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11.
Peter Hans 《Acta Astronautica》1984,11(1):81-89
(A spaceborne scatterometer for wind field measurement)—For correct weather forecasting over the continent, the knowledge of the weather conditions across the oceans is of importance. The Skylab S-193 experiment, as well as Seasat, have shown that global wind measurements across the ocean with the aid of a microwave sensor is technically feasible. For this reason, a Wind Scatterometer will be implemented among other instruments on the first European Remote Sensing Satellite, ERS-1.In this presentation, the geophysical background of the measurement principle is briefly explained. A short discussion about the method of extraction of wind speed and wind direction out of Scatterometer measurement data follows. Finally, different sensor concepts are presented and a comparison of real and computed wind fields over the Atlantic closes the presentation about the Wind Scatterometer.Software simulators are necessary for the development and optimization of the Scatterometer system design. Such software simulators are under development at Dornier System, which holds technical responsibility for the Scatterometer. A short overview of this work is also given. 相似文献
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13.
The effect of nonequilibrium recombination after a curved two-dimensional shock wave in a hypervelocity dissociating flow of an inviscid Lighthill–Freeman gas is considered. An analytical solution is obtained with the effective shock values derived by Hornung (1976) [5] and the assumption that the flow is ‘quasi-frozen’ after a thin dissociating layer near the shock. The solution gives the expression of dissociation fraction as a function of temperature on a streamline. A rule of thumb can then be provided to check the validity of binary scaling for experimental conditions and a tool to determine the limiting streamline that delineates the validity zone of binary scaling. The effects on the nonequilibrium chemical reaction of the large difference in free stream temperature between free-piston shock tunnel and equivalent flight conditions are discussed. Numerical examples are presented and the results are compared with solutions obtained with two-dimensional Euler equations using the code of Candler (1988) [10]. 相似文献
14.
Ignazio Ciufolini Antonio Paolozzi Erricos C. Pavlis John C. Ries Rolf Koenig Richard A. Matzner Giampiero Sindoni Hans Neumayer 《Space Science Reviews》2009,148(1-4):71-104
During the past century Einstein’s theory of General Relativity gave rise to an experimental triumph; however, there are still aspects of this theory to be measured or more accurately tested. Today one of the main challenges in experimental gravitation, together with the direct detection of gravitational waves, is the accurate measurement of the gravitomagnetic field generated by the angular momentum of a body. Here, after a brief introduction on frame-dragging, gravitomagnetism and Lunar Laser Ranging tests, we describe the past measurements of frame-dragging by the Earth spin using the satellites LAGEOS, LAGEOS 2 and the Earth’s gravity models obtained by the GRACE project. We demonstrate that these measurements have an accuracy of approximately 10%. We then describe the LARES experiment to be launched in 2010 by the Italian Space Agency for a measurement of frame-dragging with an accuracy of a few percent. We finally demonstrate that a number of claims by a single individual, that the error budget of the frame-dragging measurements with LAGEOS-LAGEOS 2 and LARES has been underestimated, are indeed ill-founded. 相似文献
15.
The UN Office for Outer Space Affairs, through the IHY Secretariat and the United Nations Basic Space Science Initiative (UNBSSI), assists scientists and engineers world-wide to participate in the International Heliophysical Year (IHY) 2007. A major thrust of IHY/UNBSSI is to deploy arrays of small, inexpensive instruments such as magnetometers, radio telescopes, GPS receivers, all-sky cameras, etc. around the world to allow global measurements of ionospheric and heliospheric phenomena. The small instrument program is envisioned as a partnership between instrument providers and instrument hosts in developing nations, with the former providing the instruments, the host nation the manpower, facilities and operational support, typically at a local university. Funds are not available through IHY/UNBSSI to build the instruments; these must be obtained through the normal proposal channels. All instrument operational support for local scientists, facilities, data acquisition, etc. will be provided by the host nation. The IHY/UNBSSI can facilitate the deployment of several of these networks and existing databases and relevant software tools will be identified to promote space science activities in developing nations. Extensive data on space science have been accumulated by a number of space missions. Similarly, long-term databases are available from ground-based observations. These data can be utilized in ways different from those originally intended for understanding the heliophysical processes. This report provides an overview of IHY/UNBSSI, its achievements, future plans and outreach to the 192 member states of the United Nations. 相似文献
16.
H. Balsiger K. Altwegg P. Bochsler P. Eberhardt J. Fischer S. Graf A. Jäckel E. Kopp U. Langer M. Mildner J. Müller T. Riesen M. Rubin S. Scherer P. Wurz S. Wüthrich E. Arijs S. Delanoye J. De Keyser E. Neefs D. Nevejans H. Rème C. Aoustin C. Mazelle J.-L. Médale J. A. Sauvaud J.-J. Berthelier J.-L. Bertaux L. Duvet J.-M. Illiano S. A. Fuselier A. G. Ghielmetti T. Magoncelli E. G. Shelley A. Korth K. Heerlein H. Lauche S. Livi A. Loose U. Mall B. Wilken F. Gliem B. Fiethe T. I. Gombosi B. Block G. R. Carignan L. A. Fisk J. H. Waite D. T. Young H. Wollnik 《Space Science Reviews》2007,128(1-4):745-801
The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) will answer important questions posed by the mission’s
main objectives. After Giotto, this will be the first time the volatile part of a comet will be analyzed in situ. This is
a very important investigation, as comets, in contrast to meteorites, have maintained most of the volatiles of the solar nebula.
To accomplish the very demanding objectives through all the different phases of the comet’s activity, ROSINA has unprecedented
capabilities including very wide mass range (1 to >300 amu), very high mass resolution (m/Δ m > 3000, i.e. the ability to resolve CO from N2 and 13C from 12CH), very wide dynamic range and high sensitivity, as well as the ability to determine cometary gas velocities, and temperature.
ROSINA consists of two mass spectrometers for neutrals and primary ions with complementary capabilities and a pressure sensor.
To ensure that absolute gas densities can be determined, each mass spectrometer carries a reservoir of a calibrated gas mixture
allowing in-flight calibration. Furthermore, identical flight-spares of all three sensors will serve for detailed analysis
of all relevant parameters, in particular the sensitivities for complex organic molecules and their fragmentation patterns
in our electron bombardment ion sources. 相似文献
17.
The 1958 Space Act created separate but related military and civilian space exploration and exploitation efforts for the USA. This Viewpoint reexamines the assumptions of the act, and questions how they might be modified to fit with technical and political developments since 1958. Should separate civilian and military programmes continue? How should launch vehicles be developed and operated? What should be the major goals of the space exploration programmes? A well defined and forward looking space policy is proposed, including a lunar base programme, which will take the initiative away from the USSR. 相似文献
18.
19.
Hans Goedbloed 《Space Science Reviews》2006,122(1-4):239-246
Transonically rotating toroidal plasmas occur at all scales in the plasma universe and, recently, also in laboratory tokamak plasmas. This offers great opportunities for new insights of the effects of transonic transitions on the background equilibrium flows, and on the waves and instabilities excited. Transfer of knowledge and computational methods on MHD and two-fluid waves and instabilities in magnetically confined laboratory fusion plasmas to space and astrophysical plasmas is seriously hampered though by two related difficulties:
- in contrast to laboratory plasmas, astrophysical plasmas always have sizeable plasma flows so that they can never be described as a static equilibrium;
- these flows are usually ‘transonic’, i.e., surpass one of the critical speeds related to the different flow regimes with quite different physical characteristics.
20.
Hans Volland 《Space Science Reviews》1983,34(3):327-335
The ionospheric storm process at F layer heights is reviewed and an explanation in terms of wind-induced diffusion of atomic oxygen is given. 相似文献