The nature of terrains of different types on the surface of Venus and selection of potential landing sites for a descent probe of the <Emphasis Type="Italic">Venera-D</Emphasis> Mission

We discuss a change in the resurfacing regimes of Venus and probable ways of forming the terrain types that make up the surface of the planet. The interpretation of the nature of the terrain types and their morphologic features allows us to characterize their scientific priority and the risk of landing on their surface to be estimated. From the scientific point of view, two terrain types are of special interest and represent easily achievable targets: the lower unit of regional plains and the smooth plains associated with impact craters. Regional plains are probably a melting from the upper fertile mantle. The material of smooth plains of impact origin is a well-mixed and representative sample of the Venusian crust. The lower unit of regional plains is the most widespread one on the surface of Venus, and it occurs within the boundaries of all of the precalculated approach trajectories of the lander. Smooth plains of impact origin are crossed by the approach trajectories precalculated for 2018 and 2026.     

The particle background of the <Emphasis Type="Italic">X-IFU</Emphasis> instrument

In this paper we are going to review the latest estimates for the particle background expected on the X-IFU instrument onboard of the ATHENA mission. The particle background is induced by two different particle populations: the so called “soft protons” and the Cosmic rays. The first component is composed of low energy particles (< 100s keV) that get funnelled by the mirrors towards the focal plane, losing part of their energy inside the filters and inducing background counts inside the instrument sensitivity band. The latter component is induced by high energy particles (> 100 MeV) that possess enough energy to cross the spacecraft and reach the detector from any direction, depositing a small fraction of their energy inside the instrument. Both these components are estimated using Monte Carlo simulations and the latest results are presented here.     

The Cryogenic AntiCoincidence detector for ATHENA X-IFU: a scientific assessment of the observational capabilities in the hard X-ray band

ATHENA is a large X-ray observatory, planned to be launched by ESA in 2028 towards an L2 orbit. One of the two instruments of the payload is the X-IFU: a cryogenic spectrometer based on a large array of TES microcalorimeters, able to perform integral field spectrography in the 0.2–12 keV band (2.5 eV FWHM at 6 keV). The X-IFU sensitivity is highly degraded by the particle background expected in the L2 orbit, which is induced by primary protons of both galactic and solar origin, and mostly by secondary electrons. To reduce the particle background level and enable the mission science goals, the instrument incorporates a Cryogenic AntiCoincidence detector (CryoAC). It is a 4 pixel TES based detector, placed < 1 mm below the main array. In this paper we report a scientific assessment of the CryoAC observational capabilities in the hard X-ray band (E > 10 keV). The aim of the study has been to understand if the present detector design can be improved in order to enlarge the X-IFU scientific capability on an energy band wider than the TES array. This is beyond the CryoAC baseline, being this instrument aimed to operate as anticoincidence particle detector and not conceived to perform X-ray observations.     

Calibration of the ART-XC mirror modules at MSFC

The Astronomical Röntgen Telescope X-ray Concentrator (ART-XC) is a hard X-ray telescope with energy response up to 30 keV, to be launched on board the Spectrum Röntgen Gamma (SRG) spacecraft in 2018. ART-XC consists of seven identical co-aligned mirror modules. Each mirror assembly is coupled with a CdTe double-sided strip (DSS) focal-plane detector. Eight X-ray mirror modules (seven flight and one spare units) for ART-XC were developed and fabricated at the Marshall Space Flight Center (MSFC), NASA, USA. We present results of testing procedures performed with an X-ray beam facility at MSFC to calibrate the point spread function (PSF) of the mirror modules. The shape of the PSF was measured with a high-resolution CCD camera installed in the focal plane with defocusing of 7 mm, as required by the ART-XC design. For each module, we performed a parametrization of the PSF at various angular distances Θ. We used a King function to approximate the radial profile of the near on-axis PSF (Θ < 9 arcmin) and an ellipse fitting procedure to describe the morphology of the far off-axis angular response (9 < Θ < 24 arcmin). We found a good agreement between the seven ART-XC flight mirror modules at the level of 10%. The on-axis angular resolution of the ART-XC optics varies between 27 and 33 arcsec (half-power diameter), except for the spare module.     

Kinematics of the structure of the active region in Orion-KL

The kinematics of the superfine structure of the active star-forming region in the dense molecular cloud Orion-KL has been investigated in the Н₂О maser emission for the period 1998–2003. It has been established that the surrounding gas inflows onto the disk and is transferred in a spiral trajectory to the center. An excess angular momentum as it is accumulated is carried away by a bipolar outflow; a highvelocity central flow surrounded by low-velocity components is formed. The outer low-velocity component observed at the detection limit has a diameter Ø₃ ≈ 4.5 AU, further out, Ø₂ ≈ 0.5 AU and Ø₁ ≈ 0.24 AU. The gas transfer velocity increases exponentially as the center is approached. The maser emission from the central flow is decisive. A rise in the velocity leads to a flow discontinuity and a reduction in the amount of inflowingmaterial and, accordingly, the emission level. The emission in the period under consideration was reduced exponentially for ~6 months, whereupon its restoration began.     

Coastal observatory for long-term measurement and real time data processing of oceanological parameters

A coastal observatory for long-term continuous measurements of oceanological parameters and real-time data transfer via the Internet to remote users is described. The observatory was designed at the Shirshov Institute of Oceanology (SIO) and tested at its southern branch (SB) in the Black Sea. The architecture, components, and design principles of the observatory are discussed along with its application for solving problems of water dynamics in the coastal zone. Results of field tests are given.     

Molecular and isotopic characteristics of gas hydrate-bound hydrocarbons in southern and central Lake Baikal

We investigated the molecular composition (methane, ethane, and propane) and stable isotope composition (methane and ethane) of hydrate-bound gas in sediments of Lake Baikal. Hydrate-bearing sediment cores were retrieved from eight gas seep sites, located in the southern and central Baikal basins. Empirical classification of the methane stable isotopes (δ¹³C and δD) for all the seep sites indicated the dominant microbial origin of methane via methyl-type fermentation; however, a mixture of thermogenic and microbial gases resulted in relatively high methane δ¹³C signatures at two sites where ethane δ¹³C indicated a typical thermogenic origin. At one of the sites in the southern Baikal basin, we found gas hydrates of enclathrated microbial ethane in which ¹³C and deuterium were both highly depleted (mean δ¹³C and δD of –61.6‰ V-PDB and –285.4‰ V-SMOW, respectively). To the best of our knowledge, this is the first report of C₂ δ¹³C–δD classification for hydrate-bound gas in either freshwater or marine environments.     

Optical characteristics of coastal waters and atmosphere near the south coast of the crimea at the end of summer 2008

We present the results of measurements of optical characteristics of waters (the beam attenuation coefficient, volume scattering function, sea water reflectance, and Secchi depth) and optical characteristics of the atmosphere (aerosol optical thickness, content of vapors, and the ?ngstr?m exponent) carried out in September 2008 on the oceanographic platform near Katsiveli. We carried out the comparative analysis of hydrooptical characteristics measured in various years. The optical type of sea waters in the period of observations is determined.     

Use of detrital foods and assimilation of nitrogen by coastal detritivores

Two killifish common in east coast U.S.A. salt marshes,Cyprinodon variegatus Lacepede andFundulus heteroclitus Walbaum, differ in their ability to assimilate nitrogen from and grow on detritus.C. variegatus grew on a diet of detritus ofSpartina alterniflora Loisel, whileF. heteroclitus did not. In addition, when the fish were fed¹⁵N-labeledS. alterniflora detritus,¹⁵N:¹⁴N ratios inC. variegatus were higher than were ratios inF. heteroclitus. Therefore, even though both species ingest large amounts of detritus,C. variegatus makes more effective use of this portion of its diet. These dietary differences are corroborated by anatomical differences that suggest thatC. variegatus should make better use of detrital or plant tissues thanF. heteroclitus. In the label experiment, the degree of label in both fish was directly proportional to the degree of label in the food treatments. In previously published experiments designed to compare plant substrate with attached microbes as nitrogen sources for detritivores, %¹⁵N incorporated by a polychaete was also directly proportional to %¹⁵N in the detrital food. Therefore, it is difficult to distinguish between plant substrate and microbes as nitrogen sources for this detritivore.