排序方式： 共有44条查询结果，搜索用时 15 毫秒
21.
Dennis C. Reuter S. Alan Stern John Scherrer Donald E. Jennings James W. Baer John Hanley Lisa Hardaway Allen Lunsford Stuart McMuldroch Jeffrey Moore Cathy Olkin Robert Parizek Harold Reitsma Derek Sabatke John Spencer John Stone Henry Throop Jeffrey Van Cleve Gerald E. Weigle Leslie A. Young 《Space Science Reviews》2008,140(1-4):129-154
The New Horizons instrument named Ralph is a visible/near infrared multi-spectral imager and a short wavelength infrared spectral imager. It is one of the core instruments on New Horizons, NASA’s first mission to the Pluto/Charon system and the Kuiper Belt. Ralph combines panchromatic and color imaging capabilities with SWIR imaging spectroscopy. Its primary purpose is to map the surface geology and composition of these objects, but it will also be used for atmospheric studies and to map the surface temperature. It is a compact, low-mass (10.5 kg) power efficient (7.1 W peak), and robust instrument with good sensitivity and excellent imaging characteristics. Other than a door opened once in flight, it has no moving parts. These characteristics and its high degree of redundancy make Ralph ideally suited to this long-duration flyby reconnaissance mission. 相似文献
22.
Ball Henry W. Harris H. G. Hiatt Jay 《IEEE transactions on aerospace and electronic systems》1967,(2):285-296
As part of a hypervelocity instrumentation development program, it was desirable to include a radiometer system for measuring absolute radiation from projectile flow fields. A system employing a photomultiplier tube was designed, and laboratory and range experiments were conducted to investigate its performance characteristics. The laboratory experiments show that the linearity, saturation, and noise characteristics are suitable for this measurement; the system bandwidth is adequate to allow low frequency calibrations to be applied to high frequency measurements; and a derived expression for radiometer sensitivity variation as a function of photomultiplier supply voltage is reasonably correct. The results of the range experiments imply that the system response is sufficient to reproduce accurately input pulses as narrow as one microsecond and that a particular analytical technique for calculating the form of the radiative input to the radiometer from the projectile stagnation region is valid. Principles involved in the design of photomultiplier radiometer circuits of this type are discussed in detail. 相似文献
23.
Whitten Gary Roberts Arthur Sadowski Henry Hein Richard 《Aerospace and Electronic Systems Magazine, IEEE》1986,1(10):8-18
In this paper we discuss a simple temperature-driven segmentation technique that can be used for autonomous terminal guidance of anti-tank munitions. A ratio between two images from different IR bands is taken to form an emissivity independent image that is a function of temperature only. Size and temperature discrimination can then be used to find hot spots of interest. Candidate targets are segmented from the image about the points of interest using an.algorithm that finds all regions in multi-region objects and does not require a priori intensity information. Size and gross shape features are used to determine if the segmented objects are to be classified as targets. The key to this approach is the initial hot spot extraction. The temperature dependent ratio image allows quick and confident screening of the entire field of view, so that only the regions of interest require further processing. The described techniques effectively found tanks in the presence of common battlefield clutter when used with synthetic IR imagery provided by Georgia Tech Research Institute. The simplicity, effectiveness and potential speed of this technique make it ideal for autonomous guidance of expendable anti-tank weapons, especially where only low resolution IR imagery is available. 相似文献
24.
<正>机体制造商对于新一代飞机供应链所做的策略调整已经影响到售后服务市场的格局。在此调整的过程中航空产业链中的各方都面临着巨大的挑战,制造商通过业务集成加大对售后服务市场的掌控,但管理其庞大的内部业务远比想象中更困难,维修企业则面临更加激烈的市场竞争。在新一代波音787和空客A350飞机的研制过程中,波音公司和空客公司开始将更多地设计和制造工作转移给系统或部件供应商,这一转变同样也映射到了售后服务市场,影响到售后服务市场的格局,其中独立维修企业的感触最深。在售后服务市场中,负责集成和总 相似文献
25.
更安全、更好、更快、更廉价不仅仅是对维修生产的要求,同时也适用于维修人员的培训。为此,需要开发新的培训工具。这些工具通过改进后变得更为灵活和功能强大。 相似文献
26.
Henry Canaday 《航空维修与工程》2014,(5)
<正>在航空公司新的库存模式中,零备件需求预测软件、物流管理专家、零部件分销商、制造商将扮演着越来越重要的角色。在过去,航空公司为了保障航班的正常运营,会贮存大量的库存件。而现在,在激烈的市场竞争和高成本压力下,航空公司逐渐开始改变原有库存模式,寻求可靠的备件配送方式,以尽量缩短其周转时间。可靠的备件配送方式要求必须在正确的时间将正确的备件运送至正确的地 相似文献
27.
Over the past fifteen years, major U.S. initiatives for the development of new launch vehicles have been remarkably unsuccessful. The list is long: NLI, SLI, and X-33, not to mention several cancelled programs aimed at high speed airplanes (NASP, HSCT) which would share some similar technological problems.The economic aspects of these programs are equally as important to their success as are the technical aspects. In fact, by largely ignoring economic realities in the decisions to undertake these programs and in subsequent management decisions, space agencies (and their commercial partners) have inadvertently contributed to the eventual demise of these efforts.The transportation revolution that was envisaged by the promises of these programs has never occurred. Access to space is still very expensive; reliability of launch vehicles has remained constant over the years; and market demand has been relatively low, volatile and slow to develop. The changing international context of the industry (launching overcapacity, etc.) has also worked against the investment in new vehicles in the U.S. Today, unless there are unforeseen technical breakthroughs, orbital space access is likely to continue as it has been with high costs and market stagnation.Space exploration will require significant launching capabilities. The details of the future needs are not yet well defined. But, the question of the launch costs, the overall demand for vehicles, and the size and type of role that NASA will play in the overall launch market is likely to influence the industry. This paper will emphasize the lessons learned from the economic and management perspective from past launch programs, analyze the issues behind the demand for launches, and project the challenges that NASA will face as only one new customer in a very complex market situation. It will be important for NASA to make launch vehicle decisions based as much on economic considerations as it does on solving new technical challenges. 相似文献
28.
Henry R. Hertzfeld 《Space Policy》1987,3(2):100-103
Attempts to rebuild US commercial launch capabilities through stimulating private industry will be constrained by the fact that free-market competition does not really exist in the space industry. As the worldwide supply of launch vehicles grows, the policy now offered by the US government is only likely to fragment the US space launch vehicle industry. The author argues in favour of a proposal to establish a quasi-governmental corporation for space launches which would both safeguard the interests of government and commercial users and ensure that business acumen was applied. 相似文献
29.
Henry E. Kandrup 《Space Science Reviews》2002,102(1-4):101-114
This review summarises several different lines of argument suggesting that one should not expect cuspy nonaxisymmetric galaxies to exist as robust, long-lived collisionless equilibria, i.e., that such objects should not be idealised as time-independent solutions to the collisionless Boltzmann equation. 相似文献
30.
K. Mukai J. M. Bonnet-Bidaut S. Bowyer P. A. Charles L. Chiappetti J. T. Clarke R. H. D. Corbet J. P. Henry G. J. Hill S. M. Kahn L. Maraschi J. Osborne A. Treves M. van der Klis J. van Paradijs S. D. Vrtilek 《Space Science Reviews》1985,40(1-2):151-155
The AM Her type object E2003+225 was observed with EXOSAT, IUE and ground-based telescopes on 1983 Oct. 12. The brightness of the ultrasoft X-ray component allowed the Objective Grating Spectrometer (OGS) to be used, which gave a model-independent determination of the temperature of the blackbody spectrum. The star was observed again on 1984 July 24 by IUE with simultaneous optical spectrophotometry. The high resolution of this observation revealed complex line profiles, and a systematic velocity much smaller than previously reported. The composite energy distribution is presented. 相似文献