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151.
John N. Opiela 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Material density is an important, yet often overlooked, property of orbital debris particles. Many models simply use a typical density to represent all breakup fragments. While adequate for modeling average characteristics in some applications, a single value material density may not be sufficient for reliable impact damage assessments. In an attempt to improve the next-generation NASA Orbital Debris Engineering Model, a study on the material density distribution of the breakup fragments has been conducted and summarized in this paper. 相似文献
152.
Hiroshi Matsui John C. Foster Donald L. Carpenter Iannis Dandouras Fabien Darrouzet Johan De Keyser Dennis L. Gallagher Jerry Goldstein Pamela A. Puhl-Quinn Claire Vallat 《Space Science Reviews》2009,145(1-2):107-135
The electric field and magnetic field are basic quantities in the plasmasphere measured since the 1960s. In this review, we first recall conventional wisdom and remaining problems from ground-based whistler measurements. Then we show scientific results from Cluster and Image, which are specifically made possible by newly introduced features on these spacecraft, as follows. 1. In situ electric field measurements using artificial electron beams are successfully used to identify electric fields originating from various sources. 2. Global electric fields are derived from sequences of plasmaspheric images, revealing how the inner magnetospheric electric field responds to the southward interplanetary magnetic fields and storms/substorms. 3. Understanding of sub-auroral polarization stream (SAPS) or sub-auroral ion drifts (SAID) are advanced through analysis of a combination of magnetospheric and ionospheric measurements from Cluster, Image, and DMSP. 4. Data from multiple spacecraft have been used to estimate magnetic gradients for the first time. 相似文献
153.
Makhosonke Berthwell Dubazane John Bosco Habarulema Jean Claude Uwamahoro 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(1):326-336
For the first time, empirical model of daytime vertical drift based on Empirical Orthogonal functions (EOF) decomposition technique is presented. Day-to-day variability of drift inferred from horizontal (H) geomagnetic field data around dip latitude for the period of 2008–2013 is used to both develop and validate the model. Results show that the EOF technique is promising with modelled values and data giving correlation coefficient values of at least 0.90 for geomagnetic conditions of both and within 2008–2013. Independent model validation shows that in situ values from ion velocity meter (IVM) instrument on-board C/NOFS satellite are closer to model estimates than the climatological Scherliess-Fejer (SF) model incorporated within the International Reference Ionosphere (IRI). 相似文献
154.
The objective of the 2009 Mars Science Laboratory (MSL), which is planned to follow the Mars Exploration Rovers and the Phoenix lander to the surface of Mars, is to explore and assess quantitatively a site on Mars as a potential habitat for present or past life. Specific goals include an assessment of the past or present biological potential of the target environment and a characterization of its geology and geochemistry. Included in the 10 investigations of the MSL rover is the Sample Analysis at Mars (SAM) instrument suite, which is designed to obtain trace organic measurements, measure water and other volatiles, and measure several light isotopes with experiment sequences designed for both atmospheric and solid-phase samples. SAM integrates a gas chromatograph, a mass spectrometer, and a tunable laser spectrometer supported by sample manipulation tools both within and external to the suite. The sub-part-per-billion sensitivity of the suite for trace species, particularly organic molecules, along with a mobile platform that will contain many kilograms of organic materials, presents a considerable challenge due to the potential for terrestrial contamination to mask the signal of martian organics. We describe the effort presently underway to understand and mitigate, wherever possible within the resource constraints of the mission, terrestrial contamination in MSL and SAM measurements. 相似文献
155.
G. Randall Gladstone Steven C. Persyn John S. Eterno Brandon C. Walther David C. Slater Michael W. Davis Maarten H. Versteeg Kristian B. Persson Michael K. Young Gregory J. Dirks Anthony O. Sawka Jessica Tumlinson Henry Sykes John Beshears Cherie L. Rhoad James P. Cravens Gregory S. Winters Robert A. Klar Walter Lockhart Benjamin M. Piepgrass Thomas K. Greathouse Bradley J. Trantham Philip M. Wilcox Matthew W. Jackson Oswald H. W. Siegmund John V. Vallerga Rick Raffanti Adrian Martin J.-C. Gérard Denis C. Grodent Bertrand Bonfond Benoit Marquet François Denis 《Space Science Reviews》2017,213(1-4):447-473
The ultraviolet spectrograph instrument on the Juno mission (Juno-UVS) is a long-slit imaging spectrograph designed to observe and characterize Jupiter’s far-ultraviolet (FUV) auroral emissions. These observations will be coordinated and correlated with those from Juno’s other remote sensing instruments and used to place in situ measurements made by Juno’s particles and fields instruments into a global context, relating the local data with events occurring in more distant regions of Jupiter’s magnetosphere. Juno-UVS is based on a series of imaging FUV spectrographs currently in flight—the two Alice instruments on the Rosetta and New Horizons missions, and the Lyman Alpha Mapping Project on the Lunar Reconnaissance Orbiter mission. However, Juno-UVS has several important modifications, including (1) a scan mirror (for targeting specific auroral features), (2) extensive shielding (for mitigation of electronics and data quality degradation by energetic particles), and (3) a cross delay line microchannel plate detector (for both faster photon counting and improved spatial resolution). This paper describes the science objectives, design, and initial performance of the Juno-UVS. 相似文献
156.
J. Isbert J.H. Adams Jr. H.S. Ahn G.L. Bashindzhagyan K.E. Batkov M. Christl A.R. Fazely O. Ganel R.M. Gunashingha T.G. Guzik J. Chang K.C. Kim E.N. Kouznetsov Z.W. Lin M.I. Panasyuk A.D. Panov W.K.H. Schmidt E.S. Seo N.V. Sokolskaya John W. Watts J.P. Wefel J. Wu V.I. Zatsepin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The Advanced Thin Ionization Calorimeter (ATIC) Balloon Experiment had a successful test flight and a science flight in 2000–01 and 2002–03 and an unsuccessful launch in 2005–06 from McMurdo, Antarctica, returning 16 and 19 days of flight data. ATIC is designed to measure the spectra of cosmic rays (protons to iron). The instrument is composed of a Silicon matrix detector followed by a carbon target interleaved with scintillator tracking layers and a segmented BGO calorimeter composed of 320 individual crystals totaling 18 radiation lengths to determine the particle energy. BGO (Bismuth Germanate) is an inorganic scintillation crystal and its light output depends not only on the energy deposited by particles but also on the temperature of the crystal. The temperature of balloon instruments during flight is not constant due to sun angle variations as well as differences in albedo from the ground. The change in output for a given energy deposit in the crystals in response to temperature variations was determined. 相似文献
157.
158.
As well as providing practical information on Earth-besetting problems, space science and exploration are vital tools for capturing the public imagination and encouraging young people's interest in space. The relatively small scale of some scientific instruments also allows mission participation by developing countries. Citing the work of the UN and various NGOs in promoting study and distribution of space science data, the authors recommend that it be given a higher profile and suggest a number of projects -- the Mars drill study in Egypt, refurbishment of a telescope facility in Sri Lanka -- involving developing countries that should be followed up, as well as listing ongoing successful projects. The UN is urged to continue its annual workshops on space science (apparently under threat) and to ensure its inclusion in the forthcoming UNISPACE III Conference. 相似文献
159.
John Heise 《Space Science Reviews》1985,40(1-2):79-90
Hot white dwarfs are objects that copiously emit in the Extreme Ultraviolet and soft X-ray range. They are the brightest sources seen in the Low Energy Telescope of EXOSAT, with countrates up to 25 cnts/s. in contrast to their optical and UV spectrum the total flux and spectral distribution at soft X-ray energies are highly sensitive to the effective temperature, structure and elemental composition of the dwarf's atmosphere. The imaging soft X-ray experiments onboard EXOSAT cover with large sensitivity the spectral region where the peak of emission of hot white dwarfs is expected to occur.I here review some of the (preliminary) results obtained so far with broadband X-ray photometry on a dozen or so white dwarfs, and some of the high-resolution spectra obtained for three white dwarfs with the grating spectrometers. 相似文献
160.
John P. Bradley 《Space Science Reviews》1991,56(1-2):131-138
Electron transparent thin sections (30–100 nm thick) of interplanetary dust particles and other fine-grained meteoritic materials are produced using an ultramicrotome equipped with a diamond knife. An analytical electron microscope (AEM) is imployed to examine indigenous physical properties (e.g. porosity), mineralogy, and petrography. Large data sets of quantitative point count analyses obtained from thin sections enable direct mineralogical comparison of IDPs and Halley. 相似文献