SMART-1 mission description and development status     

G. D. Racca  A. Marini  L. Stagnaro  J. van Dooren  L. di Napoli  B. H. Foing  R. Lumb  J. Volp  J. Brinkmann  R. Grünagel  D. Estublier  E. Tremolizzo  M. McKay  O. Camino  J. Schoemaekers  M. Hechler  M. Khan  P. Rathsman  G. Andersson  K. Anflo  S. Berge  P. Bodin  A. Edfors  A. Hussain  J. Kugelberg  N. Larsson  B. Ljung  L. Meijer  A. Mrtsell  T. Nordebck  S. Persson  F. Sjberg 《Planetary and Space Science》2002,50(14-15)

SMART-1 is the first of the Small Missions for Advanced Research in Technology of the ESA Horizons 2000 scientific programme. The SMART-1 mission is dedicated to testing of new technologies for future cornerstone missions, using Solar-Electric Primary Propulsion (SEPP) in Deep Space. The chosen mission planetary target is the Moon. The target orbit will be polar with the pericentre close to the South-Pole. The pericentre altitude lies between 300 and 2000 km, while the apocentre will extend to about 10,000 km. During the cruise phase, before reaching the Moon, the spacecraft thrusting profile allows extended periods for cruise science. The SMART-1 spacecraft will be launched in the spring of 2003 as an auxiliary passenger on an Ariane 5 and placed into a Geostationary Transfer Orbit (GTO). The expected launch mass is about 370 kg, including 19 kg of payload. The selected type of SEPP is a Hall-effect thruster called PPS-1350. The thruster is used to spiral out of the GTO and for all orbit maneuvers including lunar capture and descent. The trajectory has been optimised by inserting coast arcs and the presence of the Moon's gravitational field is exploited in multiple weak gravity assists.The Development Phase started in October 1999 and is expected to be concluded by a Flight Acceptance Review in January 2003. The short development time for this high technology spacecraft requires a concerted effort by industry, science institutes and ESA centres. This paper describes the mission and the project development status both from a technical and programmatic standpoint.  相似文献   

Marine conditions in central Sweden during the early Preboreal as inferred from a stable oxygen isotope gradient     

Kristian Schoning  Fredrik Klingberg  Stefan Wastegrd 《第四纪科学杂志》2001,16(8):785-794

The marine benthic fauna and the δ¹⁸O_c of foraminifers and ostracods from six sites situated on a west–east transect through central Sweden have been analysed in order to estimate the palaeosalinity and palaeocirculation in this shallow‐marine environment. The measurements have been undertaken on material from the early Preboreal, when the Baltic Basin was in contact with the North Sea through straits in central Sweden. The δ¹⁸O_c values have a more negative value towards the east, indicating decreasing salinity. This was the result of limited possibilities for marine water to penetrate into the Baltic Basin and the mixing with freshwater from the melting Fennoscandian ice‐sheet. Four water masses existed in the area: a surface layer of freshwater, marine water from the North Sea, brackish–marine intermediate water on the Swedish west coast and brackish Yoldia Sea water in the Baltic Basin. The chronology is based on radiocarbon dates of marine fossils and, at one site, on the occurrence of the Vedde Ash (10 400–10 300 ¹⁴C yr BP). This is the first record from marine settings in Sweden. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Holocene recolonization and extinction of the pond turtle, Emys orbicularis (L., 1758), in Europe     

Robert S. Sommer  Arne Persson  Nina Wieseke  Uwe Fritz 《Quaternary Science Reviews》2007,26(25-28):3099-3107

We reconstruct the Holocene range fluctuations of the European pond turtle (Emys orbicularis) for northern and Central Europe. Based on 529 subfossil records and radiocarbon dating of critical finds, we provide evidence that E. orbicularis experienced a rapid range expansion with Holocene warming. Phylogeographic data argue for a colonization of northern and Central Europe from a glacial refuge located in the south-eastern Balkans. Already in the Late Preboreal (9100–8600 cal BC) the species occurred in northern Central Europe and was widespread in Denmark and southern Sweden (Skåne) during the Boreal (8600–7100 cal BC). The maximum range extension occurred during the Holocene climatic optimum (Atlantic: 7100–3750 cal BC), with records in southern England, middle Sweden, and northern Estonia. After the early Subboreal (3750–1750 cal BC) northern populations collapsed, coinciding with a climatic cooling and oceanization. Northern populations were most likely established via long distance dispersal (rafting using rivers debouching in the North and Baltic Seas); after northern Europe was reached, a minimum dispersal of 50 km per 100 years may be hypothesized for the Boreal.  相似文献   

Validation of a field filtration technique for characterization of suspended particulate matter from freshwater. Part II. Minor, trace and ultra trace elements     

Fredrik dman  Thomas Ruth  Ilia Rodushkin  Christer Pontr 《Applied Geochemistry》2006,21(12):2112-2134

A field filtration method for the concentration and separation of suspended particulate matter (SPM) from freshwater systems and the subsequent determination of minor, trace and ultra trace elements (As, Ba, Be, Cd, Co, Cr, Cs, Cu, Ga, Hf, Mo, Nb, Ni, Pb, Rb, Sb, Sc, Sn, Sr, Ta, Th, Tl, U, V, W, Zn and Zr) is validated with respect to detection limits, precision and bias. The validation comprises the whole procedure including filtration, sample digestion and instrumental analysis. The method includes two digestion procedures (microwave acid digestion and alkali fusion) in combination with inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). Total concentrations of these 27 trace and minor elements have been determined in suspended particulate matter (SPM) from lake and river water with low levels of suspended solids (<2 mg L⁻¹ DW), and a wide range of element concentrations. The precision of the method including filtration, digestion and instrumental determination ranges between 8% and 18% RSD for most elements on a dry weight basis. Higher recovery after acid digestion is found for some elements, probably because of volatilization or retention losses in the fusion procedure. Other elements show higher recovery after fusion, which is explained by more efficient decomposition of refractory mineral phases relative to the non-total acid digestion. Non-detectable concentrations of some elements are reported due to small differences between blank filter levels and the amounts of elements present on the filters after sampling. The method limits of detection range between 0.7 ng and 2.65 μg, as estimated from the blank filter samples. These detection limits are 10–550 times higher compared to the corresponding instrumental limits of detection. The accuracy and bias of the overall analytical procedure was assessed from replicate analysis of certified reference materials. A critical evaluation of the instrumental capabilities of the ICP-QMS instrumentation in comparison with a double focusing sector field plasma mass spectrometry technique (ICP-SFMS) is also included. It was found that a modified microwave acid digestion procedure in combination with ICP-SFMS could replace ICP-AES determinations and fusion digestions for most of the investigated elements. Guidelines and limitations for this time- and labour- efficient procedure, offering accurate results for the majority of elements studied are discussed.  相似文献