一次雨、雪、霰天气的观测

一、充分了解天气背景和发展趋势(一)降雪前首都机场天气背景从2010年3月12日05时(UTC)时开始,首都机场一直维持东南风,风向在110°～140°之间,风速在3～5米/秒之间。同时,云量也在逐步增加,云层不断下沉增厚,到了13日的19:40时以后,首都机场已经是漫天层积云,云底高1200米,且相对湿度也在明显上升。由于云层的夜间保温效应,降雪前,本场地面气温较前几日明显偏高(在2℃以上)。     

Responsibility,capability, and Active SETI: Policy,law, ethics,and communication with extraterrestrial intelligence

With recently growing interest in the Active Search for Extraterrestrial Intelligence (SETI), in which humankind would send intentional signals to extraterrestrial civilizations, there have been increased concerns about appropriate policy, as well as the role of space law and ethics in guiding such activities. Implicit in these discussions are notions of responsibility and capability that affect judgments about whether humans or other civilizations should initiate transmissions. Existing protocols that guide SETI research address transmissions from Earth, but there is debate over whether these guidelines should inform de novo transmissions as well. Relevant responsibilities to address include (1) looking out for the interests of humankind as a whole, (2) being truthful in interstellar messages, and (3) benefiting extraterrestrial civilizations. Our capabilities as a species and a civilization affect how well we can fulfill responsibilities, as seen when we consider whether we will be able to reach consensus about message contents (and whether that would be desirable), and whether we have the capacity to decode messages from beings that rely on different sensory modalities. The interplay of these responsibilities and capabilities suggests that humankind should place increased emphasis on Active SETI.     

Operation and performance of a second generation, solid state, star tracker, the ASC

The Advanced Stellar Compass (ASC) is a second generation star tracker, consisting of a CCD camera and its associated microcomputer. The ASC operates by matching the star images acquired by the camera with its internal star catalogs. An initial attitude acquisition (solving the lost in space problem) is performed, and successively, the attitude of the camera is calculated in celestial coordinates by averaging the position of a large number of star observations for each image. Key parameters of the ASC for the Ørsted satellite and Astrid II satellite versions are: mass as low as 900 g, power consumption as low as 5.5W, relative attitude angle errors less than 1.4 arcseconds in declination, and 13 arcseconds in roll, RMS, as measured at the Mauna Kea, HI observatories of the University of Hawaii in June 1996.     

Announcement - GIScience 2000, First International Conference on Geographic Information Science,Savannah Marriott River Front,Savannah, Georgia,USA, October 28–31, 2000

Spatial Cognition and Computation -     

International coordination in the era of faster, better, cheaper

Space agencies around the world are seeking innovative approaches to reduce the time and expense of space-based activities, including observation of the Earth and acquisition of environmental data for Earth science research. As government budgets are squeezed, agencies search for innovative approaches to streamline program management, introduce new technology, and share costs with external partners. International cooperation has been a mainstay of Earth observation activity from the beginning of space exploration. It continues to be true that global problems require global solutions, and governments recognize the need to share the investment in understanding and monitoring the planet. Agencies need to carefully consider how changes in their program development and management practices might impact cooperative ventures. Improved communication, enhanced strategic planning, and coordinated rather than comprehensive missions are all tools agencies can use to maintain or improve partnerships.     

膨胀循环发动机技术的发展、应用与展望

系统总结了国内外膨胀循环发动机技术的发展和应用情况,在分析未来航天发展需求、研究膨胀循环发动机技术发展方向的基础上,对膨胀循环发动机技术未来的发展进行了展望.     

Survey of modeling,planning, and ground verification of space robotic systems

Space robotic systems are expected to play an increasingly important role in future space activities. Nevertheless, dynamics modeling and motion planning of a space robot are much more complex than those of a fixed-base robot, due to the dynamic coupling between the manipulator and its base. On the other hand, in order to assure the success of on-orbital missions, many experiments are required to verify the key algorithms on the ground before the space robot is launched. In this paper, the main research achievements on dynamics modeling, path planning, and ground verification are reviewed, and future studies are recommended. Firstly, we summarize the essential modeling concepts, and deduce the kinematics and dynamics equations of a space robot. Secondly, the main motion planning approaches are discussed. Then, different ground verification systems, including the air-bearing table, neutral buoyancy, airplane flying, free-falling motion, suspension system, and hybrid system, are introduced. Finally, the future research trends are forecasted.     

Some Features of Solar Proton Events on March 7, 2011, and on February 20, 2014

Cosmic Research - The paper presents the results of studying two solar proton events—on March 7, 2011, and on February 20, 2014—which are associated with solar flares having almost the...