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Mura A.,Istituto di Fisica Dello Spazio Interplanetario
Planetary and Space Science | Year: 2012

The time scales and loss rates for sodium in the exosphere of Mercury are studied here. Sodium comes from release processes occurring at the planetary surface; the amount of surface sodium that is available for release (mostly through thermal- or photon-stimulated desorption) is limited. Loss processes deplete the surface concentration of sodium, which is continuously refilled by diffusion from the interior of regolith grains or by chemical sputtering. Ejected sodium particles may either escape the gravity, also aided by the radiation pressure acceleration, or be photoionized, or fall back onto the surface. Falling particles may either stick to the surface or bounce. A Monte Carlo model, simulating all these processes, is used to obtain the exosphere densities, the global loss rates at different true anomaly angles, and typical time scales for small-term variations, taking into account planets orbit and rotation speed. Assuming an impulsive event, which causes the enhancement of sodium in the exosphere, the model gives the time scales for the exosphere to recover to a steady-state condition. It is found that time scales go from one or two hour (close to perihelion) to half day (close to aphelion). The escape probability ranges from 20% at perihelion and aphelion up to 40% at true anomaly angles of about 60° and 300°. © 2011 Elsevier Ltd. All rights reserved. Source

Orleanski P.,Polish Academy of Sciences | Michalska M.,Polish Academy of Sciences | Nowosielski W.,Polish Academy of Sciences | Ciechanowicz M.,Max Planck Institute for Radio Astronomy | And 11 more authors.
2012 19th International Conference on Microwaves, Radar and Wireless Communications, MIKON 2012 | Year: 2012

The Local Oscillator Subsystem (LOS/S) is a part of the HIFI (Heterodyne Instrument for the Far Infrared) project, an infrared heterodyne instrument for astronomical observations on the ESA HERSCHEL Space Observatory. Local Oscillator Subsystem uses the set of sensitive microwave components, essential for frequency multiplication from K/Ka Bands to 480/1910GHz. The paper presents the methods of biasing of the LOU independent microwave amplifiers and diodes. The special care at the design phase was given to different methods of protection against wrong biasing of such components. The results of the protection, implemented in LCU hardware and software, are discussed at the paper, based on the lessons learned from more than four years of pre-launch activities and almost three years of HIFI operations on the orbit. © 2012 IEEE. Source

Kokoulin R.P.,National Research Nuclear University MEPhI | Bogdanov A.G.,National Research Nuclear University MEPhI | Gromushkin D.M.,National Research Nuclear University MEPhI | Mannocchi G.,Istituto di Fisica Dello Spazio Interplanetario | And 7 more authors.
Bulletin of the Russian Academy of Sciences: Physics | Year: 2011

Characteristics of muon bundles detected with the DECOR detector are compared to predictions based on different hadron interaction models and various assumptions as to the spectrum and mass composition of primary cosmic rays. The intensity of primary cosmic rays derived from the muon bundle data is considerably higher than that measured by means of the fluorescence technique. Either changes in the hadron interaction characteristics at ultrahigh energies or a revision of the energy calibration in the fluorescence technique of measuring EAS energy is required to explain these results. © 2011 Allerton Press, Inc. Source

Vixie G.,University of Idaho | Barnes J.W.,University of Idaho | Bow J.,University of Idaho | Le Mouelic S.,CNRS Nantes Laboratory of Planetology and Geodynamics | And 9 more authors.
Planetary and Space Science | Year: 2012

Titan shows its surface through many methane windows in the 15 μm region. Windows at shorter wavelengths also exist, polluted by scattering off of atmospheric haze that reduces the surface contrast. At visible wavelengths, the surface of Titan has been observed by Voyager I, the Hubble Space Telescope, and ground-based telescopes. We present here global surface mapping of Titan using the visible wavelength channels from Cassini's Visual and Infrared Mapping Spectrometer (VIMS). We show global maps in each of the VIMS-V channels extending from 0.35 to 1.05 μm. We find methane windows at 0.637, 0.681, 0.754, 0.827, 0.937, and 1.046μm and apply an RGB color scheme to the 0.754, 0.827 and 0.937μm windows to search for surface albedo variations. Our results show that Titan appears gray at visible wavelengths; hence scattering albedo is a good approximation of the Bond albedo. Maps of this genre have already been made and published using the infrared channels of VIMS. Ours are the first global maps of Titan shortward of 0.938μm. We compare the older IR maps to the new VIMS-V maps to constrain surface composition. For instance Tui Regio and Hotei Regio, referred to as 5μm bright spots in previous papers, do not distinguish themselves at all visible wavelengths. The distinction between the dune areas and the bright albedo spots, however, such as the difference between Xanadu and Senkyo, is easily discernible. We employ an empirically derived algorithm to remove haze layers from Titan, revealing a better look at the surface contrast. © 2011 Elsevier Ltd. All rights reserved. Source

Bogdanov A.G.,National Research Nuclear University MEPhI | Gromushkin D.M.,National Research Nuclear University MEPhI | Kokoulin R.P.,National Research Nuclear University MEPhI | Mannocchi G.,Istituto di Fisica Dello Spazio Interplanetario | And 6 more authors.
Physics of Atomic Nuclei | Year: 2010

A new method for studying extensive air showers is considered. The method is based on the phenomenology of the localmuon density. It is shown that measurement ofmuon-density spectra at various zenith angles makes it possible to obtain information about the energy spectrum, mass composition, and interaction of cosmic rays over a broad range of energies (1015-1018 eV) by using a single array of comparatively small size. The results obtained from a comparison of experimental data on muon bundles from the DECOR coordinate detector with the results of simulation performed under various assumptions on the properties of the primary flux and for various hadron-interaction models are presented, and possible versions of the interpretation of these results are discussed. © 2010 Pleiades Publishing, Ltd. Source

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