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311.
M R Patel A Bérces T Kerékgyárto Gy Rontó H Lammer J C Zarnecki 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,33(8):1247-1252
The ultraviolet (UV) environment of Mars has been investigated to gain an understanding of the variation of exposure throughout a Martian year, and link this flux to biological effects and possible survival of organisms at the Martian surface. To gain an idea of how the solar UV radiation varies between different regions, including planned landing sites of two future Mars surface missions, we modelled the total solar UV surface flux throughout one Martian year for two different dust scenarios. To understand the degree of solar UV stress on micro-organisms and/or molecules essential for life on the surface of Mars, we also calculated the biologically effective dose (BED) for T7 and Uracil in relevant wavelength regions at the Martian surface as a function of season and latitude, and discuss the biological survival rates in the presence of Martian solar UV radiation. High T7/Uracil BED ratios indicate that even at high latitudes where the UV flux is significantly reduced, the radiation environment is still hostile for life due to the persisting UV-C component of the flux. 相似文献
312.
Frequency estimation techniques for high dynamic trajectories 总被引:7,自引:0,他引:7
Vilnrotter V.A. Hinedi S. Kumar R. 《IEEE transactions on aerospace and electronic systems》1989,25(4):559-577
A comparison is presented of four different estimation techniques applied to the problem of continuously estimating the rapidly varying parameters of a sinusoidal signal, observed in the presence of additive noise. Frequency estimates are emphasized, although phase and/or frequency rate are also estimated by some of the algorithms. These parameters are related to the velocity, position, and acceleration of the maneuvering receiver or transmitter. Estimated performance at low carrier-to-noise ratios and high dynamics is investigated for the purpose of determining the useful operating range of an approximate maximum likelihood estimator, an extended Kalman filter, a cross-product automatic frequency loop and a phase-locked loop. Numerical simulations are used to evaluate performance while tracking a common trajectory exhibiting high dynamics 相似文献
313.
M. M. Freund T. Hirao T. Matsumoto S. Sato T. Watabe G. K. Brubaker L. Duband B. Grossman N. Larkin S. Lumetta A. E. Lange 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1993,13(12):505-508
We describe the design and calibration of the Far-Infrared Photometer (FIRP), one of four focal plane instruments on the Infrared Telescope in Space (IRTS). The FIRP will provide absolute photometry in four bands centered at 150, 250, 400, and 700 μm with spectral resolution λ/Δλ ≈ 3 and spatial resolution ΔΘ = 0.5 degrees. High sensitivity is achieved by using bolometric detectors operated at 300 mK in an AC bridge circuit. The closed-cycle 3He refrigerator can be recycled in orbit. A 2 K shutter provides a zero reference for each field of view. More than 10% of the sky will be surveyed during the ≈3 week mission lifetime with a sensitivity of <10−13 W·cm−2·sr−1 per 0.5 degree pixel. 相似文献
314.
E. Mi&#x;úrov R.A. Tigranyan M. Prasli
ka 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1981,1(14):225-230
Changes of deoxyribonucleoprotein in the spleen, thymus and liver of rats exposed to wegithlessness or artifical gravity on board biosatellites Cosmos 782 and Cosmos 936 after 20 days of flight were investigated. The level of polydeoxyribonucleotides in the spleen and thymus of rats exposed during the flight to weightlessness increased 4 – 11 hours after landing, suggesting breakdown of a part of the deoxyribonucleoprotein present. The use of artifical gravity prevented this breakdown in the thymus but not in the spleen. The breakdown was accompanied in the majority of cases by a decrease in teh deoxyribonucleoprotein content. We believe the breakdown of deoxyribonucleoprotein is due to a nonspecific stress reaction to the change from the weightless state to that of terrestrial gravity during landing. The polydeoxyribonucleotide level and amount of deoxyribonucleoprotein in the majority of cases returned to normal values during the 25 days of readaptation. No substantial change of deoxyribonucleoprotein was found in the liver. The different findings in the three organs are due to the fact that breakdown of deoxyribonucleoprotein takes place in sensitive cells underlying pycnosis. These cells are found in the spleen and thymus, but not in the liver. 相似文献
315.
The numerical investigation of the impact of time-dependent accelerations (vibrations) on the flow and heat and mass transfer in the melt is carried out for the case of modeling the crystal growth by the floating zone method under conditions of microgravity that exist onboard spacecraft. The effects of the Archimedean buoyancy force and of vibrations of the free surface of fluid are considered separately. When solving the problem of the effect of the vibrations of the free surface of fluid, the previously obtained data were used. It is shown that vibrations of the free surface have a much stronger effect on the processes under consideration than the buoyancy. Some problems that are related to the newly discovered effects are discussed. The use of vibroprotected systems and a rotating magnetic field can help solve these problems. We plan to continue our investigations in future spacecraft experiments, in particular, at the International Space Station, which is under construction at the moment. 相似文献
316.
The Monitor-E spacecraft executed uncontrolled flight due to emergency situation, no telemetry information on parameters of the spacecraft’s attitude motion being available. So, the problem arose to determine the spacecraft’s rotational motion from the accessible indirect information—the electric current provided by solar batteries. In this paper the integrated statistical technique is described, that allows one to solve this problem. The values of current, obtained over the time interval some tens of minutes long, have been processed simultaneously by the least squares method using the integration of the equations of spacecraft’s rotational motion. As a result of processing, the initial conditions of motion were estimated, and the spacecraft’s moments of inertia were updated, as well as the angles, specifying solar batteries position in the spacecraft-fixed coordinate system. The results of processing of 12 data sets are presented, which allowed us to reconstruct the actual rotational motion of the spacecraft. 相似文献
317.
G.D. Aburjania L.S. Alperovich A.G. Khantadze O.A. Kharshiladze 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(4):624-627
The paper presents a physical mechanism of large-scale vortex electric field generation in the ionospheric E- and F-layers. It shows that the planetary-scale, synoptic short-period (from several second to several hours) and fast processes (with propagation velocity higher than 1 km/s) produce a planetary-scale internal vortex electric field. Its value may far exceed that of the dynamo-field generated in the same ionospheric layer by local wind motion. We found, that an ionospheric source of the vortex electric field is spatial inhomogeneity of the geomagnetic field. 相似文献
318.
气固紊流剪切流中颗粒弥散的拉格朗日模拟 总被引:1,自引:0,他引:1
本文提出了一种对于气固两相紊流剪切流中圆形固体颗粒弥散的拉格朗日拟计算方法,其中考虑了颗粒间的磁撞对流体相和颗料相的影响,应用该方法对一气固紊流剪切流场进行了模拟计算,并对有、无颗粒间磁撞情况下的模拟计算结果与Lavieville用大涡模拟方法的研究结果进行了比较,并进行了讨论。 相似文献
319.
The Navy Navigation Satellite System (TRANSIT) has provided 100% system reliability since being declared operational October 11, 1968. TRANSIT continues to carry out its function of precise, reliable, all weather navigation for the United States Navy and nearly 80,000 worldwide commercial users. TRANSIT's utility has been expanded to provide precise positioning information to those in the fields of geodesy and doppler surveying. While TRANSIT's history is illustrious, its life is limited. The transition from TRANSIT as the Navy's satellite navigation system to NAVSTAR GPS is planned for the 1990' s, with the result that TRANSIT is now scheduled for phase out by the United States Navy in 1994. This paper (essentially an update of reference [1]) will show the current status and plans for TRANSIT, following a brief historical overview. 相似文献
320.
V Switzer RC rdBogo G A Mickley 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1994,14(10):443-451
Application of the degeneration sensitive, cupric-silver staining method to brain sections of male Sprague-Dawley rats irradiated 4 days before sacrifice with 155 Mev protons, 2-8 Gy at 1 Gy/min (N=6) or 22-l0lGy at 20 Gy/min (N=16) or with 18.6 Mev electrons, 32-67 Gy at 20 Gy/min (N=20), doses which elicit behavioral changes (accelerod or conditioned taste aversion), resulted in a display of degeneration of astrocyte-like cell profiles which were not uniformly distributed. Plots of 'degeneration scores' (counts of profiles in 29 areas) vs. dose for the proton and electron irradiations displayed a linear dose response for protons in the range of 2-8 Gy. In the 20-100 Gy range, for both electrons and protons the points were distributed in a broad band suggesting a saturation curve. The dose range in which these astrocyte-like profiles becomes maximal corresponds well with the dose range for the X-ray eradication of a subtype of astrocytes, 'beta astrocytes'. 相似文献