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101.
本文考虑到干涉仪对电离层中不同尺度不规则性的滤波作用、结合密云米波综合孔径系统、提出了电离层E_(?)层是电离层不规则性影响该系统的主要根源。不规则性的尺度约在700~1000米的范围。再考虑到E_(?)层的漂移运动,提出了文中所描述的模型。用电子计算机进行了E_(?)层对综合射束污染的模拟计算,结果指出:射束主瓣的增益下降约10%,副瓣由13%增大到18%;综合射束在赤经方向出现不对称性,从而引起约0.6秒的赤经误差;射束的边缘处和两个扇形区出现了杂瓣。 相似文献
102.
本文给出了一个在观测中辨别光球横向磁场指向的一个判据。并证明了光球横向电流与横向磁场的指向无关,因而完全可以由向量磁象仪测定。 相似文献
103.
Valerio Iafolla David M. Lucchesi Sergio Nozzoli Francesco Santoli 《Celestial Mechanics and Dynamical Astronomy》2007,97(3):165-187
We have estimated a preliminary error budget for the Italian Spring Accelerometer (ISA) that will be allocated onboard the
Mercury Planetary Orbiter (MPO) of the European Space Agency (ESA) space mission to Mercury named BepiColombo. The role of
the accelerometer is to remove from the list of unknowns the non-gravitational accelerations that perturb the gravitational
trajectory followed by the MPO in the strong radiation environment that characterises the orbit of Mercury around the Sun.
Such a role is of fundamental importance in the context of the very ambitious goals of the Radio Science Experiments (RSE)
of the BepiColombo mission. We have subdivided the errors on the accelerometer measurements into two main families: (i) the
pseudo-sinusoidal errors and (ii) the random errors. The former are characterised by a periodic behaviour with the frequency
of the satellite mean anomaly and its higher order harmonic components, i.e., they are deterministic errors. The latter are
characterised by an unknown frequency distribution and we assumed for them a noise-like spectrum, i.e., they are stochastic
errors. Among the pseudo-sinusoidal errors, the main contribution is due to the effects of the gravity gradients and the inertial forces, while among the random-like errors the main disturbing effect is due to the MPO centre-of-mass displacements produced by the onboard High Gain Antenna (HGA) movements and by the fuel consumption and sloshing. Very subtle to be considered
are also the random errors produced by the MPO attitude corrections necessary to guarantee the nadir pointing of the spacecraft.
We have therefore formulated the ISA error budget and the requirements for the satellite in order to guarantee an orbit reconstruction
for the MPO spacecraft with an along-track accuracy of about 1 m over the orbital period of the satellite around Mercury in
such a way to satisfy the RSE requirements. 相似文献
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The absorption spectrum and thermal radiation fluxes in the lower atmosphere of Venus are calculated using the theory of molecular state interference in the strong collision approximation. Comparison is made with the absorption and radiative transfer calculations in terms of the statistical theory of collisional line broadening and based on an empirical form factor. The calculations show that the line broadening mechanism does not affect the thermal regime of the atmosphere at heights above 60 km, but affects significantly the behavior of the greenhouse effect below the cloud layer. 相似文献
106.
We have performed new simulations of two different scenarios for the excitation and depletion of the primordial asteroid belt, assuming Jupiter and Saturn on initially circular orbits as predicted by the Nice Model of the evolution of the outer Solar System [Gomes, R., Levison, H.F., Tsiganis, K., Morbidelli, A., 2005. Nature 435, 466-469; Tsiganis, K., Gomes, R., Morbidelli, A., Levison, H.F., 2005. Nature 435, 459-461; Morbidelli, A., Levison, H.F., Tsiganis, K., Gomes, R., 2005. Nature 435, 462-465]. First, we study the effects of sweeping secular resonances driven by the depletion of the solar nebula. We find that these sweeping secular resonances are incapable of giving sufficient dynamical excitation to the asteroids for nebula depletion timescales consistent with estimates for solar-type stars, and in addition cannot cause significant mass depletion in the asteroid belt or produce the observed radial mixing of different asteroid taxonomic types. Second, we study the effects of planetary embryos embedded in the primordial asteroid belt. These embedded planetary embryos, combined with the action of jovian and saturnian resonances, can lead to dynamical excitation and radial mixing comparable to the current asteroid belt. The mass depletion driven by embedded planetary embryos alone, even in the case of an eccentric Jupiter and Saturn, is roughly 10-20× less than necessary to explain the current mass of the main belt, and thus a secondary depletion event, such as that which occurs naturally in the Nice Model, is required. We discuss the implications of our new simulations for the dynamical and collisional evolution of the main belt. 相似文献
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110.
分别对Hinode光学望远镜SOT观测太阳黑子的本影和半影图像以及太阳米粒组织图像进行了空间频谱计算和相关计算,分析了太阳不同结构区域图像的时域和空域特性对哈特曼波前探测精度的影响。计算和分析结果表明,在子孔径波面倾斜小于0.25″情况下,米粒组织图像采样时间在2 min内、本影和半影采样时间在4 min内,对子孔径波面倾斜探测精度的影响极小;并且由太阳目标特性引起的哈特曼波面探测误差随波面畸变量的增大而增大。这些研究结果可为太阳望远镜哈特曼波前探测器研制和应用提供依据和参考。 相似文献