ESA Science & Technology - Publication Archive
Aims.The aim of this paper is to investigate the surface composition of the two asteroids 21 Lutetia and 2867 Steins, targets of the Rosetta space mission.
Methods.We observed the two asteroids through their full rotational periods with the Infrared Spectrograph of the Spitzer Space Telescope to investigate the surface properties. The analysis of their thermal emission spectra was carried out to detect emissivity features that diagnose the surface composition.
Results. For both asteroids, the Christiansen peak, the Reststrahlen, and the Transparency features were detected. The thermal emissivity shows a clear analogy to carbonaceous chondrite meteorites, in particular to the CO-CV types for 21 Lutetia, while for 2867 Steins, already suggested as belonging to the E-type asteroids, the similarity to the enstatite achondrite meteorite is confirmed.
New large-scale CO surveys of the first and second Galactic quadrants and the nearby molecular cloud complexes in Orion and Taurus, obtained with the CfA 1.2 m telescope, have been combined with 31 other surveys obtained over the past two decades with that instrument and a similar telescope on Cerro Tololo in Chile, to produce a new composite CO survey of the entire Milky Way. The survey consists of 488,000 spectra that Nyquist or beamwidth (1/8 °) sample the entire Galactic plane over a strip 4°-10° wide in latitude, and beamwidth 1/4 ° sample nearly all large local clouds at higher latitudes. Compared with the previous composite CO survey of Dame et al. (1987), the new survey has 16 times more spectra, up to 3.4 times higher angular resolution, and up to 10 times higher sensitivity per unit solid angle.
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:
A summary of the PEP study is on the "Planetary Entry Probes (PEP)" page, linked form the right-hand menu.
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 Œm 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.
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.
The present study makes the first scientific use of this operation mode. We estimate the X-ray spectroscopic temperature of SPT-CL J2332-5358 (at redshift z = 0.32) to be T = 9.3 [+3.3][-1.9] keV, implying a high mass, M500 = 8.8 ± 3.8 × 1014 solar masses. For SPT-CL J2342-5411, at z = 1.08, the available X-ray data do not allow us to directly estimate the temperature with good confidence. However, using our measured luminosity and scaling relations we estimate that T = 4.5 ± 1.3 keV and M500 = 1.9 ± 0.8 × 1014 solar masses. We find a good agreement between the X-ray masses and those estimated from the Sunyaev-Zel'dovich effect.
The May 2010 issue of Astronomy & Astrophysics is a special feature devoted to the new results obtained with the infrared satellite AKARI, a JAXA project with the participation of ESA. It includes 17 articles dealing with various subjects. Some papers are based on the AKARI all-sky survey, which has just been released. Others are dedicated to pointed observations of many astronomical targets from solar system bodies to distant galaxies.
An ESA TRP activity was carried out by cosine Research (NL), Micronit (NL), Kayser-Threde (DE), SRON (NL), DTU (DK) and MPE (DE) with the goal of improving the angular resolution of Silicon Pore X-ray Optics. Silicon Pore Optics is the European baseline mirror technology for the International X-ray Observatory (IXO), one of the three L-class mission candidates under the Cosmic Vision 2015-2025 program.
This ESA TRP funded activity, 'High Performance X-Ray Optics', started late 2007. The entire production chain of these light-weight and modular X-ray optics has been reviewed, improved, demonstrated and tested, from silicon plate manufacture, over ribbing, dicing, wedging, coating, stacking, assembly and integration up to petal level.