Contributions in international conferences: 98

Listed below are my contributions, either talks or posters, to international conferences, ordered in time. For each, all the contribtion details, including the abstract, and links to NASA/Ads and BibTeX entry are available. See the entire list in NASA/Ads.

J. Hanus, P. Vernazza, M. Marsset, F. Marchis, B. Carry, T. Santana-Ros, M. Birlan, M. Viikinkoski, J. Durech, M. Kaasalainen & and the Large Asteroid Survey with SPHERE

American Astronomical Society, DPS meeting #49, October 2017 (NASA/Ads, BibTeX)

ESO allocated to our Large Asteroid Survey with SPHERE (LASS) program 152 hours of observations over four semesters (PI: Pierre Vernazza, run ID: 199.C-0074) to carry out disk-resolved images of 38 large (D>100 km) main-belt asteroids (sampling the four main compositional classes) at high angular-resolution with VLT/SPHERE throughout their rotation in order to derive their 3-D shape, the size distribution of the largest craters, and their density. LASS program is introduced in more details by Marchis et al. in this session. Here we focus on the preliminary shape modeling of a few individual asteroids that were targeted in the first semester of the LASS program by the SPHERE Extreme AO system. To obtain the 3D shape model with a local topography, we utilize the All-Data Asteroid modelling (ADAM, Viikinkoski et al. 2015, A&A, 576, A8) procedure that allows simultaneous inversion of optical lightcurves, stellar occultations and disk-resolved images. Because ADAM minimizes the difference between the Fourier transformed image and a projected polyhedral model, we do not require any a priori extraction of boundary contours. Utilization of AO images allows ADAM to scale the shape model in size, which essentially leads to a volume estimate.We derive preliminary shape models for selected asteroids and compare them with models based on disk-resolved images obtained by the Near InfraRed Camera (Nirc2) mounted on the W. M. Keck II telescope. We illustrate the performance of the ADAM procedure and the shape model improvement due to the unprecedented quality of the SPHERE images.

F. Marchis, P. Vernazza, M. Marsset, J. Hanus, B. Carry, M. Birlan, T. Santana-Ros, B. Yang & and the Large Asteroid Survey with SPHERE (LASS)

American Astronomical Society, DPS meeting #49, October 2017 (NASA/Ads, BibTeX)

Asteroids in our solar system are metallic, rocky and/or icy objects, ranging in size from a few meters to a few hundreds of kilometers. Whereas we now possess constraints for the surface composition, albedo and rotation rate for all D?100 km main-belt asteroids, the 3-D shape, the crater distribution, and the density have only been measured for a very limited number of these bodies (N?10 for the first two). Characterizing these physical properties would allow us to address entirely new questions regarding the earliest stages of planetesimal formation and their subsequent collisional and dynamical evolution.ESO allocated to our program 152 hours of observations over 4 semesters to carry out disk-resolved observations of 38 large (D>100 km) main-belt asteroids (sampling the four main compositional classes) at high angular-resolution with VLT/SPHERE throughout their rotation in order to derive their 3-D shape, the size distribution of the largest craters, and their density (PI: P. Vernazza). These measurements will allow investigating for the first time and for a modest amount of observing time the following fundamental questions: (A) Does the asteroid belt effectively hosts a large population of small bodies formed in the outer solar system? (B) Was the collisional environment in the inner solar system (at 2-3 AU) more intense than in the outer solar system (>5AU)? (C) What was the shape of planetesimals at the end of the accretion process?We will present the goals and objectives of our program in the context of NASA 2014 Strategic Plan and the NSF decadal survey "Vision and Voyages" as well as the first observations and results collected with the SPHERE Extreme AO system. A detailed analysis of the shape modeling will be presented by Hanus et al. in this session.

F. Spoto, P. Tanga, A. Del Vigna, B. Carry, W. Thuillot, P. David, F. Mignard, A. Milani & G. Tommei

American Astronomical Society, DPS meeting #49, October 2017 (NASA/Ads, BibTeX)

Since October 2016, the short term (ST) processing of Solar System Objects (SSOs) by Gaia is up and running, and it has produced almost 600 alerts. A crucial point in the chain is the possibility of performing a short arc orbit determination as soon as the object has been detected, which allows the follow up of the object from the ground.The method we present has been recentely developed for two mainreasons: 1) search for imminent impactors within the NEO - Confirmation Page(imminent impactors are asteroids that could impact the Earth infew days from their discovery) 2) validation of the SSO-ST Gaia pipeline.We show some good confirmations on objects that could have been discovered by Gaia, and some properties of the Gaia astrometry for the short term.

M. Birlan, F. Colas, F. Cochard, B. Carry, P. Vernazza, S. Fornasier S. & D. Perna

Asteroids, Comets, Meteors, April 2017 (NASA/Ads, BibTeX)

The presentation concerns a novel asset for spectroscopy of Near-Earh Asteroids, which will be installed in Pic du Midi Observatory, in France.

K. Graves, D. Minton, M. Hirabayashi, B. Carry & F. E. DeMeo

American Astronomical Society, DPS meeting #48, October 2016 (NASA/Ads, BibTeX)

High resolution spectral observations of small S-type and Q-type Near Earth Asteroids (NEAs) have shown two important trends. The spectral slope of these asteroids, which is a good indication of the amount of space weathering the surface has received, has been shown to decrease with decreasing perihelion and size. Specifically, these trends show that there are less weathered surfaces at low perihelion and small sizes. With recent results from all-sky surveys such as the Sloan Digital Sky Survey's (SDSS) Moving Object Catalog, we have gained an additional data set to test the presence of these trends in the NEAs as well as the Mars Crossers (MCs) and the Main Belt. We use an analog to the spectral slope in the SDSS data which is the slope through the g', r' and i' filters, known as the gri-slope, to investigate the amount of weathering that is present among small asteroids throughout the inner solar system. We find that the trend of the gri-slope decreases with decreasing size at nearly the same rate in the Main Belt as in the MC and NEA regions. We propose that these results suggest a ubiquitous presence of Q-types and S-types with low spectral slopes at small sizes throughout the inner solar system, from the Main Belt to the NEA region. Additionally, we suggest that the trend of decreasing spectral slope with perihelion may only be valid at perihelia of approximately less than 1 AU. These results suggest a change in the interpretation for the formation of Q-type asteroids. Planetary encounters may help to explain the high fraction of Q-types at low perihelia, but another process which is present everywhere must also be refreshing the surfaces of these asteroids. We suggest the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect as a possible mechanism.

F. DeMeo, B. Carry, D. Polishook, R. Binzel, B. Burt & N. Moskovitz

American Astronomical Society, DPS meeting #48, October 2016 (NASA/Ads, BibTeX)

The existence of iron meteorite samples suggest that a number of planetesimals differentiated fully and were subsequently disrupted. Within the current asteroid belt, there is little evidence of bodies that fully differentiated into core, mantle and crust layers (Moskovitz et al. 2008). However, because it has been suggested that differentiation can occur within the interior of a body while the primitive exterior remains intact (Elkins-Tanton et al. 2011), an understanding of the diversity of compositions from differentiated parent bodies is critical. Asteroid families, as constituents of a disrupted progenitor body, provide a glimpse into the interior of their progenitors. However, asteroid families, while spectrally unique from one another, are spectrally similar within each family (Parker et al., 2008, Masiero et al. 2011). Using the Sloan Digital Sky Survey (SDSS) to search for a "needle in a haystack" we identify candidate basaltic and olivine-rich asteroids that are dynamically associated with asteroid families to constrain the amount of differentiation that could have occurred within the parent asteroid. Using FIRE on the 6-meter Magellan Telescope and SpeX on the 3-meter IRTF Telescope we measure near-infrared spectra of more than thirty of these candidates, most of which are part of the Eunomia and Flora families. Results of these observations are presented in this talk.

M. Marsset, B. Carry, C. Dumas, P. Vernazza, E. Jehin, S. Sonnett. & T. Fusco

American Astronomical Society, DPS meeting #48, October 2016 (NASA/Ads, BibTeX)

(6) Hebe is a large main-belt asteroid, accounting for about half a percent of the mass of the asteroid belt. Its spectral characteristics and close proximity to dynamical resonances within the main-belt (the 3:1 Kirkwood gap and the nu6 resonance) make it a probable parent body of the H-chondrites and IIE iron meteorites found on Earth.We present new AO images of Hebe obtained with the high-contrast imager SPHERE (Beuzit et al. 2008) as part of the science verification of the instrument. Hebe was observed close to its opposition date and throughout its rotation in order to derive its 3-D shape, and to allow a study of its surface craters. Our observations reveal impact zones that witness a severe collisional disruption for this asteroid. When combined to previous AO images and available lightcurves (both from the literature and from recent optical observations by our team), these new observations allow us to derive a reliable shape model using our KOALA algorithm (Carry et al. 2010). We further derive an estimate of Hebe's density based on its known astrometric mass.

M. Devogele, P. Tanga, P. Bendjoya, J.-P. Rivet, J. Surdej, S. J. Bus, J. Sunshine, A. Cellino, H. Campins, J. Licandro, N. Pinilla-Alonso & B. Carry

American Astronomical Society, DPS meeting #48, October 2016 (NASA/Ads, BibTeX)

Polarimetry constitutes one of the fundamental tools for characterizing the surface texture and composition of airless Solar System bodies. In 2006, polarimetric observations led to the discovery of a new type of asteroids, which displays a peculiar polarimetric response. These asteroids are collectively known as "Barbarians", from (234) Barbara the first discovered one.The most commonly accepted explanation for this perculiar polarization response seems to be the presence of a high percentage of fluffy-type Calcium Aluminium-rich Inclusions (CAIs), whose optical properties could produce the observed polarization. Their reflectance spectra also exibit an absorption feature in the near-infrared around 2.1-2.2 microns, that is characteristic of this peculiar group.Based on these results, we organized a systematic polarimetric and near-infrared observational campaign of known Barbarians or candidate asteroids. These campaigns include members of the family of 1040 Klumpkea, 2085 Henan and 729 Watsonia, which are known to contain Barbarian and/or L-type asteroids also suspected to have such a polarimetric behaviour. We have made use of the ToPo polarimeter at the 1m telescope of the Centre pédagogique Planète et Univers (C2PU, Observatoire de la Côte d'Azur, France). The spectroscopic observations in the near-infrared were obtained with the SpeX instrument at the NASA's InfraRed Telescope Facility (IRTF).By combining polarimetry and spectroscopy we find a correlation between the abundance of CAIs and the inversion angle of the phase-polarization curve of Barbarian asteroids. This is the first time that a direct link has been established between a specific polarimetric response and the surface composition of asteroids. In addition, we find a considerable variety of CAI abundance from one object to the other, consistent with a wide range of possible albedos. Since these asteroids constitute a reservoir of primitive Solar System material, understanding their origin can shed light on the processes driving the formation and transport of the refractory minerals that first condensed in the protoplanetary disk.

D. Hestroffer, F. Arenou, J. Desmars, V. Robert, W. Thuillot, J.-E. Arlot, B. Carry, P. David, S. Eggl, C. Fabricius, M. Kudryashova, V. Lainey, F. Spoto, P. Tanga & Gaia DPAC

American Astronomical Society, DPS meeting #48, October 2016 (NASA/Ads, BibTeX)

The Gaia ESA space mission will provide astrometric observations of a large number of celestial bodies, with unprecedented accuracy, and in an homogenous reference frame (to become the optical ICRF). The Gaia satellite is monitoring regularly the whole celestial sphere, with one complete scan in about 6month, down to approximately magnitude V?20.7. It will provide after its nominal lifetime, (5 years, 2014-2019) about 70 astrometric points for several hundred thousands of solar system objects, asteroids from the Near-Earth region to Centaurs and bright TNOs, as well as planetary satellites and comets. The highly precise astrometric and photometric data is bound to lead to huge advances in the science of small Small Solar System Bodies (e.g. Tanga et al. 2016 P&SS, Hestroffer et al. 2014 COSPAR #40 ; Mignard et al. 2007 EMP).The first Gaia data release (GDR#1) is foreseen for Q3-2016 and will provide highly precise positions of selected stars down to mag V~20. While solar system objets data is foreseen for the next data release (in 2017), science of Solar System will also highly benefit from the Gaia stellar catalogue. We will present the status of the satellite and Gaia mission, and details on the stellar data that will be published in this GDR#1. We discuss the catalogue content, number of stars, parameters and precisions, and the process of cross-matching and validation. We also touch upon the construction of combined Tycho-Gaia TGAS catalogue.A Gaia data daily processing is devoted to the identification of Solar System Objects. During this process the detection of new (or critical) objects arises and leads to the triggering of scientific alerts to be found on the web gaiafunsso.imcce.fr. We have also set up an international follow-up network called Gaia-FUN-SSO to validate the detection in space. For this goal, in case of detection the observational data must be sent to the MPC by the observers. Besides, Gaia should benefit for the classical astrometric reduction, for future as well as for past observations, which is part of the NAROO project (Robert et al. 2015 A&A). We will also touch upon the next releases steps, and the SSO data from Gaia observations that will be published.

S. Bouquillon, M. Altmann, F. Taris, C. Barache, T. Carlucci, P. Tanga, W. Thuillot, J. Marchant, I. Steele, T. Lister, J. Berthier, B. Carry, P. David, A. Cellino, D. Hestroffer, A. Andrei & R. Smart

American Astronomical Society, DPS meeting #48, October 2016 (NASA/Ads, BibTeX)

The Ground Based Optical Tracking group (GBOT) consists of about ten scientists involved in the Gaia mission by ESA. Its main task is the optical tracking of the Gaia satellite itself [1]. This novel tracking method in addition to radiometric standard ones is necessary to ensure that the Gaia mission goal in terms of astrometric precision level is reached for all objects. This optical tracking is based on daily observations performed throughout the mission by using the optical CCDs of ESO's VST in Chile, of Liverpool Telescope in La Palma and of the two LCOGT's Faulkes Telescopes in Hawaii and Australia. Each night, GBOT attempts to obtain a sequence of frames covering a 20 min total period and close to Gaia meridian transit time. In each sequence, Gaia is seen as a faint moving object (Rmag ~ 21, speed > 1"/min) and its daily astrometric accuracy has to be better than 0.02" to meet the Gaia mission requirements. The GBOT Astrometric Reduction Pipeline (GARP) [2] has been specifically developed to reach this precision.More recently, a secondary task has been assigned to GBOT which consists detecting and analysing Solar System Objects (SSOs) serendipitously recorded in the GBOT data. Indeed, since Gaia oscillates around the Sun-Earth L2 point, the fields of GBOT observations are near the Ecliptic and roughly located opposite to the Sun which is advantageous for SSO observations and studies. In particular, these SSO data can potentially be very useful to help in the determination of their absolute magnitudes, with important applications to the scientific exploitation of the WISE and Gaia missions. For these reasons, an automatic SSO detection system has been created to identify moving objects in GBOT sequences of observations. Since the beginning of 2015, this SSO detection system, added to GARP for performing high precision astrometry for SSOs, is fully operational. To this date, around 9000 asteroids have been detected. The mean delay between the time of observation and the submission of the SSO reduction results to the MPC is less than 12 hours allowing rapid follow up of new objects.[1] Altmann et al. 2014, SPIE, 9149.[2] Bouquillon et al. 2014, SPIE, 9152.

F. Spoto, P. Tanga, F. Mignard & B. Carry

American Astronomical Society, DPS meeting #48, October 2016 (NASA/Ads, BibTeX)

The ESA Gaia mission, currently surveying the sky from the L2 Lagrangian Point, is providing astrometry of stars and asteroids, at the sub-milliarcsec accuracy. However, the exploitation of this unprecedented capacity of investigation, requires to tackle some specific issues, mostly related to the peculiar properties of the Gaiadata.Orbit determination and improvement have to be tuned at several levels, from the preliminary short-arc solution, up to the most extreme dynamical modeling taking into account observations on a long time span. More specifically, asteroid positions determined by Gaia are very accurate in one direction only, and are affected by a large correlation of the uncertainties in the equatorial coordinates. In order to make the best possible exploitation of Gaia astrometry, we are adapting the software tools to correctly take into account suchcorrelation. We will discuss preliminary results obtained while validating our approach on some asteroid observations by Gaia, that provide for the first time a quantitative evaluation of the reachable accuracy onreal data.In particular, we will discuss the contribution of Gaia relative to the whole available record of observations, and the differences found in the accuracy of alerts (daily processing) with respect to the exploitation of better calibrations. The impact of the first Gaia data release (GDR1) and following on the prediction of stellar occultations by asteroids, is also addressed.

K. Muinonen, A. Cellino, A. Dell Oro, P. Tanga, M. Delbo, F. Mignard, W. Thuillot, J. Berthier, B. Carry, D. Hestroffer, M. Granvik & G. Fedorets

COSPAR, July 2016 (NASA/Ads, BibTeX)

Since the start of its regular observing program in summer 2014, the Gaia mission has carried out systematic photometric, spectrometric, and astrometric observations of asteroids. In total, the unique capabilities of Gaia allow for the collection of an extensive and homogeneous data set of some 350,000 asteroids down to the limiting magnitude of G = 20.7 mag. The Gaia performance remains excellent over the entire available brightness range. Starting from 2003, a working group of European asteroid scientists has explored the main capabilities of the mission, defining the expected scientific impact on Solar System science. These results have served as a basis for developing the Gaia data reduction pipeline, within the framework of the Data Processing and Analysis Consortium (DPAC). We describe the distribution of the existing and forecoming Gaia observations in space and time for different categories of objects. We illustrate the peculiar properties of each single observation, as these properties will affect the subsequent exploitation of the mission data. We will review the expected performances of Gaia, basically as a function of magnitude and proper motion of the sources. We will further focus on the areas that will benefit from complementary observational campaigns to improve the scientific return of the mission, and on the involvement of the planetary science community as a whole in the exploitation of the Gaia survey. We will thus describe the current and future opportunities for ground-based observers and forthcoming changes brought by Gaia in some observational approaches, such as stellar occultations by transneptunian objects and asteroids. We will show first results from the daily, short-term processing of Gaia data, all the way from the onboard data acquisition to the ground-based processing. We illustrate the tools developed to compute predictions of asteroid observations, we discuss the procedures implemented by the daily processing, and we illustrate some tests and validations of the processing of the asteroid observations. Overall, our findings are consistent with the expectations from the performances of Gaia and of the subsequent data reduction. As to the long-term processing of Gaia data, we expect to derive masses, sizes, average densities, spin properties, reflectance spectra, albedos, as well as new taxonomic classifications for large numbers of asteroids. In this review, we will describe the prospects for Gaia photometry and spectrophotometry. We will describe inverse methods for sparse photometric data using the so-called Lommel-Seeliger ellipsoids. We will further describe the modeling of Gaia spectra for the compositional studies of asteroids, as well as the prospects for a new Gaia asteroid taxonomy. Gaia data will open a new era in asteroid science, allowing us to answer fundamental questions concerning, for example, the interrelation between asteroid internal structure and surface properties.

M. Kudryashova, P. Tanga, F. Mignard, B. Carry, C. Ordenovic, P. David & D. Hestroffer

American Astronomical Society, DDA meeting #47, May 2016 (NASA/Ads, BibTeX)

After a commissioning period, the astrometric mission Gaia of the European Space Agency (ESA) started its survey in July 2014. Throughout passed two years the Gaia Data Processing and Analysis Consortium (DPAC) has been treating the data. The current schedule anticipates the first Gaia Data Release (Gaia-DR1) toward the end of summer 2016. Nevertheless, it is not planned to include Solar System Objects (SSO) into the first release. This is due to a special treatment required by solar system objects, as well as by other peculiar sources (multiple and extended ones). In this presentation, we address issues and recent achivements in SSO processing, in particular validation of SSO-short term data processing chain, GAIA-SSO alerts, as well as the first runs of SSO-long term pipeline.

S. A. Jacobson, F. DeMeo, A. Morbidelli, B. Carry, D. Frost & D. Rubie

47th Lunar and Planetary Science Conference, March 2016 (NASA/Ads, BibTeX)

The ratio of crust to mantle material in the asteroid belt indicates that these bodies originate as ejecta from giant impacts on the growing terrestrial planets.

F. DeMeo, D. Polishook, B. Carry, N. Moskovitz, B. Burt & R. P. Binzel

American Astronomical Society, DPS meeting #47, November 2015 (NASA/Ads, BibTeX)

Olivine-dominated asteroids, classified as A-types with near-infrared spectral measurements are largely thought to be the mantle remnants of disrupted differentiated small bodies. These A-type asteroids hold clues to asteroid differentiation and to the collisional history of those differentiated bodies. Preliminary studies of the abundance and distribution of A-type asteroids were performed by Carvano et al. (2010) and DeMeo & Carry (2013, 2014) using the Sloan Digital Sky Survey (SDSS). To confidently identify these olivine-dominated A-type asteroids, however, near-infrared spectral measurements are needed to identify the distinct broad and deep 1-micron olivine absorption feature. Using the Sloan Digital Sky Survey Moving Object Catalog to select A-type asteroid candidates, we have performed a near-infrared spectral survey of over 70 asteroids with SpeX on the IRTF. We present the abundance and distribution of A-type asteroids throughout the main asteroid belt and compare these results with similar surveys for basalt-rich V-type asteroids (e.g. Moskovitz et al. 2008). This work is supported by NASA under grant number NNX12AL26G issued through the Planetary Astronomy Program.

M. Pajuelo, B. Carry, F. Vachier, J. Berthier, P. Descamp, W. J. Merline, P. M. Tamblyn, A. Conrad, A. Storrs, J.-L. Margot, F. Marchis, P. Kervella & J. H. Girard

American Astronomical Society, DPS meeting #47, Nov 2015 (NASA/Ads, BibTeX)

The satellite of the Cybele asteroid (107) Camilla was discovered in March 2001 using the Hubble Space Telescope (Storrs et al., 2001, IAUC 7599). From a set of 23 positions derived from adaptive optics observations obtained over three years with the ESO VLT, Keck-II and Gemini-North telescopes, Marchis et al. (2008, Icarus 196) determined its orbit to be nearly circular.In the new work reported here, we compiled, reduced, and analyzed observations at 39 epochs (including the 23 positions previously analyzed) by adding additional observations taken from data archives: HST in 2001; Keck in 2002, 2003, and 2009; Gemini in 2010; and VLT in 2011. The present dataset hence contains twice as many epochs as the prior analysis and covers a time span that is three times longer (more than a decade).We use our orbit determination algorithm Genoid (GENetic Orbit IDentification), a genetic based algorithm that relies on a metaheuristic method and a dynamical model of the Solar System (Vachier et al., 2012, A&A 543). The method uses two models: a simple Keplerian model to minimize the search-time for an orbital solution, exploring a wide space of solutions; and a full N-body problem that includes the gravitational field of the primary asteroid up to 4th order.The orbit we derive fits all 39 observed positions of the satellite with an RMS residual of only milli-arcseconds, which corresponds to sub-pixel accuracy. We found the orbit of the satellite to be circular and roughly aligned with the equatorial plane of Camilla. The refined mass of the system is (12 ± 1) x 1018 kg, for an orbital period of 3.71 days.We will present this improved orbital solution of the satellite of Camilla, as well as predictions for upcoming stellar occultation events.

R. Kokotanekova, P. Lacerda, C. Snodgrass, M. Lockhart, S. Lorek, N. Peixinho, A. Thirouin, B. Carry, B. Davidsson, S. Fornasier, M. Wyatt & O. Hainaut

European Planetary Science Congress, October 2015 (NASA/Ads, BibTeX)

We will present the first results from a magnitudelimited survey of over 60 Kuiper belt objects (KBOs) observed within a Large Program at the 3.6-m ESO New Technology Telescope (NTT). The multi-band observations are used to obtain lightcurves for targets from all KBO dynamical classes. We are aiming to derive the individual targets' physical and rotational characteristics as well as to use the bulk properties of the different KBO populations as sources of information for their formation mechanisms and collisional history.

L. Eyer, L. Rimoldini, B. Holl, P. North, S. Zucker, D. Evans, D. Pourbaix, S. T. Hodgkin, W. Thuillot, N. Mowlavi & B. Carry

Living Together: Planets, Host Stars and Binaries, July 2015 (NASA/Ads, BibTeX)

On the 19th of December 2013, the Gaia spacecraft was successfully launched by a Soyuz rocket from French Guiana and started its amazing journey to map and characterize one billion celestial objects with its one billion pixel camera. In this presentation, we briefly review the general goals of the mission and describe what has happened since launch, including the Ecliptic Pole scanning mode. We also focus especially on binary stars, starting with some basic observational aspects, and then turning to the remarkable harvest that Gaia is expected to yield for these objects.

D. Hestroffer, P. David, A. Hees, I. Kovalenko, M. Kudryashova, W. Thuillot, J. Berthier, B. Carry, N. Emelynaov, M. Fouchard, V. Lainey, C. Le Poncin-Lafitte, R. Stoica & P. Tanga

American Astronomical Society, DDA meeting #46, May 2015 (NASA/Ads, BibTeX)

After its successful launch in December 2013, and commissioning period, ESA's astrometric space mission Gaia has now started its scientific operations. In addition to the 3D census of our Milky Way with high precision parallax, proper motion, and other parameters derived for a billion of stars, Gaia will also provide a scientific harvest for Solar System Objects (SSO) science. The high precision astrometry and photometry that will be regularly collected for about 300,000 asteroids - during the 5years nominal mission time - will enable significant improvements on fundamental observational data for a very large number of objects.I will describe the current status of the satellite and observations, the Gaia-FUN-SSO follow-up network, data releases policy, and data validations. We will also present the expected results on the dynamics of asteroids and comets, asteroid masses and binary asteroids, tests of GR, and prospects of SSO science (satellites, stellar occultations, etc.) with the Gaia stellar catalogue.Acknowledgements: Thanks to the Gaia DPAC CU4 consortium, and the Labex ESEP (No 2011-LABX-030) & Initiative d'excellence PSL* (convention No ANR-10-IDEX-0001-02)

C. Dumas, F. Gourgeot, B. Carry, P. Lacerda, F. Merlin, F. Vachier, A. Barucci & J. Berthier

American Astronomical Society, AAS Meeting #225, January 2015 (NASA/Ads, BibTeX)

The trans-Neptunian 136108 Haumea is a very fast rotator (~3.9h). It also displays a highly elongated shape and hosts two small moons, all covered with crystalline water ice, similarly to their central body. Haumea is also known to be the largest member of a TNO family, itself the outcome of a catastrophic collision likely responsible for Haumea's unique characteristics.We report here on the analysis of a new set of near-infrared Laser Guide Star assisted observations of Haumea obtained with the IFU spectrograph SINFONI at the ESO-Very Large Telescope Observatory. Combined with previous data published by Dumas et al. (2011), and using photometric light curve measurements (Lacerda 2009, Lellouch et al. 2011) to associate each spectrum with Haumea's corresponding rotational phase, we were able to derive an accurate rotationally resolved spectroscopic study of the surface of this trans-neptunian. A particular region of interest was the dark-red spot identified on the surface of Haumea from multi-band light curve analysis (Lacerda et al. 2008). We will present the results of applying Hapke modeling to our data-set, and our conclusions regarding the surface heterogeneity of Haumea. Additionally, thanks to the IFU capabilities to reconstruct images from our spectral cube, we were able to obtain relative astrometric position measurements for the two satellites and constrain dynamical models for their orbital motion.

W. Thuillot, B. Carry, J. Berthier, P. David, D. Hestroffer & P. Rocher

SF2A-2014: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics. Eds.: J. Ballet, December 2014 (NASA/Ads, BibTeX)

In the frame of the DPAC consortium preparing the Gaia mission, a specific follow-up activity has been set up in order to ensure best scientific return related to solar-system-object (SSO) science. This activity encompasses a system of alerts for newly detected objects provided by CNES, the French data center in charge of the Solar System data processing, and IMCCE, to organize and publish the alerts, and to retrieve the objects astrometry and feed the Minor Planet Center database.
We are expecting in particular the detection of new near-Earth objects (NEO) at low solar elongation, or even inner-Earth objects. Owing to its observing mode, the satellite will not be able to monitor these objects after discovery and they could be lost. It is thus important to consolidate and improve their orbital parameters. This is the objective of the SSO ground-based follow-up. Once the objective is reached, it is possible to update the auxiliary database of orbital elements used within the Gaia data reduction pipeline for identifying the known SSOs and to allow Gaia to subsequently identify these objects properly during its mission.
In order to reach these goals we have carried out two main activities: -- We have developed a pipeline for processing the Gaia raw data that will be received, and for disseminating only the topocentric data useful for observers in an automatized way -- We have set up a worldwide network of observing stations, the Gaia-FUN-SSO network (shortly described at https://www.imcce.fr/gaia-fun-sso/). At this date, 55 observing sites have registered and many participants have already contributed to several training campaigns for NEO observations.
We will describe both activities and we will give preliminary results regarding the Gaia Solar System alerts, depending on the status of the triggering system during this early stage of the mission.

A. Matter, M. Delbo, B. Carry & P. Tanga

SF2A-2014: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics. Eds.: J. Ballet, December 2014 (NASA/Ads, BibTeX)

Density and internal structures are among the most important characteristics of asteroids, yet these properties are also some of the least known. For distant asteroids (in the Main Belt and beyond) these properties were up to now accessible only for the largest (>100 km in size) asteroids. Going to smaller and fainter asteroids can revolutionize our understanding because we will be sampling a new regime in physical properties. Here we discuss how ground-based optical interferometry with the GRAVITY instrument can be used to observe the motion of asteroid satellites to determine the mass of small binary systems. Following the expected sensitivity performances in K-band of GRAVITY, we present a sample of binary targets potentially observable in single-field mode. The feasibility of such observations will strongly be dependent on the ability of the control software of GRAVITY to track objects moving at high rate on the sky (differential motion of 10 mas.s-1). Although the dual-field mode could allow to increase the sample of small binary asteroids observable, it seems to be currently unfeasible given the high differential motion of asteroids.

D. Hestroffer, J. Berthier, B. Carry, P. David, V. Lainey, N. Rambaux, W. Thuillot, J.-E. Arlot, D. Bancelin, F. Colas, J. Desmars, H. Devillepoix, M. Fouchard, A. Ivantsov, I. Kovalenko & V. Robert

Proceedings of the Journées 2013 "Systèmes de réference spatio-temporels": Scientific developments from highly accurate space-time reference systems, Observatoire de Paris, December 2014 (NASA/Ads, BibTeX)

The Gaia mission is to be launched on December 19th, 2013 by the European Space Agency (ESA). Solar System science is well covered by the mission and has been included since the early stages of its concept and development. We present here some aspects on the astrometry and dynamics of Solar System Objects (SSO) - in particular asteroids, comets and satellites - as well as ground-based support. We also touch upon the future of SSO astrometry that will be achieved indirectly, after mission completion, from the Gaia astrometric catalogue.

M. Küppers, L. O'Rourke, D. Bockele-Morvan, V. Zakharov, S. Lee, P. Von Allmen, B. Carry, D. Teyssier, A. Marston, T., Müller, J. Crovisier, M. A. Barucci & R. Moreno

American Geophysical Union, December 2014 (NASA/Ads, BibTeX)

The snowline conventionally divides Solar System objects into dry bodies, ranging out to the main asteroid belt, and icy bodies beyond the belt. Recently, the detection of dust emission from "main-belt comets" and of hydration features and possible water ice absorption on some main-belt asteroids together with theories of migration of small bodies in the solar system cast some doubts on the classical picture. Ceres, contributing about 30 % of the mass of the asteroid belt, is thought to be differentiated into an icy core and a silicate mantle and hydrated minerals were found on infrared spectra of its surface. A marginal detection of OH, a photodissociation product of water was reported in 1991, but questioned by later, more sensitive observations.. Observations of Ceres with the Heterodyne Instrument for the Far Infrared (HIFI) on the Herschel Space Observatory in the context of the MACH 11 guaranteed time program and with a follow up DDT program detected water vapour from Ceres on 3 occasions in 2012 and 2013. The production rate of water on Ceres is a few times 1026-1. The signal from the water vapour from Ceres was found to be linearly polarized during some of the observations, with the absorption being stronger in the horizontal branch. The measured line area ratio of up to 2.5 between H and V polarizations is so far unexplained. The water signal varies on time scales of hours. Those variations are interpreted as localized sources on Ceres surface rotating into and out of the hemisphere visible by Herschel. The time variability is consistent with those sources being dark features known from ground-based adaptive optics observations. The water vapour on Ceres may be either produced by near surface ice heated by sunlight (cometary activity) or by cryovolcanoes or geysers getting their energy from Ceres' interior. In the first case the production rate is expected to peak around perihelion, while for volcanic the time variations are expected to be more stochastic. The existing observations appear consistent with the cometary hypothesis, but do not allow to clearly distinguish between those possibilities. Upon its arrival at Ceres in 2015, the DAWN spacecraft may provide insight into the sources and mechanisms of water production at Ceres.

D. Bancelin, W. Thuillot, A. Ivantsov, J. Desmars, M. Assafin, S. Eggl, D. Hestroffer, P. Rocher, B. Carry, P. David & Gaia-FUN-SSO team

Gaia-FUN-SSO-3, November 2014 (NASA/Ads, BibTeX)

W. Thuillot, B. Carry, P. David, J. Berthier & D. Hestroffer

Gaia-FUN-SSO-3, November 2014 (NASA/Ads, BibTeX)

Gaia-FUN-SSO (shortly described at https://www.imcce.fr/gaia-fun-sso/) is a ground-based network of observatories set up in the framework of the Gaia consortium (DPAC-CU4) for the follow-up of critical Solar System objects to be discovered from space by the Gaia satellite. Its goal is to retrieve from the ground a newly detected object and to complement the astrometry measurements carried out by Gaia to determine its heliocentric orbit. Data from both Gaia and the ground-based network will be sent to the Minor Planet Center, used to determine the orbit and thus to update the database of minor planet orbits, which is subsequently used by Gaia for the identification of moving objects. We are expecting the detection of many asteroids, mainly from the main belt, and also new near-Earth objects (NEO) at low solar elongation. Owing to the specific conditions of Gaia observations, we even expect the detection of objects whose orbit is fully contained within Earth's orbit (called inner-Earth or Atira asteroids). Several training campaigns have already been organized with the network and it is now able to enter in an operating mode when alerts will be triggered. We describe here the expected number of discoveries, the network, its activity, and the data processing of the central node of the network set in place for the operating mode.

J. Durech, J. Hanus, M. Delbo, V. Ali-Lagoa & B. Carry

American Astronomical Society, DPS meeting #46, November 2014 (NASA/Ads, BibTeX)

Convex shape models and spin vectors of asteroids are now routinely derived from their disk-integrated lightcurves by the lightcurve inversion method of Kaasalainen et al. (2001, Icarus 153, 37). These shape models can be then used in combination with thermal infrared data and a thermophysical model to derive other physical parameters - size, albedo, macroscopic roughness and thermal inertia of the surface. In this classical two-step approach, the shape and spin parameters are kept fixed during the thermophysical modeling when the emitted thermal flux is computed from the surface temperature, which is computed by solving a 1-D heat diffusion equation in sub-surface layers. A novel method of simultaneous inversion of optical and infrared data was presented by Durech et al. (2012, LPI Contribution No. 1667, id.6118). The new algorithm uses the same convex shape representation as the lightcurve inversion but optimizes all relevant physical parameters simultaneously (including the shape, size, rotation vector, thermal inertia, albedo, surface roughness, etc.), which leads to a better fit to the thermal data and a reliable estimation of model uncertainties. We applied this method to selected asteroids using their optical lightcurves from archives and thermal infrared data observed by the Wide-field Infrared Survey Explorer (WISE) satellite. We will (i) show several examples of how well our model fits both optical and infrared data, (ii) discuss the uncertainty of derived parameters (namely the thermal inertia), (iii) compare results obtained with the two-step approach with those obtained by our method, (iv) discuss the advantages of this simultaneous approach with respect to the classical two-step approach, and (v) advertise the possibility to use this approach to tens of thousands asteroids for which enough WISE and optical data exist.

M. Delbo, P. Tanga, G. Van Belle, A. Matter, B. Carry & M. J. Creech-Eakman

Resolving The Future Of Astronomy With Long-Baseline Interferometry Proceedings of a conference held 28-31 March 2011, at New Mexico Institute of Mining and Technology, September 2014 (NASA/Ads, BibTeX)

Density and internal structures are among the most critical characteristics of asteroids, yet these properties are also some of the least known. For distant asteroids (in the Main Belt and beyond), they were, until now, accessible only for some of the largest (>100 km in size) asteroids. Going to smaller and fainter asteroids can revolutionize our understanding by sampling a new regime in physical properties. Here we discuss how asteroid satellites can be observed by ground-based interferometers and the data that can be obtained. This is the most accurate approach for measuring the mass of an asteroid without a spacecraft.

W. Thuillot, B. Carry, J. Berthier, P. David, H. Devillepoix & D. Hestroffer

Asteroids, Comets, Meteors, July 2014 (NASA/Ads, BibTeX)

L. O'Rourke, T. Müller, B. Altieri, C. Kiss, M. Küppers, M. A. Barucci, D. Bockele-Morvan, B. Gonzalez-Garcia, E. Dotto, M. Yoshikawa, B. Carry, M. Kidger, M. Sanchez-Portal, R. Vavrek, D. Teyssier & A. Marston

Asteroids, Comets, Meteors, July 2014 (NASA/Ads, BibTeX)

The Herschel MACH-11 (Measurements of 11 Asteroids & Comets with Herschel) Programme has as its prime goal to observe those asteroids & comets which have been or will be visited by spacecraft or those which are being studied with a similar goal in mind. The following near-Earth asteroids (NEAs) form part of the list of targets making up this program and will be addressed in this analysis: - 1999 JU3 (Hayabusa 2 mission target) - 1999 RQ36 (OSIRIS-REx mission target) - 1996 FG3 (Marco-Polo R backup mission target) - (99942) Apophis (Study target)
An additional NEA (not part of the MACH-11 program) will also be reviewed, namely 2005 YU55.
Each target was observed using the PACS Photometer of the Herschel Space Observatory (Pilbratt et al 2010). The extracted fluxes from each observation campaign were fed into a thermophysical model which has been validated against a large database of asteroids including targets of other spacecraft missions. In all cases, radiometric properties of each target have been derived and will be presented, with their impact on already published data being analysed & discussed.

T. Müller, D. Bockelee-Morvan, B. Carry, M. Küppers, E. Lellouch & L. O'Rourke

Asteroids, Comets, Meteors, July 2014 (NASA/Ads, BibTeX)

We obtained a dual-band thermal lightcurve of the largest asteroid (1) Ceres with the Herschel Space Observatory on April 23/24, 2013. The measurements were taken with the PACS instrument in the 70- and 160-micron bands in parallel. They span a time interval of 12 hours --- one measurement every hour --- to cover approximately 120 % of the Ceres rotation period of 9.1 hours. Due to the very high stability of the PACS detectors, we were able to detect a rotation-related thermal flux variation of about 1 % (peak-to-peak). We interpret our thermal measurements with a thermophysical model [1] based on a Ceres size and shape model which was derived from HST observations [2], combined with the spin-axis orientation presented in [3], and a rotation period from [4]. We studied the object's thermal properties and investigated the origin of the thermal lightcurve in the context of the available surface albedo map. We will present our results of these high-precision photometric measurements with Herschel-PACS.

M. Küppers, L. O'Rourke, D. Bockele-Morvan, V. Zakharov, S. Lee, P. von Allmen, B. Carry, D. Teyssier, A. Marston, T. Müller, J. Crovisier, M. A. Barucci & R. Moreno

Asteroids, Comets, Meteors, July 2014 (NASA/Ads, BibTeX)

We report the detection of water vapour on (1) Ceres, the first unambiguous discovery of water on an object in the asteroid main belt. Most of the water vapour stems from localized regions at low latitude, possibly from surface features known from adaptive-optics observations. We suggest either cometary-type sublimation from the near surface or cryovolcanism as the origin of the waver vapour.
The snowline conventionally divides Solar System objects into dry bodies, ranging out to the main asteroid belt, and icy bodies beyond the belt. Recently, the detection of dust emission from "main-belt comets" and of hydration features and possible water ice absorption on some main-belt asteroids, together with theories of migration of small bodies in the solar system, cast some doubts on the classical picture.
Ceres is thought to be differentiated into an icy core and a silicate mantle and hydrated minerals were found on infrared spectra of its surface. A marginal detection of OH, a photodissociation product of water was reported in 1991, but questioned by later, more sensitive observations. We observed Ceres with the Heterodyne Instrument for the Far Infrared (HIFI) on the Herschel Space Observatory in the context of the MACH 11 guaranteed time program and with a follow-up DDT program. The observations took place in Nov. 2011, Oct. 2012, and March 2013. We searched for the signature of water in the ground state line of ortho-water at 556.936 GHz. After a non-detection in the first observation, an absorption line is clearly visible in all other observations. In March 2013, water is detected in emission as well (at 3 sigma level). The production rate of water on Ceres is a few times 1026 s-1.
The signal from the water vapour from Ceres was found to be linearly polarized during some of the observations, with the absorption being stronger in the horizontal branch. The measured line-area ratio of up to 2.5 between H and V polarizations is so far unexplained.
The water signal varies on timescales of hours. We interpret this variation as localized sources on Ceres surface rotating into and out of the hemisphere visible for Herschel. The time variability is consistent with those sources being dark features known from ground-based adaptive-optics observations.
The water vapour on Ceres may be either produced by near-surface ice heated by sunlight (cometary activity) or by cryovolcanoes or geysers getting their energy from the Ceres interior. In the first case, the production rate is expected to peak around perihelion, while for volcanic activity the time variations are expected to be more stochastic. The existing observations appear consistent with the cometary hypothesis, but do not allow to clearly distinguish between those possibilities. Upon its arrival at Ceres in 2015, the Dawn spacecraft may provide insight into the sources and mechanisms of water production at Ceres.

F. DeMeo, R. Binzel, B. Carry, D. Polishook & N. Moskovitz

Asteroids, Comets, Meteors, July 2014 (NASA/Ads, BibTeX)

Very red featureless asteroids (spectroscopic D-types) are expected to have formed in the outer Solar System far from the Sun. They comprise the majority of asteroids in the Jupiter Trojan population, and are also commonly found in the outer main belt and among Hildas. The first evidence for D-types in the inner and middle parts of the main belt was seen in the Sloan Digital Sky Survey (SDSS).
Here we report follow-up observations of SDSS D-type candidates in the near-infrared. Based on follow up observations of 13 SDSS D-type candidates, we find a ~20% positive confirmation rate. Known inner belt D-types range in diameter from roughly 7 to 30 km. Based on these detections we estimate there are ~100 inner belt D-types with diameters between 2.5 and 20 km. The lower and upper limits for total mass of inner belt D-types is 2 x 1016 kg to 2 x 1017 kg which represents 0.01-0.1% of the mass of the inner belt.
The inner belt D-types have albedos at or above the upper end typical for D-types [6] which raises the question as to whether these inner belt bodies represent only a subset of D-types, they have been altered by external factors such as weathering processes, or if they are compositionally distinct from other D-types. All D-types and candidates have diameters less than 30 km, yet there is no obvious parent body in the inner belt. Dynamical models have yet to show how D-types originating from the outer Solar System could arrive at the inner reaches of the main belt under current scenarios of planet formation and subsequent Yarkovsky drift.

F. DeMeo, B. Carry, R. Binzel, N. Moskovitz, D. Polishook & B. Burt

American Astronomical Society, AAS Meeting #224, June 2014 (NASA/Ads, BibTeX)

We expect there to have been many bodies in the Main Asteroid Belt (MB) sufficiently heated at the time of solar system formation to allow their interiors to differentiate into an iron core and silicate-rich crust and mantle. Evidence for early solar system differentiation includes the diversity of iron meteorites that imply the existence of over 60 distinct parent bodies (Mittlefehldt et al. 2006). Searches have been performed to identify silicate-rich basaltic crust material (spectral V-type asteroids) in the outer MB have been successful (e.g., Roig et al. 2006, Masi et al. 2008, Moskovitz et al. 2008, Solontoi et al. 2012). The olivine-rich mantles of differentiated asteroids should have produced substantially greater volumes (and therefore substantially greater numbers) of remnant asteroids compared with basaltic and iron samples. Yet olivine-rich asteroids (A-types) are one of the rarest asteroid types (Bus & Binzel 2002, DeMeo et al. 2009). An alternative way to search for differentiated bodies that have been heavily or completely disrupted is to identify these spectral A-type asteroids, characterized by a very wide and deep 1 micron absorption indicative of large amounts (> 80%) of olivine. Burbine et al. (1996) proposed that these asteroids are only found among the largest because most were "battered to bits" due to collisions, so smaller A-types were below our detection limit. Using the Sloan Digital Sky Survey Moving Object Catalog to select A-type asteroid candidates, we have conducted a near-infrared spectral survey of asteroids over 12 nights in the near-infrared in an effort to determine the distribution and abundance of crustal and mantle material across the Main Asteroid Belt (MB). From three decades of asteroid spectral observations only ~10 A-type asteroids have been discovered. In our survey we have detected >20 A-type asteroids thus far throughout the belt, tripling the number of known A-types. We present these spectra and their distribution throughout the MB. We estimate the total mass of mantle material present in the belt today and discuss the implications.

D. Hestroffer, J. Berthier, B. Carry, P. David, W. Thuillot, J.-E. Arlot, D. Bancelin, M. Fouchard, A. Ivantsov, I. Kovalenko, V. Lainey, C. Leponcin-Lafitte & P. Tanga

European Planetary Science Congress, April 2014 (NASA/Ads, BibTeX)

The ESA astrometric mission Gaia has been launched in December 2013. It is currently in its commissioning phase, with the first scientific data expected to be downloaded in June 2014. Gaia has the capability to observe, in addition to about one billion of stars, a large number of solar system objects (SSO). The satellite and telescope will continuously scan the sky during 5 years, providing high precision astrometry and photometry for about 300,000 asteroids (and several tens of planetary satellites and comets), as well as modest imaging for a fraction of them. The nominal limiting magnitude is expected to be V=20, however the end of the commissioning will show the actual performances for the faint targets.

D. Bockelee-Morvan, M. Küppers, L. O'Rourke, V. Zakharov, S. Lee, P. Von Allmen, B. Carry, D. Teyssier, A. Marston, T. Müller, J. Crovisier, M. A. Barucci & R. Moreno

European Planetary Science Congress, April 2014 (NASA/Ads, BibTeX)

We report the detection of water vapour on (1) Ceres, the first unambiguous discovery of water on an object in the asteroid main belt. Most of the water vapour stems from localized regions at low latitude, possibly from surface features known from adaptive optics observations. We suggest either cometary-type sublimation from the near surface or cryovolcanism as the origin of the waver vapour.

F. DeMeo, R., Binzel, B. Carry, N. Moskovitz & D. Polishook

American Astronomical Society, AAS Meeting #223, January 2014 (NASA/Ads, BibTeX)

Very red featureless asteroids (spectroscopic D-types) are common among Jupiter Trojans, Hildas, and the outer main belt, and are thought to have formed in the outer solar system. Dynamical models of planetary migration and orbital drift by the Yarkovsky effect predict these D-types could have been transported as close to the sun as the middle main belt, but not closer. We detect D-types in the inner main belt, where they are not expected, through follow-up observations of 13 D-type candidates as determined by SDSS colors. Near-infrared spectroscopic measurements were taken using SpeX on the IRTF. Known inner belt D-types range in diameter from roughly 7 to 30 kilometers. Based on these detections we estimate there are about 100 inner belt D-types with diameters between 2.5 and 20km. The total mass of inner belt D-types is 4x1016 kg which represents 0.01% of the mass of the inner belt (note Vesta alone accounts for 2/3 of the inner belt mass). Dynamical models have yet to show how D-types could penetrate into the inner reaches of the Main Belt.

F. DeMeo, B. Carry, R. Binzel, N. Moskovitz & D. Polishook

Workshop on Planetesimal Formation and Differentiation, Proceedings of the conference held 27-29 October, October 2013 (NASA/Ads, BibTeX)

We present results of a spectral survey detecting olivine-rich mantle remnants (spectral A-type asteroids) of disrupted differentiated bodies more than doubling the known sample.

J. D. Drummond, B. Carry, W. J. Merline, c. Dumas, H. Hammel, S. Erard, A. Conrad, P. Tamblyn & C. Chapman

American Astronomical Society, DPS meeting #45, October 2013 (NASA/Ads, BibTeX)

With NASA's Dawn Mission now on its way to dwarf-planet Ceres, there is considerable interest in refining that object's size and pole. At the level of a few percent, there has been a discrepancy in the polar and equatorial dimensions of the object, as measured by HST imaging vs. ground-based adaptive optics. To attempt to improve the dimensions and pole, we have analyzed a suite of adaptive optics images that we obtained at the Keck and VLT observatories from 2001 to 2010. We use a new method that we recently developed to combine data from multiple epochs and we attempt to account for limb darkening. We find that Ceres is best modeled as an oblate spheroid with equatorial and polar diameters of 966±10 km and 884±4 km, respectively. Although our equatorial diameter is within 1% of HST results (Thomas et al. 2005, Nature 437, 224-226) the polar dimension is some 3% smaller, more in line with the analysis of a subset of our AO images by Carry et al. (2008, A&A 478, 235-244). Thus, in addition to a more oblate spheroid, we predict that Dawn will find that Ceres shows strong limb darkening when it arrives in 2015. From three methods, all depending on the orientation of Ceres over the nine years of our observations, we determine its spin-vector coordinates to lie within 3° of (287°, +64°) in equatorial EQJ2000 reference frame (346°, +82°] in ECJ2000), in agreement with previous studies, pointing to a small 3° obliquity between the spin and orbital poles.

F. DeMeo & B. Carry

American Astronomical Society, DPS meeting #45, October 2013 (NASA/Ads, BibTeX)

The distribution of asteroids across the Main Belt has been studied for decades to understand the current compositional distribution and what that tells us about the formation and evolution of our solar system. In this work, we reexamine the architecture of the asteroid belt by determining the bias-corrected distribution of 99.99% of its mass based on compositional information provided by ground-based and space-based measurements. The main belt's most massive classes are C, B, P, V and S in decreasing order. Excluding the four most massive asteroids, (1) Ceres, (2) Pallas, (4) Vesta and (10) Hygiea that heavily skew the values, primitive material (C-, P-types) account for more than half main-belt and Trojan asteroids by mass, most of the remaining mass being in the S-types. All the other classes are minor contributors to the material between Mars and Jupiter. Additionally, we present the taxonomic distribution of asteroids as a function of size. The relative mass contribution of each class changes as a function of size in each region of the Main Belt. We report an updated view of the distribution of asteroid compositions according to distance and size.

F. Marchis, J. Berthier, F. Vachier, J. Durech, P. Descamps & B. Carry

American Astronomical Society, DPS meeting #45, October 2013 (NASA/Ads, BibTeX)

(87) Sylvia is the first minor planet known to possess two moons (Marchis et al. Nature 2005). Combining Adaptive Optics data from 8-10m class telescopes, with lightcurve observations and the result of an exceptional stellar occultation on Jan. 6 2013, we report new insights on the dynamical and physical properties of (87) Sylvia. Based on Keck, Gemini and VLT AO observations collected from 2001 to 2011 we derived the mutual orbits of the system which can be fitted by a simple Kepler model (J2=0). From this model, we predicted the relative positions of the moons at the time of this event with an accuracy better than 10 km on the Earth. 50 observers were mobilized along the path of the event and 16 of them reported an occultation, 4 of them by Romulus, the outer moon of Sylvia. A new non-convex shape model of Sylvia's primary was built (Deq = 270 ± 3 km, leading to a density of 1.3±0.1 g.cm-3

D. Hestroffer, P. David, J. Berthier, B. Carry, V. Lainey, P. Tanga, W. Thuillot, J.-E. Arlot, D. Bancelin, M. Fouchard & A. Ivantsov

European Planetary Science Congress, September 2013 (NASA/Ads, BibTeX)

The ESA astrometric mission Gaia, that will be launched in 2013 Q4, has the capability to observe a large number of solar system objects. Gaia will continuously scan the sky during 5 years providing high precision astrometry and photometry as well as modest imaging for about 300,000 asteroids and several tens of planetary satellites and comets down to magnitude V?20. We will present some direct scientific outcome from the astrometry of the bodies in the various classes (NEOs, MBAs, Trojans, Centaurs and TNOs, comets and satellites). This encompass astrometry of moving and resolved body from an essentially 1D signal, and by combining the 5 years data orbit determination and/or improvement, asteroid mass determination, non gravitational forces, local test of general relativity (GR), reference frames linking. We will also present the ground-based support for follow-up in alert of critical object, and touch upon the scientific exploitation for planetary satellites dynamics, stellar occultations and other applications from combination of the ground-based and space-based data.

F. Colas, O. Mousis, R. Hueso, J.-P. Beaulieu, S. Bouley, B. Carry, A. Klotz, C. Pellier, J.-M. Petit & P. Rousselot

European Planetary Science Congress, September 2013 (NASA/Ads, BibTeX)

Amateur contributions to professional publications have increased exponentially over the last decades in the field of Planetary Astronomy. Here we review the different domains of the field in which collaborations between professional and amateur astronomers are effective and regularly lead to scientific publications. We discuss the instruments, detectors, softwares and methodologies typically used by amateur astronomers to collect the scientific data in the different domains of interest.

A. Conrad, W. J. Merline, A. La Camera, P. Boccacci, M. Bertero, T. Herbst, M. Kuerster, B. Carry, J. D. Drummond, M. Norris & J. Christou

44th Lunar and Planetary Science Conference, March 2013 (NASA/Ads, BibTeX)

Asteroid satellites help determine mass, density, and composition. LINC-NIRVANA will yield a factor of 3 improvement in the limiting separation for detections.

F. Gourgeot, C. Dumas, B. Carry, F. Merlin, D. Hestroffer & P. Lacerda

American Astronomical Society, DPS meeting #44, October 2012 (NASA/Ads, BibTeX)

With it being approximately 2000 x 1600 x 1000 km in size, (136108) Haumea's extreme elongation makes it unique among known dwarf planets. The shape of this fascinating Kuiper Belt Object (KBO) is the result of a rotational deformation due to its extremely short 3.9-hour rotation period (Rabinowitz et al. 2006) which could be explained by a past dramatic collision (Brown et al. 2007 ; Ragozzine & Brown 2007; Snodgrass et al. 2010). Although a high bulk density estimated at a range of 2.6 to 3.3 g.cm-3 (Rabinowitz et al. 2006) suggests a more rocky composition than other KBOs, Haumea and its satellites are considered by a crystalline water-ice multiple system (Dumas et al. 2011). Moreover, Haumea has become the second Kuiper Belt Object after Pluto to show observable signs of surface features. Indeed, a region darker and redder than average on the surface of Haumea has been identified (Lacerda, 2010). In this contribution, we present Spectro-Imaging observations of Haumea obtained in the Near Infra- Red [1.6 to 2.4 ?m] with the integral-field spectrograph SINFONI mounted on UT4 at the ESO Very Large Telescope. We present some results combining data from several epochs.

W. J. Merline, H. A. Weaver, P. Tamblyn, C. Neyman, S. A. Stern, B. Carry, J. Spencer, A. Conrad, M. Showalter, C. Olkin, A. Steffl, S. Sheppard, M. Buie & B. Enke

American Astronomical Society, DPS meeting #44, October 2012 (NASA/Ads, BibTeX)

We report AO imaging observations from Keck Observatory of NEA 2005 YU55 during the night of its close approach to Earth on 2011 Nov 9 UT. Our goals were to acquire estimates of the size, shape, and pole direction as well as search for satellites.

J. D. Drummond, W. J. Merline, A. Conrad, C. Dumas, P. Tamblyn, J. Christou, B. Carry & C. Chapman

American Astronomical Society, DPS meeting #44, October 2012 (NASA/Ads, BibTeX)

From Adaptive Optics (AO) images of (9) Metis at 14 epochs over 2008 December 8 and 9 at Gemini North, triaxial ellipsoid diameters of 218x175x112 km are derived with fitting uncertainties of 3x3x47 km. However, by including just two more AO images from Keck-II in June and August of 2003 in a global fit, the fitting uncertainty of the small axis drops by more than a third because of the lower sub-Earth latitude afforded in 2003 (-28°) compared to 2008 (+47°), and the triaxial ellipsoid diameters become 218x175x129 km with fitting uncertainties of 3x3x14 km. We have estimated the systematic uncertainty of our method to be 4.1, 2.7, and 3.8%, respectively, for the three diameters. These values were recently derived (Drummond et al., in prep) from a comparison of KOALA (Carry et al, Planetary and Space Science 66, 200-212) and our triaxial ellipsoid analysis of four asteroids. Quadratically adding this systematic error with the fitting error, the total uncertainty for Metis becomes 9x5x15 km. Concurrently, we find an EQJ2000 rotational pole at ($alpha;,$delta;)=(185°, +19°) or in ecliptic coordinates, (λ,β)=(176°, +20° in ECJ2000).

F. DeMeo & B. Carry

American Astronomical Society, DPS meeting #44, October 2012 (NASA/Ads, BibTeX)

Each compositional class of asteroid is a relic of the temperature and composition conditions in which it formed. The current distribution reveals the history of the Solar System, and each body acts as a marker of any mixing that occurred since formation. The remnant of a primordial temperature gradient, seen as transition from the S class to C class dominating in different regions of the asteroid belt has been a paradigm for three decades (Gradie & Tedesco 1982, Science, 216, 1405). In this work, we reexamine the architecture of the asteroid belt by determining the bias-corrected distribution of 99.99% of its mass based on compositional information provided by ground-based and space-based measurements. We report an updated view of the distribution of asteroid compositions. This material is based upon work supported by the National Science Foundation under Grant No. 0907766.

B. Carry, J. Berthier, F. Vachier & M. Küppers

European Planetary Science Congress, September 2012 (NASA/Ads, BibTeX)

In recent years, many efforts have been undertaken to extract the astrometry, photometry, and colors of Solar System Small Bodies from large surveys and widefield camera, such as the SDSS Moving Object Catalog or EuroNear. Since 2006, the IMCCE provides a service, called SkyBoT, that list all the Solar System Objects in a given field of view for a given epoch. Such a tool is of high interest for any data mining purpose of large archives. We will present an extension of SkyBoT from ground-based to space-based geometries. As a demonstration, we will present our search for serendipitously observed asteroids in the data archive of the OSIRIS instrument on-board the ESA Rosetta mission.

M. Küppers, L. O'Rourke, D. Bockelee-Morvan, J. Crovisier, B. Carry, D. Teyssier, R. Vavrek, T. Müller & B. Gonzalez Garcia

European Planetary Science Congress 2012, September 2012 (NASA/Ads, BibTeX)

Asteroid (1) Ceres may contain substantial amounts of water ice in its crust. Even a small fraction of water ice on Ceres' surface would produce measurable amount of water vapour. Past searches for a water exosphere through observations of the dissociation product OH led to inconclusive results. We are using the Heterodyne Instrument for the Far Infrared (HIFI) onboard Herschel to search for water vapour emission and absorption. A first observation close to Ceres' aphelion did not result in water detection, leading to an upper limit of about 1026 s-1. A second observation closer to perihelion will be performed end of 2012 or early 2013. In addition, we will report on the search for absorption features from water vapour and organic molecules in spectra taken with Herschel's Photodetector Array Camera and Spectrometer (PACS).

L. Jorda, N. Thomas, F. Scholten, F. Preusker, R. Gaskell, P. Lamy, S. Marchi, P. Vernazza, B. Carry, S. Hviid, H. Sierks, H. Keller & M. Kaasalainen

COSPAR, July 2012 (NASA/Ads, BibTeX)

The asteroid (21) Lutetia has been observed by several instruments aboard ESA's ROSETTA spacecraft on July 10, 2010. The OSIRIS imaging system allowed the reconstruction of the topography of its surface. A number of intriguing features appeared on the images and/or on the topographic models: boulders, landslides, craters with various profiles, among others. The combination of these data with light curves and adaptive optics profiles allowed to retrieve the global shape of the asteroid, which yielded an estimate of its volume. Combined with the accurate mass determination from the radio science RSI instrument, a very high density of 3.4 g/cm^{3} was obtained.

A. Compre, J. Frouard & B. Carry

Proceedings of the workshop "Orbital Couples: Pas de Deux in the Solar System and the Milky Way". Held at the Observatoire de Paris, 10-12 October 2011. Editors: F. Arenou, May 2012 (NASA/Ads, BibTeX)

Nowadays more than 200 asteroids have been identified as multiple. These systems are found all over the Solar System (Near-Earth, Main-Belt and Trojan asteroids, Trans-Neptunian objects). The study of the stability of these multiple systems is quite complex, because of their irregular shapes, and requires a full body-full body approach. More specifically, in the case of satellites of asteroids (when one of the body is much greater than the others), the shape of the main object has a major influence on the motion of the small bodies. This perturbation can be more important than the perturbation of the Sun or of the planets. The introduction of this shape effect in a numerical integration requires the knowledge of many coefficients of the spherical harmonic expansion of the gravitational potential; their computation is performed using the software SHTOOLS and a shape model. Once the coefficients of the gravitational potential are determined, the dynamics of the asteroid satellites is described thanks to the software NIMASTEP, for the full short periodic motion, and, thanks to a home-made program (developed by J. Frouard), for the averaged long periodic motion. Two applications are presented here: the search for mean-motion, gravitational and secular resonances in the triple system (87) Sylvia, explaining its present and future configuration, and the validation of orbit for the binary system (41) Daphne.

M Küppers, L. O'Rourke, D. Bockelee-Morvan, J. Crovisier, B. Carry, D. Teyssier, R. Vavrek, T. Müller, M. A. Barucci, B. Gonzalez-Garcia & MACH 11 Team

Asteroids, Comets, Meteors, May 2012 (NASA/Ads, BibTeX)

Ceres is believed to possess an ice-rich crust, opening up the possibility of an exosphere around it. We searched for water vapour around Ceres with Herschel/HIFI. No line signal was detected, suggesting a very low surface ice coverage on Ceres.

W. J. Merline, J. D. Drummond, P. Tamblyn, C. Neyman, B. Carry, A. Conrad, C. Chapman, J. Christou, C. Dumas & B. Enke

Asteroids, Comets, Meteors, May 2012 (NASA/Ads, BibTeX)

We report on our efforts to search for faint satellites of Pluto using Keck 2 adaptive optics (AO). Last year, using HST, Showalter et al. 2011 (IAUC 9221) discovered a new, faint satellite ("P4") around Pluto, demonstrating that Pluto is even richer with orbiting material than was thought previously. That discovery led to speculations that these small satellites could be a source of debris (from random impacts) that could pose a hazard to the New Horizons (NH) spacecraft during its 2015 Pluto flyby. The ejecta would form a cloud around Pluto. The NH project began an aggressive program of HST- and ground-based studies to identify additional as-yet-unseen satellites or debris rings in the system. Only several days into their campaign, a 5th satellite "P5" was discovered with HST (Showalter et al. 2012, IAUC 9253). The output of these studies will be used to plan a contingency ("safe-haven") trajectory through the system. The Keck observations support and complement the new HST observations. Real objects in the HST images may be hidden by bad pixels or diffraction spikes, and Keck may have advantages in some regions of parameter space, such as interior to Charon. r Observing in a near-IR band, the Keck imaging provides additional constraints on the objects, but this makes the observations particularly challenging because of the sky brightness. We have made an effort to optimize the Keck AO observations. Near-IR imaging requires tradeoffs between sky brightness and post-correction Strehl. Expectations and our early results favor H-band in typical conditions. Contrary to prior experience with V 14 targets, we find Laser-Guide-Star AO correction to be far more effective than using Pluto as the wavefront source (NGS). We have achieved imaging that could detect satellites smaller than Nix at good S/N, even in a relatively short (15 min) span.

M. Kaasalainen, M. Viikinkoski, B. Carry & J. Durech

Asteroids, Comets, Meteors, May 2012 (NASA/Ads, BibTeX)

We consider inversion methods for shape reconstruction with complementary data sources. We present a generally applicable shape support for non-starlike shapes. New models of Kleopatra and Hermione are presented.

J. Durech, M. Delbo & B. Carry

Asteroids, Comets, Meteors, May 2012 (NASA/Ads, BibTeX)

We will present a new general method that combines asteroid photometry in the optical with thermal IR radiometry to derive physical models of asteroids. The method includes both data types at once and optimizes all the relevant physical parameters.

C. Dumas, B. Carry, D. Hestroffer, F. Merlin, P. Lacerda & F. Gourgeot

EPSC-DPS Joint Meeting 2011, held 2-7 October 2011 in Nantes, October 2011 (NASA/Ads, BibTeX)

In this contribution, we report spectro-imaging observations of all three components of the Haumea system performed in 2007 with the ESO-VLT nearinfrared integral-field spectrograph SINFONI and its Laser Guide Star Facility [6]. Our data and related compositional modeling show that the surface of the outer satellite Hiiaka is mostly coated with crystalline water ice, as in the case of the central body Haumea [7], [8], whose surface appears to be made of large grains of water ice, almost entirely in its crystalline form. We also discuss possible sources of heat to maintain water in its crystalline state. Finally, we report on the preliminary analysis of a similar highcontrast spectroscopic data set obtained this year on Haumea, but for a different rotational phase than our 2007 observations.

L. O'Rourke, T. Müller, I. Valtchanov, B. Altieri, B. M. Gonzalez-Garcia, B. Bhattacharya, L. Jorda, B. Carry, M. Küppers, O. Groussin, K. Altwegg, M. A. Barucci, D. Bockelee-Morvan, J. Crovisier, E. Dotto, P. Garcia-Lario, M. Kidger, A. Llorente, R. Lorente, A. P. Marston, M. Sanchez Portal, R. Schulz, M. Sierra, D. Teyssier & R. Vavrek

EPSC-DPS Joint Meeting 2011, held 2-7 October 2011 in Nantes, October 2011 (NASA/Ads, BibTeX)

Prior to and around ESA Rosetta's flyby of (21) Lutetia, a collaborative observation campaign using another ESA satellite, the ESA Herschel Space Observatory, was performed whereby Herschel's two photometers observed the asteroid in the far infrared, at wavelengths not covered by the Rosetta instruments. The Herschel observations, fed into a thermophysical model (TPM) using as input a flyby image based shape model (built upon Rosetta OSIRIS instrument observations) were further correlated with ~70 multi-wavelength (IRAS, ISOVISIR, IRTF, Akari, ESO-TIMMI2, Spitzer-IRAC) observations of Lutetia. We confirm the albedo measured by Rosetta and derive a "true" H-mag value based upon the cross-sections of the asteroid observed from all aspect angles. From our measurements we find that (21) Lutetia has an extremely low thermal inertia as well as a very low surface temperature. In addition, we have been able to identify a hill/crater surface feature located on the asteroids southern region not observed by Rosetta. We conclude that only through the merging of in-situ flyby based observations and remote sensing observations can a true global picture be obtained of this peculiar asteroid.

J. D. Drummond, W. J. Merline, A. Conrad, J. Christou, P. Tamblyn & B. Carry

EPSC-DPS Joint Meeting 2011, held 2-7 October 2011 in Nantes, October 2011 (NASA/Ads, BibTeX)

The triaxial ellipsoid dimensions and rotational pole of the large asteroid (19) Fortuna were found from only three nights of adaptive optics images in November 2009 at the 8 meter Gemini North telescope at &lambda$ = 2.15 μm. The dimensions and pole, as well as images, are supported by the model derived from lightcurve inversions and stellar occultations. Fortuna should perhaps be considered a candidate for a Standard Triaxial Ellipsoid.

M. Küppers, R. Moissl, P. J. Gutirrez, J.-B. Vincent, S. Besse, L. Jorda, H. Sierks & B. Carry

EPSC-DPS Joint Meeting, held 2-7 October 2011 in Nantes, October 2011 (NASA/Ads, BibTeX)

A crater structure of about 21 km diameter is the most prominent feature on the hemisphere of Asteroid (21) Lutetia that was observed by the OSIRIS cameras during the flyby of the Rosetta spacecraft. It shows the presence of landslides, numerous large boulders, and the largest colour variations found on the surface of the asteroid. We present evidence that it is the youngest large geological feature seen by Rosetta, and we show that there are variations in composition or size of its surface material.

B. Carry, M. Kaasalainen, W. J. Merline, J. D. Drummond, J. Durech, J. Berthier & A. Conrad

EPSC-DPS Joint Meeting 2011, held 2-7 October 2011 in Nantes, October 2011 (NASA/Ads, BibTeX)

We describe our on-going observing program to determine the physical properties of asteroids from groundbased facilities. We combine disk-resolved images from adaptive optics, optical lightcurves, and stellar occultations to put tighter constraints on the spin, 3-D shape, and size of asteroids. We will discuss the relevance of the determination of physical properties to help understand the asteroid population (e.g., density, composition, and non-gravitational forces). We will then briefly describe our multi-data inversion algorithm KOALA (Carry et al. 2010a, Kaasalainen 2011, see also Kaasalainen et al., same meeting), which allows the determination of certain physical properties of an asteroid from the combination of different techniques of observation. A comparison of results obtained with KOALA on asteroid (21) Lutetia, prior to the ESA Rosetta flyby, with the high spatial resolution images returned from that flyby, will then be presented, showing the high accuracy of KOALA inversion. Finally, we will describe our current development of the algorithm, and focus on examples of other asteroids currently being studied with KOALA.

M. Kaasalainen, M. Viikinkoski, B. Carry, J. Durech, P. Lamy, L. Jorda, F. Marchis & D. Hestroffer

EPSC-DPS Joint Meeting 2011, held 2-7 October 2011 in Nantes, October 2011 (NASA/Ads, BibTeX)

Irregularly shaped bodies with at most partial in situ data are a particular challenge for shape reconstruction and mapping. We have created an inversion algorithm and software package for complementary data sources, with which it is possible to create shape and spin models with feature details even when only groundbased data are available. The procedure uses photometry, adaptive optics or other images, occultation timings, and interferometry as main data sources, and we are extending it to include range-Doppler radar and thermal infrared data as well. The data sources are described as generalized projections in various observable spaces, which allows their uniform handling with essentially the same techniques, making the addition of new data sources inexpensive in terms of computation time or software development. We present a generally applicable shape support that can be automatically used for all surface types, including strongly nonconvex or non-starlike shapes. New models of Kleopatra (from photometry, adaptive optics, and interferometry) and Hermione are examples of this approach. When using adaptive optics images, the main information from these is extracted from the limb and terminator contours that can be determined much more accurately than the image pixel brightnesses that inevitably contain large errors for most targets. We have shown that the contours yield a wealth of information independent of the scattering properties of the surface. Their use also facilitates a very fast and robustly converging algorithm. An important concept in the inversion is the optimal weighting of the various data modes. We have developed a mathematicallly rigorous scheme for this purpose. The resulting maximum compatibility estimate, a multimodal generalization of the maximum likelihood estimate, ensures that the actual information content of each source is properly taken into account, and that the resolution scale of the ensuing model can be reliably estimated. We have applied our procedure to several asteroids, and the ground truth from the Rosetta/Lutetia flyby confirmed the ability of the approach to recover shape details (see also Carry et al., this meeting). We have created a general flyby-version of the procedure to construct full models of planetary targets for which probe images are only available of a part of the surface (a typical setup for many planetary missions). We have successfully combined flyby images with photometry (Steins) and adaptive optics images (Lutetia); the portion of the surface accurately determined by the flyby constrains the shape solution of the "dark side" efficiently.

D. Koschny, G. Drolshagen & B. Carry

Gaia follow-up network for the solar system objects : Gaia FUN-SSO workshop proceedings, June 2011 (NASA/Ads, BibTeX)

In 2008, ESA started a new optional programme called Space Situational Awareness programme. One part of it deals with the impact threat of near-Earth objects for the Earth. This paper intends to inform the Gaia asteroid community about this programme and explores possible synergies.

A. Conrad, B. Carry, w. J. Merline, J. D. Drummond, C.Chapman, P. Tamblyn, J. Christou, C. Dumas, H. Weaver & Rosetta OSIRIS Instument Team

American Geophysical Union, December 2010 (NASA/Ads, BibTeX)

We report the results of our campaign to improve our understanding of the physical characteristics of asteroid (21) Lutetia ahead of the Rosetta flyby in 2010 July. This included measurements of shape, size, pole, density, and a search for satellites. We utilized primarily adaptive optics (AO) on large ground-based telescopes (Keck, Gemini, and VLT). We coordinated these efforts with HST observations (Weaver et al. 2010, A&A 518, A4), made in support of Rosetta's ALICE UV spectrometer. Preliminary results were supplied to Rosetta mission teams in fall of 2009 to assist in planning for the mission. Observations and analyses were complete and submitted for publication before the flyby (Drummond et al. 2010, A&A, in press; Carry et al. 2010, A&A, in press). Using more than 300 AO images of Lutetia, which subtended only slightly more than two resolution-elements (0.10") for these large telescopes, we were able to derive accurate size and shape information, as well as a pole and spin period. We modeled the size and shape using both a triaxial-ellipsoid model and a 3D radius-vector model. The radius-vector model used our new technique of multi-dataset inversion, called KOALA (for Knitted Occultation, Adaptive optics, and Lightcurve Analysis), in which we utilized not only our AO imaging, but also 50 lightcurves spanning 48 years. We combined the best aspects of each model to produce our best-estimate 3D shape model, a hybrid having ellipsoid-equivalent dimensions of 124 x 101 x 93 km (± 5 x 4 x 13 km) and effective diameter 105 ± 7 km. We found the spin axis of Lutetia to lie within 5° of [long, lat (52,-6)] or [RA DEC (52,+12)] and determined an improved sidereal period of 8.168270 ± 0.000001 h. We predicted the geometry of Lutetia during the flyby and showed that the southern hemisphere would be in seasonal shadow at that time. The model suggested the presence of several concavities and irregularities that may be associated with large impacts. The model matches remarkably the Rosetta imaging in both shape and absolute size, and we take this as a validation of our technique. The overall size-scaling required of our model to match best the Rosetta images appears to be only 2.0%, while the RMS deviation of points on our model contours from the Rosetta contours is about 2.7 km (about 2.5%). The detailed shape, as well as the a- and b-dimensions of the object, will ultimately be better determined from the Rosetta flyby imaging; but knowledge of the pole, spin period, and c-dimension may still depend heavily on our ground-based solutions. Using two separately determined (pre-Rosetta) masses and the volume from our hybrid shape model, we estimate a density of 3.5 ± 1.1 or 4.3 ± 0.8 g/cc, favoring an enstatite-chondrite (EC) composition for this large M-type asteroid (Chapman et al. 2010, DPS), although other compositions are formally allowed.

M. Birlan, A. Nedelcu, P. Vernazza, R. Binzel, B. Carry, F. DeMeo, A. Barucci & M. Fulchignoni

American Astronomical Society, DPS meeting #42, October 2010 (NASA/Ads, BibTeX)

The Roseta mission flyby of the asteroid 21 Lutetia was scheduled for July 10, 2010 and the event was accomplished with a brilliant success. 21 Lutetia has an "estimated" diameter of (98.3 ± 5.9) km and is the largest body in the main-belt ever visited until now by a space mission. The asteroid is located in the inner part of the main belt, in an orbit with low eccentricity and inclination (a=2.4348 a.u., e=0.16, i=3.06°). The large amount of colors and spectral data of Lutetia, and the polarimetric and radiometric albedoes are giving puzzling results, with non-unique solution of the asteroid taxonomy.We present near-infrared observations in the 0.8-4 micron spectral range performed during the last opposition in 2010, a few months before the flyby of the Rosetta spacecraft. Our observations were obtained with SpeX/IRTF in remote observing mode from CODAM - Paris Observatory in March 1 and 2, April 15, and May 16, 2010. The data of March and May were obtained in remarkable weather conditions (humidity between 1 and 4% and no wind). Three spectra in Prism mode (0.8-2.5 micron) and four spectra in LXD mode (2.2-3.8 micron) will be presented together with the physical ephemeris of the asteroid. We reached a SNR of 200 in Prism mode and of about 80 in LXD mode. The North Pole geometry of the object covers almost all latitudes between +90° and -30°.These high S/N spectra show very important spectral homogeneity for Lutetia. The spectra are flat and independent of the Lutetia's rotational phase. In the 0.8-1.6 micron, 1.6-2.4 micron and 2.8-3.3 micron wavelength ranges, we do not see any absorption band at the 0.5% level. This implies a dry surface. This implies also that signature of silicates such olivine and iron-rich pyroxenes are not present on the asteroid surface.

C. Chapman, W. J. Merline, B. Carry, H. A. Weaver, A. Conrad & J. D. Drummond

American Astronomical Society, DPS meeting #42, October 2010 (NASA/Ads, BibTeX)

On 10 July 2010, Rosetta successfully flew by the large main-belt asteroid 21 Lutetia, providing a rare chance to compare close-up, spatially resolved observations and compositional interpretations with the lengthy, detailed record of Earth-based telescopic data. Lutetia (and two other asteroids) originally defined the M taxonomic type (Zellner & Gradie 1976, AJ 81, 262). This mnemonic for metal never exclusively meant iron core, but included enstatite chondrites (EC), which are colored by metal grains. In the mid-1990s, some M-types (W's) were found to have 3 micron absorption bands indicating hydration; Rivkin et al. (2000 Icarus 145, 351) originally included Lutetia in this class. During four decades, Lutetia has been observed by radiometry, polarimetry, lightcurve photometry, spectrophotometry (UV into mid-IR), thermal IR, radar, and direct imaging. Lutetia's estimated mass, size, and shape tend to rule out low (carbonaceous chondrite) or high (nickel-iron) densities, but are not definitive. Relatively dense, high-albedo CV and CO chondrites were suggested as analogs for Lutetia (cf. Barucci et al. 2005 A&A 430, 313) but are marginal or ruled out by spectral traits that define the M/W types and separate them from C-like types. W's are uncommon but not extremely rare in the main belt, so one would expect sampling by meteorites, yet the only hydrated ECs are clasts within the unusual Kaidun meteorite. If Lutetia is not a hydrated EC, then it may be either (a) not significantly hydrated, (b) masked by unknown surface properties analogous to space weathering, (c) a mixture of known meteorite types (like the 2008 TC3 = Almahata Sitta meteorite), or (d) an unknown or extreme kind of meteorite, like Allende but with a superabundance of CAIs. Since Rosetta's remote-sensing techniques resemble those employed from Earth, it may not fully resolve these issues.

B. Carry, W. J. Merline, M. Kaasalainen, M., Conrad, A., Drummond, J. D., Dumas, C., Kueppers, M. & OSIRIS Instrument Team

American Astronomical Society, DPS meeting #42, October 2010 (NASA/Ads, BibTeX)

We recently developed a shape reconstruction algorithm, dubbed KOALA (Kaasalainen, IPI 2010; Carry et al., Icarus 2010), which allows the determination of the size, shape, and spin properties of asteroids from a combined data set of disk-resolved images, optical lightcurves, and stellar occultations.Using adaptive optics (AO) imaging systems on the Keck and VLT telescopes, we acquired more than 300 images of the main-belt asteroid (21) Lutetia in 2007 and 2008. We combined these images with 50 lightcurves spanning some 48 years and including data taken almost up until the time of flyby. We produced a 3D shape model of Lutetia and determined the spin pole and rotation rate (Carry et al., submitted to A&A).On 2010 July 10, the International Rosetta Mission of the European Space Agency successfully encountered (21) Lutetia. The images recorded by the OSIRIS camera on-board Rosetta revealed our shape prediction to be accurate. We will present the KOALA (Knitted Occultation, Adaptive-optics, and Lightcurve Analysis) method, and a comparison of our shape model with the high-resolution images acquired by Rosetta during the flyby.

W. J. Merline, B. Carry, J. D. Drummond, A. Conrad, C. Chapman, M. Kaasalainen, C. Leyrat, H. A. Weaver, P. Tamblyn, J. Christou, C. Dumas, A. Kryszczynska, F. Colas, L. Bernasconi, R. Behrend, F. Vachier, M. Polinska, R. Roy, R. Naves, R. Poncy & P. Wiggins

American Astronomical Society, DPS meeting #42, October 2010 (NASA/Ads, BibTeX)

Prior to the flyby of (21) Lutetia by Rosetta, we initiated a campaign of observations to characterize the system, primarily using ground-based adaptive optics (AO) on large telescopes, including Keck, Gemini, and VLT. We coordinated these efforts with HST observations (Weaver et al. 2010 A&A in press) made in support of the Rosetta ALICE UV spectrometer. Lutetia was 0.10" in diameter, allowing disk-resolved imaging with AO and tracking of its shape during rotation. We modeled the shape using both a triaxial-ellipsoid model (Drummond et al. 2010 A&A submitted) and a full 3D radius-vector model (Carry et al. 2010 A&A submitted, in which we combine AO imaging with decades of lightcurve data to produce an improved 3D model using our inversion algorithm KOALA). To overcome limitations in each model, we combined the best aspects of each to produce our best-estimate 3D shape model, a hybrid having ellipsoid-equivalent dimensions of 124 x 101 x 93 km (± 5 x 4 x 13 km) and effective diameter 105 ± 7 km. We find the spin axis of Lutetia to lie within 5 deg of [long, lat (52,-6)] or [RA DEC (52,+12)], and determine an improved sidereal period of 8.168270 ± 0.000001 h. We predicted the geometry of Lutetia during the flyby and showed that the southern hemisphere would be in seasonal shadow at that time. The model suggests the presence of several concavities that may be associated with large impacts. Using two separately determined masses and the volume of our hybrid model, we estimate a density of 3.5 ± 1.1 or 4.3 ± 0.8 g/cc, favoring an enstatite-chondrite composition for this large M-type asteroid, although other compositions are formally allowed. No satellites larger than 1 km diameter were detected in the AO-data over a significant fraction of the Hill sphere (10-240 asteroid radii).

L. Jorda, P. Lamy, S. Besse, C. Capanna, B. Carry, G. Faury, R. Gaskell, G. Gesquire, O. Groussin, P. Gutierrez, M. Kaasalainen, W Sabolo, H. Sierks, S. Spjuth & OSIRIS Team

American Astronomical Society, DPS meeting #42, October 2010 (NASA/Ads, BibTeX)

The Rosetta spacecraft of the European Space Agency flew by the asteroid 21 Lutetia on July, 10, 2010 on its way to its final target, comet 67P/Churyumov-Gerasimenko. A total of 460 images have been acquired by OSIRIS during the flyby, with a minimum pixel scale of 64 m at closest approach (hereafter CA) with the narrow angle camera. Several filters have been used, covering a wavelength range from the far UV (0.25 microns) to the end of the visible spectrum (1.0 microns). The phase angle went through 11°-0°-160°, reaching opposition 18 min before CA. We report here on a preliminary interpretation of the images of the asteroid acquired by OSIRIS, the imaging system aboard Rosetta. These images are combined with pre-flyby light curves and adaptive optics measurements to retrieve the shape and the rotational parameters of the asteroid. The bulk physical properties: size, surface, volume, moments of inertia, gravity field, are then extracted from the shape.

C. Snodgrass, C. Tubiana, L.-B. Vincent, H. Sierks, S. Hviid, R. Moissl, H. Boehnhardt, C. Barbieri, D. Koschny, P. Lamy, H. Rickman, R. Rodrigo, B. Carry, S. Lowry, R. Laird, P. Weissman, A. Fitzsimmons, S. Marchi & OSIRIS Team

American Astronomical Society, DPS meeting #42, October 2010 (NASA/Ads, BibTeX)

The discovery of P/2010 A2 by the LINEAR survey in January 2010 revealed an object displaying a large trail of material similar in shape to a cometary tail although no central condensation or coma could be detected. The appearance of this object in an asteroidal orbit in the inner main belt attracted attention as a potential new member of the Main Belt Comets class (MBCs) but the discovery of a nucleus, with an estimated diameter of 120 m, around 1500 km away from the trail implied that the extended object we were seeing could be the debris trail from a recent collision rather than the tail of a comet. Due to the low inclination of its orbit, it is difficult to conclude about the nature of P/2010 A2 from Earth-based data only, as different scenarios lead to the same appearance in the orbital configuration at the times of observations. We present here another set of images, acquired from the unique viewing geometry provided by ESA's Rosetta spacecraft en route to comet 67P/Churyumov-Gerasimenko. Albeit faint (22 magnitude), the object could be observed by the high-resolution camera OSIRIS. We used a Finson-Probstein model to simulate the shape of the trail, and estimate the time of emission and β parameter (ratio between solar radiation pressure and gravity) for the dust grains. Simulations were compared to the OSIRIS images and ground based observations acquired at NTT and Palomar telescopes. Thanks to the different phase angle provided by Rosetta, we could reduce the number of solutions to a unique model, leading to the conclusive demonstration that the trail is due to a single event rather than a period of cometary activity.

F. DeMeo, B. Carry, F. Marchis, M. Birlan, R. Binzel, S. Bus, P. Descamps, A. Nedelcu & H. Bouy

American Astronomical Society, DPS meeting #42, October 2010 (NASA/Ads, BibTeX)

We present near-infrared spectral measurements of Themis family asteroid (379) Huenna (D~98km) and its 6km satellite using SpeX on the NASA IRTF. The companion was farther than 1.5" from the primary at the time of observations and was 5 magnitudes dimmer. We describe a method for separating and extracting the signal of a companion asteroid when the signal is not entirely resolved from the primary. The spectra of (379) Huenna and its secondary are very similar, suggesting the secondary is either a fragment of the primary from a past collision or is a fragment from the collision that created the Themis family.

B. Carry, W. J. Merline, J. D. Drummond, M. Kaasalainen, A. Conrad, C. Leyrat, E. Dotto, C. Chapman & Lutetia Koala Team

European Planetary Science Congress, September 2010 (NASA/Ads, BibTeX)

The ESA/NASA mission Rosetta will encounter main belt asteroid (21) Lutetia on 2010 July 10. Prior to this encounter, we had imaged Lutetia with large ground-based telescopes equipped with adaptive optics (AO). Using our KOALA algorithm, we combined more than 300 images of Lutetia, together with 50 optical lightcurves, to derive Lutetia's physical properties. We released a shape model constraining Lutetia's volume and orientation to help mission planners prepare for the flyby. We will discuss our results compared with the high spatial-resolution images acquired by Rosetta.

C. Snodgrass, B. Carry, C. Dumas & O. Hainaut

European Planetary Science Congress, September 2010 (NASA/Ads, BibTeX)

Brown et al. (2007) announced the discovery of the first collisional family in the Trans-Neptunian Region after finding a group of objects with very similar spectral features that could be linked dynamically with 136108 Haumea (2003 EL61). These objects all show the same almost pure water ice spectral signature observed in Haumea, and Brown et al. postulate that the family was formed in a collision with the large and already differentiated proto-Haumea early in the history of the Solar System, leaving the overly dense and fast spinning core with a thin covering of water ice as Haumea and generating a family of pure water ice bodies from the outer layers. Ragozzine & Brown (2007) published a list of further potential family members selected on dynamical grounds (including known family members, the list contains 36 objects), but little was known about the surface properties of many of these objects as most are smaller and consequently too faint for the near-infrared spectroscopy that can confirm the presence of water ice on their surfaces.
We began a programme at ESO in 2008 to measure the physical characteristics of these proposed family members with two goals; to confirm the membership of the family for each body by detecting the signature of water ice on the surface and secondly to test the idea that they were composed almost entirely of water ice by placing limits on the density of the bodies. We look for water ice on bodies too small for spectroscopy using optical and near-infrared colours using the ESO instruments EFOSC2 at the NTT and HAWK-I at the VLT. A unique strength of using the new HAWK-I imager is that this instrument contains a medium band filter (CH4) that covers the water absorption band at 1.5 microns, making the (J-CH4) colour very sensitive to this absorption feature and therefore a strong indicator of water ice. We place constraints on the density of the bodies by measuring light-curves (using EFOSC2): The elongation (from the light-curve amplitude) and rotation period then constrain the minimum bulk density of the body, with higher values than 1 g.cm-3 ruling out a pure water ice composition.
We find that most of the candidates do not have water-ice surfaces, based on observations of 22 of the 36 candidates. Those that do are clustered in orbital element space near to the proposed collision, showing that the fragments from the collision did not spread far. The current confirmed members can all be explained by a dispersion velocity of < 125 m.s-1 , much lower than would be expected for a catastrophic collision with a body of the size of the proto-Haumea. Proposed explanations for this include a grazing impact and merger or a collision with a smaller moon rather than Haumea itself, but there is still debate as to the true source of this family of objects.
Due to the small number of confirmed family members, we cannot place strong constraints on the density of these objects. We present our latest results from this project, including new observations taken in February 2010.

L. Jorda, P. Lamy, S. Besse, C. Capanna, B. Carry, G. Faury, R. Gaskell, G. Gesquiere, O. Groussin & M. Kaasalainen

European Planetary Science Congress, Septempber 2010 (NASA/Ads, BibTeX)

The Rosetta spacecraft of the European Space Agency flew by the asteroid 21 Lutetia on July, 10, 2010 on its way to its final target, comet 67P/Churyumov-Gerasimenko. We report here on a preliminary interpretation of the images of the asteroid acquired by OSIRIS, the imaging system aboard Rosetta. These images are combined with pre-flyby light curves and adaptive optics measurements to retrieve the shape and the rotational parameters of the asteroid. The bulk physical properties: surface, volume, moments of inertia, gravity field, are then deduced from the shape.

O. Groussin, P. Lamy, S. Fornasier, L. Jorda, M. Kaasalainen & B. Carry

European Planetary Science Congress, September 2010 (NASA/Ads, BibTeX)

We report on Spitzer Space Telescope observations of asteroids 21 Lutetia and 2867 Steins performed on 10-11 Dec. 2005 and 22 Nov. 2005 respectively. We obtained the thermal light curve of both objects over one rotation, using the infrared spectrograph (IRS) in low-resolution mode, which covers the wavelength range 5.2-38 μm. Assuming a beaming factor (roughness) in the realistic range 0.7-1.0, we derived a thermal inertia of 0-30 J.K-1.m-2.s-1/2 for Lutetia and 0-150 J.K-1.m-2.s-1/2 for Steins. The thermal lightcurves of Lutetia and Steins are well reproduced in shape and phase by our model, but best interpreted by assuming inhomogeneities in the thermal properties of the surface, with two different regions of different roughness.

C. Dumas, B. Carry, F. Merlin, D. Hestroffer, P. Vernazza & M. Kaasalainen

American Astronomical Society, DPS meeting #41, September 2009 (NASA/Ads, BibTeX)

We present recent results obtained using the suites of adaptive optics instruments NACO and SINFONI installed at the 8m Yepun telescope of the ESO-VLT. The combination of the high-angular resolution and high contrast capabilities of these instruments allowed us to carry out an unprecedented near-infrared spectro-imaging study of the surface properties of the Haumea triple trans-Neptunian system, the surface of the igneous main-belt asteroid Vesta, and of the B-type asteroid Pallas. The integral field spectrograph SINFONI was used along with the VLT laser guide star facility to separate Haumea from its two companions and provide high signal-to-noise H- and K- band spectra of the central TNO and its brightest satellite Hi'iaka, revealing that both surfaces are coated with crystalline water ice. SINFONI was also used to obtain disk-resolved spectroscopy of Vesta surface and map the spatial variation of the shape and depth of the pyroxene band. Although our surface coverage was only partial, we could investigate possible trends between spectral slopes and albedo values across Vesta. Finally, combining our NACO images of Pallas with some images obtained at the Keck Observatory, we could define a revised determination of the size, shape model and spin orientation for Pallas, as well as derive albedo maps covering nearly 80% of its surface.

A. Conrad, W. Merline, J. Drummond, B. Carry, P. Tamblyn, C. Chapman, C. Dumas & H. Weaver

American Geophysical Union, December 2009 (NASA/Ads, BibTeX)

In support of the NASA/ESA Rosetta mission's plans to observe asteroid (21) Lutetia during a 2010 July flyby, and in conjunction with a larger ground-based plus HST campaign to support this mission, we observed Lutetia from Keck and Gemini-North during several nights spanning 2008 Oct through 2009 Jan. Observations were made using adaptive optics in the near-IR, primarily at K-band (2.1 micron), and were timed to coincide with the asteroid's most recent opposition at a distance of about 1.4 AU. From these data, we determined Lutetia's triaxial size and shape to be 132 x 101 x 76 km, with maximum expected uncertainties of 4 x 3 x 31 km. The spin pole is found to be at (RA, Dec) = (48, +9) deg or ecliptic (long, lat) = (49,-8) deg, with a formal uncertainty radius (not including systematics) of 3 deg. We have calibrated our technique of deriving dimensions of asteroids from AO images against Pluto and 4 satellites of Saturn with accurate diameters, and we expect that our systematics (included in the size uncertainties above) are no more than 3%. We also searched for satellites and our preliminary results indicate no detection of a satellite larger than about 1 km over a significant fraction of the Hill sphere (10-240 asteroid radii). Improved limits are expected from a more refined analysis. We are grateful for telescope time made available to us by S. Kulkarni and M. Busch (Cal Tech) for a portion of this dataset. We also thank our collaborators on Team Keck, the Keck science staff, for making possible some of these observations and for observing time granted at Gemini under NOAO time allocation. Plane-of-sky short and long axes of (21) Lutetia taken from Keck AO images on 2008 Dec 2.

J. Berthier, D. Hestroffer, B. Carry, F. Vachier, V. Lainey, N. Emelyanov, W. Thuillot, J.-E. Arlot & Ephemerides Service, Imcce

European Planetary Science Congress, September 2009 (NASA/Ads, BibTeX)

Ephemerides of solar system bodies are needed for many applications such as operation of the telescopes, prediction of instruments performance, planing of observation campaigns, reduction of astrometric, photometric, or spectrometric data, analysis of space probe images, etc. Dynamical and physical studies of the small bodies of the solar system based on stellar occultation, astrometry, photometry, radiometry and high angular resolution observations also show the need of having good ephemerides over mid-term time scales. In this paper we give a presentation of Miriade, the new version of the IMCCE ephemeris service on the web. It is a major upgrade from the previous services available at IMCCE providing positional and physical ephemerides of planets and small bodies (asteroids, comets, satellites) of the solar system as well as some physical data. Miriade is part of the more general IMCCE-VO solar system portal in the Virtual Observatory (VO) framework, making use of a name resolver for the solar system bodies, and providing many functions.

J. Drummond, A. Conrad, W. Merline & B. Carry

American Astronomical Society, DPS meeting #41, September 2009 (NASA/Ads, BibTeX)

In a campaign to study the Rosetta mission target, asteroid (21) Lutetia, we obtained 81 images on December 2, 2008, at 2.12 microns with adaptive optics (AO) on the Keck-II 10 m telescope. From these nearly consecutive images obtained over a quarter of rotation, we have determined the asteroid's triaxial ellipsoid diameters to be 132x101x76 km, with formal uncertainties of 1 km for the equatorial dimensions, and 31 km for the shortest axis. This latter uncertainty occurs because the observations were made at the relatively high sub-Earth latitude of -69 degrees. From these observations we determine that Lutetia's pole lies at 2000.0 coordinates of RA=48, Dec=+9, or Ecliptic coordinates of [49;-8], with a formal uncertainty radius of 3 deg. (The other possible pole is eliminated by considering its lightcurve history.) The rotational pole derived for the lightcurve inversion model (available at http://astro.troja.mff.cuni.cz/ projects/asteroids3D/web.php), is only 5 deg from ours, but comparing our images to the lightcurve inversion model we find that Lutetia is more pointed than the model. Our technique of deriving the dimensions of asteroids from AO images has been calibrated against Pluto and 4 satellites of Saturn with precise diameters, and we find that any systematic errors can be no more than 1-3%.
We acknowledge the assistance of other team members Christophe Dumas (ESO), Peter Tamblyn (SwRI), and Clark Chapman (SwRI). We also thank Hal Weaver (JHU/APL) as the lead for our collaboration with the Rosetta mission. We are grateful for telescope time made available to us by S. Kulkarni and M. Busch (Cal Tech) for a portion of our overall Lutetia effort. We also thank our collaborators on Team Keck, the Keck science staff, for making possible some of the Lutetia observations and for their participation. Additional Lutetia observations were acquired at Gemini North under NOAO time allocation.

P. Vernazza, B. Carry, J. Emery, J. Hora, D. Cruikshank, R. Binzel, J. Jackson, J. Helbert & A. Maturilli

American Astronomical Society, DPS meeting #41, September 2009 (NASA/Ads, BibTeX)

We report an unexpected variability among mid-infrared spectra (IRTF and Spitzer data) of 8 S-type asteroids for which all other remote sensing interpretations (e.g. VNIR spectroscopy, albedo) yield similar compositions. Compositional modelling making use of their mid-IR spectra only yields surprising alternative conclusions: 1) these objects are not "compositionally similar" as the inferred abundances of their main surface minerals (olivine and pyroxene) differ from one another by 35%. 2) Carbonaceous chondrite and ordinary chondrite meteorites provide an equally good match to each asteroid spectrum.
Following the laboratory work of Ramsey & Christensen (1998), we interpret this variability to be physically caused by differences in surface particle size. Mid-IR measurements of surfaces having particle sizes that are large compared to the 8-13 micron wavelength range yield compositional interpretations that remain compatible with other types of remote sensing. Surfaces having grain sizes near or below the 8-13 micron wavelength scale of mid-IR measurements yield divergent compositional interpretations. Thus for asteroids, we find mid-infrared measurements are a powerful tool for inter-comparison of surface properties for objects of known compositions. Those yielding compatible mid-IR compositional interpretations likely have large particle sizes on their surfaces. Divergent compositional interpretations are more likely indicative of surfaces dominated by particles at or below the 8-13 micron scale of mid-IR radiation. Thus for mid-IR measurements of objects whose surface properties are not known, a reliable compositional interpretation based solely on linear deconvolution of mid-IR measurements with existing spectral libraries is problematic.

A. Conrad, W. Merline, J. Drummond, B. Carry, C. Dumas, R. Campbell, R. Goodrich, C. Chapman & P. Tamblyn

40th Lunar and Planetary Science Conference, March 2009 (NASA/Ads, BibTeX)

We report results from recent high-angular-resolution observations of asteroids using adaptive optics (AO) on large telescopes.

D. Hestroffer, W. Thuillot, S. Mouret, F. Colas, P. Tanga, F. Mignard, M. Delbo & B. Carry

SF2A-2008: Proceedings of the Annual meeting of the French Society of Astronomy and Astrophysics, November 2008 (NASA/Ads, BibTeX)

The ESA cornerstone mission Gaia, to be launched during end-2011, will observe ~ 250,000 small bodies. These are mostly main belt asteroids, but also Near-Earth objects, Trojans, and a few comets, or planetary satellites. The scientific harvest that Gaia will provide - given the high astrometric accuracy (at sub-milli-arcsec level), valuable photometric measurements (at milli-mag level), and moderate imaging (about 2,000 objects will be resolved) - will have a major impact on our knowledge of this population in terms of composition, formation and evolution tep{mignard07}. There are nevertheless some intrinsic limitations in particular due to the unavoidable limited duration of the mission (5 years), the peculiar observing strategy that is not optimised to the observation of solar system objects, and last, the limited imaging possibilities. We can thus identify two kind of complementary data and ground-based observations, whether they are part of the Gaia Data Processing and Analysis Consortium (DPAC), or not, but provide a strong leverage to the Gaia science.
We discuss different aspects of additional observations from ground (yet not exclusively) either in preparation to the Gaia mission, in alert during the mission, or after the mission as additional complementary information. Observations of a set of well defined and selected targets, with different telescopes and instrumentation, will increase the scientific output in three particular and important topics: mass of asteroids, their bulk density and possible link to their taxonomy, and non-gravitational forces.

D. Farrelly, D. Hestroffer, S. Astakhov, E. Lee, A. Doressoundiram, B. Carry & J. Berthier

European Planetary Science Congress, September 2008 (NASA/Ads, BibTeX)

Near-symmetric binaries - i.e., binaries with roughly samesized partners - appear to dominate the known population of binaries in the Kuiper-belt. Herein the mass- and sizeratio distributions, as well the resulting orbit properties, of Kuiper-belt binaries predicted by the chaos-assisted capture formation model are presented.

A. Conrad, B. Carry, J. Drummond, W. Merline, C. Dumas, W. Owen, C. Chapman, P. Tamblyn, R. Goodrich & R. Campbell

American Astronomical Society, DPS meeting #40, September 2008 (NASA/Ads, BibTeX)

As part of our ongoing programs to use adaptive optics (AO) to study asteroids for size, shape, and presence of satellites, we observed asteroid (41) Daphne during its recent close (1.05 AU) opposition. In March 2008, we discovered a small satellite to Daphne at Keck (Conrad et al. 2008, IAUC 8939; Merline et al. 2008, ACM 2008, #8370). Follow up observations at Keck and VLT allowed us to refine the orbit. The unusually short period of the satellite (~1.1 day) and the estimated size (239x183x153 km) from our observations lead to a density near 2.0 g/cc. This is significantly higher than most other large C-types with densities determined from presence of a moon (Merline et al. 2002, Asteroids III, 289). Because of this surprising density, and because we expect to derive an exceptionally accurate volume from our data, we are placing special emphasis on our size and shape determinations. One of the peculiarities is that this object is highly irregular in shape. We demonstrate several methods of determining the volume, including triaxial ellipsoid fits, detailed shape modeling, and improving estimates by using existing lightcurve information (e.g., from Kaasalainen et al.).

J. Drummond, W. Merline, A. Conrad, C. Dumas & B. Carry

American Astronomical Society, DPS meeting #40, September 2008 (NASA/Ads, BibTeX)

As part of our study of resolved asteroids using adaptive optics (AO) on large telescopes (>8; m), we have identified several that can serve as Standard Triaxial Ellipsoid Asteroids (STEAs), suitable for radar and thermo-physical calibration. These objects are modeled well as triaxial ellipsoids, having: 1) small uncertainties on their three dimensions as determined with AO; 2) rotational poles well determined from both lightcurves and AO; and 3) good sidereal periods from lightcurves. Although AO allows the opportunity to find an asteroid's dimensions and rotational pole in one night, we have developed a method to combine AO observations from different oppositions to pool into a global solution. The apparent orientation and sizes of STEAs can be predicted to within a few degrees and a few km over decades. Currently, we consider 511 Davida, 52 Europa, 2 Pallas, and 15 Eunomia as STEAs. Asteroids that are not well modeled as ellipsoids, clearly showing departures from ellipsoid figures in AO images, include 129 Antigone and 41 Daphne. We will show movies of images and models of these asteroids.

A. Conrad, W. Merline, J. Drummond, B. Carry, C. Dumas, P. Tamblyn, R. Campbell, R. Goodrich & D. Le Mignant

39th Lunar and Planetary Science Conference, March 2008 (NASA/Ads, BibTeX)

We present imaging data on three asteroids, using adaptive optics and having high spatial and rotational resolution. The resulting shapes can be compared with previous shape models derived from inversion of lightcurve data, and the agreement is generally good.

J. Berthier, D. Hestroffer, B. Carry, J. Durech, P. Tanga, M. Delbo & F. Vachier

"Asteroids, Comets, Meteors" Meeting, Jul 2008 (NASA/Ads, BibTeX)

Introduction: Ephemerides of solar system bodies are most needed in many applications. They are useful to the astronomer to prepare his observations proposal, for accurate thermal modeling, or in analyzing observational data, also for predicting instruments performances of moving and extended objects, etc. Since the pioneering work of Russel it is well known that light-curve of asteroids encompass information on their shape, making them more than only point-like source. And since then, space-probes during their fly-by to asteroids revealed all complex aspects of their macroscopic scale and surface features.
SSODNetWe have developed at the IMCCE a service, named Solar System Object Database NETwork, that offers many possibilities, among which: a name resolver for small bodies of the solar system (and planetary bodies); a data node with a search engine that offers easy inter-connection of various worldwide database; and a computing node for generating position ephemerides as well as ephemerides for the physical observations. This node is similar to the famous JPL Horizons, but with some fundamental technical aspects allowing different use though generic web-service and Virtual Observatory protocol.
Physical ephemerides: The service offers in particular some original features for the computation of asteroids physical ephemerides taking into account their spin and shape models made available from e.g. lightcurve inversion and/or high resolution imaging from optical telescopes, and radar observations. Also different visualizations and data-format outputs are available for uploading and directly through a web-service. For instance one can generate a fits file showing the orientation, brightness distribution, size, etc, that can be used for further convolution with an instrument PSF or transfer function as well as the Aladin system based at CDS. To these one can also add an radial velocity map. In future developments we will include albedo and thermal maps, and comets models. A synthetic database for general studies of the Gaia mission is also in construction.

W. Merline, A. Conrad, J. Drummond, B. Carry, C. Dumas, P. Tamblyn, C. Chapman, W. Owen, D. Durda, R. Campbell & R. Goodrich

"Asteroids, Comets, Meteors" Meeting, July 2008 (NASA/Ads, BibTeX)

Introduction. We report the discovery of a small satellite to large C-type asteroid (41) Daphne, using adaptive optics on Keck II. The satellite appears to have the most extreme mass ratio (106) of any binary known. It is also in a particularly close orbit for this class of binary. We consider how difficult is such a detection for large asteroids in the Main Belt, and what consequences it may have for the main-belt binary population and frequency. Because these observations were taken with the intention of not only a deep satellite search, but also rotationally resolved imaging of the primary, we are able to also determine accurately the shape, size, and pole position of the primary. The resulting volume estimate, coupled with the mass from the satellite orbit, will allows us to determine an exceptionally accurate density for this object.
Background. This was a combined effort of two programs, one to determine the shape, sizes, and poles of large main-belt asteroids and one to search for companions to main-belt asteroids. Our main objective in the particular run was to acquire good sizes and shapes for asteroids already known to have companions, and thus improve the volume and hence the densities. Improved size permits improved estimates of albedo, in turn allowing better interpretation of surface composition. If we have a good estimate of the mass, e.g. from the presence of a satellite, uncertainty in an asteroid's volume is the overwhelming uncertainty in attempts to derive its density. Of course, density is the single most critical observable having a bearing on bulk composition, porosity, and internal structure. We can also achieve good surface maps if the objects is large enough, e.g. for our observations of Ceres.
Observations. Our observations were made with the Keck II adaptive-optics imaging system NIRC2/AO on 2008 Mar 28 UT. At this time, asteroid (41) Daphne was approximately 1.09 AU from Earth, and had an angular size of about 0.22". The presents the most favorable size until the year 2031. A small satellite was discovered very close to the primary. The pair was tracked for over 3 hours, resulting in a surprisingly long (0.3") orbital track of the satellite.
Characteristics. Because this discovery was made only a few days before the deadline for this abstract, we have only been able to make preliminary estimates of the system parameters. From the single arc of the orbit, we had at first estimate a semi-major axis of about 443 km, but revised estimates put it at closer to 405 km. The orbital period estimate on our first report was 1.6 days, but this may be revised downward. The most unsual aspect is that this object appears to have the most extreme size ratio of any known binary. The brightness difference of the pair is about 10 magnitudes, giving a size of less than 2 km, and a mass ratio of about 1 million, significantly exceeding typical binaries. In addition, for this class of binary (large main-belt asteroid, with small secondary), undoubted produced via the SMAT (Smashed Asteroid Target) mechanism of Durda et al. (2004), it is also the closest known pair (5.5 primary radii, while most known are at about 10).
Discussion. Such objects may be common, but undetected. With a very high eccentricity, this main-belt object was exceptionally close during these observations. It is possible that many more such close, small satellites exist, and indeed with a typical size distribution and the collision results of Durda et al. (2004), one might expect many more. This may affect the previously claimed binary frequency for the larger main belt objects, which is much lower than in other populations. In addition, some benefit has been gained by the substantially improved AO system at Keck, providing higher Strehl and contrast, allowing us to detect such faint satelletes close to a bright object.

P. Rousselot, O. Mousis, C. Dumas, E. Jehin, J. Manfroid, B. Carry & J.-M. Zucconi

"Asteroids, Comets, Meteors" Meeting, July 2008 (NASA/Ads, BibTeX)

The dwarf-planet (IAU 2006) Ceres, whose mass represents 30 to 40% of the Main Belt, was discovered in 1801 by the Italian astronomer Giuseppe Piazzi. Ceres possesses several intriguing physical characteristics. Among them, a mean density estimated to be near 2.1 g.cm-3, suggests that the shape of Ceres is the result of a rocky core surrounded by an ice-rich mantle.
A large number of multi-wavelengths observations of Ceres' surface have been carried out in the past years in order to investigate the presence of ices. Thus, some near infrared spectra have been found compatible with the presence of water ice in some regions of Ceres' surface.
Moreover, long-exposure IUE spectra of the region around the limbs of Ceres have been conducted by A'Hearn & Feldman (1992) to explore the possibility that OH resulting from the photodissociation of atmospheric water vapor might escape. They reported the detection of OH above the northern limb of Ceres after perihelion while no evidence of this radical has been found off the southern hemisphere before perihelion.
High resolution spectra were acquired with the Ultraviolet and Visual Echelle Spectrograph (UVES) of the ESO VLT under very good seeing, low airmass (~1.3) and photometric weather. The slit was placed within a few arcseconds off both Ceres' poles to search for the 309 nm OH emission lines which would reveal water escaping from the dwarf planet.
After data reduction with the UVES ESO pipeline and the subtraction of a solar spectrum in order to remove the contamination from sunlight reflected by Ceres within the slit no OH emission line is detected on both northern or southern poles. We will present our observations which permit to derive an upper limit for the OH quantity along the line of sight, as well as for the water production rate of Ceres. Because our observations were conducted with a combination telescope+instrument more sensitive than IUE they contradict the positive detection published by A'Hearn & Feldman. We will discuss the possible reasons for this contradictory result.

A. Conrad, W. Merline, J. Drummond, B. Carry, C. Dumas, P. Tamblyn, C. Chapman, R. Campbell & R. Goodrich

"Asteroids, Comets, Meteors" Meeting, July 2008 (NASA/Ads, BibTeX)

Introduction: We present imaging data on 4 larger asteroids, taken with adaptive optics (AO) on large telescopes, with high spatial and rotational resolution. The resulting shapes can be compared with previous shape models derived from inversion of lightcurve data, and the agreement is generally good. The orbit of a satellite discovered orbiting one of these, taken together with volume estimates determined from shape measurements, will yield an exceptionally accurate density for that object.
Resolved Asteroid Program: The physical and statistical study of asteroids requires accurate knowledge of their shape, size, and pole position. Improved size permits improved estimates of albedo, in turn allowing better interpretation of surface composition. In those cases where we have an estimate of the mass, e.g. from the presence of a satellite, uncertainty in an asteroid's volume is the overwhelming uncertainty in attempts to derive its density. Of course, density is the single most critical observable having a bearing on bulk composition, porosity, and internal structure.
Direct, accurate, measurements of asteroid shapes, sizes, and poles are now possible for larger asteroids, which can be well resolved using AO on large ground-based telescopes.

B. Carry, C. Dumas, M. Kaasalainen, J. Berthier, R. Gil-Hutton, W. Merline, J. Drummond, D. Hestroffer, M. Fulchignoni, A. Conrad & S. Erard

"Asteroids, Comets, Meteors" Meeting, July 2008 (NASA/Ads, BibTeX)

Introduction Asteroid 2 Pallas is the third largest asteroid and until very recently, its physical properties were only loosely constrained. We developed a tool allowing us to combine asteroid shapes measured from adaptive optics (AO) images with light-curves (LC) inversion techniques. LC inversion brings long-term constrains on asteroid spin axis and 3-D shape, without providing absolute measure of its size, nor any surface information. On the other hand, high angular-resolution images provide a direct measurement of an asteroid shape and absolute size, as well as albedo information, but require good rotational phase sampling to derive pole and shape solutions.
Observations We thus compiled near-infrared, high angular-resolution images, with equivalent spatial resolution of about 60 km, obtained within six observation programs conducted at the Keck II Observatory (2) and the ESO Very Large Telescope (4) between 2003 and 2007. The observations span a range of sub-Earth latitudes and longitudes on the asteroid, providing constraints on Pallas' shape from different observing geometries.
Spin, Size and 3-D Shape From LC/AO combined analysis, we removed the ambiguity of the pole solution resulting from the LC only observations. We determined that the coordinates of Pallas' spin vector are within 5 deg of (λ=35°, β=-12°) in ECJ2000.0. We also derived a 3-D model (2038 facets - 276 x 266 x 243 km ± 10 km) rendering Pallas' shape. Such a model allows refined volume measurement. Considering Pallas' mass measurement distribution, its density (2.8 to 5.4 g.cm-3) is now limited by the mass uncertainty. Pallas' tri-axial values found here are smaller (but consistent) with HST measurements, implying a higher density. We also detected a large, flat surface feature, which may have been created by the impact that formed the Pallas family.
Surface Mapping We produced near-infrared broad-band albedo maps of Pallas' surface. These maps, covering 40%, 40% and 70% of Pallas' surface in J, H and K-band respectively, reveal albedo variations of nearly 10% across its surface.

B. Carry, P. Vernazza & C. Dumas

Asteroids, Comets, Meteors"Asteroids, Comets, Meteors" Meeting, July 2008 (NASA/Ads, BibTeX)

Introduction: Asteroid (4) Vesta, target of NASA's Dawn mission, is the only known asteroid with a possibly differentiated internal structure. Geological diversity across Vesta's surface has been first reported from Earth-based disk-integrated spectrophotometry; and HST imagery revealed strong albedo variations across its surface, whose origin has not yet been determined. Ion irradiation experiments on Eucrite meteorite have shown that, if solar wind ions do reach the surface of Vesta, its reflectance spectrum should be much redder and its albedo lower. Thus, the similar albedo and NIR reflectance spectrum displayed by Vesta and the HED meteorites reveals Vesta's surface to be either (a) free from heavy space weathering, or (b) continuously refreshed. Both processes have been discussed: the action of local magnetic field (with a required strength at the surface of only ~0.2 μT) has been proposed to explain Vesta shielding from solar wind ions (space weathering), and regolith activity will bring fresh material on surface. Regolith processes can be triggered by global seismic activities (from the giant crater relaxation), or the fall of small-sized debris (~1m) launched from the impact basin and remained in Vesta's gravitational influence.
Observations: We observed Vesta over the 1.1-2.4 μm range during the Science Verification program of SINFONI, the ESO integral-field spectrograph mounted on Cassegrain focus of UT4 at VLT. The observations were obtained in August and October 2004, under good atmospherical conditions, while the asteroid was fully resolved by the system: SINFONI provides a spetral resolution of ~1500 over the range and the AO correction provided a resolution element of about 80 milli-arcsec at 2 micron, corresponding to ~95 km on Vesta.
Surface Analysis: We will present the results inferred from near-infrared wavelength: 1. We compared Vesta's spectra to those of laboratory measured HED meteorites and Augite minerals (clinopyroxene) catalogued in the RELAB database in order to investigate Vesta's pyroxene composition: no clinopyroxene-rich area was detected, and Vesta's overall spectrum is consistent with howardite meteorites. 2. We mapped the distribution of spectral slope and compared it to the albedo distribution obtained from HST to test the magnetic field hypothesis, although the definitive answer will come from NASA Dawn mission.

A. Conrad, R. Campbell, R. Goodrich, D. Le Mignant, W. Merline, J. Drummond, C. Dumas & B. Carry

American Astronomical Society, DPS meeting #39, October 2007 (NASA/Ads, BibTeX)

The impact of a 10-meter telescope on solar-system science began in 1994 when comet Shoemaker-Levy 9 collided with Jupiter. Shortly after Keck's observation of this event, the advent of adaptive optics ushered in an explosion of solar-system observation opportunities, including volcanoes on Io, binary asteroids, rings of outer planets, clouds on Titan, shapes of main belt asteroids, imaging near-Earth asteroids, and the study of larger-than-Pluto Kuiper Belt Objects. Seeing limited (non-AO) observations also continue, including the color characterization of Kuiper Belt Objects, and, more recently, measuring the post-impact chemical abundances of Comet 9P/Tempel 1. The continuing discoveries of planets around other stars, one of Keck's greatest achievements, stands as another example of non-AO science which, although not strictly classified as solar-system science, has major implications for understanding our own solar system.
As we enter the next phase of adaptive optics capability, which for Keck includes a new wavefront controller with a limiting magnitude of 14.5, and a laser guide-star system with a limiting magnitude of 18, new solar-system discovery opportunities are within our grasp. While meeting the technical challenges of these new technologies, ground-based observing faces the related challenge of scheduling telescope time to meet the phase coverage requirements and ability to react to time-critical events required for efficient exploration of the solar-system from the ground.
We review the last 10 years of discovery, and discuss the opportunities and challenges of future technologies and scheduling strategies. In addition to this overview, we also provide specifics of recent work by the authors, including characterization of asteroid (511) Davida's physical properties.

M. Kaasalainen, F. Marchis & B. Carry

American Astronomical Society, DPS meeting #39, October 2007 (NASA/Ads, BibTeX)

While disk-integrated photometry is the main source of information on most asteroids, adaptive optics can provide some disk-resolved data on many larger (main-belt) asteroids. Asteroid models from lightcurve inversion agree well with the obtained AO images (Marchis et al. 2006, Icarus 185,39), but even more detailed models can be obtained by combining the two sources in inversion. In addition to giving more detail to existing models, the approach can also be used to obtain models of asteroids for which the photometric data are yet insufficient alone. This also helps to calibrate the inversion and deconvolution processes related to the separate sources; e.g., whether features apparently revealed by AO post-processing are real or artificial. We present some examples and discuss the resolution level of topographic detail in the resulting models. Hundreds of asteroids can be mapped in this way in the near future.

B. Carry, M. Kaasalainen, C. Dumas, J. Berthier, W. Merline, A. Conrad, D. Hestroffer, M. Fulchignoni & S. Erard

American Astronomical Society, DPS meeting #39, October 2007 (NASA/Ads, BibTeX)

We imaged Pallas at high-angular resolution in the J, H and K near-infrared bands using adaptive-optics-equipped cameras at the Keck II and ESO VLT observatories during its 2003 and 2005 oppositions (angular diameter of 0.44 and 0.57 arcsec respectively).
The J-, H- and K-band theoretical resolution element of 28, 37 and 45 km respectively on Pallas' surface were restored by image deconvolution [MISTRAL, Conan et al., 2000]. The very high spatial resolution of the images (~10 resolution elements across the diameter in K) allowed us to extract the edge contour of the asteroid from the individual images using a wavelet analysis and to model its size (276 x 256 x 248 km, ± 10 km).
From comparison between our AO-measured edges and previous lightcurve inversion results [Torppa et al., 2003], we were able to refine Pallas' shape model as well as the solution for its spin vector coordinates (Ecliptic J2000.0 λ=34 ± 5° and β=-11 ± 5°).
We will present the results of our analysis, including the first near-infrared maps of Pallas revealing albedo variations of 4 percent across its surface.

B. Carry, C. Dumas, M. Fulchignoni, T. Fusco & W. Merline

American Astronomical Society, DPS meeting #38, September 2006 (NASA/Ads, BibTeX)

Adaptive optics NIRC2 images of asteroid 1 Ceres have been obtained at Keck Observatory on Sep. 22 and 28, 2002 at phase angle of 7° and 5° respectively. Their optimal spatial resolution was restored using the Mistral deconvolution algorithm [Conan and al., ESO Messenger 2000]. Analysis of our set of deconvolved images allowed us to determine the direction of the spin axis (α=289±-5°, δ=69±5°), which is in agreement with previous study [Thomas et al., Nature 2005], and to produce J/H/K -band high-spatial resolution maps covering 80% of Ceres surface. These first near-infrared maps reveal several albedo features whose intensity variation is of the order of ±6% with respect to the mean surface albedo. The finest details visible on the surface of Ceres are about 40km wide and the largest surface feature sustains a diameter of about 160km. We will present the results of our analysis, including the multi-color near-infrared maps and their reprojection onto a 3-D model of Ceres.

C. Dumas, W. Merline, A. Barucci, C. de Bergh, B. Carry, M. Fulchignoni, A. Guilbert & F. Merlin

American Astronomical Society, DPS meeting #38, September 2006 (NASA/Ads, BibTeX)

We recently started a program of observations of small solar system bodies using SINFONI, the new [1.0-2.5] μm near-infrared integral-field adaptive-optics-equipped spectrograph installed at the Cassegrain focus of the Yepun 8m telescope at the ESO-Paranal observatory. In this poster we will present our first results obtained on the surface of Pluto's satellite Charon and the large main-belt asteroid 4 Vesta. A separate presentation given at this DPS meeting by Merlin et al. will cover the results obtained on the large Trans-Neptunians Objects 2003 UB313 and 2003 EL61.
High-SNR reflectance spectra (R~1500) of Charon were obtained in 2005 across the H-K spectral bands for three separate orbital positions of the satellite corresponding to intermediate elongations from Pluto (~0.6"). Combined with the published HST-NICMOS results, these data confirmed that the 2.21 μm absorption band attributed to ammonia hydrate is present over the entire surface of Charon. We will present the complete analysis of our spectral data using Hapke models for bi-directional reflectance of solid ices.
We also observed the differentiated asteroid 4 Vesta with SINFONI across the J and H+K bands (R~3000 and 1500 respectively) at various rotational phases in order to map the distribution of minerals on its surface. The observations were obtained in August and October 2004, while the asteroid displayed an aspect angle close to 0°, and Vesta (angular diameter 0.5") was fully resolved by the system. The 3-D spectroscopic capabilities of SINFONI, combined with the availability of an adaptive optics mode, are perfectly adapted to carryout a detailed mineralogical study of the surface of small solar system bodies. We will present the results of mapping the variations in the strength and shape of the pyroxene and olivine bands across the surface of Vesta and how they compare with the HST results obtained during the 1994 opposition.