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951.
Space Exploration educators worldwide are confronting challenges and embracing opportunities to prepare students for the global 21st century workforce. The National Space Biomedical Research Institute (NSBRI), established in 1997 through a NASA competition, is a 12-university consortium dedicated to space life science research and education. NSBRI's Education and Public Outreach Program (EPOP) is advancing the Institute's mission by responding to global educational challenges through activities that: provide teacher professional development; develop curricula that teach students to communicate with their peers across the globe; provide women and minority US populations with greater access to, and awareness of science careers; and promote international science education partnerships.A recent National Research Council (NRC) Space Studies Board Report, America's Future in Space: Aligning the Civil Program with National Needs, acknowledges that “a capable workforce for the 21st century is a key strategic objective for the US space program… (and that) US problems requiring best efforts to understand and resolve…are global in nature and must be addressed through mutual worldwide action”. [1] This sentiment has gained new momentum through a recent National Aeronautics and Space Administration (NASA) report, which recommends that the life of the International Space Station be extended beyond the planned 2016 termination. [2] The two principles of globalization and ISS utility have elevated NSBRI EPOP efforts to design and disseminate science, technology, engineering and mathematics (STEM) educational materials that prepare students for full participation in a globalized, high technology society; promote and provide teacher professional development; create research opportunities for women and underserved populations; and build international educational partnerships.This paper describes select EPOP projects and makes the case for using innovative, emerging information technologies to transfer space exploration knowledge to students, engage educators from across the globe in discourse about science curricula, and foster multimedia collaborations that inform citizens about the benefits of space exploration for life on Earth. Special references are made to educational activities conducted at professional meetings in Austria, Canada, France, China, Greece, Italy, Russia, Scotland and Spain.  相似文献   
952.
Unloading law for a LEO spacecraft with two-gimbals solar array   总被引:1,自引:0,他引:1  
Y. W. Jan  J. C. Chiou   《Acta Astronautica》2002,51(12):312-854
The purpose of this paper is to present a modified cross-product unloading law that can be used to provide an open-loop compensation control design to counteract the predominant effects of the gravity gradient torque. The modified cross-product unloading law, is successfully applied to a three-axis stabilized, nadir-pointed LEO spacecraft with two-gimbals solar array. The variation of the two solar array orientations can significantly change the spacecraft's moment of inertia during the nominal operation mode, which can produce significant momentum accumulation in the roll–yaw body plane and cause large yaw pointing error. A rigorous study of momentum management performance capability has been conducted by using a high-fidelity performance simulation software that contains models of four environmental disturbance torque (gravity gradient, aerodynamic, solar, and magnetic). The simulation results show that the proposed momentum unloading control law has enabled a substantial reduction in the maximum accumulated roll momentum, which results in improving the pointing accuracy of the LEO spacecraft enormously.  相似文献   
953.
Started 16 years ago, the ESEME program has led to a number of important findings. We note a simple and unified view of phase transitions, which has been applied to the development of biological patterns, and a very fast thermalization mode that we coined the “piston effect”. This effect has been applied to control the cryogenic reservoirs of the Ariane 5 rocket. All these findings have been obtained thanks to the good coordination of the ESA and CNES space facilities and the construction of high technology experimental modules. The future of the program is linked to the CNES DECLIC facility and the ESA Fluid Science Laboratory (FSL). DECLIC has been designed to increase the temperature regulation above the critical point of water (550 K) so as to investigate chemical reactions under conditions of supercritical water, and in relation to the promising applications of waste treatment by supercritical oxidation. Thanks to the construction of a special vibrational Experiment Container for FSL, the thermal and mechanical behavior of fluids under forced vibration can be investigated. The results of such studies will help to estimate the effect of g-jitter on fluids, and control gases and liquids in space.  相似文献   
954.
Sumner DY 《Astrobiology》2001,1(1):57-70
Analysis of the carbon isotopic composition of carbonates is a valuable tool for studying microbial processes and looking for evidence of life. Microbial fixation of CO2 and conversion of organic carbon to CO2 can produce measurable delta 13C shifts in a microbial mat environment. Diffusion modeling demonstrates that substantial isotopic shifts can develop within the mat and in the diffusion boundary layer in the fluid when CO2 fixation is rapid and prolonged for several hours. Carbonates that precipitate during rapid CO2 fixation can preserve these microbially produced isotopic shifts. However, continued precipitation during intervals when respiration dominates or after the cessation of active microbial growth commonly dilutes autotrophic isotopic signatures. Thus, preserved isotopic signatures rarely reflect the magnitude of isotopic shifts within the mat. Interpretation of observed isotopic shifts in microbial mat carbonate depends on fully characterizing ambient delta 13C and eliminating other origins for isotopic shifts. The carbon isotopic composition of reservoirs can vary substantially, both on Earth and on other planets. Characterizing the reservoir composition and any changes through time is critical to evaluating microbially induced shifts. In addition, careful evaluation of non-microbial causes for shifts in isotopic composition is essential for a reliable interpretation. Complicating processes include recrystallization, calcite precipitation over extended periods of time, variable precipitation rates and water chemistry, and mixing of carbonates having different isotopic signatures.  相似文献   
955.
Bubble Technology Industries Inc. (BTI), with the support of the Canadian Space Agency, has finished the construction of the Canadian High-Energy Neutron Spectrometry System (CHENSS). This spectrometer is intended to measure the high energy neutron spectrum (approximately 1-100 MeV) encountered in spacecraft in low earth orbit. CHENSS is designed to fly aboard a US space shuttle and its scientific results should facilitate the prediction of neutron dose to astronauts in space from readings of different types of radiation dosimeters that are being used in various missions.  相似文献   
956.
CIVA     
CIVA (Comet Infrared and Visible Analyser) is an integrated set of imaging instruments, designed to characterize the 360 panorama (CIVA-P) as seen from the Rosetta Lander Philae, and to study surface and subsurface samples (CIVA-M). CIVA-P is a panoramic stereo camera, while CIVA-M is an optical microscope coupled to a near infrared microscopic hyperspectral imager. CIVA shares a common Imaging Main Electronics (IME) with ROLIS. CIVA-P will characterize the landing site, with an angular sampling (IFOV) of 1.1 mrad: each pixel will image a 1 mm size feature at the distance of the landing legs, and a few metres at the local horizon. The panorama will be mapped by 6 identical miniaturized micro-cameras covering contiguous FOV, with their optical axis 60 apart. Stereoscopic capability will be provided by an additional micro-camera, identical to and co-aligned with one of the panoramic micro-camera, with its optical axis displaced by 10 cm. CIVA-M combines two ultra-compact and miniaturised microscopes, one operating in the visible and one constituting an IR hyperspectral imaging spectrometer: they will characterize, by non-destructive analyses, the texture, the albedo, the molecular and the mineralogical composition of each of the samples provided by the Sample Drill and Distribution (SD2) system. For the optical microscope, the spatial sampling is 7 μm; for the IR, the spectral range (1–4 μm) and the spectral sampling (5 nm) have been chosen to allow identification of most minerals, ices and organics, on each pixel, 40 μm in size. After being studied by CIVA, the sample could be analysed by a subsequent experiment (PTOLEMY and/or COSAC). The process would be repeated for each sample obtained at different depths and/or locations.  相似文献   
957.
The VIRTIS (Visual IR Thermal Imaging Spectrometer) experiment has been one of the most successful experiments built in Europe for Planetary Exploration. VIRTIS, developed in cooperation among Italy, France and Germany, has been already selected as a key experiment for 3 planetary missions: the ESA-Rosetta and Venus Express and NASA-Dawn. VIRTIS on board Rosetta and Venus Express are already producing high quality data: as far as Rosetta is concerned, the Earth-Moon system has been successfully observed during the Earth Swing-By manouver (March 2005) and furthermore, VIRTIS will collect data when Rosetta flies by Mars in February 2007 at a distance of about 200 kilometres from the planet. Data from the Rosetta mission will result in a comparison – using the same combination of sophisticated experiments – of targets that are poorly differentiated and are representative of the composition of different environment of the primordial solar system. Comets and asteroids, in fact, are in close relationship with the planetesimals, which formed from the solar nebula 4.6 billion years ago. The Rosetta mission payload is designed to obtain this information combining in situ analysis of comet material, obtained by the small lander Philae, and by a long lasting and detailed remote sensing of the comet, obtained by instrument on board the orbiting Spacecraft. The combination of remote sensing and in situ measurements will increase the scientific return of the mission. In fact, the “in situ” measurements will provide “ground-truth” for the remote sensing information, and, in turn, the locally collected data will be interpreted in the appropriate context provided by the remote sensing investigation. VIRTIS is part of the scientific payload of the Rosetta Orbiter and will detect and characterise the evolution of specific signatures – such as the typical spectral bands of minerals and molecules – arising from surface components and from materials dispersed in the coma. The identification of spectral features is a primary goal of the Rosetta mission as it will allow identification of the nature of the main constituent of the comets. Moreover, the surface thermal evolution during comet approach to sun will be also studied.  相似文献   
958.
Explicit expressions are derived for the bias and the variance of the maximum likelihood (ML) estimator of the Gumbel distribution.  相似文献   
959.
Solar Neutrinos     
The current status of solar neutrino experiments is reviewed. All the experimental measurements show deficits of solar neutrinos. Non monotonic suppression indicates that the problem may naturally be explained by neutrino oscillations, but not by modifying solar models. A new experiment shows very promising results. We hope that a definite answer to the question of whether solar neutrinos are oscillating will be obtained in the very near future. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
960.
Detection and diagnosis of sensor and actuator failures using IMMestimator   总被引:1,自引:0,他引:1  
An approach to detection and diagnosis of multiple failures in a dynamic system is proposed. It is based on the interacting multiple-model (IMM) estimation algorithm, which is one of the most cost-effective adaptive estimation techniques for systems involving structural as well as parametric changes. The proposed approach provides an integrated framework for fault detection, diagnosis, and state estimation. It is able to detect and isolate multiple faults substantially more quickly and more reliably than many existing approaches. Its superiority is illustrated in two aircraft examples for single and double faults of both sensors and actuators, in the forms of “total”, “partial”, and simultaneous failures. Both deterministic and random fault scenarios are designed and used for testing and comparing the performance fairly. Some new performance indices are presented. The robustness of the proposed approach to the design of model transition probabilities, fault modeling errors, and the uncertainties of noise statistics are also evaluated  相似文献   
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