365 research outputs found
Philosophy and updating of the asteroid photometric catalogue
The Asteroid Photometric Catalogue now contains photometric lightcurves for 584 asteroids. We discuss some of the guiding principles behind it. This concerns both observers who offer input to it and users of the product
Puzzling asteroid 21 Lutetia: our knowledge prior to the Rosetta fly-by
A wide observational campaign was carried out in 2004-2009 aimed to complete
the ground-based investigation of Lutetia prior to the Rosetta fly-by in July
2010. We have 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 analyzed them together with previously published data
to retrieve information on Lutetia's surface properties. Values of lightcurve
amplitudes, absolute magnitude, opposition effect, phase coefficient and BVRI
colors of Lutetia surface seen at near pole-on aspect have been determined. We
defined more precisely parameters of polarization phase curve and showed their
distinct deviation from any other moderate-albedo asteroid. An indication of
possible variations both in polarization and spectral data across the asteroid
surface was found. To explain features found by different techniques we propose
that (i) Lutetia has a non-convex shape, probably due to the presence of 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 with particle size less than 20 microns; (iii) the closest meteorite
analogues of Lutetia's surface composition are particular types of carbonaceous
chondrites or Lutetia has specific surface composition not representative among
studied meteorites
Atmospheric Stability & Turbulence from Temperature Profiles over Sicily During Summer 2002 & 2003 HASI Balloon Campaigns
Experimental results and interpretation of the temperature measurements data retrieved during the balloon campaigns (in 2002 and in 2003) for testing HASI (Huygens Atmospheric Structure Instrument), launched from the Italian Space Agency Base in Trapani (Sicily), are presented. Both ascending and descending phases are analysed; data reveal interesting features near the tropopause (present in the region between 11km-14km), where temperature cooling can be related to layers with strong winds (2002 flight); in the troposphere a multistratified structure of the temperature field is observed and discussed (particularly in the 2003 flight) Finally, stability and turbulence of the atmosphere are analysed; the buoyancy N2 parameters for both the flights show lowers value respect to standard tropospheric values corresponding to a lower stability of the atmosphere; still there is a higher stability above the tropopause. The energy spectrum of temperature data is consistent with the Kolmogorov theory: the characteristic k(sup -5/3) behaviour is reproduced
First albedo determination of 2867 Steins, target of the Rosetta mission
We present the first albedo determination of 2867 Steins, the asteroid target
o f the Rosetta space mission together with 21 Lutetia. The data were obtained
in polarimetric mode at the ESO-VLT telescope with the FORS1 instrument in the
V and R filters. Observations were carried out from Jun e to August 2005
covering the phase angle range from 10.3 deg. to 28.3 deg., allowing the
determination of the asteroid albedo by the well known experimenta l
relationship between the albedo and the slope of the polarimetric curve at th e
inversion angle. The measured polarization values of Steins are small,
confirming an E-type cla ssification for this asteroid, as already suggested
from its spectral propertie s. The inversion angle of the polarization curve in
the V and R filters is resp ectively of 17.3 +/-1.5deg. and 18.4+/-1.0 deg.,
and the corresponding sl ope parameter is of 0.037+/-0.003 %/deg and
0.032+/-0.003 %/deg. On the basis of its polarimetric slope value, we have
derived an albedo of 0.45 +/-0.1, that gives an estimated diameter of 4.6 km,
assuming an absolute V ma gnitude of 13.18 mag.Comment: 4 pages, 4 figures, letter accepted for pubblication on A&
United States and Western Europe cooperation in planetary exploration
A framework was sought for U.S.-European cooperation in planetary exploration. Specific issues addressed include: types and levels of possible cooperative activities in the planetary sciences; specific or general scientific areas that seem most promising as the main focus of cooperative efforts; potential mission candidates for cooperative ventures; identification of special issues or problems for resolution by negotiation between the agencies, and possible suggestions for their resolutions; and identification of coordinated technological and instrumental developments for planetary missions
Applied Cyberpsychology: Military and Defence Applications
Virtual environments are synthetic computer simulations that represent activities at a high degree of realism. Virtual environments have numerous applications for military and defence purposes, ranging from allowing personnel to experience realistic, high-pressure situations with a sense of presence, but in the absence of real world risk, to modelling threats to national and international infrastructure to improve resilience. Emerging opportunities also exist for communication and intelligence gathering, exploring on-line social cognition and group behaviour, and understanding how to mitigate the negative effects of combat-related stress disorders, for example. In this chapter we introduce psychological theory and contemporary cyberpsychology research, and offer an albeit very brief introduction to the rapidly developing application of technology to better understand human behaviour and facilitate performance for military and defence purposes
Inhomogeneities on the surface of 21 Lutetia, the asteroid target of the Rosetta mission
CONTEXT: In July 2010 the ESA spacecraft Rosetta will fly-by the main belt
asteroid 21 Lutetia. Several observations of this asteroid have been so far
performed, but its surface composition and nature are still a matter of debate.
For long time Lutetia was supposed to have a metallic nature due to its high
IRAS albedo. Later on it has been suggested to have a surface composition
similar to primitive carbonaceous chondrite meteorites, while further
observations proposed a possible genetic link with more evolved enstatite
chondrite meteorites. AIMS: In order to give an important contribution in
solving the conundrum of the nature of Lutetia, in November 2008 we performed
visible spectroscopic observations of this asteroid at the Telescopio Nazionale
Galileo (TNG, La Palma, Spain). METHODS: Thirteen visible spectra have been
acquired at different rotational phases. RESULTS: We confirm the presence of a
narrow spectral feature at about 0.47-0.48 micron already found by Lazzarin et
al. (2009) on the spectra of Lutetia. We also find a spectral feature at about
0.6 micron, detected by Lazzarin et al. (2004) on one of their Lutetia's
spectra. More importantly, our spectra exhibit different spectral slopes
between 0.6 and 0.75 micron and, in particular, we found that up to 20% of the
Lutetia surface could have flatter spectra. CONCLUSIONS: We detected a
variation of the spectral slopes at different rotational phases that could be
interpreted as possibly due to differences in the chemical/mineralogical
composition, as well as to inhomogeneities of the structure of the Lutetia's
surface (e.g., the presence of craters or albedo spots) in the southern
hemisphere.Comment: 3 pages, 2 figures. Accepted for publication in Astronomy and
Astrophysics. Updated on 25 March 2010
Recommended from our members
Marco Polo: A near Earth object sample return mission
From Introduction:
MARCO POLO is a joint European-Japanese sample return mission to a Near-Earth Object. In late 2007 this mission was selected by ESA, in the framework of COSMIC VISION 2015-2025, for an assessment scheduled to last until mid 2009.
This Euro-Asian mission will go to a primitive Near-Earth Object (NEO), such as a C or D type asteroid. The spacecraft will rendezvous with the object, and over an extended period scientifically characterize it at multiple scales and bring samples back to Earth for detailed scientific investigation
- …