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881.
Selected results from experiments investigating the potentially specific radiobiological importance of the cosmic HZE (= high Z, energetic) particles are discussed. Results from the Biostack space flight experiments, which were designed to meet the experimental requirements imposed by the microdosimetric nature of this radiation field, clearly indicate the existence of radiation mechanisms which become effective only at higher values of LET (linear energy transfer). Accelerator irradiation studies are reviewed which conform with this conjecture. The recently discovered production of "micro-lesions" in mammalian tissues by single HZE particles is possibly the most direct evidence. Open questions concerning the establishment of radiation standards for manned spaceflight, such as late effects, interaction with flight dynamic parameters, and weightlessness, are indicated. 相似文献
882.
883.
A closed-form solid-state solution for a simple one-dimensional smoother is presented. The target position-velocity dynamics are modeled as a linear discrete Gauss-Markov process: the discrete position measurements are assumed to be independent and identically normally distributed. Analytical results derived from estimating optimum steady-state position and velocity are given as well as the improvement provided by smoothing relative to pure filtering estimates. Analytical results, including appropriate limiting cases, show that the ratios of the RMS smoothing to the RMS filtering error are from 1/2 to 1 in position and from 1/2 to 1/√2 in velocity. As a numerical example a highly maneuvering target characterized by an acceleration width of 30 m/s2 is considered 相似文献
884.
885.
M.C. Zolcinski D.J. Forrest J.M. Ryan E.L. Chupp G. Kanbach C. Reppin E. Rieger G.H. Share 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(11):193-196
We have searched for anisotropic X-ray bremsstrahlung photon production from relativistic electrons by studying the heliocentric angular dependence of 53 flares detected at energies above 300 keV. We have found no evidence for a higher rate of detectable flares near the limb at the 80% confidence level. This result implies that the X-ray directivity as defined by the ratio of photon intensity at 75° and 0° of heliocentric angle is less than 1.5 above 300 keV and strongly rejects any flare model predicting X-ray production from a radial “beam” of energetic electrons. 相似文献
886.
887.
Magnetic field experiment for Voyagers 1 and 2 总被引:1,自引:1,他引:0
K. W. Behannon M. H. Acuna L. F. Burlaga R. P. Lepping N. F. Ness F. M. Neubauer 《Space Science Reviews》1977,21(3):235-257
The magnetic field experiment to be carried on the Voyager 1 and 2 missions consists of dual low field (LFM) and high field magnetometer (HFM) systems. The dual systems provide greater reliability and, in the case of the LFM's, permit the separation of spacecraft magnetic fields from the ambient fields. Additional reliability is achieved through electronics redundancy. The wide dynamic ranges of ± 0.5 G for the LFM's and ± 20 G for the HFM's, low quantization uncertainty of ± 0.002 ( = 10–5 G) in the most sensitive (± 8 ) LFM range, low sensor RMS noise level of 0.006 , and use of data compaction schemes to optimize the experiment information rate all combine to permit the study of a broad spectrum of phenomena during the mission. Objectives include the study of planetary fields at Jupiter, Saturn, and possibly Uranus; satellites of these planets; solar wind and satellite interactions with the planetary fields; and the large-scale structure and microscale characteristics of the interplanetary magnetic, field. The interstellar field may also be measured. 相似文献
888.
L. Koch-Miramond R. Rocchia J. Davelaar F. A. Jansen R. H. Becker R. Braun 《Space Science Reviews》1985,40(3-4):521-526
The X-ray properties of the supernova remnant G 29.7-0.3 are discussed based on spectral data from the EXOSAT satellite. In the 2 to 10 keV range a featureless power-law spectrum is obtained, the best-fit parameters being: energy spectral index =-0.77, hydrogen column density on the line of sight NH=2.3.1022 cm–2. The incident X-ray flux from the source is (3.6±0.1) 1011 erg cm–2 s–1 in the 2 to 10 keV range corresponding to an intrinsic luminosity of about 2. 1036 erg s–1 for a distance of 19 kpc. The source was not seen with the imaging instrument thus constraining the hydrogen column density to be NH=(3.3 ±0.3) 1022 cm–2 and the energy spectral index =1.0±0.15. This new observation is consistent with emission by a synchroton nebula presumably fed by an active pulsar. An upper limit of 1.5% for the pulsed fraction in the range of periods 32ms to 104 s has been obtained. 相似文献
889.
D. H. Fairfield 《Space Science Reviews》1979,23(3):427-448
The Earth's magnetopause is the boundary between a hot tenuous plasma in the magnetosphere and a cooler denser plasma in the magnetosheath. Both of these plasmas contain magnetic fields whose directions are usually different but whose magnitudes are often comparable. Efforts to understand the structure of the magnetosphere have been hampered by the variability and complexity of this boundary. Waves on the magnetopause surface propagate toward the magnetotail and produce the multiple boundary crossings frequently seen by spacecraft. Boundary velocities are poorly known and range anywhere within an order of magnitude of 10 km s–1. Typical thicknesses are probably on the order of a few hundred km which is a few times the gyroradius of a thermal proton. Although conclusive direct evidence for a field component, B
n
, across the magnetopause has not been found, this lack of evidence may reflect the difficulty in determining B
n
in the presence of magnetopause waves rather than the real absence of this component. Considerable indirect evidence exists for an open magnetosphere, but the importance of the reconnection process thought to produce open field lines has recently been questioned.Proceedings of the Symposium on Solar Terrestrial Physics held in Innsbruck, May–June 1978. 相似文献
890.
Kaplan L.J. Ormsby J.F.A. Fowle E.N. Johnson K.R. Bates R.H.T. Bickel S.H. 《IEEE transactions on aerospace and electronic systems》1969,(4):654-660
A satellite has been designed for application to radar calibration. Electromagnetic and mechanical characteristics of the satellite and their influence on the selection of shape and other parameters are discussed. Theoretical and experimental scattering data are included. 相似文献