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181.
We review the structure and dynamics of the solar chromosphere with emphasis on the quiet Sun and properties that are relevant
to element fractionation mechanisms. Attention is given to the chromospheric magnetic field, its connections to the photosphere,
and to the dynamical evolution of the chromosphere. While some profound advances have been made in the “unmagnetized” chromosphere,
our knowledge of the magnetically controlled chromosphere, more relevant for the discussion of element fractionation, is limited.
Given the dynamic nature of the chromosphere and the poorly understood magnetic linkage to the corona, it is unlikely that
we will soon know the detailed processes leading to FIP fractionation.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
182.
183.
Peter Hoppe 《Space Science Reviews》2008,138(1-4):43-57
Primitive meteorites and interplanetary dust particles contain small quantities of dust grains with highly anomalous isotopic compositions. These grains formed in the winds of evolved stars and in the ejecta of stellar explosions, i.e., they represent a sample of circumstellar grains that can be analyzed with high precision in the laboratory. Such studies have provided a wealth of information on stellar evolution and nucleosynthesis, Galactic chemical evolution, grain growth in stellar environments, interstellar chemistry, and the inventory of stars that contributed dust to the Solar System. Among the identified circumstellar grains in primitive solar system matter are diamond, graphite, silicon carbide, silicon nitride, oxides, and silicates. Circumstellar grains have also been found in cometary matter. To date the available information on circumstellar grains in comets is limited, but extended studies of matter returned by the Stardust mission may help to overcome the existing gaps. 相似文献
184.
Recent technological advances in the development of instruments and platforms like aircraft, balloons, satellites, the space station and, very recently, Zeppelin dirigibles, have opened up many new applications for remote sensing. This paper is an attempt to summarise and compare advantages and disadvantages as well as limitations, restrictions and perspectives of passive remote sensing instruments used on the different platforms and it should help to select the best platform for a special application for Earth observation. 相似文献
185.
186.
Peter Köpke Heinrich Quenzel 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(5):29-32
Numerical modelling is used to search for the most suitable conditions, with the object of determining the atmospheric turbidity (aerosol optical depth) from upward emerging spectral radiances in cloudfree pixels over water surfaces. The most suitable conditions are those where the influence of the turbidity on the radiance most strongly outweighs that of the other optically acting constituents. Since the actual values of these constituents of atmosphere and surface are usually known only within certain limits, using the most suitable conditions minimizes the uncertainty in the turbidity to be derived from satellite measurements. As a result, favorable zenith angles of the satellite and favorable wavelengths are presented for an atmosphere with maritime aerosols with and without Saharan dust. The results represent an advance on a paper published by the authors in 1981 [1]. 相似文献
187.
Peter H. Schultz Carolyn M. Ernst Jennifer L. B. Anderson 《Space Science Reviews》2005,117(1-2):207-239
The NASA Discovery Deep Impact mission involves a unique experiment designed to excavate pristine materials from below the
surface of comet. In July 2005, the Deep Impact (DI) spacecraft, will release a 360 kg probe that will collide with comet
9P/Tempel 1. This collision will excavate pristine materials from depth and produce a crater whose size and appearance will
provide fundamental insights into the nature and physical properties of the upper 20 to 40 m. Laboratory impact experiments
performed at the NASA Ames Vertical Gun Range at NASA Ames Research Center were designed to assess the range of possible outcomes
for a wide range of target types and impact angles. Although all experiments were performed under terrestrial gravity, key
scaling relations and processes allow first-order extrapolations to Tempel 1. If gravity-scaling relations apply (weakly bonded
particulate near-surface), the DI impact could create a crater 70 m to 140 m in diameter, depending on the scaling relation
applied. Smaller than expected craters can be attributed either to the effect of strength limiting crater growth or to collapse
of an unstable (deep) transient crater as a result of very high porosity and compressibility. Larger then expected craters
could indicate unusually low density (< 0.3 g cm−3) or backpressures from expanding vapor. Consequently, final crater size or depth may not uniquely establish the physical
nature of the upper 20 m of the comet. But the observed ejecta curtain angles and crater morphology will help resolve this
ambiguity. Moreover, the intensity and decay of the impact “flash” as observed from Earth, space probes, or the accompanying
DI flyby instruments should provide critical data that will further resolve ambiguities. 相似文献
188.
An essential part of increment preparation for the ISS is the training of the flight crews. Each international partner is responsible for the basic training of its own astronauts, where a basic knowledge is taught on space science and engineering, ISS systems and operations and general astronaut skills like flying, diving, survival, language, etc. The main parts of the ISS crew training are the Advanced Training, e.g., generic ISS operations; nominal and malfunction systems operations and emergencies, and the Increment-Specific Training, i.e., operations and tasks specific to a particular increment. The Advanced and Increment-Specific Training is multilateral training, i.e., each partner is training all ISS astronauts on its contributions to the ISS program. Consequently, ESA is responsible for the Basic Training of its own astronauts and the Advanced and Increment-Specific Training of all ISS crews after Columbus activation on Columbus Systems Operations, Automated Transfer Vehicle (ATV), and ESA payloads.
This paper gives an overview of the ESA ISS Training Program for Columbus Systems Operations and ATV, for which EADS Space Transportation GmbH is the prime contractor. The key training tasks, the training flow and the training facilities are presented. 相似文献
189.
190.
Natriuretic peptide-sensitive guanylyl cyclase expression is down-regulated in human melanoma cells at simulated weightlessness 总被引:1,自引:0,他引:1
Krassimira Ivanova Peter Eiermann Wasiliki Tsiockas Jens Hauslage Ruth Hemmersbach Rupert Gerzer 《Acta Astronautica》2011,68(7-8):652-655
The membrane-bound guanylyl cyclases A and B (GC-A/B), which are receptors for natriuretic peptides, are expressed in cancer cells including melanomas and may represent new anticancer targets. Here, we report down-regulation of GC-A/B expression in human metastatic melanoma cells at simulated weightlessness in comparison to 1g conditions, suggesting attenuation of metastatic potential in weightlessness. 相似文献