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21.
D. Müller J.J. Connel A. Decourchelle R. Mewaldt S. Reynolds A. Strong H. Völk M. Wiedenbeck 《Space Science Reviews》2001,99(1-4):353-373
The experimental basis of cosmic-ray astrophysics consists of detailed measurements of the cosmic-ray intensity arriving near earth, of observations of photons in all wavelength bands generated by cosmic ray interactions in the interstellar medium or in the cosmic-ray sources, and of laboratory studies of high energy particle interactions. In addition, a large body of astronomical information on the composition of stellar atmospheres and of the interstellar medium, including interstellar dust grains, is required to bring cosmic-ray data into context with subjects such as nucleosynthesis and evolution of the galaxy. This report will summarize some of these observational questions, will discuss specific experimental needs in current research, and will review some of the key measurements that can be expected for the near future. This review will neither be complete nor attempt to establish observational priorities. However, it will illustrate the variety of observational activities that are required to achieve progress. 相似文献
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The Lunar Orbiter Laser Altimeter Investigation on the Lunar Reconnaissance Orbiter Mission 总被引:3,自引:0,他引:3
David E. Smith Maria T. Zuber Glenn B. Jackson John F. Cavanaugh Gregory A. Neumann Haris Riris Xiaoli Sun Ronald S. Zellar Craig Coltharp Joseph Connelly Richard B. Katz Igor Kleyner Peter Liiva Adam Matuszeski Erwan M. Mazarico Jan F. McGarry Anne-Marie Novo-Gradac Melanie N. Ott Carlton Peters Luis A. Ramos-Izquierdo Lawrence Ramsey David D. Rowlands Stephen Schmidt V. Stanley Scott III George B. Shaw James C. Smith Joseph-Paul Swinski Mark H. Torrence Glenn Unger Anthony W. Yu Thomas W. Zagwodzki 《Space Science Reviews》2010,150(1-4):209-241
The Lunar Orbiter Laser Altimeter (LOLA) is an instrument on the payload of NASA’s Lunar Reconnaissance Orbiter spacecraft (LRO) (Chin et al., in Space Sci. Rev. 129:391–419, 2007). The instrument is designed to measure the shape of the Moon by measuring precisely the range from the spacecraft to the lunar surface, and incorporating precision orbit determination of LRO, referencing surface ranges to the Moon’s center of mass. LOLA has 5 beams and operates at 28 Hz, with a nominal accuracy of 10 cm. Its primary objective is to produce a global geodetic grid for the Moon to which all other observations can be precisely referenced. 相似文献
23.
The National Transonic Facility, NTF, is a high Reynolds Number facility where the increase in Reynolds Number is obtained by operating at high pressures and low temperatures. Liquid nitrogen is allowed to vaporize, making gaseous nitrogen the test medium with temperatures extending down to approximately 100 degrees Kelvin. These factors have created unique, new challenges to those developing sensors and instrumentation. Pressure vessels, thermal enclosures or elaborate temperature compensations schemes, are needed for environmental protection and special materials are needed for sensors and model fabrication. The need for a new measurement, model deformation, was also created. An extensive program to develop the unique sensors and instrumentation was initiated. The data acquisition system and systems to measure aerodynamic forces and pressures, model attitude, and model deformation, are discussed. 相似文献
24.
Heidbreder Glenn R. Mitchell Richard L. 《IEEE transactions on aerospace and electronic systems》1967,(1):5-13
The amplitude and power of a large family of radio signals are observed to have log-normal probability density functions. Among these are signals propagated through random inhomogeneous media, a notable example being low frequency atmospheric radio noise. Of greater importance are certain radar targets that have been observed to have essentially log-normal density functions. Both ships and space vehicles may fall into this category. Curves of probability of detection vs. signal-to-noise ratio for the case of log-normal signals in Gaussian noise have been computed and are presented in this paper. The curves apply for square-law detection with varying degrees of postdetection linear integration. Both fully correlated and completely uncorrelated fluctuating signals are considered. It is shown that for log-normal signal distributions having large variances, the probability of detection differs significantly from that obtained using curves based on an assumed Rayleigh signal distribution. 相似文献
25.
A. N. Parmar A. P. Reynolds N. E. White 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1993,13(12):355-360
We report on the evolution in the X-ray spectrum of the transient X-ray pulsar EXO 2030+375 during part of an outburst in 1985 May–August. The overall continuum spectral shape is similar to that of other accreting pulsars and can be represented by a power-law spectrum modified at low energies by significant absorption and at high-energies either by an exponential cut-off or by the effects of cyclotron scattering. As the luminosity decreased by a factor 100, the X-ray spectrum became harder with the photon index decreasing from 1.83 ± 0.01 to 1.29 ± 0.01. In addition, the high-energy cutoff decreased from 20 to 10 keV during the same interval. If the cutoff is interpreted in terms of cyclotron resonance scattering, then this implies a magnetic field strength that decreased from 2.6 × 1012 G to 1.3 × 1012 G. This variation implies that the cutoff energy does not provide a reliable measure of the surface magnetic field strength in this system. 相似文献
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This paper is concerned with the communications channel between a planetary flyby or orbiting spacecraft and an ejected probe that is traveling toward the planet. Since the mission requires that a significant part of the probe's transmitted energy be reflected from the irregular planet's surface, we will be concerned with the effect of the scattered signal for line-of-sight communications. The statistical distribution of the received field and the fading rate are considered so that the fading margin may be determined for some required probability of satisfactory performance. Typical examples are given for a Martian atmospheric probe. 相似文献
28.
Since they were first introduced in the early 1990s, lithium ion batteries have enjoyed unprecedented growth and success in the consumer marketplace. Combining excellent performance with affordability, they have become the product of choice for portable computers and cellular phones. Building on the same energy and life cycle attributes, which marked their consumer market success, but adding new high power storage capability, lithium ion technology is now poised to play a similar role in the transportation, military, and space sectors. With major program in various aspects of electric and hybrid electric vehicles, Saft has developed a family of battery products that address the power and energy storage where lightweight, long life, and excellent energy or power storage capabilities are needed. Significant progress in the packaging and control of high power, yet compact, batteries has been accomplished for a variety of vehicle applications. This paper discusses the charger and balancing strategies of one of this family of products 相似文献