procedure utilizing color and albedo measurements for 465 asteroids.

International audience; The Permittivity Waves and Altimetry (PWA) experiment is part of the Huygens Atmospheric Structure Instrument (HASI) presently ‘en route’ toTitan as a part of the HUYGENS Probe carried by the Saturn orbiter CASSINI. When HUYGENS lands upon Titan, the Mutual Impedance (MI) probe, part of the PWA experiment will be set to a special mode to measure the complex permittivity of the surface. We discuss here the capabilities of the instrument relative to several possible surface models currently under discussion. For a liquid surface, PWA will provide additional permittivity measurements to the Surface Science Package (SSP) measurements. In the case of a solid surface, with an estimation of the probe penetration from SSP acceleration data and under the assumption of homogeneity, the complex permittivity can be derived. Moreover, if the surface layer is well known up to a few tens of centimeters, we would also have knowledge of the permittivity of the underlying material. Although PWA-MI provides only permittivity measurements it should contribute greatly to identifying Titan's surface structure and composition in synergy with the other HUYGENS instruments.

The ROSETTA spacecraft will fly-by a few asteroids during its course to the final cometary target. The candidate asteroids presently are 3840 Ministrobel (S-type), 2703 Siwa and 140 (C-type).With the limited data presently available on these bodies we calculated some approximate quantities which may be useful to select the fly-by trajectories of the ROSETTA probe. In particular we derived the zones in which particles could stably orbit by analyzing Hills problem of three hierarchical masses—the sun, the asteroid and the orbiting particle. Then, following the approach of Hamilton and Burns, the effects of solar radiation pressure and of the ellipticity of the orbits were also taken into account. In this way for each asteroid we could calculate not only a classical quantity like the radius of the Hill sphere, but also the critical starting orbital distance (as a function of orbital inclination) within which most orbits remain bound to the asteroid, and outside which most escape as a consequence of perturbations. Moreover we determined the orbital stability zone, defined as the union of all the numerically integrated orbits showing long-term stability, for each of the target asteroids. The particular shape of these zones would suggest to have the spacecrafts close approach out of the orbital plane of the asteroids. To further investigate this problem and, in particular, to take into account the irregular shape of the asteroids, we developed a model using a polyhedral representation of the central rotating body, following a theory developed by Werner and Scheeres. This model is described here and the first orbital integration results are presented. © 1999 Elsevier Science Ltd. All rights reserved.

The ROSETTA spacecraft will fly-by a few asteroids during its course to the final cometary target. The candidate asteroids presently are 140 Siwa (C-type) and 4979 Otawara. An alternative interesting trajectory reaching four asteroids (5331 Erimomisaki, 905 Universitas, 1515 Perrotin and 4247 Grahamsmith) has also been found by ESA. With the limited data presently available on these bodies we calculated some approximate quantities which may be useful to select the fly-by trajectories of the ROSETTA probe. Some first information are provided by the classical quantities such as the radius of the Hill sphere. Then, exploiting the results of Hamilton and Burns (1991), we determined the orbital stability zone, i.e. the union of all the numerically integrated orbits showing long-term stability, for each of the above asteroids. As was suggested by Hamilton and Burns (1991) the particular shape of these zones would suggest to have the spacecraft's close approach out of the orbital plane of the asteroids. The results of a large set of numerical integrations are then presented, strengthening and broadening the conclusions of the analytical calculations. The stability zone appears to be severely limited by the effect of the solar radiation pressure which sweeps away small particles from the asteroid vicinity. In the case of 140 Siwa the borders of the zone (for mm-sized particles) stretch to about 420 RA in the X – Y plane and 162 RA in the Z direction, mainly due to the apocenter distance reached by particles placed on initial highly eccentric orbits.

The analysis of visible and near-infrared reflectance spectra of C-class objects has revealed the presence of features that appear to indicate a history of aqueous alteration on their surfaces. This result can provide constraints on our understanding of the early Solar System. We have recorded spectra covering 0.48–0.92 μm for 29 C-class objects with orbital semimajor axes between 2.3 and 3.6 AU. About 70% of the observed objects show features produced as the result of aqueous alteration processes.

The Eos family detected by Hirayama in 1918 has been always considered to be compositionally homogeneous. To investigate the composition and the homogeneity of the members of this family, we started a spectroscopic survey at the European Southern Observatory (ESO) with wavelength coverage ranging from 4800 to 9200 A. We observed 45 Eos asteroid members, which constitutes the first large survey of this family. Our results reveal the Eos objects have spectral signature characterizing the whole family: a maximum at λ ∼ 8000–8500 A and a reflectivity gradient spanning a continuous range. Only two of the 45 investigated objects seem to be interlopers. While the lower range of this spectral distribution has been easily connected with CO–CV chondrites, we have found no satisfactory meteorite counterpart to the upper range. We have interpreted the spread out of Eos spectra to be the results of compositional variation among the Eos members, implying that the Eos parent body was partially differentiated. Moreover, a space weathering effect has been proven to be present, but with a minor role played in the diversity of Eos family, the major role being the compositional variation.

In this paper we present the results of several observational campaigns carried out during 1996 at the 1.2 m telescope of the Haute Provence Observatory (France) and at the 1.5m Danish, 0.9m Dutch, 0.6m Bochum and 0.5m telescopes of the European Southern Observatory (ESO, La Silla, Chile), in order to enlarge the available sample of know asteroid rotational periods. A total of 64 single night lightcurves for 15 asteroids were obtained. The rotational periods have been determined for 12 objects, with different quality code: 424 Gratia ( P syn = 19.47 h), 440 Theodora ( P syn = 4.828 h), 446 Aeternitas ( P syn = 15.85 h), 491 Carina ( P syn = 14.87 h), 727 Nipponia ( P syn = 4.6 h), 732 Tjilaki ( P syn = 12.34 h), 783 Nora ( P syn = 34.4 h), 888 Parysatis ( P syn = 5.49 h), 1626 Sadeya ( P syn = 3.438 h), 2209 Tianjin ( P syn = 9.47 h), 2446 Lunacharsky ( P syn = 3.613 h) and 3776 Vartiovuori ( P syn = 7.7 h). For 1246 Chaka, 1507 Vaasa and 1994 Shane the complete rotational phase was not covered and for two of them it was possible to find only an indication of the rotational period.

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.\ud \ud 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.

The Fourier coefficients of 254 composite lightcurves of 53 asteroids are analysed, continuing a previous work (Barucci et al., Icarus 78 , 311–322, 1989), with the aim of inferring asteroidal shapes and possible albedo variegations. Coefficients are obtained only from good quality photometric data of asteroids for which a reliable estimate of the orientation of the spin axis is available. For each of the 53 asteroids an indicative shape is derived, on the basis of the coefficients resulting from the Fourier analysis. The shapes determined for 243 Ida and 951 Gaspra are confirmed by the Galileo images. Most of the analysed asteroids show a quasi-regular shape, probably due to a bias on the diameters of the sample; the remaining part, having smaller diameters, seems to show an irregular shape. The obtained results cannot be interpreted in a statistical sense but they can constitute a promising starting point for the understanding of the evolution of asteroidal population.

We present the results of photometric observations of 12 asteroids, performed from 1985 through 1989 at the Astronomical Observatory of Teramo (Italy), Astronomical Observatory of Turin (Italy), and European Southern Observatory (ESO, La Silla, Chile). Using the EA pole determination method described in G. De Angelis ( Planet. Space Sci. , 41, 285-290, 1993), we have obtained the first spin and shape solution of 85 to and 360 Carlova and an improvement of the previous determinations for 12 Victoria, 192 Nausikaa and 423 Diotima, for which we determined for the first time the sidereal period and the sense of rotation. We have checked the determinations obtained by other authors for the asteroids 3 Juno, 6 Hebe, 20 Massalia, 43 Ariadne, and 52 Europa, and suggested a very rough estimate of the spin and shape parameters of 115 Thyra.

High resolution spectroscopy of the impacts and impact sites of comet P/Shoemaker-Levy 9 in Jupiter has been performed at the Pic-du-Midi observatory, France. The transient emission of seven emission lines from five different metals (Na, Fe, Ca, Li, K) and of the Hα line have been identified in spectra from the fresh impact sites of fragments L and Q1.

A comparison of the G-mode (Barucci et al., Icarus 72, 304, 1987) and three-parameter (Tedesco et al., Astron. J. 97, 580, 1989) asteroid taxonomic classification systems is presented. Using a common data set we demonstrate that, at a 94% confidence level, the two methods yield the same classifications. We discuss the significance and future application of this result.

In this paper we present a model of the shape and surface features of the asteroid 243 Ida, second fly-by target of the Galileo mission. We obtained this model by applying the lightcurve inversion method (Fulchignoni and Barucci, B.A.A.S. 20, 866, 1988), already used for the model of 951 Gaspra (Barucci et al., Astron. Astrophys. 266, 385–394, 1992), on the whole sample of available lightcurves obtained during five oppositions between 1984 and 1993 (Binzel, Icarus 72, 135–208, 1987; Gonano-Beurer et al., Astron. Astrophys. 254, 393–396, 1992; Binzel et al., Icarus 105, 310–325, 1993; Mottola et al., Planet. Space Sci. 42, 21–25, 1994). The comparison of our model with the first Galileo image of 243 Ida gives another “ground truth” for the used method based on observations from the Earth.

International audience

International audience

A program of physical studies of asteroids has been carried out using two types of detectors: photoelectric photometer and CCD camera. In this paper we report the results of photometric observations of 10 asteroids. We have obtained a total of 35 single night lightcurves and we have determined rotational periods for the asteroids 1520 Imatra (P = 5.23 h), 1534 Nasi (P = 9.75 h), 2078 Nanking (P = 6.473 h), 2241 Alcathous (P = 9.41 h), 3103 1982 BB (P= 5.709 h), 3139 Shantou (P = 8.33 h), 3259 Brownlee (P = 9.24 h), 4455 Ruriko (P = 4.23 h).

Near-infrared (J, H and K bands) spectra of nine dark asteroids (chosen among a sample of supposed primitive objects between C and D classes) have been obtained at the Mauna Kea Observatory (Hawaii) with the 2.2-m telescope using KSPEC as spectrograph. The aim of this work was to search for evidence of the presence of organic materials in these objects as found in other planetary bodies as 5145 Pholus, and in some cometary nuclei. A careful analysis of the data has revealed flat or slightly redder spectra than the solar one for all observed asteroids. No evidence of distinct absorption features was found.

The atmospheric turbulence, responsible for "seeing" effects, leads to severe limitations on the spatial resolution of groundbased optical telescopes. It is now feasible to efficiently compensate in real time for these detrimental effects by using adaptive optics in the near infrared. The impressive capabilities of this new method offer exciting opportunities for the observation of Solar System bodies that are small but resolvable by large telescopes reaching their diffraction limit. We report on observations of Pallas and Titan carried with the first operational adaptive optics system dedicated to astronomical observing, called "COME-ON" (based on data collected at ESO 3.6-m telescope on 01-08 January and 01-05 May, 1991). We briefly describe the system and summarize its current performance as well as that expected in the near future. Preliminary results obtained on minor planets and Titan, such as the shape of asteroids at different dates and features on Titan's disk, are presented. Future plans to study Solar System objects at the diffraction limit with the COME-ON instrument are also presented.

Identified as a possible flyby target for the Cassini spacecraft, asteroid 302 Clarissa became the focus of our observing programme in 1991. Multichannel photoelectric observations were performed at Calar Alto Observatory in Spain during four nights (from 29 October to 2 November 1991). Although a subsequent change in the mission scenario removed the asteroids from consideration for the Cassini mission, the ground-based observations yielded a substantial amount of information on this asteroid. A sidereal rotation period of 14.381±0.002 h with lightcurve amplitude of 0.6 mag has been determined. Considerations on the use of continuous photometry for observations of asteroids are given.

Photometric observational results are reported of a wide international campaign carried out for the asteroid 951 Gaspra. This S-type asteroid was the first flyby target of the Galileo spacecraft. The solar phase angle dependence of the light curve amplitudes and magnitudes are analyzed. A G value of about 0.29 is obtained for the light curve maxima.

Aims. We determine the physical properties (spin state and shape) of asteroid (21) Lutetia, target of the ESA Rosetta mission, to help in preparing for observations during the flyby on 2010 July 10 by predicting the orientation of Lutetia as seen from Rosetta. Methods. We use our novel KOALA inversion algorithm to determine the physical properties of asteroids from a combination of optical lightcurves, disk-resolved images, and stellar occultations, although the latter are not available for (21) Lutetia. Results. We find the spin axis of (21) Lutetia to lie within 5 degrees of ({\lambda} = 52 deg., {\beta} = -6 deg.) in Ecliptic J2000 reference frame (equatorial {\alpha} = 52 deg., {\delta} = +12 deg.), and determine an improved sidereal period of 8.168 270 \pm 0.000 001 h. This pole solution implies the southern hemisphere of Lutetia will be in "seasonal" shadow at the time of the flyby. The apparent cross-section of Lutetia is triangular as seen "pole-on" and more rectangular as seen "equator-on". The best-fit model suggests the presence of several concavities. The largest of these is close to the north pole and may be associated with large impacts., Comment: 17 pages, 5 figures, 3 tables, submitted to Astronomy and Astrophysics

Aims. A wide observational campaign was carried out in 2004–2009 that aimed to complete the ground-based investigation of Lutetia prior to the Rosetta fly-by in July 2010. Methods. We obtained BVRI photometric and V-band polarimetric measurements over a wide range of phase angles, and visible and infrared spectra in the 0.4–2.4 μm range. We analyze them with previously published data to retrieve information about Lutetia's surface properties. Results. Values of lightcurve amplitudes, absolute magnitude, opposition effect, phase coefficient, and BVRI colors of Lutetia surface seen at near pole-on aspect are determined. We define more precisely parameters of polarization phase curve and show their distinct deviation from any other moderate-albedo asteroid. An indication of possible variations in both polarization and spectral data across the asteroid surface are found. To explain features found by different techniques, we propose that (i) Lutetia has a non-convex shape, probably due to a large crater, and heterogeneous surface properties probably related to surface morphology; (ii) at least part of the surface is covered by a fine-grained regolith of particle size smaller than 20 μm; (iii) the closest meteorite analogues of Lutetia's surface composition are particular types of carbonaceous chondrites, or Lutetia has specific surface composition that is not representative among studied meteorites. Fil: Belskaya, I. N.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia. Kharkiv Karazin National University; Ucrania Fil: Fornasier, S.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia. Université Paris Diderot - Paris 7; Francia Fil: Krugly, Yu N.. Kharkiv Karazin National University; Ucrania Fil: Shevchenko, V. G.. Kharkiv Karazin National University; Ucrania Fil: Gaftonyuk, N. M.. Crimean Astrophysical Observatory; Ucrania Fil: Barucci, M. A.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia Fil: Fulchignoni, M.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia. Université Paris Diderot - Paris 7; Francia Fil: Gil Hutton, Ricardo Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; Argentina

International audience; The Huygens Probe measured the electrical conductivity of Titan atmosphere from about 140 km down to the surface, employing relaxation and mutual impedance techniques. Previous analyses have shown some differences on the conductivity measurements obtained with two independent sensors - Relaxation Probe (RP) and Mutual Impedance Probe (MIP). A 20-fold maximum discrepancy occurred around the conductivity peak at 60-70 km. To understand the nature of such discrepancy, we reassess the RP data by taking into account a geometrical factor related to the electrode finite size and the Debye length of the ionized medium. The present analysis implies replacing the standard Laplace field distribution by a more elaborated model considering the Poisson equation and the resistance between the RP electrodes and the medium. Although a complete understanding of the conductivity profile is still missing, this work brings RP and MIP data to a much better agreement. The conductivity maximum difference derived from the two sensors is now lower a factor of 2. This reassessment is also useful for future instruments and missions.

International audience; Context. In July 2010 the ESA spacecraft Rosetta will fly by the main belt asteroid 21 Lutetia. Several observations of this asteroid have been performed so far, but its surface composition and nature are still a matter of debate. For a long time Lutetia was supposed to have a metallic nature due to its high IRAS albedo. Later on it has been suggested that the asteroid has a surface composition similar to primitive carbonaceous chondrite meteorites, while further observations proposed a possible genetic link with more evolved enstatite chondrite meteorites. Aims: We performed visible spectroscopic observations of 21 Lutetia in November 2008 at the Telescopio Nazionale Galileo (TNG, La Palma, Spain) to make a decisive contribution to solving the conundrum of its nature. Methods: Thirteen visible spectra were acquired at different rotational phases and subsequently analyzed. Results: We confirm a narrow spectral feature at about 0.47-0.48 mum which was already found by Lazzarin et al. (2004, A&A, 425, L25) in the spectra of Lutetia. We also confirm an earlier find of Lazzarin et al. (2004), who detected a spectral feature at about 0.6 mum in one of their Lutetia's spectra. More remarkable is the difference of our spectra though, which exhibit different spectral slopes between 0.6 and 0.75 mum and, in particular, we found that up to 20% of the Lutetia surface could have flatter spectra. Conclusions: We detected a variation of the spectral slopes at different rotational phases that could be interpreted as possibly due to differences in the chemical/mineralogical composition as well as to inhomogeneities of the structure of the Lutetia's surface (e.g., to craters or albedo spots) in the southern hemisphere.

International audience; On 5 September 2008, the Rosetta spacecraft encountered the asteroid 2867 Steins on its way to the comet 67P/Churyumov-Gerasimenko. This was the first of two planned asteroid fly-bys performed by the probe, the second fly-by being with the much larger asteroid 21 Lutetia in July 2010. The VIRTIS imaging spectrometer (IFOV 0.250 mrad, overall spectral range 0.25-5.1 mum) onboard Rosetta acquired data of Steins already before the closest approach phase, when the target was spatially unresolved, in order to obtain a light curve of the asteroid in the infrared spectral range extending up to 5 mum, that was never explored before. The VIRTIS light curve campaign started at 11:30 UTC onboard time, when the spacecraft was about 221,377 km away from the target, and ended at 17:58 UTC, at a distance of 20,741 km away from Steins. During this timeframe, the solar phase angle of the asteroid was roughly constant, ranging from 38.2° to 36.3°. Assuming the most recent value derived for the rotational period of Steins ( Lamy et al., 2008), the VIRTIS observations covered slightly more than one rotation of the asteroid. In this interval, VIRTIS collected 8 hyperspectral cubes where Steins was captured 119 times, both in the visual and in the infrared range. Given the low signal and the unresolved appearance of the source, for which the instrument was not designed, only a small subset of wavelengths turned out to be suitable to sample the light curve. Nevertheless, in both the VIS and NIR ranges we find a similar trend, with two different maxima and minima during one rotational period, and amplitudes consistent with the results in the visual range obtained in previous works, including the data set acquired by the OSIRIS camera onboard Rosetta. We also report the presence of a new broad feature centered at approximately 0.81-0.82 mum, which is seen in the visual data throughout the rotation of the asteroid.

The Huygens Atmospheric Structure Instrument (HASI) is a multisensor package which has been designed to measure the physical quantities characterizing the atmosphere of Titan. After a short summary of the available information on Titan’s atmosphere, the HASI is described as well as its capabilities to improve our knowledge of the larger Saturnian satellite.