1,721,025 research outputs found
Sample Return Missions from Minor Bodies: Achievements, Future Plan and Observational Support
No full textWe are entering in a new era of space exploration signed by sample return missions. Since the Apollo and Luna Program, the study of extraterrestrial samples in laboratory is gathering an increased interest of the scientific community so that nowadays exploration program of the Solar System is characterized by swelling sample return missions. Beside lunar samples, the NASA Stardust mission was the first successful space mission that on 15 January 2006 brought to Earth solid extraterrestrial samples collected from comet 81P/Wild 2 coma. Grains were collected during cometary fly-by into aerogel and once on Earth have been extracted for laboratory analyses. In the coming two decades many space missions on going or under study will harvest samples from minor bodies. Measurements required for detailed analysis that cannot be performed from a robotic spacecraft, will be carried out on Earth laboratories with the highest analytical accuracy attainable so far. An intriguing objective for the next sample return missions is to understand the nature of organic compounds. Organic compounds found in Stardust grains even if processed to large extend during aerogel capturing are here reported. Major objectives of Marco Polo mission are reported. Various ground-based observational programs within the framework of general characterizations of families and classes, cometary-asteroid transition objects and NEOs with cometary albedo are discussed and linked to sample return mission
The Actual Optical Design and Preliminary Optomechanical Tolerances of the High Resolution Imaging Channel for the BepiColombo mission to Mercury
No full textThis paper deals with the optical design and preliminary optomechanical tolerances of HRIC, the High Resolution
Imaging Channel of the SIMBIO-SYS instrument, selected as part of the scientific payload for the ESA cornerstone
BepiColombo mission to Mercury. Under the lead of Italy (Principal Investigator: E. Flamini), the project is based on an
international co-operation with Institutes from France and Switzerland. Starting from the stringent scientific requirement
of 5m ground pixel scale @ 400 km from the planet surface, a robust optical design based on a catadioptric Ritchey-
Chretien configuration modified with a dedicated corrector camera has been achieved. The optimized configuration is
convenient in terms of image quality, number of optical elements, and total length. The channel guarantees a corrected
FoV of about 1.5° and allows the achievement of the required resolution with a detector of 2k × 2k pixels. The telescope
is diffraction limited, thanks to its focal ratio (F/8), and shows an optimised radiometric flux within the operative spectral
range (400 - 900 nm). The channel is equipped with one panchromatic and 3 selective filters. The operation plan foresees
the coverage of at least 20% of the whole Hermean surface with the HRIC. The preliminary optomechanical tolerances
and the corresponding image quality have been analyzed. Further thermo-mechanical analysis is in progress, which is
beeing analyzed by means of ray-tracing tools for image quality evaluation
The Optical Design of the High Resolution Imaging Channel for the SIMBIO-SYS experiment on the BepiColombo Mission to Mercury
No full textThis paper deals with the optical design of the High Resolution Imaging Channel (HRIC) of the SIMBIO-SYS instrument, selected as part of the scientific payload for the ESA cornerstone BepiColombo mission to Mercury. Under the lead of Italy, the project is based on an international cooperation with Institutes from France and Switzerland. The
HRIC design starts from the scientific requirement of 5 m ground pixel scale at 400 km from the planet surface and is based on a catadioptric Ritchey-Chretien configuration modified with a dedicated three lens corrector. The optimised configuration is convenient in terms of image quality, number of optical elements, total length and mass budget. The channel guarantees
a corrected FoV of about 1.47 and allows the achievement of the required resolution with the selected APS hybrid detector of 2k x 2k pixels with a pixel size of 10 m. The telescope is diraction limited, thanks to its focal ratio (F/8), and shows an optimised radiometric flux within the operative spectral range (400 - 900 nm), which guarantees a good S/N. The channel is equipped with 1 panchromatic and 3 selective filters. The operation plan foresees the coverage of at least 20% of the Hermean surface with the HRIC
Mercury’s radius change estimates revisited using high incidence angle MESSENGER data
No full textEstimates of Mercury’s radius decrease obtained using the amount of strain recorded by tectonics on the planet
range from 0.5 km to 2 km. These latter figures appear too low with respect to the radius contraction (up to 5-6
km) predicted by the most accredited studies based on thermo-mechanical evolution models. For this reason, it
has been suggested that there may be hidden strain accommodated by features yet unseen on Mercury. Indeed,
as it has been already cautioned by previous studies, the identification of tectonic features on Mercury might be
largely biased by the lighting geometry of the used basemaps. This limitation might have affected the results of
the extrapolations for estimating the radius change. In this study, we mapped tectonic features at the terminator
thus using images acquired at high sun incidence angle (>50) that represents the optimal condition for their
observation. In fact, images with long shadows enhance the topography and texture of the surface and are ideal
to detect tectonic structures. This favorable illumination conditions allowed us to infer reliable measurements of
spatial distribution (i.e. frequency, orientation, and areal density) of tectonic features which can be used to estimate
the average contractional strain and planetary radius decrease. We digitized tectonic structures within a region
extending for an area of about 12 million sq. km (16% of planet’s surface). More than 1300 tectonic lineaments
were identified and interpreted to be compressional features (i.e. lobate scarps, wrinkle ridges, and high relief
ridges) with a total length of more than 12300 km. Assuming that the extensional strain is negligible within the
area, the average contractional strain calculated for the survey area is 0.21–0.28% (0.24% for =30). This
strain, extrapolated to the entire surface, corresponds to a contraction in radius of about 2.5–3.4 km (2.9 km for
=30). Interestingly, the values of contractional strain and radius decrease obtained in the present study are up to
five times higher with respect to previous estimates. Our results are more compatible with recent studies suggesting
that the Mercury’s radius contraction could have been up to 5-6 km throughout its thermal evolution than previous
results, supporting the idea that Mercury could have recorded more tectonism than that required to account for 1-2
km of radial contraction. These estimates should be confirmed by further observations over significant portions of
the planet and at most favorable sun angle conditions using data from the MESSENGER orbital phase and the high
resolution basemaps which will be provided by the next BepiColombo mission
GIADA (Grain Impact Analyser and Dust Accumulator) prepares for the comet 67P/Churyumov-Gerasimenko encounter,
No full textMAPPING MERCURY’S TECTONIC FEATURES AT THE TERMINATOR: IMPLICATIONS FOR RADIUS CHANGE ESTIMATES AND THERMAL HISTORY MODELS.
No full textPrior to the MESSENGER mission only 45% of the Mercury’s surface was imaged by
Mariner 10. By using the latter data for mapping
tectonic features it was suggested that the detected
compressional structures can account for a planetary
radius contraction of less than 1 km (0.43-0.64 km). These results have been slightly revised by recent
studies using images acquired during the three
MESSENGER flybys. In fact, several previously
unobserved compressional features (including the
longest known to date on Mercury) have been discovered, increasing the total number of known contractional
features by approximately one third and thus
bringing the amount of estimated radius contraction to
0.8 km. However, these estimates yet appear too
low with respect to the amount of radius contraction
(up to 5-6 km) predicted by the most accredited studies
based on thermo-mechanical evolution models
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dame: A distributed web based framework for knowledge discovery in databases
Full text linkMassive data sets explored in many e-science communities, as in the Astrophysics case, are gathered by a very large number of techniques and stored in very diversified and often-incompatible data repositories. Moreover, we need to integrate services across distributed, heterogeneous, dynamic virtual organizations formed from the different resources within a single enterprise and/or from external resource sharing and service provider relationships. The DAME project aims at creating a distributed e-infrastructure to guarantee integrated and asynchronous access to data collected by very different experiments and scientific communities in order to correlate them and improve their scientific usability. The project consists of a data mining framework with powerful software instruments capable to work on massive data sets, organized by following Virtual Observatory standards, in a distributed computing environment. The integration process can be technically challenging because of the need to achieve a specific quality of service when running on top of different native platforms. In these terms, the result of the DAME project effort is a service-oriented architecture, by using appropriate standards and incorporating Cloud/Grid paradigms and Web services, that will have as main target the integration of interdisciplinary distributed systems within and across organizational domains
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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