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W. F. Huebner 《Space Science Reviews》2008,138(1-4):5-25
In this introductory presentation, material is categorized according to our state of knowledge: What do we know, what do we think we know but don’t know certainly, and what do we not know but often describe it as if it were a well-established fact about comets, their nuclei, their composition, and processes within comets and their nuclei. The material is presented not with the intend to criticize laboratory work simulating condition in comet nuclei, or observers analyzing their observations, nor modelers using data from both these sources to improve our understanding and make predictions. The intent is to provoke discussion and dialog between these groups to avoid overstating the results. What is a Comet? A comet is a diffuse appearing celestial phenomenon moving in an orbit about the Sun. The central body, the nucleus, is composed of ice and dust. It is the source of all cometary activity, including comae and tails. We distinguish between molecular (including atoms and ions) and dust comae. At heliocentric distances of about 1 AU and less, the hydrogen coma typically has dimensions larger than the Sun. The tails are composed of dust, neutral atoms and molecules, and plasma. 相似文献
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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