Evidence of climatic warming in the southern Urals region derived from borehole temperatures and meteorological data     

Inessa V. Golovanova  Robert N. Harris  Galina V. Selezniova  Petr Stulc 《Global and Planetary Change》2001,29(3-4)

Thirty borehole temperature–depth profiles in the central and southern Urals, Russia were scrutinized for evidence of ground surface temperature histories. We explored two inversion schemes: a simple ramp inversion in which solutions are parameterized in terms of an onset time and magnitude of change and a more sophisticated functional space inverse algorithm in which the functional form of the solution is left unspecified. To enhance and potentially identify latitudinal differences in the ground surface temperature signal, we subdivided the data into three groups based on geographic proximity and simultaneously inverted the borehole temperature–depth logs. The simultaneous inversions highlighted 13 temperature–depth logs that could not both fit a common ground surface temperature history and a priori models within reasonable bounds. Our results confirm that this is an effective way to reduce site-specific noise from an ensemble of boreholes. Each inversion scheme gives comparable results indicating locally variable warming on the order of 1°C starting between 1800 and 1900 AD. Similarly surface air temperature records from 12 nearby meteorological stations exhibit locally variable warming also on the order of 1°C of warming during the 20th century. To explore the degree to which borehole temperatures and surface air temperature (SAT) time series are responding to the same signal, we average the SAT data into the same three groups and used these averages as a forcing function at the Earth's surface to generate synthetic transient temperature profiles. Root mean square (RMS) misfits between these synthetic temperature profiles and averaged temperature–depth profiles are low, suggesting that first-order curvature in borehole temperatures and variations in SAT records are correlated.  相似文献   

A high speed near infrared photometer for lunar occultation studies     

Ashok  N. M.  Chandrasekhar  T.  Ragland  Sam  Bhatt  H. C. 《Experimental Astronomy》1994,4(3-4):177-188

A recently developed near infrared high speed photometer intended for lunar oc-cultation studies is described. The primary scientific objective is to reach milli arc second levels of angular resolution so that circumstellar structure of the occulted sources can be resolved. Near infrared sky brightness close to the lunar limb is also studied. Angular diameter derived from the observed occultation of IRC +20169 is presented and system performance discussed.  相似文献   

Formation Flying Satellites: Control By an Astrodynamicist     

Kyle T. Alfriend  Srinivas R. Vadali  Hanspeter Schaub 《Celestial Mechanics and Dynamical Astronomy》2001,81(1-2):57-62

Satellites flying in formation is a concept being pursued by the Air Force and NASA. Potential periodic formation orbits have been identified using Hill's (or Clohessy Wiltshire) equations. Unfortunately the gravitational perturbations destroy the periodicity of the orbits and control will be required to maintain the desired orbits. Since fuel will be one of the major factors limiting the system lifetime it is imperative that fuel consumption be minimized. To maximize lifetime we not only need to find those orbits which require minimum fuel we also need for each satellite to have equal fuel consumption and this average amount needs to be minimized. Thus, control of the system has to be addressed, not just control of each satellite. In this paper control of the individual satellites as well as the constellation is addressed from an astrodynamics perspective.  相似文献   

The BepiColombo Mercury surface element     

M. Novara   《Planetary and Space Science》2001,49(14-15)

Several versions of a Mercury surface element, part of the ESA BepiColombo Mercury Cornerstone mission to be launched in 2009, have been studied. The major constraint on system design has been the need to maximise the useful system mass on the surface of Mercury. The absence of atmosphere on the planet forces the adoption of a purely propulsive descent and landing system. The need to maintain the shock level at landing below limits which are acceptable to the payload imposes the adoption of a precise guidance, navigation & control system, which allows a drastic reduction of the landing speed, and therefore the adoption of an airbag landing system. Surface mobility is an obvious requirement for the purpose of geochemical exploration, since selected rocks have a much higher scientific yield than the average regolith. Geophysical investigations require that thermal, accelerometric, and densitometric probes be brought in contact with subsurface regions, to a depth of several metres. Magnetometric measurements may need deployment of sensors to some distance from the bulk of the lander body. The thermal environment on the surface of Mercury is extreme, even in the polar regions that will be targeted by the BepiColombo lander, while the solar flux rises seasonally to 10 times the one experienced in Earth orbit. The need to provide a low-temperature heat sink to sensors is particularly critical, if these are installed on a small-size, small-mass mobile deployment device. A consequence of the landing in a polar region will be the extremely variable lighting conditions, with extended portions of the surface shrouded in darkness by any small surface obstacle. Limitations on communications between Earth and the deployed payload will be caused by the low available data rate and by visibility windows (contact may be restricted to as little as <10 min every 9.5 h). This will impose a high degree of autonomy to be built into the payload systems.  相似文献   

CSCO_3 CYCLES IN SALAWUSU RIVER BASINSINCE 150KA B.P.     

LUO Kai-li    LI Bao-sheng    ZHU Yi-zhi  JIN He-ling  ZHANG David Dian  YAN Man-cun  LI Hou-xin  YAO Chun-xia  ZHANG Yu-hongf . Department of Geography  South China Normal University  Guangzhou  P. R. China  . State Key Labor 《中国地理科学(英文版)》2001,11(4):336-342

About 70years ago，Frenc卜卜alaeohdoglst回LL sc卜dars al卜ome and a卜road卜ave successively con－HARD de Chardin P．et al．Initiated the Quaternary ducted large amount ofwork on the Later Quaternarygeologlcal research In the ＞alawusu River Basin of strata（TEILHARD，1924； YUAN，1978； LI，1987；desert region of Northern China and established th，ZHENG，1989； SUN et al，1996； LI et al，1993），Salawusu Formation门EILHARD，1924）．Sine，then，palaeobiology…  相似文献   

Exposure age,terrestrial age and pre‐atmospheric radius of the Chinguetti mesosiderite: Not part of a much larger mass     

K. C. WELTEN  P. A. BLAND  S. S. RUSSELL  M. M. GRADY  M. W. CAFFEE  J. MASARIK  A. J. T. JULL  H. W. WEBER  L. SCHULTZ 《Meteoritics & planetary science》2001,36(7):939-946

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Final tidal evolution of orbit-orbit resonances     

Th. Pauwels 《Celestial Mechanics and Dynamical Astronomy》1994,59(2):101-127

In this paper we describe a model for the tidal evolution of an orbit-orbit resonance between two satellites of the same planet. We let the system evolve till infinity or until the resonance is destroyed. We find that there are asymptotic values for the eccentricities and inclinations. We list the possible final stages that a resonance can achieve, we give a few examples, and finally we discuss the limitations of the model and its possible applications to real systems.  相似文献   

Erratum to J. M. Adelson, G. R. Helz, and C. V. Miller (2001) Reconstructing the rise of recent coastal anoxia; molybdenum in Chesapeake Bay sediments. Geochimica et Cosmochimica Acta65, 237-252.     

J.M AdelsonG.R Helz  C.V Miller 《Geochimica et cosmochimica acta》2002,66(24):4367

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Rotational broadening and Doppler tomography of the quiescent X-ray nova Centaurus X-4     

M. A. P. Torres  J. Casares  I. G. Martínez-Pais  P. A. Charles 《Monthly notices of the Royal Astronomical Society》2002,334(1):233-240

We present a library of 47 open-cluster integrated spectra, mostly obtained at CASLEO (San Juan, Argentina) in the range  3600 < λ < 7400 Å  , which are made available at CDS. The data are combined with previous spectra to obtain 10 high signal-to-noise ratio basic templates in the young and intermediate-age domains, which are also provided in the library. These Galactic disc templates represent the increased time resolution spectral evolution of a stellar population unit around the Solar metallicity level. The improved signal-to-noise ratio of the present templates with respect to previous template lists, together with their increased time resolution, allowed us to improve the fundamental parameters of some open clusters. The present spectral library will be useful for several astrophysical applications, particularly for population syntheses of star-forming giant galaxies.  相似文献   

Multiple stellar populations in the Sextans dwarf spheroidal galaxy?     

M. Bellazzini  F.R. Ferraro  E. Pancino † 《Monthly notices of the Royal Astronomical Society》2001,327(1):L15-L20

We present wide-field     multiband ( BVI ) CCD photometry (down to     of the very low surface brightness dwarf spheroidal galaxy Sextans. In the derived colour–magnitude diagrams we find evidence suggesting the presence of multiple stellar populations in this dwarf spheroidal. In particular, we discover (i) a blue horizontal branch tail that appears to lie on a brighter sequence with respect to the prominent red horizontal branch and the RR Lyrae stars, very similar to what was found by Majewski et al. for the Sculptor dwarf spheroidal, (ii) hints of a bimodal distribution in colour of the red giant branch stars, (iii) a double red giant branch bump. All of these features suggest that (at least) two components are present in the old stellar population of this galaxy: the main one with     and a minor component around     . The similarity to the Sculptor case may indicate that multiple star formation episodes are also common in the most nearby dwarf spheroidals that ceased their star formation activity at very early epochs.  相似文献