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241.
Noise in wireless systems from solar radio bursts 总被引:1,自引:0,他引:1
L.J. Lanzerotti D.E. Gary G.M. Nita D.J. Thomson C.G. Maclennan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,36(12):2253-2257
Solar radio bursts were first discovered as result of their interference in early defensive radar systems during the Second World War (1942). Such bursts can still affect radar systems, as well as new wireless technologies. We have investigated a forty-year record of solar radio burst data (1960–1999) as well as several individual radio events in the 23rd solar cycle. This paper reviews the results of a portion of this research. Statistically, for frequencies f 1 GHz (near current wireless bands), there can be a burst with amplitudes >103 solar flux units (SFU; 1 SFU = 10−22 W/m2) every few days during solar maximum conditions, and such burst levels can produce problems in contemporary wireless systems. 相似文献
242.
V D Kern S Bhattacharya R N Bowman F M Donovan C Elland T F Fahlen B Girten M Kirven-Brooks K Lagel G B Meeker O Santos 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2001,27(5):1023-1030
During the construction phase of the International Space Station (ISS), early flight opportunities have been identified (including designated Utilization Flights, UF) on which early science experiments may be performed. The focus of NASA's and other agencies' biological studies on the early flight opportunities is cell and molecular biology; with UF-1 scheduled to fly in fall 2001, followed by flights 8A and UF-3. Specific hardware is being developed to verify design concepts, e.g., the Avian Development Facility for incubation of small eggs and the Biomass Production System for plant cultivation. Other hardware concepts will utilize those early research opportunities onboard the ISS, e.g., an Incubator for sample cultivation, the European Modular Cultivation System for research with small plant systems, an Insect Habitat for support of insect species. Following the first Utilization Flights, additional equipment will be transported to the ISS to expand research opportunities and capabilities, e.g., a Cell Culture Unit, the Advanced Animal Habitat for rodents, an Aquatic Facility to support small fish and aquatic specimens, a Plant Research Unit for plant cultivation, and a specialized Egg Incubator for developmental biology studies. Host systems (Figure 1A, B: see text), e.g., a 2.5 m Centrifuge Rotor (g-levels from 0.01-g to 2-g) for direct comparisons between g and selectable g levels, the Life Sciences Glovebox for contained manipulations, and Habitat Holding Racks (Figure 1B: see text) will provide electrical power, communication links, and cooling to the habitats. Habitats will provide food, water, light, air and waste management as well as humidity and temperature control for a variety of research organisms. Operators on Earth and the crew on the ISS will be able to send commands to the laboratory equipment to monitor and control the environmental and experimental parameters inside specific habitats. Common laboratory equipment such as microscopes, cryo freezers, radiation dosimeters, and mass measurement devices are also currently in design stages by NASA and the ISS international partners. 相似文献
243.
J.-P. Delaboudiniere R.A. Stern A. Maucherat F. Portier-Fozzani W.M. Neupert J.B. Gurman R.C. Catura J.R. Lemen L. Shing G.E. Artzner J. Brunaud A.H. Gabriel D.J. Michels J.D. Moses B. Au K.P. Dere R.A. Howard R. Kreplin J.M. Defise C. Jamar P. Rochus J.P. Chauvineau J.P. Marioge F. Clette P. Cugnon E.L. Van Dessel 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1997,20(12):2231-2237
The SOHO (SOlar and Heliospheric Observatory) satellite was launched on December 2nd 1995. After arriving at the Earth-Sun (L1) Lagrangian point on February 14th 1996, it began to continuously observe the Sun. As one of the instruments onboard SOHO, the EIT (Extreme ultraviolet Imaging Telescope) images the Sun's corona in 4 EUV wavelengths. The He II filter at 304 Å images the chromosphere and the base of the transition region at a temperature of 5 − 8 × 104 K; the Fe IX–X filter at 171 Å images the corona at a temperature of 1.3 × 106 K; the Fe XII filter at 195 Å images the quiet corona outside coronal holes at a temperature of 1.6 × 106 K; and the Fe XV filter at 284 Å images active regions with a temperature of 2.0 × 106 K. About 5000 images have been obtained up to the present. In this paper, we describe also some aspects of the telescope and the detector performance for application in the observations. Images and movies of all the wavelengths allow a look at different phenomena present in the Sun's corona, and in particular, magnetic field reconnection. 相似文献
244.
P.S. Babcock D.M. Auslander R.C. Spear 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(12):263-270
Reliability of closed life support systems will depend on their ability to continue supplying the crew's needs in the face of perturbations and equipment failures. These dynamic considerations interact with the basic static (equilibrium) design through the sizing of storages, the specification of excess capacities in processors, and the choice of system initial state (total mass in the system). This paper uses a very simple system flow model to examine the possibilities for system failures even when there is sufficient storage to buffer the immediate effects of the perturbation. Two control schemes are shown which have different dynamic consequences in response to component failures. 相似文献
245.
F.H. Schubert R.A. Wynveen P.D. Quattrone 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(12):279-288
Extended manned space missions will require regenerative life support techniques. Past U.S. manned missions used nonregenerative expendables, except for a molecular sieve-based carbon dioxide removal system aboard Skylab. The resupply penalties associated with expendables becomes prohibitive as crew size and mission duration increase. The U.S. Space Station, scheduled to be operational in the 1990's, is based on a crew of four to sixteen and a resupply period of 90 days or greater. It will be the first major spacecraft to employ regenerable techniques for life support. The paper uses the requirements for the Space Station to address these techniques. 相似文献
246.
G. Smoot G. De Amici S.D. Friedman C. Witebski N. Mandolesi R.B. Partridge G. Sironi L. Danese G. De Zotti 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
New measurements of the Cosmic Background Radiation temperature at 12 cm, 6.3 cm, 3 cm, 0.9 cm and 0.3 cm have made in July 1982 from the White Mountain High Altitude Research Station. The results are presented and the existence of spectral distortions discussed. 相似文献
247.
V. I. Moroz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(12):113-121
There is important progress now in the identifications and measurements of primary (parent) molecules in the inner coma of Comet Halley. H2O, CO2 and CO are definitely in the list, CH and some complicate organic molecules are suspected. Gas production rate for water vapor is QH2O 1030 s−1. The bulk of data doesn't contradict to the Whipple model of nucleus (with clathrate modification). Pronounced spatial structure of gaseous flow in the coma was observed, but in general measured properties of neutral gas in the coma of Comet Halley are not very different from predicted. Situation for dust is different. In situ dust measurements show that size spectrum and optical properties of particles in coma are substantively declining from predicted on the base of groundbased photometry. However there are discrepancies between Vega and Giotto dust counter data. Dust in the inner coma didn't prevent the succesful imaging of nucleus by TV on Vega 1 and 2. 相似文献
248.
B V Worgul W Krebs J P Koniarek 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1989,9(10):315-323
Efforts to assess radiation risk in space have been complicated by the considerable unknowns regarding the biological effects of the heavy ion component (HZE particles) of the cosmic rays. The attention has focused primarily on the assignation of a quality factor (Q) which would take into account the greater effectiveness of heavy ions vis-a-vis other forms of ionizing radiation. If however, as the so-called "Microlesion Theory" allows, the passage of HZE particles through living tissue produces unique biological damage, the traditional use of Q becomes meaningless. Therefore, it is critical to determine if microlesions, in fact, do exist. While the concept does not necessarily require detectable morphological damage, "tunnel-lesions" or holes in ocular tissues have been cited as evidence of microlesions. These data, however, are open to reinterpretation. On-going light, scanning and transmission electron microscopic studies of the corneas, lenses and retinas of rat eyes exposed to 450 MeV/amu 56Fe ions thus far have not revealed tunnel-lesion damage. The morphological effects of the heavy ions have been found to be qualitatively similar to the changes following other kinds of ionizing radiation. 相似文献
249.
A. Kiraga Z. K
os V. N. Oraevsky V. C. Dokukin S. A. Pulinets 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1995,15(12):21-24
There were several cases when modulated electron beam had been injected from APEX satellite into an otherwise unmodified ionospheric plasma. The beams were formed from 2 μs pulses repeated at a rate of 40kHz. Injections took place in the altitude range 400–1100km over Europe. The onboard receiver connected to the dipole antenna swept the frequency interval 1–10 MHz in 1 sec. Due to a relatively narrow receiver bandwidth (15 kHz), moderate frequency step (50 kHz), slow changes of fn and fc (local electron plasma and gyro frequencies) fine structure of excited emissions was detected. In many cases, a very prominent doublet could be convincingly identified as a (fn,fu=sqrt(fn*fn+fc*fc)) band, with fn practically equal to the local plasma frequency in the unperturbed ionosphere. Determination of plasma frequency is of prime importance in analysis of complex structures composed from various harmonics fn,fc,fu. Complexity is manifested as coalescing of various harmonics with maxima shifted from nominal frequencies or splitting them into components due to mixing of local and propagation effects. Despite the existence of strong emissions on frequencies characteristic for the unperturbed ionosphere, very strong broadcasting transmissions are frequently cut off, even when the beam is directed upward. Most typical spectra are discussed. 相似文献
250.
A Lazcano E Díaz-Villagómez T Mills J Oró 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1995,15(3):345-356
The most frequently invoked explanation for the origin of metabolic pathways is the retrograde evolution hypothesis. In contrast, according to the so-called "patchwork" theory, metabolism evolved by the recruitment of relatively inefficient small enzymes of broad specificity that could react with a wide range of chemically related substrates. In this paper it is argued that both sequence comparisons and experimental results on enzyme substrate specificity support the patchwork assembly theory. The available evidence supports previous suggestions that gene duplication events followed by a gradual neoDarwinian accumulation of mutations and other minute genetic changes lead to the narrowing and modification of enzyme function in at least some primordial metabolic pathways. 相似文献