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81.
Paddison F.C. Shipley C.A. Maffett A.L. Dawson M.H. 《IEEE transactions on aerospace and electronic systems》1978,(1):27-34
A laboratory method to determine the magnitude and position of radar reflection sources on complex targets is described. In addition the method provides a way to measure the modification of the radar cross section (RCS) due to multipath. The method has application in modeling RCS for radar and electronic countermeasure (ECM) system performance analysis and in the study of the extent to which the signature of the target could be altered. The equipment described, termed MACROSCOPE, was developed for RCS studies by the U.S. Army and is described in limited distribution bution literature. The application to marine targets is new with this paper, as is the technique of measuring the RCS of parts of the target and analytically combining them to represent the whole. An illustration of the need for this type of laboratory equipment was illustrated by the extensive search for full scale data which could be compared to scale model data to validate the technique. 相似文献
82.
An improved power converter model is developed by combining the average and discrete modeling techniques. The parameter determination of the proposed discrete-average model is shown to be dependent on the type of duty cycle control law and the nature of the error processor used in the feedback loop. Furthermore, the paper pinpoints deficiencies of the conventional loop gain measurement technique which is widely used in industries. 相似文献
83.
K. Yoshimura K. Abe H. Fuke S. Haino T. Hams M. Hasegawa A. Horikoshi K.C. Kim T. Kumazawa A. Kusumoto M.-H. Lee Y. Makida S. Matsuda Y. Matsukawa J.W. Mitchell A.A. Moiseev J. Nishimura M. Nozaki R. Orito J.F. Ormes K. Sakai M. Sasaki E.S. Seo Y. Shikaze R. Shinoda R.E. Streitmatter J. Suzuki K. Takeuchi N. Thakur K. Tanaka T. Yamagami A. Yamamoto T. Yoshida 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
84.
Peter C. Thomas Joseph Veverka Michael F. A’Hearn Lucy Mcfadden Michael J. S. Belton Jessica M. Sunshine 《Space Science Reviews》2005,117(1-2):193-205
The Deep Impact mission will provide the highest resolution images yet of a comet nucleus. Our knowledge of the makeup and
structure of cometary nuclei, and the processes shaping their surfaces, is extremely limited, thus use of the Deep Impact
data to show the geological context of the cratering experiment is crucial. This article briefly discusses some of the geological
issues of cometary nuclei. 相似文献
85.
H. M. Fischer J. D. Mihalov L. J. Lanzerotti G. Wibberenz K. Rinnert F. O. Gliem J. Bach 《Space Science Reviews》1992,60(1-4):79-90
The Energetic Particles Investigation (EPI) instrument operates during the pre-entry phase of the Galileo Probe. The major science objective is to study the energetic particle population in the innermost regions of the Jovian magnetosphere — within 4 radii of the cloud tops — and into the upper atmosphere. To achieve these objectives the EPI instrument will make omnidirectional measurements of four different particle species — electrons, protons, alpha-particles, and heavy ions (Z > 2). Intensity profiles with a spatial resolution of about 0.02 Jupiter radii will be recorded. Three different energy range channels are allocated to both electrons and protons to provide a rough estimate of the spectral index of the energy spectra. In addition to the omnidirectional measurements, sectored data will be obtained for certain energy range electrons, protons, and alpha-particles to determine directional anisotropies and particle pitch angle distributions. The detector assembly is a two-element telescope using totally depleted, circular silicon surfacebarrier detectors surrounded by a cylindrical tungsten shielding with a wall thickness of 4.86 g cm-2. The telescope axis is oriented normal to the spherical surface of the Probe's rear heat shield which is needed for heat protection of the scientific payload during the Probe's entry into the Jovian atmosphere. The material thickness of the heat shield determines the lower energy threshold of the particle species investigated during the Probe's pre-entry phase. The EPI instrument is combined with the Lightning and Radio Emission Detector (LRD) such that the EPI sensor is connected to the LRD/EPI electronic box. In this way, both instruments together only have one interface of the Probe's power, command, and data unit. 相似文献
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The 2007 US National Research Council Decadal Survey for Earth Science and Applications from Space was the first consensus perspective produced by the US Earth Science community of the relative priorities among a sequence of 17 satellite missions over the course of the next decade. However, the Decadal Survey only captured the perspective of the science community, leading to questions about the inclusion of broader priorities from constituent communities and stakeholders. We present a stakeholder value network analysis for the NASA/NOAA Earth Observation Program. The analysis includes a rigorous articulation of the needs and objectives of 13 major stakeholders and a complete stakeholder value network with 190 individual “value flows” that capture the interactions between all the stakeholders. It produces a novel stakeholder map, graphically indicating the outputs most likely to create a lasting Earth Science program. The most important value loops and program outputs are used to derive a set of high-level program goals that suggest what NASA and NOAA should do, as well as how they should conduct business. The analysis concludes that international partnerships represent a strong potential partner for certain science missions with greater potential value delivery than currently-prioritized efforts with defense stakeholders and concludes that weather and land-use missions, in addition to climate missions, should be given highest priority; water, human health, and solid Earth missions should be given lower priority based on each science category's potential for delivering value to the entire stakeholder network. 相似文献
89.
F. G. von der Dunk E. Back-Impallomeni S. Hobe R. M. Ramirez de Arellano 《Space Policy》2004,20(3):149-156
At a time when scientific and commercial interest in the Moon is being reinvigorated it is becoming fashionable for ordinary individuals to ‘buy’ plots on the lunar surface, with the ‘vendors’ arguing that an absence of specific prohibition of individual private activity in space makes such action legal. It is therefore time for the legal community to address this situation by investigating just how legal such activity is—and bringing their findings to the attention of governments. This can be done through an examination of the relationship between national law and international space law, of the provisions of international space law—especially Article 2 of the Outer Space Treaty—and by answering any claims to private ownership of immovable property. Aside from the fact that individuals appear to be being duped, the pursuit of property claims on the Moon could impede future activities aimed at benefiting society. 相似文献
90.
A.?I.?EfimovEmail author L.?A.?Lukanina I.?V.?Chashei S.?F.?Kolomiets M.?K.?Bird M.?P?tzold 《Cosmic Research》2018,56(1):1-10
In 2013 and 2015, investigations of the internal solar wind were carried out using the method of two-frequency radio sounding by signals from the Mars Express European spacecraft. The values of the S- and X-bands’ frequency and the differential frequency were registered with a sampling rate of 1s at the American and European networks of ground-based tracking stations. The spatial distribution of the frequency fluctuation’s level has been studied. It has been shown that the intensity of frequency fluctuation considerably decreases at high heliolatitudes. In some radio sounding sessions, quasiperiodic oscillations of sub-mHz band have been observed in the temporal spectra of frequency fluctuations; they are supposed to be associated with the density inhomogeneities, the sizes of which are close to the turbulence outer scale. 相似文献