The Mawrth Vallis region of Mars: A potential landing site for the Mars Science Laboratory (MSL) mission

The primary objective of NASA's Mars Science Laboratory (MSL) mission, which will launch in 2011, is to characterize the habitability of a site on Mars through detailed analyses of the composition and geological context of surface materials. Within the framework of established mission goals, we have evaluated the value of a possible landing site in the Mawrth Vallis region of Mars that is targeted directly on some of the most geologically and astrobiologically enticing materials in the Solar System. The area around Mawrth Vallis contains a vast (>1?×?10? km2) deposit of phyllosilicate-rich, ancient, layered rocks. A thick (>150?m) stratigraphic section that exhibits spectral evidence for nontronite, montmorillonite, amorphous silica, kaolinite, saponite, other smectite clay minerals, ferrous mica, and sulfate minerals indicates a rich geological history that may have included multiple aqueous environments. Because phyllosilicates are strong indicators of ancient aqueous activity, and the preservation potential of biosignatures within sedimentary clay deposits is high, martian phyllosilicate deposits are desirable astrobiological targets. The proposed MSL landing site at Mawrth Vallis is located directly on the largest and most phyllosilicate-rich deposit on Mars and is therefore an excellent place to explore for evidence of life or habitability.     

Validation and comparison of coordinated turn aircraft maneuvermodels

A major challenge posed by aircraft tracking problems is the nondeterministic nature of an aircraft flight, due to the difficulty of predicting the pilot's actions. Accurate aircraft maneuver models are however highly desirable, particularly in air defense applications, to achieve accurate tracking and prediction. Through analysis of actual fighter aircraft trajectories and comparison with the Singer maneuver model, particularly in terms of prediction performance, coordinated turn (CT) aircraft maneuver models are presented, compared, and validated. A more general CT model is shown to better model actual trajectories than the classical CT model used in the literature     

Relationship of psychological and physiological parameters during an Arctic ski expedition.

Considerable data (primarily physiological) have been collected during expeditions in extreme environments over the last century. Physiological measurements have only recently been examined in association with the emotional or behavioral state of the subject. Establishing this psychophysiological relationship is essential to understanding fully the adaptation of humans to the stresses of extreme environments. This pilot study investigated the simultaneous collection of physiological, psychological and behavioral data from a two-man Greenland expedition in order to model how specific relationships between physiological and psychological adaptation to a polar environment may be identified. The data collected describes changes in adrenal and other hormonal activity and psychological functioning. Levels of cortisol and testosterone were calculated. Factors influencing the plasma profiles of the aforementioned included 24-hour sunlight, high calorific intake of more than 28 000 kJ/day and extreme physical exercise. There was a difference between individual psychological profiles as well as self-report stress and physiological stress.     

Psychology and culture during long-duration space missions

The objective of this paper is twofold: (a) to review the current knowledge of cultural, psychological, psychiatric, cognitive, interpersonal, and organizational issues that are relevant to the behavior and performance of astronaut crews and ground support personnel and (b) to make recommendations for future human space missions, including both transit and planetary surface operations involving the Moon or Mars. The focus will be on long-duration missions lasting at least six weeks, when important psychological and interpersonal factors begin to take their toll on crewmembers. This information is designed to provide guidelines for astronaut selection and training, in-flight monitoring and support, and post-flight recovery and re-adaptation.     

Hierarchical adaptive Kalman filtering for interplanetary orbitdetermination

A modular and flexible approach to adaptive Kalman filtering has recently been introduced using the framework of a mixture-of-experts regulated by a gating network. Each expert is a Kalman filter modeled with a different realization of the unknown system parameters. The unknown or uncertain parameters can include elements of the state transition matrix, observation mapping matrix, process noise covariance matrix, and measurement noise covariance matrix. The gating network performs on-line adaptation of the weights given to individual filters based on performance. The mixture-of-experts approach is extended here to a hierarchical architecture which involves multiple levels of gating. The proposed architecture provides a multilevel hypothesis testing capability. The utility of the hierarchical architecture is illustrated via the problem of interplanetary navigation (Mars Pathfinder) using simulated radiometric data. It serves as a useful tool for assisting navigation teams in the process of selecting the parameters of the navigational filter over various operating regimes. It is shown that the scheme has the capability of detecting changes in the system parameters and switching filters appropriately for optimal performance. Furthermore, the expectation-maximization (EM) algorithm is shown to be applicable in the proposed framework     

Partnerships in remote sensing : A theme with some examples

This article reviews the revolution in remote sensing which has taken place over the past 25 years. This revolution could not have occurred without the closest cooperation among government agencies, industry and academia. International cooperation is shown to be essential in carrying out the bold missions planned for the next decade. The article reviews the history of the NASA-NOAA relationship, and the history of international partnerships with emphasis on development of the operational METSAT system. The government-industry partnership is also reviewed, with case studies to examine the evolution of METSAT sensor design, LANDSAT commercialization, and the NOAA Administrator's new initiative to facilitate development of a commercial Ocean Color Instrument. Government interaction with academia, in the form of National Science Foundation programmes and government-university ‘cooperative institutes’, is reviewed. The author concludes by showing how plans for integrating research and operations on Space Station platforms can only succeed through an alliance of all the remote-sensing players.     

等离子喷涂Al_2O_3涂层的电击穿机理

采用大气等离子喷涂技术在铜基体上沉积了Al2O3涂层。采用XRD和SEM对涂层微观结构进行了表征。通过探讨孔隙率和吸潮行为对绝缘性能的影响,分析了等离子喷涂Al2O3涂层结构与电绝缘失效机理的关系。结果表明:等离子喷涂Al2O3涂层较致密,界面结合较好。随涂层厚度不同其孔隙率在5%~7%范围变化。等离子喷涂Al2O3涂层结构中的孔洞是电绝缘失效的主要部位且呈典型电晕击穿形貌。电晕击穿诱发的裂纹沿击穿方向扩展形成击穿隧道。击穿方向与电极极性无关而由击穿孔洞位置决定。涂层厚度与涂层击穿强度呈现倒数关系。吸潮会诱发导电通路形成降低Al2O3涂层抗击穿能力。