Origin of planetary atmospheres

The near absence of noble gases on earth, other than those of radioactive origin, indicates that the earth was formed by the accumulation of planetesimals; this process systematically excluded all constituents that did not enter into the solid phase. The atmosphere and the ocean with many of its dissolved salts have arisen from gases emitted from the earth's interior, a process that continues today. The oxygen in the earth's atmosphere plus a greater quantity that has been removed from the atmosphere to oxidize geologic materials, has arisen mainly from a small excess of photosynthesis over decay of organic material. The atmospheres of Mars and Venus have probably arisen in a manner similar to the atmosphere on earth, by emission from the planetary interiors. However, they have not received any oxygen from photosynthesis and so are nearly oxygen free. Mars has very little water in its atmosphere, and this can be explained by its lower than freezing average surface temperature. Venus also has very little water, and this requires an ad hoc explanation; one possibility is that Venus was formed from much drier planetesimals than was the earth. Mercury and the moon are virtually without atmospheres. Although some gases may be emitted from their interiors, they are presumably rapidly lost by escape. Whatever atmosphere they possess is probably due to the neutralized solar wind that impinges upon them. The outer planets retained volatiles, including hydrogen and helium, to a much greater extent than did the terrestrial planets.     

Molecular spectroscopy of planetary atmospheres

Summary Clearly spectroscopy has already provided considerable insight into the nature of the planetary atmospheres. Several molecular constituents have been positively identified and upper limits have been placed on the abundances of others which are of particular significance in devising planetary models. But, equally clearly, the inadequacy of the spectral data, due to low spectral and/or spatial resolution, renders deductions of abundances, temperatures and pressures very uncertain. With the sole exception of the Martian CO₂ abundance, knowledge of the concentrations of planetary atmospheric constituents is unsatisfactory, and all numbers given must be regarded as only crude estimates. This latter comment applies equally well to the derived temperatures and pressures.What is urgently needed is the development of a reasonably complete theory of line formation in planetary atmospheres. This, coupled with more detailed spectroscopic work, should produce numerical values of atmospheric parameters which can be used with assurance.This work was performed with the aid of NASA Grant NsG-101-61 with funds administered by the University of California.     

Fourier spectroscopy in planetary research

The application of Fourier Transform Spectroscopy (FTS) to planetary research is reviewed. The survey includes FTS observations of the Sun, all the planets except Uranus and Pluto, the Galilean satellites and Saturn's rings. Instrumentation and scientific results are considered. The prospects and limitations of FTS for planetary research in the forthcoming years are discussed.     

Communication system architecture for planetary exploration

Future human missions to Mars will require effective communications supporting exploration activities and scientific field data collection. Constraints on cost, size, weight, and power consumption for all communications equipment make optimization of these systems very important. These information and communication systems connect people and systems together into coherent teams performing the difficult and hazardous tasks inherent in planetary exploration. The communication network supporting vehicle telemetry data, mission operations, and scientific collaboration must have excellent reliability and flexibility. We propose hybrid communication architectures consisting of space-based links, a surface-based deployable mid-range communications network and a cluster of short-range links to solve the problems of connectivity and bandwidth, while meeting the other constraints of weight and power. A network of orbiting satellites could cover much of the planet surface, but this space-based capability may not be optimal for cost or performance. Specifically, a minimal space-based capability can be augmented using mobile cellular repeaters deployable by robots and human EVA. This method results in an increase in the number of radio nodes, but the distances separating them is decreased. This results in a significant increase in bandwidth and decrease in radio power, and therefore, node size, complexity, and power consumption. This paper will discuss the results of field testing such hybrid radio systems for the support of scientific surveys. System analysis of design tradeoffs will yield insight into optimal solutions that will be compared to other approaches providing a method of effectively evaluating new candidate architectures     

行星机构的可靠性分析与计算

行星机构的结构设计缺陷、制造与安装误差、支撑构件刚度不足等原因可能会使系统发生一定程度的偏载,从而会影响整个机构的使用寿命与可靠性。利用最小次序统计量的概念建立了行星齿轮系的可靠度计算模型,模型反映了偏载对齿轮系可靠性的影响。首先,对行星机构进行了详细的运动学和力学分析,计算得到了各个齿轮的随机载荷历程。根据Miner线性疲劳累积损伤法则,将随机载荷历程转化为等效恒幅载荷谱,并将其作为可靠性模型的载荷输入变量。然后,将特定齿轮的疲劳寿命数据进行统计处理,将统计结果作为可靠性模型的强度输入变量。最后,根据模型的计算结果定量地说明了偏载对行星齿轮系可靠性的影响程度,同时利用随机截尾数据处理方法对可靠性模型的有效性进行了验证。     

Tracking of DABS-Equipped Aircraft

The Discrete Address Beacon System (DABS) is scheduled to replace the Air Traffic Control Beacon System (ATCRBS) as the prime sensing tool for air traffic control in the 1980's. The design of DABS requires knowledge of the tracking accuracy obtainable as a function of various system parameters. In particular, the potential value of air-to-ground telemetry of turn-rate data and its effect on intermittent positive control (IPC) must be assessed. The design of DABS tracking algorithms is discussed, and the results obtained with a Kalman tracker simulation are given. The major finding is that turn-rate telemetry of moderate accuracy can improve tracking by a factor of 6 to 10.     

直升机行星传动轮系故障诊断研究进展

行星传动轮系是直升机传动系统的核心部件,是直升机健康和使用监测系统(HUMS)重要的监测对象。直升机行星传动轮系具有结构复杂紧凑、组件繁多、工况瞬时多变以及使用环境恶劣等特点,导致直升机行星传动轮系振动信号污染严重、成分复杂,具有较强的非平稳性和耦合调制特征。另外复杂的故障模式、较少的故障样本,也都增加了直升机行星传动轮系故障诊断的难度。面对这些难题,研究人员在基于信号降噪与信号分离、时频分析与解耦解调、数学建模与模式识别的故障诊断技术上取得了丰硕的成果。面对仍然存在的一些亟待研究和解决的问题,提出了直升机行星传动轮系故障诊断技术的研究方向以及未来的发展趋势。     

Optimal Tracking of Maneuvering Targets

Maneuvering target motion is modeled by introducing a binary random variable in the target state equation. The optimal estimate is shown to be a weighted combination of two Kalman filter estimates with weights depending on the likelihood ratio for the detection of a maneuver. A tracking scheme is proposed for maneuvering target tracking and illustrated in an example.     

Doppler Radar Tracking of Hostile Fire

Two fixed parameters define a two-dimensional projectile track relative to a radar: an arrival angle, and the expected distance of closest approach (miss distance). Both parameters can be obtained explicitly, the angle from the history of the phase difference between two elements of an interferometer antenna, and the miss distance from the history of the Doppler frequency.     

Maritime Containers Tracking Trial Results

There are approximately 7 million maritime-style containers within Canada, and 70 million within the US. The interiors of such containers are rarely inspected. With market globalization, a large amount of these containers enter North America on a daily basis. Such containers may include contraband or dangerous items that present an economic or security risk. Despite significant security improvements, only 3 to 5 % of the maritime containers, that arrive in, or transition through, North America, go through physical inspection. Current container tracking technologies based on GPS consume high DC power, are costly, require line-of-sight with satellites, and are often too large to be covert. It is possible to overcome some of these limitations by basing the tracking system on the FM broadcast signal which is an alternative man-made signal that is reasonably ubiquitous, provides a geographically-unique frequency spectrum and is about 100,000 times as strong as a GPS satellite signal. This allows the development of a low-cost, low-power and miniature FM receiver that can record frequency spectrums and compare them to known data in order to trace the path that the container has taken for less than $10 per container. This presents the first results of highway trials (train and sea trials are currently being conducted) of such a low-cost, covert, non-GPS based technology (called FM Tag) that records the worldwide displacement of containers and displays the path undertaken by the container while in transit. As an added security benefit, the tag is also capable of detecting container door openings. In addition to presenting the first trial results, this covers the innovative engineering aspects of using the metal enclosure of a maritime container as a VBF antenna, thereby eliminating the need to add an external antenna and achieving the goal of being 100% covert.     

湍流传感器的发展

一种用于发现和测量湍流,并且通过飞行控制系统能自动消除其影响的激光雷达（LIDAR）湍流传感器已在一架A340-300飞机上进行了飞行试验。     

Clock Synchronization from Satellite Tracking

The tracking of synchronous satellites to provide propagation delays for the synchronization of clocks is described. The tracking is accomplished by range measurements to the satellite from three stations using signals transponded by the satellite. These same signals also functioned as the timing signals for the synchronization of other stations' clocks. Although the range measurements were of low resolution by usual standards, approximately 3000 meters, they provided the delays necessary to synchronize clocks to 40 microseconds or better. These results were obtained over a 4-month period using two satellites with measurements from five stations in the United States and South America.     

光线追踪求交算法的研究及其实现

本文对光线追踪求交算法进行了深入讨论。文中结合形体设计实例说明了此算法的正确性和实用性。     

建筑卷扬机摆线针轮行星减速器优化设计

本文采用复合形法对摆线行星机构以摆线轮和输出轴圆盘体积之和最小为目标函数进行优化设计，并给出某快速电动卷扬机优化设计实例。