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| PEP Assessment Study - Internal Final Presentation |
The assessment study of Planetary Entry Probes (PEP) for Venus and three of the outer planets (Saturn, Uranus, and Neptune) has been performed at ESA's Concurrent Design Facility (CDF) and ran from 14 April to 30 June 2010. The internal final presentation has been prepared by the PEP/CDF team and summarizes the outcome of the PEP assessment study. This presentation can be downloaded below as a PDF (link to publication).
Contents of the presentation:
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| - | Introduction | | - | Systems | | - | Mission analysis | | - | Aerothermodynamics | | - | Thermal | | - | Entry, Descent & Landing | | - | Payload | | - | Configuration | | - | Structures | | - | Mechanisms |
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| - | Guidance & Navigation Control | | - | Power | | - | Communications | | - | Data Handling System | | - | Ground Segment & Operations | | - | Programmatics/ AIV | | - | Risk | | - | Annex I: Atmospheric Models
for Outer Planets |
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A summary of the PEP study is on the "Planetary Entry Probes (PEP)" page, linked form the right-hand menu. |
| Publication date: 30 Jun 2010 |
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| Detection of hydrated silicates in crustal outcrops in the northern plains of Mars |
| The composition of the ancient martian crust is a key ingredient in deciphering the environment and evolution of early Mars. We present an analysis of the composition of large craters in the martian northern plains based on data from spaceborne imaging spectrometers. Nine of the craters have excavated assemblages of phyllosilicates from ancient, Noachian crust buried beneath the plains' cover. The phyllosilicates are indistinguishable from those exposed in widespread locations in the southern highlands, demonstrating that liquid water once altered both hemispheres of Mars. |
| Publication date: 24 Jun 2010 |
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| INTEGRAL/IBIS 7-year All-Sky Hard X-Ray Survey – Part II: Catalog of Sources |
| This paper is the second in a series devoted to the hard X-ray (17-60 keV) whole sky survey performed by the INTEGRAL observatory over seven years. Here we present a catalog of detected sources which includes 521 objects, 449 of which exceed a 5 sigma detection threshold on the time-averaged map of the sky, and 53 were detected in various subsamples of exposures. Among the identified sources with known and suspected nature, 262 are Galactic (101 low-mass X-ray binaries, 95 high-mass X-ray binaries, 36 cataclysmic variables, and 30 of other types) and 219 are extragalactic, including 214 active galactic nuclei (AGNs), 4 galaxy clusters, and galaxy ESO 389-G 002. The extragalactic (|b|>5 deg) and Galactic (|b|<5 deg) persistently detected source samples are of high identification completeness (respectively ~96% and ~94%) and valuable for population studies. |
| Publication date: 23 Jun 2010 |
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| The thermal structure of Venusian night-time mesosphere as observed by VIRTIS-Venus Express |
The mapping IR channel of the Visual and Infrared Thermal Imaging Spectrometer (VIRTIS-M) on board the Venus Express spacecraft observes the CO2 band at 4.3 ¼m at a spectral resolution adequate to retrieve the atmospheric temperature profiles in the 65-96 km altitude range.
Observations acquired in the period June 2006 - July 2008 were used to derive average temperature fields as a function of latitude, subsolar longitude (i.e.: local time, LT) and pressure. Coverage presented here is limited to the nighttime because of the adverse effects of daytime non-LTE emission on the retrieval procedure, and to southernmost latitudes because of the orientation of the Venus-Express orbit. Maps of air temperature variability are also presented as the standard deviation of the population included in each averaging bin.
At the 100 mbar level (about 65 km above the reference surface) temperatures tend to decrease from the evening to the morning side, despite a local maximum observed around 20-21LT. The cold collar is evident around 65S, with a minimum temperature at 3LT. Moving to higher altitudes, local time trends become less evident at 12.6 mbar (about 75 km) where the temperature monotonically increases from middle-latitudes to the southern pole. Nonetheless, at this pressure level, two weaker local time temperature minima are observed at 23LT and 2LT equatorward of 60S. Local time trends in temperature reverse about 85 km, where the morning side is the warmer.
The variability at the 100 mbar level is maximum around 80S and stronger toward the morning side. Moving to higher altitudes, the morning side always shows the stronger variability. Southward of 60S, standard deviation presents minimum values around 12.6 mbar for all the local times. |
| Publication date: 22 Jun 2010 |
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| A relativistically broadened O VIII Ly-alpha line in the ultra-compact X-ray binary 4U 0614+091 |
| Ultra-compact X-ray binaries consist of a neutron star or black hole that accretes material from a white dwarf-donor star. The ultra-compact nature is expressed in very short orbital periods of less than 1 hour. In the case of 4U 0614+091 oxygen-rich material from a CO or ONe white dwarf is flowing to the neutron star. This oxygen-rich disc can reflect X-rays emitted by the neutron star giving a characteristic emission spectrum. We have analyzed high-resolution RGS and broad band EPIC spectra of 4U 0614+091 obtained by the XMM-Newton satellite. We detect a broad emission feature at ~0.7 keV in both instruments, which cannot be explained by unusual abundances of oxygen and neon in the line of sight, as proposed before in the literature. We interpret this feature as O VIII Ly-alpha emission caused by reflection of X-rays off highly ionized oxygen, in the strong gravitational field close to the neutron star. |
| Publication date: 21 Jun 2010 |
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| Superrotation of Venus' atmosphere analyzed with a full general circulation model |
| A general circulation model (GCM) has been developed for the Venus atmosphere, from the surface up to 100 km altitude, based on the GCM developed for Earth at our laboratory. Key features of this new GCM include topography, diurnal cycle, dependence of the specific heat on temperature, and a consistent radiative transfer module based on net exchange rate matrices. This allows a consistent computation of the temperature field, in contrast to previous GCMs of Venus atmosphere that used simplified temperature forcing. The circulation is analyzed after 350 Venus days (111 Earth years). Superrotation is obtained above roughly 40 km altitude. Below, the zonal wind remains very small compared to observed values, which is a major pending question. The meridional circulation consists of equator-to-pole cells, the dominant one being located within the cloud layers. The modeled temperature structure is globally consistent with observations, though discrepancies persist in the stability of the lowest layers and equator-pole temperature contrast within the clouds (10 K in the model compared to the observed 40 K). In agreement with observational data, a convective layer is found between the base of the clouds (around 47 km) and the middle of the clouds (55-60 km altitude). The transport of angular momentum is analyzed, and comparison between the reference simulation and a simulation without diurnal cycle illustrates the role played by thermal tides in the equatorial region. Without diurnal cycle, the Gierasch-Rossow-Williams mechanism controls angular momentum transport. The diurnal tides add a significant downward transport of momentum in the equatorial region, causing low latitude momentum accumulation. |
| Publication date: 12 Jun 2010 |
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| Puzzling asteroid 21 Lutetia: our knowledge prior to the Rosetta fly-by |
| Aims. A wide observational campaign was carried out in 2004-2009 that aimed to complete the ground-based investigation of Lutetia prior to the Rosetta fly-by in July 2010.
Methods. We obtained BVRI photometric and V-band polarimetric measurements over a wide range of phase angles, and visible and infrared spectra in the 0.4-2.4 micron range. We analyze them with previously published data to retrieve information about Lutetia's surface properties. Results. Values of lightcurve amplitudes, absolute magnitude, opposition effect, phase coefficient, and BVRI colors of Lutetia surface seen at near pole-on aspect are determined. We define more precisely parameters of polarization phase curve and show their distinct deviation from any other moderate-albedo asteroid. An indication of possible variations in both polarization and spectral data across the asteroid surface are found. To explain features found by different techniques, we propose that (i) Lutetia has a non-convex shape, probably due to a large crater, and heterogeneous surface properties probably related to surface morphology; (ii) at least part of the surface is covered by a fine-grained regolith of particle size smaller than 20 micron; (iii) the closest meteorite analogues of Lutetia's surface composition are particular types of carbonaceous chondrites, or Lutetia has specific surface composition that is not representative among studied meteorites. |
| Publication date: 03 Jun 2010 |
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