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31.
32.
The influence of isolation and confinement on social support and depressed mood was examined in a study of 235 men and women who spent a year at McMurdo Station in Antarctica, and a study of 77 men and women who spent a year at the Amundson-Scott South Pole Station. Although availability of support remained unchanged, there was a significant decrease in reported satisfaction with support obtained, as well as a significant increase in depressed mood. Satisfaction with support was inversely associated with depressed mood at the beginning and end of isolation and confinement. At the end of winter, this association varied by source of support. High levels of tension-anxiety, depression and anger preceded an increase in advice seeking, but high levels of advice seeking also preceded an increase in tension-anxiety and depression. Results suggest a significant erosion of social support under conditions of prolonged isolation and confinement, leading to an increase in depressed mood. 相似文献
33.
Michael J. S. Belton Kenneth P. Klaasen Maurice C. Clary James L. Anderson Clifford D. Anger Michael H. Carr Clark R. Chapman Merton E. Davies Ronald Greeley Donald Anderson Lawrence K. Bolef Timothy E. Townsend Richard Greenberg James W. Head III Gerhard Neukum Carl B. Pilcher Joseph Veverka Peter J. Gierasch Fraser P. Fanale Andrew P. Ingersoll Harold Masursky David Morrison James B. Pollack 《Space Science Reviews》1992,60(1-4):413-455
34.
John O. Goldsten Edgar A. Rhodes William V. Boynton William C. Feldman David J. Lawrence Jacob I. Trombka David M. Smith Larry G. Evans Jack White Norman W. Madden Peter C. Berg Graham A. Murphy Reid S. Gurnee Kim Strohbehn Bruce D. Williams Edward D. Schaefer Christopher A. Monaco Christopher P. Cork J. Del Eckels Wayne O. Miller Morgan T. Burks Lisle B. Hagler Steve J. DeTeresa Monika C. Witte 《Space Science Reviews》2007,131(1-4):339-391
A Gamma-Ray and Neutron Spectrometer (GRNS) instrument has been developed as part of the science payload for NASA’s Discovery
Program mission to the planet Mercury. Mercury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) launched
successfully in 2004 and will journey more than six years before entering Mercury orbit to begin a one-year investigation.
The GRNS instrument forms part of the geochemistry investigation and will yield maps of the elemental composition of the planet
surface. Major elements include H, O, Na, Mg, Si, Ca, Ti, Fe, K, and Th. The Gamma-Ray Spectrometer (GRS) portion detects
gamma-ray emissions in the 0.1- to 10-MeV energy range and achieves an energy resolution of 3.5 keV full-width at half-maximum
for 60Co (1332 keV). It is the first interplanetary use of a mechanically cooled Ge detector. Special construction techniques provide
the necessary thermal isolation to maintain the sensor’s encapsulated detector at cryogenic temperatures (90 K) despite the
intense thermal environment. Given the mission constraints, the GRS sensor is necessarily body-mounted to the spacecraft,
but the outer housing is equipped with an anticoincidence shield to reduce the background from charged particles. The Neutron
Spectrometer (NS) sensor consists of a sandwich of three scintillation detectors working in concert to measure the flux of
ejected neutrons in three energy ranges from thermal to ∼7 MeV. The NS is particularly sensitive to H content and will help
resolve the composition of Mercury’s polar deposits. This paper provides an overview of the Gamma-Ray and Neutron Spectrometer
and describes its science and measurement objectives, the design and operation of the instrument, the ground calibration effort,
and a look at some early in-flight data. 相似文献
35.
The Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) on the New Horizons Mission
Ralph L. McNutt Jr. Stefano A. Livi Reid S. Gurnee Matthew E. Hill Kim A. Cooper G. Bruce Andrews Edwin P. Keath Stamatios M. Krimigis Donald G. Mitchell Barry Tossman Fran Bagenal John D. Boldt Walter Bradley William S. Devereux George C. Ho Stephen E. Jaskulek Thomas W. LeFevere Horace Malcom Geoffrey A. Marcus John R. Hayes G. Ty Moore Nikolaos P. Paschalidis Mark E. Perry Bruce D. Williams Paul Wilson IV Lawrence E. Brown Martha B. Kusterer Jon D. Vandegriff 《Space Science Reviews》2009,145(3-4):381-381
36.
Space debris: Assessing risk and responsibility 总被引:1,自引:0,他引:1
Andrew M. Bradley Lawrence M. Wein 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
We model the orbital debris environment by a set of differential equations with parameter values that capture many of the complexities of existing three-dimensional simulation models. We compute the probability that a spacecraft gets destroyed in a collision during its operational lifetime, and then define the sustainable risk level as the maximum of this probability over all future time. Focusing on the 900- to 1000-km altitude region, which is the most congested portion of low Earth orbit, we find that – despite the initial rise in the level of fragments – the sustainable risk remains below 10-3 if there is high (>98%) compliance to the existing 25-year postmission deorbiting guideline. We quantify the damage (via the number of future destroyed operational spacecraft) generated by past and future space activities. We estimate that the 2007 FengYun 1C antisatellite weapon test represents ≈1% of the legacy damage due to space objects having a characteristic size of ?10 cm, and causes the same damage as failing to deorbit 2.6 spacecraft after their operational life. Although the political and economic issues are daunting, these damage estimates can be used to help determine one-time legacy fees and fees on future activities (including deorbit noncompliance), which can deter future debris generation, compensate operational spacecraft that are destroyed in future collisions, and partially fund research and development into space debris mitigation technologies. Our results need to be confirmed with a high-fidelity three-dimensional model before they can provide the basis for any major decisions made by the space community. 相似文献
37.
Piyush M. Mehta Andrew Walker Earl Lawrence Richard Linares David Higdon Josef Koller 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Satellite drag coefficients are a major source of uncertainty in predicting the drag force on satellites in low Earth orbit. Among other things, accurately predicting the orbit requires detailed knowledge of the satellite drag coefficient. Computational methods are an important tool in computing the drag coefficient but are too intensive for real-time and predictive applications. Therefore, analytic or empirical models that can accurately predict drag coefficients are desired. This work uses response surfaces to model drag coefficients. The response surface methodology is validated by developing a response surface model for the drag coefficient of a sphere where the closed-form solution is known. The response surface model performs well in predicting the drag coefficient of a sphere with a root mean square percentage error less than 0.3% over the entire parameter space. For more complex geometries, such as the GRACE satellite, the Hubble Space Telescope, and the International Space Station, the model errors are only slightly larger at about 0.9%, 0.6%, and 1.0%, respectively. 相似文献
38.
Nitrous oxide as a rocket propellant 总被引:1,自引:0,他引:1
Nitrous oxide is introduced as a multi-purpose propellant for spacecraft. Potential space applications of this propellant are given. Based on comparison to conventional systems, a multi-mode nitrous oxide propulsion concept is expected to deliver higher performance. Main features of a self-pressurising, nitrous oxide storage system are described. A nitrous oxide catalytic decomposition technique is suggested for restartable spacecraft propulsion. Up-to-date experimental results are presented. A conclusion describes the long-term feasibility of novel nitrous oxide propulsion option concepts. 相似文献
39.
John H. Heinbockel Tony C. Slaba Steve R. Blattnig Ram K. Tripathi Lawrence W. Townsend Thomas Handler Tony A. Gabriel Lawrence S. Pinsky Brandon Reddell Martha S. Clowdsley Robert C. Singleterry John W. Norbury Francis F. Badavi Sukesh K. Aghara 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The protection of astronauts and instrumentation from galactic cosmic rays and solar particle events is one of the primary constraints associated with mission planning in low earth orbit or deep space. To help satisfy this constraint, several computational tools have been developed to analyze the effectiveness of various shielding materials and structures exposed to space radiation. These tools are now being carefully scrutinized through a systematic effort of verification, validation, and uncertainty quantification. In this benchmark study, the deterministic transport code HZETRN is compared to the Monte Carlo transport codes HETC-HEDS and FLUKA for a 30 g/cm2 water target protected by a 20 g/cm2 aluminum shield exposed to a parameterization of the February 1956 solar particle event. Neutron and proton fluences as well as dose and dose equivalent are compared at various depths in the water target. The regions of agreement and disagreement between the three codes are quantified and discussed, and recommendations for future work are given. 相似文献
40.
Lawrence Freedman 《Space Policy》1985,1(2):131-134
Professor Freedman examines the argument that, with the claimed potential of ballistic missile defence deriving from SDI, there has been a strategic revolution in favour of the defence. He argues that such a revolution will only come despite technological trends and not because of them, ie from building an entirely new strategic relationship with the active cooperation of the USSR, and concludes that the strident advocacy of strategic defensive systems allows the opportunity of avoiding the real dilemmas that confront us in the nuclear age by pretending that there is a technological way out. 相似文献