332 research outputs found
Multicolor Photometry of the Uranus Irregular Satellites Sycorax and Caliban
We report on accurate BVRI photometry for the two Uranus irregular satellites
Sycorax and Caliban. We derive colours, showing that
Sycorax is bluer than Caliban. Our data allows us to detect a significant
variability in the Caliban's light-curve, which suggests an estimated period of
about 3 hours. Despite it is the brighter of the two bodies, Sycorax does not
display a strong statistically significant variability. However our data seem
to suggest a period of about 4 hoursComment: 17 pages, 2 eps figures, in press in Astronomical Journa
Fluids mobilization in Arabia Terra, Mars: depth of pressurized reservoir from mounds self-similar clustering
Arabia Terra is a region of Mars where signs of past-water occurrence are
recorded in several landforms. Broad and local scale geomorphological,
compositional and hydrological analyses point towards pervasive fluid
circulation through time. In this work we focus on mound fields located in the
interior of three casters larger than 40 km (Firsoff, Kotido and unnamed crater
20 km to the east) and showing strong morphological and textural resemblance to
terrestrial mud volcanoes and spring-related features. We infer that these
landforms likely testify the presence of a pressurized fluid reservoir at depth
and past fluid upwelling. We have performed morphometric analyses to
characterize the mound morphologies and consequently retrieve an accurate
automated mapping of the mounds within the craters for spatial distribution and
fractal clustering analysis. The outcome of the fractal clustering yields
information about the possible extent of the percolating fracture network at
depth below the craters. We have been able to constrain the depth of the
pressurized fluid reservoir between ~2.5 and 3.2 km of depth and hence, we
propose that mounds and mounds alignments are most likely associated to the
presence of fissure ridges and fluid outflow. Their process of formation is
genetically linked to the formation of large intra-crater bulges previously
interpreted as large scale spring deposits. The overburden removal caused by
the impact crater formation is the inferred triggering mechanism for fluid
pressurization and upwelling, that through time led to the formation of the
intra-crater bulges and, after compaction and sealing, to the widespread mound
fields in their surroundings
Geometric calibration of Colour and Stereo Surface Imaging System of ESA's Trace Gas Orbiter
There are many geometric calibration methods for "standard" cameras. These
methods, however, cannot be used for the calibration of telescopes with large
focal lengths and complex off-axis optics. Moreover, specialized calibration
methods for the telescopes are scarce in literature. We describe the
calibration method that we developed for the Colour and Stereo Surface Imaging
System (CaSSIS) telescope, on board of the ExoMars Trace Gas Orbiter (TGO).
Although our method is described in the context of CaSSIS, with camera-specific
experiments, it is general and can be applied to other telescopes. We further
encourage re-use of the proposed method by making our calibration code and data
available on-line.Comment: Submitted to Advances in Space Researc
Evaluation of an Area-Based matching algorithm with advanced shape models
Nowadays, the scientific institutions involved in planetary mapping are working on new strategies to produce accurate high resolution DTMs from space images at planetary scale, usually dealing with extremely large data volumes. From a methodological point of view, despite the introduction of a series of new algorithms for image matching (e.g. the Semi Global Matching) that yield superior results (especially because they produce usually smooth and continuous surfaces) with lower processing times, the preference in this field still goes to well established area-based matching techniques. Many efforts are consequently directed to improve each phase of the photogrammetric process, from image pre-processing to DTM interpolation. In this context, the Dense Matcher software (DM) developed at the University of Parma has been recently optimized to cope with very high resolution images provided by the most recent missions (LROC NAC and HiRISE) focusing the efforts mainly to the improvement of the correlation phase and the process automation. Important changes have been made to the correlation algorithm, still maintaining its high performance in terms of precision and accuracy, by implementing an advanced version of the Least Squares Matching (LSM) algorithm. In particular, an iterative algorithm has been developed to adapt the geometric transformation in image resampling using different shape functions as originally proposed by other authors in different applications
Le Lune di Padova / The Moons of Padova
Catalogo della mostra iconografica "Le Lune di Padova".
Osservatorio Astronomico di Padova, 16 luglio - 30 settembre 2019.
La Luna è l’oggetto celeste a noi più vicino e anche quello che più di ogni altro, nel corso dei secoli, ha acceso la curiosità , lo stupore e l’immaginazione dell’Uomo. Da Luminare della notte e da misuratore del tempo, quale essa è stata per i popoli antichi, la Luna è poi divenuta oggetto di desiderio e di conquista impossibili, come testimoniano il fantastico viaggio sulla Luna di Astolfo, narrato da Ludovico Ariosto, o quello di Barbicane, Ardan e Nicholl, magistralmente descritto dalla penna di Jules Verne. Con l’avvento dell’astronomia telescopica, fu subito chiaro che la nostra Terra non è l’unico pianeta del Cosmo a godere di un satellite naturale perennemente in moto attorno a se stessa, ma che altre, e altrettanto affascinanti Lune, ruotano con imperitura grazia attorno ad altri pianeti, sia nel nostro Sistema Solare che fuori di esso. La mostra iconografica Le Lune di Padova ha raccontato le scoperte e gli studi fatti sulla Luna, e sulle innumerevoli Lune che popolano il Cielo, dagli astronomi che a Padova sono nati o hanno operato: da Galileo, che nel 1609 per la prima volta nella storia dell’umanità rivolse il suo telescopio al nostro satellite, rivelandone la vera natura, sino i recentissimi studi sul ghiaccio lunare condotti dal team dei planetologi padovani, passando attraverso alle numerose scoperte di altre Lune che hanno costellato la storia dell’astronomia degli ultimi 400 anni
A new chronology for the Moon and Mercury
In this paper we present a new method for dating the surface of the Moon,
obtained by modeling the incoming flux of impactors and converting it into a
size distribution of resulting craters. We compare the results from this model
with the standard chronology for the Moon showing their similarities and
discrepancies. In particular, we find indications of a non-constant impactor
flux in the last 500 Myr and also discuss the implications of our findings for
the Late Heavy Bombardment hypothesis. We also show the potential of our model
for accurate dating of other inner Solar System bodies, by applying it to
Mercury.Comment: 27 pages, 13 figures, 1 table; accepted by A
Ultra-High-Resolution 1 m/pixel CaSSIS DTM Using Super-Resolution Restoration and Shape-from-Shading: Demonstration over Oxia Planum on Mars
We introduce a novel ultra-high-resolution Digital Terrain Model (DTM) processing system using a combination of photogrammetric 3D reconstruction, image co-registration, image super-resolution restoration, shape-from-shading DTM refinement, and 3D co-alignment methods. Technical details of the method are described, and results are demonstrated using a 4 m/pixel Trace Gas Orbiter Colour and Stereo Surface Imaging System (CaSSIS) panchromatic image and an overlapping 6 m/pixel Mars Reconnaissance Orbiter Context Camera (CTX) stereo pair to produce a 1 m/pixel CaSSIS Super-Resolution Restoration (SRR) DTM for different areas over Oxia Planum on Mars—the future ESA ExoMars 2022 Rosalind Franklin rover’s landing site. Quantitative assessments are made using profile measurements and the counting of resolvable craters, in comparison with the publicly available 1 m/pixel High-Resolution Imaging Experiment (HiRISE) DTM. These assessments demonstrate that the final resultant 1 m/pixel CaSSIS DTM from the proposed processing system has achieved comparable and sometimes more detailed 3D reconstruction compared to the overlapping HiRISE DT
A Possible Diapir in Athabasca Region on Mars
A circular feature was observed on Mars by the HiRISE camera. From DTM analysis its circular positive relief shape has been interpreted as diapiric phenomenon
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