Publications (106)187.23 Total impact
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Article: The 2011 October Draconids Outburst. II. Meteoroid Chemical Abundances from Fireball Spectroscopy
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ABSTRACT: On October 8, 2011 the Earth crossed dust trails ejected from comet 21P/Giacobini-Zinner in the late 19th and early 20th Century. This gave rise to an outburst in the activity of the October Draconid meteor shower, and an international team was organized to analyze this event. The SPanish Meteor Network (SPMN) joined this initiative and recorded the October Draconids by means of low light level CCD cameras. In addition, spectroscopic observations were carried out. Tens of multi-station meteor trails were recorded, including an extraordinarily bright October Draconid fireball (absolute mag. -10.5) that was simultaneously imaged from three SPMN meteor ob-serving stations located in Andalusia. Its spectrum was obtained, showing a clear evolution in the relative intensity of emission lines as the fireball penetrated deeper into the atmosphere. Here we focus on the analysis of this remarkable spectrum, but also discuss the atmospheric trajectory, atmospheric penetration, and orbital data computed for this bolide which was probably released during 21P/Giacobini-Zinner return to perihelion in 1907. The spectrum is discussed together with the tensile strength for the October Draconid meteoroids. The chemical profile evolution of the main rocky elements for this extremely bright bolide is compared with the elemental abundances obtained for 5 October Draconid fireballs also recorded during our spectroscopic campaign but observed only at a single station. Significant chemical heterogeneity between the small meteoroids is found as we should expect for cometary aggregates being formed by diverse dust components.04/2013; -
Article: A portrait of the extreme Solar System object 2012 DR30
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ABSTRACT: 2012 DR30 is a recently discovered Solar System object on a unique orbit, with a high eccentricity of 0.9867, a perihelion distance of 14.54 AU and a semi-major axis of 1109 AU, in this respect outscoring the vast majority of trans-Neptunian objects. We performed Herschel/PACS and optical photometry to uncover the size and albedo of 2012 DR30, together with its thermal and surface properties. The body is 185 km in diameter and has a relatively low V-band geometric albedo of ~8%. Although the colours of the object indicate that 2012 DR30 is an RI taxonomy class TNO or Centaur, we detected an absorption feature in the Z-band that is uncommon among these bodies. A dynamical analysis of the target's orbit shows that 2012 DR30 moves on a relatively unstable orbit and was most likely only recently placed on its current orbit from the most distant and still highly unexplored regions of the Solar System. If categorised on dynamical grounds 2012 DR30 is the largest Damocloid and/or high inclination Centaur observed so far.04/2013; -
Conference Proceeding: PRELIMINARY RESULTS FROM THE 2011-2012 MOON IMPACT FLASHES MONITORING
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ABSTRACT: Introduction: The identification and analysis of flashes produced by the impact of meteoroids on the lunar surface is one of the techniques suitable for the study of the flux of interplanetary matter impacting the Earth. The first attempts to identify impact flashes produced by large meteoroids on the lunar surface by means of telescopic observations date back to 1997 [1]. Thus, impact flashes have been unambiguously detected during the maximum activity period of sev-eral major meteor showers by using this technique, and flashes of sporadic origin have been also recorded [2-9]. This method has the advantage that the area cov-ered by one single detection instrument is much larger than the atmospheric volume monitored by meteor detectors on Earth. It can be employed when the illu-minated fraction of the lunar disk varies between 10 and 60 %, i.e., during the first and last quarters. At least two telescopes must operate in parallel imaging the same area on the Moon in order to discard false detections produced by other phenomena such as, for instance, cosmic rays. Our team is performing a monitoring of the night side of the Moon from our observatory in Sevilla. This location provides very favourable statistics of clear nights per year. We employ several telescopes equipped with high-sensitivity CCD video cameras and we have also developed our own software to iden-tify and analyze impact flashes. Here we present a pre-liminary analysis of the main lunar impact flashes re-corded during our 2011 and 2012 campaigns. Instrumentation and data analysis methods: For impact flashes detection we employ an 11" and two 14" Celestron SC telescopes, all of them endowed with f/3.3 focal reducers and Watec 902H Ultimate CCD video cameras operating in PAL mode. These generate interlaced video files with a resolution of 720x576 pixels and a frame rate of 25 fps. With this configura-tion the limiting stellar magnitude is of about 12 and we approximately monitor about 5.8·10 6 km 2 ± 10% on the lunar surface. Large enough lunar features are easily visible in the earthshine and these can be used to determine the selenographic coordinates of impact flashes. The images taken by the CCD video cameras are stored and digitized on multimedia hard disks as AVI video files. GPS time inserters are used to stamp time on every video frame with a precision of 0.001 sec-onds. These video files are analyzed with our MIDAS software (Moon Impacts Detection and Analysis Soft-ware). This is Microsoft Windows application devel-oped under C++ computer language that automatically detects flashes produced by the impact of meteoroids on the lunar surface [10]. Detection algorithms have been recently improved in order to allow for a more efficient detection of flashes. For confirmed impacts a photometric analysis is performed and the software also establishes their likely origin by trying to link them to a given known meteoroid stream or to a spo-radic source.Lunar and Planetary Science Conference; 03/2013 -
Article: Visible and near-infrared observations of asteroid 2012 DA14 during itsclosest approach of February 15th, 2013
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ABSTRACT: Near-Earth asteroid 2012 DA14 made its closest approach on February 15th, 2013, when it passed at a distance of 27,700 km from the Earth's surface (inside the geosynchronous satellite ring). It was the first time an asteroid of moderate size was predicted to get that close to the Earth, becoming bright enough to permit a detailed study from ground based telescopes. Asteroid 2012 DA14 was poorly characterized before its closest approach. The main objective of this work was to obtain new and valuable data to better understand its physical properties, and to evaluate the effects of such a close approach on the object. We acquired data using several telescopes on four Spanish observatories: the 10.4m Gran Telescopio Canarias and the 3.6m Telescopio Nazionale Galileo, both in "El Roque de los Muchachos" Observatory (ORM, La Palma); the 2.2m CAHA telescope, in "Calar Alto2 Observatory (Almeria); the f/3 0.77m telescope in "La Hita" Observatory (Toledo); and the f/8 1.5m telescope in "Sierra Nevada" Observatory (Granada). We obtained visible and near-infrared colour photometry, visible spectra and time-series photometry. Visible spectra together with visible and near-infrared color photometry of 2012 DA14 show that the object can be classified as an L-type asteroid, a not very common spectral type among the asteroid population. The time-series photometry indicates a rotational period around 9 hours, and the large amplitude of the variation suggests that the object is very elongated and irregular, with an equivalent diameter around 22m. We obtain an absolute magnitude of H_R = 24.1 +- 0.2, corresponding to 24.6 +- 0.2 in V. From the absolute photometry, together with some constraints on size and shape, we compute a geometric albedo of p_V = 0.34 +- 0.20. http://arxiv.org/abs/1303.055403/2013; -
Article: A portrait of the extreme Solar System object 2012DR30
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ABSTRACT: 2012DR30 is a recently discovered Solar System object on a unique orbit, with a high eccentricity of 0.9867, a perihelion distance of 14.54AU and a semi-major axis of 1109AU, in this respect outscoring the vast majority of trans-Neptunian objects. We performed Herschel/PACS and optical photometry to uncover the size and albedo of 2012DR30, together with its thermal and surface properties. The body is 185 km in diameter and has a relatively low V-band geometric albedo of �8%. Although the colours of the object indicate that 2012DR30 is an RI taxonomy class TNO or Centaur, we detected an absorption feature in the Z-band that is uncommon among these bodies. A dynamical analysis of the target’s orbit shows that 2012DR30 moves on a relatively unstable orbit and was most likely only recently placed on its current orbit from the most distant and still highly unexplored regions of the Solar System. If categorised on dynamical grounds 2012DR30 is the largest Damocloid and/or high inclination Centaur observed so far.Astronomy and Astrophysics 01/2013; · 4.59 Impact Factor -
Article: Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation.
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ABSTRACT: Pluto and Eris are icy dwarf planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies. Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos. Makemake is another icy dwarf planet with a spectrum similar to Eris and Pluto, and is currently at a distance to the Sun intermediate between the two. Although Makemake's size (1,420 ± 60 km) and albedo are roughly known, there has been no constraint on its density and there were expectations that it could have a Pluto-like atmosphere. Here we report the results from a stellar occultation by Makemake on 2011 April 23. Our preferred solution that fits the occultation chords corresponds to a body with projected axes of 1,430 ± 9 km (1σ) and 1,502 ± 45 km, implying a V-band geometric albedo p(V) = 0.77 ± 0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4-12 nanobar (1σ) for the surface pressure, although a localized atmosphere is possible. A density of 1.7 ± 0.3 g cm(-3) is inferred from the data.Nature 11/2012; 491(7425):566-9. · 36.28 Impact Factor -
Conference Proceeding: Stellar Occultations by Large TNOs on 2012: The February 3rd by (208996) 2003 AZ84, and the February 17th by (50000) Quaoar
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ABSTRACT: On February 2012, two stellar occultation's by large Trans-neptunian Objects (TNO's) were observed by our group. On the 3rd, an event by (208996) 2003 AZ84 was recorded from Mont Abu Observatory and IUCAA Girawali Observatory in India and from Weizmann Observatory in Israel. On the 17th, a stellar occultation by (50000) Quaoar was observed from south France and Switzerland. Both occultations are the second observed by our group for each object, and will be used to improve the results obtained on the previous events. The occultation by 2003 AZ84 is the first multi-chord event recorded for this object. From the single chord event on January 8th 2011, Braga-Ribas et al. 2011 obtained a lower limit of 573 +/- 21 km. From the 2012 occultation the longest chord has a size of 662 +/- 50 km. The other chords will permit to determine the size and shape of the TNO, and derive other physical parameters, such as the geometric albedo. The Quaoar occultation was observed from south of France (Observatoire de la Côte d'Azur, TAROT telescope and Valensole) and from Gnosca, Switzerland. Unfortunately, all three sites in France are almost at the same Quaoar's latitude, so in practice, we have two chords that can be used to fit Quaoar's limb. The resulting fit will be compared with the results obtained by Braga-Ribas et al. 2011. Braga-Ribas F., Sicardy B., et al. 2011, EPSC-DPS2011, 1060.Ribas F., Sicardy B., et al. 2011, EPSC-DPS2011, 1060.AAS/Division for Planetary Sciences Meeting Abstracts; 10/2012 -
Article: Short-term variability of 10 trans-Neptunian objects
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ABSTRACT: We present our latest results about the short-term variability of trans-Neptunian objects (TNOs). We performed broad-band CCD photometric observations using several telescopes in Spain and Chile. We present results based on three years of observations and report the short-term variability of 10 TNOs. Our sample of studied targets contains classical objects: (275809) 2001 QY297, (307251) 2002 KW14, (55636) 2002 TX300, 2004 NT33, (230965) 2004 XA192, and (202421) 2005 UQ513, a resonant body: (84522) 2002 TC302, a scattered target: (44594) 1999 OX3, and two detached objects: (145480) 2005 TB190, and (40314) 1999 KR16. For each target, light curves as well as possible rotation periods and photometric amplitudes are reported. The majority of the observed objects present a low peak-to-peak amplitude, <0.15mag. Only two objects exhibit light curve amplitudes higher than 0.15mag: (275809) 2001 QY297, and (307251) 2002 KW14. We remark two biases in the literature, previously studied in Thirouin et al. (2010) and confirmed by this new study: a bias towards objects with a small amplitude light curve and a second one against objects with a long rotational period in the data base of published rotational periods. We derived constraints on physical properties of some targets. We also report the solar phase curves of (40314) 1999 KR16, and (44594) 1999 OX3 for solar phase angles from 0 degree to around 2 degrees. Part of our discussion is focused on the study of (275809) 2001 QY297 which turned out to be an asynchronous binary system.07/2012; -
Article: "TNOs are Cool": A survey of the trans-Neptunian region. IV. Size/albedo characterization of 15 scattered disk and detached objects observed with Herschel-PACS
åp. 05/2012; 541:A92. -
Article: "TNOs are Cool": A survey of the trans-Neptunian region VI. Herschel/PACS observations and thermal modeling of 19 classical Kuiper belt objects
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ABSTRACT: Trans-Neptunian objects (TNO) represent the leftovers of the formation of the Solar System. Their physical properties provide constraints to the models of formation and evolution of the various dynamical classes of objects in the outer Solar System. Based on a sample of 19 classical TNOs we determine radiometric sizes, geometric albedos and beaming parameters. Our sample is composed of both dynamically hot and cold classicals. We study the correlations of diameter and albedo of these two subsamples with each other and with orbital parameters, spectral slopes and colors. We have done three-band photometric observations with Herschel/PACS and we use a consistent method for data reduction and aperture photometry of this sample to obtain monochromatic flux densities at 70.0, 100.0 and 160.0 \mu m. Additionally, we use Spitzer/MIPS flux densities at 23.68 and 71.42 \mu m when available, and we present new Spitzer flux densities of eight targets. We derive diameters and albedos with the near-Earth asteroid thermal model (NEATM). As auxiliary data we use reexamined absolute visual magnitudes from the literature and data bases, part of which have been obtained by ground based programs in support of our Herschel key program. We have determined for the first time radiometric sizes and albedos of eight classical TNOs, and refined previous size and albedo estimates or limits of 11 other classicals. The new size estimates of 2002 MS4 and 120347 Salacia indicate that they are among the 10 largest TNOs known. Our new results confirm the recent findings that there are very diverse albedos among the classical TNOs and that cold classicals possess a high average albedo (0.17 +/- 0.04). Diameters of classical TNOs strongly correlate with orbital inclination in our sample. We also determine the bulk densities of six binary TNOs.04/2012; -
Article: TNOs are Cool: A survey of the trans-Neptunian region V. Physical characterization of 18 Plutinos using Herschel PACS observations
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ABSTRACT: We present Herschel PACS photometry of 18 Plutinos and determine sizes and albedos for these objects using thermal modeling. We analyze our results for correlations, draw conclusions on the Plutino size distribution, and compare to earlier results. Flux densities are derived from PACS mini scan-maps using specialized data reduction and photometry methods. In order to improve the quality of our results, we combine our PACS data with existing Spitzer MIPS data where possible, and refine existing absolute magnitudes for the targets. The physical characterization of our sample is done using a thermal model. Uncertainties of the physical parameters are derived using customized Monte Carlo methods. The correlation analysis is performed using a bootstrap Spearman rank analysis. We find the sizes of our Plutinos to range from 150 to 730 km and geometric albedos to vary between 0.04 and 0.28. The average albedo of the sample is 0.08 \pm 0.03, which is comparable to the mean albedo of Centaurs, Jupiter Family comets and other Trans-Neptunian Objects. We were able to calibrate the Plutino size scale for the first time and find the cumulative Plutino size distribution to be best fit using a cumulative power law with q = 2 at sizes ranging from 120-400 km and q = 3 at larger sizes. We revise the bulk density of 1999 TC36 and find a density of 0.64 (+0.15/-0.11) g cm-3. On the basis of a modified Spearman rank analysis technique our Plutino sample appears to be biased with respect to object size but unbiased with respect to albedo. Furthermore, we find biases based on geometrical aspects and color in our sample. There is qualitative evidence that icy Plutinos have higher albedos than the average of the sample.02/2012; -
Article: "TNOs are Cool": A Survey of the Transneptunian Region IV. Size/albedo characterization of 15 scattered disk and detached objects observed with Herschel Space Observatory-PACS
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ABSTRACT: Physical characterization of Trans-Neptunian objects, a primitive population of the outer solar system, may provide constraints on their formation and evolution. The goal of this work is to characterize a set of 15 scattered disk (SDOs) and detached objects, in terms of their size, albedo, and thermal properties. Thermal flux measurements obtained with the Herschel-PACS instrument at 70, 100 and 160 \mu m, and whenever applicable, with Spitzer-MIPS at 24 and 70 \mu m, are modeled with radiometric techniques, in order to derive the objects' individual size, albedo and when possible beaming factor. Error bars are obtained from a Monte-Carlo approach. We look for correlations between these and other physical and orbital parameters. Diameters obtained for our sample range from 100 to 2400 km, and the geometric albedos (in V band) vary from 3.8 % to 84.5 %. The unweighted mean V geometric albedo for the whole sample is 11.2 % (excluding Eris); 6.9 % for the SDOs, and 17.0 % for the detached objects (excluding Eris). We obtain new bulk densities for three binary systems: Ceto/Phorcys, Typhon/Echidna and Eris/Dysnomia. Apart from correlations clearly due to observational bias, we find significant correlations between albedo and diameter (more reflective objects being bigger), and between albedo, diameter and perihelion distance (brighter and bigger objects having larger perihelia). We discuss possible explanations for these correlations.02/2012; -
Article: Minor Planet Observations [J75 OAM Observatory, La Sagra]
Minor Planet Circulars. 12/2011; 77402:3. -
Article: Minor Planet Observations [I08 Alianza S4, Cerro Burek]
Minor Planet Circulars. 11/2011; 77007:9. -
Article: Minor Planet Observations [I16 IAA-AI Atacama, San Pedro de Atacama]
Minor Planet Circulars. 11/2011; 77008:3. -
Conference Proceeding: Activity in main-belt asteroid P/2010 A2
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ABSTRACT: The dust tail of Main-Belt Asteroid P/2010 A2 (LINEAR) has been observed with several telescopes at the at the Observatorio del Roque de los Muchachos on La Palma, Spain. Application of an inverse dust tail Monte Carlo method to the images of the dust ejecta from the object implies a sustained activity over some eight months. The onset of the activity occurred in late March 2009, with a peak dust mass loss rate of about 5 kg/s in early June 2009, decreasing afterwards to 0.1 kg/s near perihelion in early December 2009. The total amount of dust released is estimated to be 5x10^7 kg, which represents about 0.3% of the nucleus mass. The nucleus diameter is D=220 +/- 40 m, assuming a bulk albedo of p=0.11, typical of a S-type asteroid. The event could have been triggered by a collision, but this cannot be decided from this dataset alone.Highlights of Spanish Astrophysics VI; 11/2011 -
Article: A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation.
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ABSTRACT: The dwarf planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1 AU is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great distance, measuring its size or detecting a putative atmosphere is difficult. Here we report the observation of a multi-chord stellar occultation by Eris on 6 November 2010 UT. The event is consistent with a spherical shape for Eris, with radius 1,163 ± 6 kilometres, density 2.52 ± 0.05 grams per cm(3) and a high visible geometric albedo, Pv = 0.96(+0.09)(-0.04). No nitrogen, argon or methane atmospheres are detected with surface pressure larger than ∼1 nanobar, about 10,000 times more tenuous than Pluto's present atmosphere. As Pluto's radius is estimated to be between 1,150 and 1,200 kilometres, Eris appears as a Pluto twin, with a bright surface possibly caused by a collapsed atmosphere, owing to its cold environment. We anticipate that this atmosphere may periodically sublimate as Eris approaches its perihelion, at 37.8 astronomical units from the Sun.Nature 10/2011; 478(7370):493-6. · 36.28 Impact Factor -
Article: Rotational fission of Trans-Neptunian Objects. The case of Haumea
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ABSTRACT: We present several lines of evidence based on different kinds of observations to conclude that rotational fission has likely occurred for a fraction of the known Trans-Neptunian Objects (TNOs). It is also likely that a number of binary systems have formed from that process in the trans-neptunian belt. We show that Haumea is a potential example of an object that has suffered a rotational fission. Its current fast spin would be a slight evolution of a primordial fast spin, rather than the result of a catastrophic collision, because the percentage of objects rotating faster than 4 hours would not be small in a maxwellian distribution of spin rates that fits the current TNO rotation database. On the other hand, the specific total angular momentum of Haumea and its satellites falls close to that of the high size ratio asteroid binaries, which are thought to be the result of rotational fissions or mass shedding. We also present N-body simulations of rotational fissions applied to the case of Haumea, which show that this process is feasible, might have generated satellites, and might have even created a "family" of bodies orbitally associated to Haumea. The orbitally associated bodies may come from the direct ejection of fragments according to our simulations, or through the evolution of a proto-satellite formed during the fission event. Also, the disruption of an escaped fragment after the fission might create the orbitally related bodies. If any of those mechanisms are correct, other rotational fission families may be detectable in the trans-neptunian belt in the future, and perhaps even TNO pairs might be found (pairs of bodies sharing very similar orbital elements, but not bound together).10/2011; -
Article: Minor Planet Observations [I16 IAA-AI Atacama, San Pedro de Atacama]
Minor Planet Circulars. 09/2011; 76020:3. -
Article: EURONEAR - Recovery, Follow-up and Discovery of NEAs and MBAs using Large Field 1-2m Telescopes
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ABSTRACT: We report on the follow-up and recovery of 100 program NEAs, PHAs and VIs using the ESO/MPG 2.2m, Swope 1m and INT 2.5m telescopes equipped with large field cameras. The 127 fields observed during 11 nights covered 29 square degrees. Using these data, we present the incidental survey work which includes 558 known MBAs and 628 unknown moving objects mostly consistent with MBAs from which 58 objects became official discoveries. We planned the runs using six criteria and four servers which focus mostly on faint and poorly observed objects in need of confirmation, follow-up and recovery. We followed 62 faint NEAs within one month after discovery and we recovered 10 faint NEAs having big uncertainties at their second or later opposition. Using the INT we eliminated 4 PHA candidates and VIs. We observed in total 1,286 moving objects and we reported more than 10,000 positions. All data were reduced by the members of our network in a team effort, and reported promptly to the MPC. The positions of the program NEAs were published in 27 MPC and MPEC references and used to improve their orbits. The O-C residuals for known MBAs and program NEAs are smallest for the ESO/MPG and Swope and about four times larger for the INT whose field is more distorted. The incidental survey allowed us to study statistics of the MBA and NEA populations observable today with 1--2m facilities. We calculate preliminary orbits for all unknown objects, classifying them as official discoveries, later identifications and unknown outstanding objects. The orbital elements a, e, i calculated by FIND_ORB software for the official discoveries and later identified objects are very similar with the published elements which take into account longer observational arcs; thus preliminary orbits were used in statistics for the whole unknown dataset. (CONTINUED)08/2011;
Top co-authors
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Institutions
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1997–2012
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Spanish National Research Council
- Andalusian Astrophysics Institute
Madrid, Madrid, Spain -
California Institute of Technology
- Jet Propulsion Laboratory
Pasadena, CA, USA
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1997–2010
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Instituto De Astrofisica De Andalucia
Granada, Andalusia, Spain
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1992–2007
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University of Granada
- Departamento de Física Aplicada
Granada, Andalusia, Spain
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2001–2002
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University of Lisbon
Lisbon, Lisbon, Portugal
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