Papers by Laurent Galluccio
2009 IEEE International Workshop on Machine Learning for Signal Processing, 2009
This paper focusses on a new clustering method called evidence accumulation clustering with dual ... more This paper focusses on a new clustering method called evidence accumulation clustering with dual rooted prim tree cuts (EAC-DC), based on the principle of cluster ensembles also known as "combining multiple clustering methods". A simple weak clustering algorithm is introduced based upon the properties of dual rooted minimal spanning trees and it is extended to multiple rooted trees. Co-association measures are proposed that account for the cluster sets obtained by these methods. These are exploited in order to obtain new ensemble consensus clustering algorithms. The EAC-DC methodology applied to both real and synthetic data sets demonstrates the superiority of the proposed methods.
Publication in the conference proceedings of EUSIPCO, Aalborg, Denmark, 2010
Unsupervised clustering on astrophyics data: Asteroid reflectance spectra survey and hyperspectral images
International audienc
Classification non supervisée de données basée sur de multiples partitionnements d'un nouveau graphe
National audienc
Astronomy & Astrophysics
Context. Observational and instrumental difficulties observing small bodies below 0.5 μm make thi... more Context. Observational and instrumental difficulties observing small bodies below 0.5 μm make this wavelength range poorly studied compared with the visible and near-infrared. Furthermore, the suitability of many commonly used solar analogues, essential in the computation of asteroid reflectances, is usually assessed only in visible wavelengths, while some of these objects show spectra that are quite different from the spectrum of the Sun at wavelengths below 0.55 μm. Stars HD 28099 (Hyades 64) and HD 186427 (16 Cyg B) are two well-studied solar analogues that instead present spectra that are also very similar to the spectrum of the Sun in the wavelength region between 0.36 and 0.55 μm. Aims. We aim to assess the suitability in the near-ultraviolet (NUV) region of the solar analogues selected by the team responsible for the asteroid reflectance included in Gaia Data Release 3 (DR3) and to suggest a correction (in the form of multiplicative factors) to be applied to the Gaia DR3 aste...
VizieR Online Data Catalog: Gaia GraL. III. New lensed systems (Delchambre+, 2019)
The Gaia GraL catalogue of clusters consist of 2,058,962 clusters with three components and 70,69... more The Gaia GraL catalogue of clusters consist of 2,058,962 clusters with three components and 70,697 clusters with four components. Each of these clusters satisfied the following conditions: i) Clusters are composed of three or four images in order to provide a sufficient number of constraints for identifying gravitational lens candidates. ii) Their constituent images have negligible parallaxes, plx, and proper motions, (pmra', pmdec) where pmra' = pmra * cos(dec). Specifically, we required that plx-3*e_plx<4mas and abs(pm)-3*epm<4mas (where eX is the mean error on X and pm stands for pmra' and pmdec). iii) The maximal angular separation between any pair of images is below or equal to 6 arcsec. iv) The absolute difference in G magnitude between components is lower or equal to 4mag. v) Clusters are located in regions with a mean field density lower than 60000 objects/deg2. The mean density of objects is computed within a radius of 30 arcsec around each cluster. Based ...
Gaia DR2 documentation Chapter 4: Solar-System Objects
VizieR Online Data Catalog: 46 open clusters GaiaDR2 HR diagrams (Gaia Collaboration, 2018)
VizieR On-line Data Catalog: J/A+A/616/A10. Originally published in: 2018A&A...616A..10GWe ha... more VizieR On-line Data Catalog: J/A+A/616/A10. Originally published in: 2018A&A...616A..10GWe have determined the membership of 46 open clusters. For the nine clusters within 250pc we determined optimised parallaxes based on the combined information extracted from the measured parallax and proper motion values. These clusters are : in Tables A1a & A3: alphaPer, Blanco1, ComaBer, Hyades, IC2391, IC2602, NGC2451A, Pleiades, Praesepe. The remaining 37 clusters are in Table A1b & A4: Coll140, IC4651, IC4665, IC4725, IC4756, NGC0188, NGC0752, NGC0869, NGC0884, NGC1039, NGC1901, NGC2158, NGC2168, NGC2232, NGC2323, NGC2360, NGC2422, NGC2423, NGC2437, NGC2447, NGC2516, NGC2547, NGC2548, NGC2682, NGC3228, NGC3532, NGC6025, NGC6281, NGC6405, NGC6475, NGC6633, NGC6774, NGC6793, NGC7092, Stock2, Trump02, Trump10. (4 data files)
Astronomy & Astrophysics, 2021
Aims. We produce a clean and well-characterised catalogue of objects within 100 pc of the Sun fro... more Aims. We produce a clean and well-characterised catalogue of objects within 100 pc of the Sun from the Gaia Early Data Release 3. We characterise the catalogue through comparisons to the full data release, external catalogues, and simulations. We carry out a first analysis of the science that is possible with this sample to demonstrate its potential and best practices for its use. Methods. Theselection of objects within 100 pc from the full catalogue used selected training sets, machine-learning procedures, astrometric quantities, and solution quality indicators to determine a probability that the astrometric solution is reliable. The training set construction exploited the astrometric data, quality flags, and external photometry. For all candidates we calculated distance posterior probability densities using Bayesian procedures and mock catalogues to define priors. Any object with reliable astrometry and a non-zero probability of being within 100 pc is included in the catalogue. Re...
Proceedings of the International Astronomical Union, 2017
Because of to its exceptional resolving power, Gaia should detect a few thousands gravitational l... more Because of to its exceptional resolving power, Gaia should detect a few thousands gravitational lensed systems. These consist in multiple images of background quasars. The estimated number of lens phenomena in the sky, however, depends on the cosmological model considered. By taking into account the observational bias that will restrict the detection of lensed quasars, identification of these up to a given limiting magnitude will constrain the cosmological parameters.We have investigated the known gravitationally lensed quasars present in the Gaia DR1, and found that a significant number of components of these systems have been measured and are present in the Gaia DR1 catalogue although quasi none of them have all their components detected. We additionally examined the immediate surroundings of QSOs from the large Quasar catalogue, LQAC3, and detected several configurations compatible with gravitational lensing phenomena. A more global strategy to systematically detect the potential...
Proceedings of the International Astronomical Union, 2017
A new asteroid taxonomy will be an important result of Gaia observations of Solar System objects.... more A new asteroid taxonomy will be an important result of Gaia observations of Solar System objects. Since Gaia observes asteroids in observing conditions and in an interval of wavelength which are slightly different with respect to normal ground-based observations, a dedicated observing campaign has been carried out at the Telescopio Nazionale Galileo in La Palma (Canary Islands, Spain). The obtained spectra have been used to generate a large number of synthetic clones, each one having slight changes with respect to its parent spectrum. These synthetic spectra are then used to feed the algorithm of taxonomic classification developed to reduce Gaia asteroid spectra. Processing of these data is in progress.
Astronomy & Astrophysics, 2016
Gaia is a cornerstone mission in the science programme of the European Space Agency (ESA). The sp... more Gaia is a cornerstone mission in the science programme of the European Space Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach. Both the spacecraft and the payload were built by European industry. The involvement of the scientific community focusses on data processing for which the international Gaia Data Processing and Analysis Consortium (DPAC) was selected in 2007. Gaia was launched on 19 December 2013 and arrived at its operating point, the second Lagrange point of the Sun-Earth-Moon system, a few weeks later. The commissioning of the spacecraft and payload was completed on 19 July 2014. The nominal five-year mission started with four weeks of special, ecliptic-pole scanning and subsequently transferred into full-sky scanning mode. We recall the scientific goals of Gaia and give a description of the as-built spacecraft that is currently (mid-2016) being operated to achieve these goals. We pay special attention to the payload module, the performance of which is closely related to the scientific performance of the mission. We provide a summary of the commissioning activities and findings, followed by a description of the routine operational mode. We summarise scientific performance estimates on the basis of in-orbit operations. Several intermediate Gaia data releases are planned and the data can be retrieved from the Gaia Archive, which is available through the Gaia home page.
The payload of the Gaia space probe includes detectors (Blue Photometer: BP and Red Photometer: R... more The payload of the Gaia space probe includes detectors (Blue Photometer: BP and Red Photometer: RP) designed to obtain spectro-photometric data from blue to red (from 330 to 1050 nm). Asteroid data obtained by these detectors will be used to derive reflectance spectra for a number of the order of 100,000 objects [3]. Based on this database , it will be possible to develop a new asteroid taxonomy. The big advantage of this will be that of including, for the first time after many years, also the blue part of the reflectance spectrum, which has been essentially lost during the last decades in all the most modern ground-based CCDbased asteroid spectroscopic surveys. The blue part of the reflectance spectrum is essential to discriminate among different sub-classes of the big C-complex, including the most primitive asteroids which are known to exist. A particular attention will be devoted to the F taxonomic class, which is characterized by interesting polarimetric properties. In order to prepare the algorithms needed for building the planned Gaia asteroid taxonomy, a campaign of spectroscopic observations covering the same wavelength interval, and obtained at the same phase angles which will characterize Gaia observations, has been carried out at TNG. The state of the art in these activities will be briefly summarized.
HAL (Le Centre pour la Communication Scientifique Directe), Jul 2, 2017
In the context of the ESA M5 (medium mission) call we proposed a new satellite mission, Theia, ba... more In the context of the ESA M5 (medium mission) call we proposed a new satellite mission, Theia, based on relative astrometry and extreme precision to study the motion of very faint objects in the Universe. Theia is primarily designed to study the local dark matter properties, the existence of Earth-like exoplanets in our nearest star systems and the physics of compact objects. Furthermore, about 15 % of the mission time was dedicated to an open observatory for the wider community to propose complementary science cases. With its unique metrology system and "point and stare" strategy, Theia's precision would have reached the sub micro-arcsecond level. This is about 1000 times better than ESA/Gaia's accuracy for the brightest objects and represents a factor 10-30 improvement for the faintest stars (depending on the exact observational program). In the version submitted to ESA, we proposed an optical (350-1000nm) on-axis TMA telescope. Due to ESA Technology readiness level, the camera's focal plane would have been made of CCD detectors but we anticipated an upgrade with CMOS detectors. Photometric measurements would have been performed during slew time and stabilisation phases needed for reaching the required astrometric precision.
Gaia spectroscopic view of asteroid collisional families: preliminary results
&lt;p&gt;The Gaia mission of the European Space Agency (ESA) was launched in December 201... more &lt;p&gt;The Gaia mission of the European Space Agency (ESA) was launched in December 2013 and began it scientific operations in July 2014. Gaia is essentially devoted to the measurement&lt;span class="Apple-converted-space"&gt;&amp;#160; &lt;/span&gt;of positions, parallaxes, proper motions, brightnesses, and colours of stars. However, Gaia has also obtained astrometric, photometric, and spectroscopic measurements for several hundreds of thousands of asteroids.&lt;span class="Apple-converted-space"&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt; &lt;p&gt;The Gaia Data Release 3 (DR3) is the first to contain low resolution reflectance spectra of 60,518 solar system small bodies, the large majority of which are asteroids of the main belt (Gaia collaboration, Galluccio, Delbo et al. 2022). The global survey properties, the methods of data production and validation are detailed in the aforementioned paper published by the journal Astronomy and Astrophysics, which accompanies the DR3, and also summarised in the presentation of Galluccio et al. (2022) at this conference (EPSC 2022).&lt;span class="Apple-converted-space"&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt; &lt;p&gt;Here we present preliminary results about the Gaia view of asteroid collisional families. We identified asteroids belonging to families during the validation of Gaia asteroid spectra. Based on the family identification of Nesvorny et al. (2015), with the addition of the New Polana and the Eulalia families from Walsh et al. (2013), we found that in the Gaia DR3 there are 25,088 asteroids that belong to 116 collisional asteroid families of the 121 listed in Tab.1. This table also reports the number of family members and the number of members with a Gaia DR3 reflectance spectrum. However, the family identification of current catalogues is conservative by construction in order to keep good separation between the families. Hence, it is very likely that (i) some of the known families are more extended than what is available in current catalogues, namely, that catalogues based on dynamical criteria do not capture the whole extent of a family, and (ii) some unknown families are yet to be identified. This implies that the aforementioned number of asteroid family members with Gaia DR3 reflectance spectra is likely an estimation lower than the true number.&lt;span class="Apple-converted-space"&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt; &lt;p&gt;We will present some important features that Gaia observed in families. One of these is the correlation between some spectral parameters, such as the slope and the depth of the 1-micron absorption band of the reflectance spectrum, and the age of members of asteroid families belonging to the so called spectroscopic S-complex (DeMeo et al. 2009). These correlations can be explained in terms of a space weathering process that reddens and reduces the 1-band depth as a function of time on S-complex asteroids.&lt;/p&gt; &lt;p&gt;For the brightest asteroids, the extension of Gaia reflectance spectra at wavelengths shorter than 0.45 micron is very useful for distinguishing the composition of primitive, carbonaceous asteroid families, which are difficult to be discriminated with the ground based spectroscopic data currently present in the literature.&lt;span class="Apple-converted-space"&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt; &lt;p&gt;References:&lt;/p&gt; &lt;p&gt;- DeMeo, F. E., Binzel, R. P., Slivan, S.~M., Bus, S. J. 2009. Icarus 202, 160&amp;#8211;180.&lt;/p&gt; &lt;p&gt;- Gaia collaboration, Galluccio, Delbo et al. 2022. A&amp;A under review.&lt;span class="Apple-converted-space"&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt; &lt;p&gt;- Nesvorn&amp;#253;, D., Bro&amp;#382;, M., &amp; Carruba, V. 2015. &amp;#160;in Asteroids IV (P. Michel, et al. eds.) University of Arizona Press, Tucson.,&lt;/p&gt; &lt;p&gt;- Walsh, K. J., Delbo, M., et al. 2013. Icarus 225, 283&amp;#8211;297.&lt;span class="Apple-converted-space"&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt; &lt;p&gt;&lt;img src="" alt="" /&gt;&lt;/p&gt; &lt;p&gt;&lt;img src="" alt="" /&gt;&lt;/p&gt;
Searching for parent bodies of differentiated meteorites in the main-belt using visible and near-infrared spectroscopy
&lt;p&gt;&lt;span dir="ltr" role="presentation"&gt;Finding a ... more &lt;p&gt;&lt;span dir="ltr" role="presentation"&gt;Finding a link between meteorites and asteroids thanks to spectroscopy gives a great insight of the composition of &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;the bodies in the asteroid population. Meteorites such as the Howardite-Ensatites-Diogenites (HEDs) have been &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;successfully linked to the asteroid Vesta (McCord et al. (1970), summary by McSween Jr. et al. (2013)), and the&lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt; ordinary chondrite meteorite population has been connected to a subtype of S-type asteroids, after having taken into &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;account space weathering processes (Binzel et al. 2001). These processes alter the surface of asteroids and modify&lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt; their reflectance spectra with respect to that of the fresher meteorites, hence they need to be taken into account&lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt; prior to comparing asteroids with meteorites spectra (Hapke 2001). Other meteorite types have been studied and &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;linked to asteroid types, but some objects still do not show convincing connections (DeMeo et al. 2022).&lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt; Linking meteorites to the primordial population of objects would give information about the formation and &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;evolution of bodies in the Solar System. Indeed, the planetesimals that formed earliest in the Solar System are &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;thought to have been fully differentiated, due to the melting induced by the heating produced by the radioactive &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;decay of&lt;/span&gt; &lt;span dir="ltr" role="presentation"&gt;26&lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;Al isotopes. This should have resulted in planetesimals presenting a basaltic crust, an olivine-dominated&lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt; mantle and an iron-rich core (DeMeo et al. 2019). However most of these primitive objects have evolved, have &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;been disrupted or integrated to other bodies (such as planets) and their formation processes and the composition of &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;their primordial crusts is not well known.&lt;/span&gt;&lt;br role="presentation" /&gt;&lt;br role="presentation" /&gt;&lt;span dir="ltr" role="presentation"&gt;We will report about searching for potential parents bodies of meteorites coming from differentiated planetesimals, &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;using literature data and the new dataset of reflectance spectra that will be released in the Gaia Data Release 3 &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;(DR3) in June 2022. This dataset will present low resolution mean reflectance spectrum of 60 518 Solar System &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;objects, acquired by Gaia&amp;#8217;s blue and red spectrophotometers (BP and RP) between August 2014 and May 2017. &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;Each spectrum will consist of 16 discrete wavelength bands that spans the visible wavelength range from 374 to &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;1034 nm (Gaia collaboration, Galluccio, Delbo et al. 2022). &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;These data should allow to look inside asteroid collisional families and search for hints of differentiation, &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;looking for members corresponding to the crust, mantle or core of a disrupted planetesimal. We intend to use these &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;data to try to link meteorites that are known to have been produced by differentiation (e.g. metallic or andesitic &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;bodies) to the primordial population of asteroids. Finding the parent body of differentiated meteorites would allow &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;to understand better the formation and differentiation of planetesimals in our Solar System.&lt;/span&gt;&lt;br role="presentation" /&gt;&lt;br role="presentation" /&gt;&lt;span dir="ltr" role="presentation"&gt;To compare the reflectance spectra of meteorites with Gaia&amp;#8217;s asteroids, we will first use a curve matching method. &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;Curve matching consists in determining whether any given spectrum is similar to a reference spectrum, by the &lt;/span&gt;&lt;span dir="ltr" role="presentation"&gt;means of a coefficient that has to be minimized (such as the&lt;/span&gt; &lt;span dir="ltr"…
Astronomy & Astrophysics
Context. The Gaia mission of the European Space Agency (ESA) has been routinely observing Solar S... more Context. The Gaia mission of the European Space Agency (ESA) has been routinely observing Solar System objects (SSOs) since the beginning of its operations in August 2014. The Gaia data release three (DR3) includes, for the first time, the mean reflectance spectra of a selected sample of 60 518 SSOs, primarily asteroids, observed between August 5, 2014, and May 28, 2017. Each reflectance spectrum was derived from measurements obtained by means of the Blue and Red photometers (BP/RP), which were binned in 16 discrete wavelength bands. For every spectrum, the DR3 also contains additional information about the data quality for each band. Aims. We describe the processing of the Gaia spectral data of SSOs, explaining both the criteria used to select the subset of asteroid spectra published in Gaia DR3, and the different steps of our internal validation procedures. In order to further assess the quality of Gaia SSO reflectance spectra, we carried out external validation against SSO reflectance spectra obtained from ground-based and space-borne telescopes and available in the literature; we present our validation approach. Methods. For each selected SSO, an epoch reflectance was computed by dividing the calibrated spectrum observed by the BP/RP at each transit on the focal plane by the mean spectrum of a solar analogue. The latter was obtained by averaging the Gaia spectral measurements of a selected sample of stars known to have very similar spectra to that of the Sun. Finally, a mean of the epoch reflectance spectra was calculated in 16 spectral bands for each SSO. Results. Gaia SSO reflectance spectra are in general agreement with those obtained from a ground-based spectroscopic campaign specifically designed to cover the same spectral interval as Gaia and mimic the illumination and observing geometry characterising Gaia SSO observations. In addition, the agreement between Gaia mean reflectance spectra and those available in the literature is good for bright SSOs, regardless of their taxonomic spectral class. We identify an increase in the spectral slope of S-type SSOs with increasing phase angle. Moreover, we show that the spectral slope increases and the depth of the 1 µm absorption band decreases for increasing ages of S-type asteroid families. The latter can be interpreted as proof of progressive ageing of S-type asteroid surfaces due to their exposure to space weathering effects.
Astronomy & Astrophysics
Context. We present the third data release of the European Space Agency's Gaia mission, Gaia DR3.... more Context. We present the third data release of the European Space Agency's Gaia mission, Gaia DR3. This release includes a large variety of new data products, notably a much expanded radial velocity survey and a very extensive astrophysical characterisation of Gaia sources. Aims. We outline the content and the properties of Gaia DR3, providing an overview of the main improvements in the data processing in comparison with previous data releases (where applicable) and a brief discussion of the limitations of the data in this release. Methods. The Gaia DR3 catalogue is the outcome of the processing of raw data collected with the Gaia instruments during the first 34 months of the mission by the Gaia Data Processing and Analysis Consortium. Results. The Gaia DR3 catalogue contains the same source list, celestial positions, proper motions, parallaxes, and broad band photometry in the G, G BP , and G RP pass-bands already present in the Early Third Data Release, Gaia EDR3. Gaia DR3 introduces an impressive wealth of new data products. More than 33 million objects in the ranges G RVS < 14 and 3100 < T eff < 14500, have new determinations of their mean radial velocities based on data collected by Gaia. We provide G RVS magnitudes for most sources with radial velocities, and a line broadening parameter is listed for a subset of these. Mean Gaia spectra are made available to the community. The Gaia DR3 catalogue includes about 1 million mean spectra from the radial velocity spectrometer, and about 220 million low-resolution blue and red prism photometer BP/RP mean spectra. The results of the analysis of epoch photometry are provided for some 10 million sources across 24 variability types. Gaia DR3 includes astrophysical parameters and source class probabilities for about 470 million and 1500 million sources, respectively, including stars, galaxies, and quasars. Orbital elements and trend parameters are provided for some 800 000 astrometric, spectroscopic and eclipsing binaries. More than 150 000 Solar System objects, including new discoveries, with preliminary orbital solutions and individual epoch observations are part of this release. Reflectance spectra derived from the epoch BP/RP spectral data are published for about 60 000 asteroids. Finally, an additional data set is provided, namely the Gaia Andromeda Photometric Survey, consisting of the photometric time series for all sources located in a 5.5 degree radius field centred on the Andromeda galaxy. Conclusions. This data release represents a major advance with respect to Gaia DR2 and Gaia EDR3 because of the unprecedented quantity, quality, and variety of source astrophysical data. To date this is the largest collection of all-sky spectrophotometry, radial velocities, variables, and astrophysical parameters derived from both low-and high-resolution spectra and includes a spectrophotometric and dynamical survey of SSOs of the highest accuracy. The non-single star content surpasses the existing data by orders of magnitude. The quasar host and galaxy light profile collection is the first such survey that is all sky and space based. The astrophysical information provided in Gaia DR3 will unleash the full potential of Gaia's exquisite astrometric, photometric, and radial velocity surveys.
Publication in the conference proceedings of EUSIPCO, Lausanne, Switzerland, 2008
Gaia spectroscopic view of the asteroid main belt and beyond
&amp;lt;div class=&quot;&quot;&amp;gt;Asteroids reflectance spectra in the visibl... more &amp;lt;div class=&quot;&quot;&amp;gt;Asteroids reflectance spectra in the visible light will be one of the novel products of the Gaia Data Release 3 (DR3). These spectra are produced from Gaia observations obtained by means of the blue and red photometers &amp;amp;#8212; the so-called BP and RP, respectively. We will review the strategy adopted to produce asteroid reflectance spectra from BP-RP data, focusing on the choice of spectro-photometric calibrations computed taking into account solar system object astrometry and suitable lists of solar-analog stars.&amp;lt;/div&amp;gt; &amp;lt;div class=&quot;&quot;&amp;gt;&amp;amp;#160;&amp;lt;/div&amp;gt; &amp;lt;div class=&quot;&quot;&amp;gt;Our preliminary investigation shows that we will be able to obtain reflectance spectra for asteroids as small as some km in the main belt, by exploiting the fact that each object has been observed multiple times by Gaia. We will show the capability of Gaia to probe the detailed compositional gradient of the main belt down to small sizes and to study correlations between spectral classes and other asteroid physical parameters, such as albedo and size.&amp;lt;/div&amp;gt; &amp;lt;div class=&quot;&quot;&amp;gt;&amp;amp;#160;&amp;lt;/div&amp;gt; &amp;lt;div class=&quot;&quot;&amp;gt;Concerning the brightest asteroids, we expect to have substantial signal at wavelengths shorter than 450 nm, allowing Gaia to examine this region of the spectrum that has been poorly investigated by ground-based asteroid spectroscopic surveys. This region is characterised by the presence of a reflectance downturn that is diagnostic for the composition of classes of primitive asteroids, for instance those including the parent bodies of carbonaceous chondrites. These asteroids may have played an important role for the delivery of prebiotic compounds to Earth during the early phases of solar system&#39; s history and, as such, are at the center of attention of the planetary science community.&amp;amp;#160;&amp;lt;/div&amp;gt;
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Papers by Laurent Galluccio