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911.
L. Prange A. Jäggi R. Dach H. Bock G. Beutler L. Mervart 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
The gravity field model AIUB-CHAMP02S, which is based on six years of CHAMP GPS data, is presented here. The gravity field parameters were derived using a two step procedure: In a first step a kinematic trajectory of a low Earth orbiting (LEO) satellite is computed using the GPS data from the on-board receiver. In this step the orbits and clock corrections of the GPS satellites as well as the Earth rotation parameters (ERPs) are introduced as known. In the second step this kinematic orbit is represented by a gravitational force model and orbit parameters. 相似文献
912.
M.N. Kouahla G. Moreels M. Faivre J. Clairemidi J.W. Meriwether G.A. Lehmacher E. Vidal O. Veliz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
A new and original stereo imaging method is introduced to measure the altitude of the OH nightglow layer and provide a 3D perspective map of the altitude of the layer centroid. Near-IR photographs of the OH layer are taken at two sites separated by a 645 km distance. Each photograph is processed in order to provide a satellite view of the layer. When superposed, the two views present a common diamond-shaped area. Pairs of matched points that correspond to a physical emissive point in the common area are identified in calculating a normalized cross-correlation coefficient (NCC). This method is suitable for obtaining 3D representations in the case of low-contrast objects. An observational campaign was conducted in July 2006 in Peru. The images were taken simultaneously at Cerro Cosmos (12°09′08.2″ S, 75°33′49.3″ W, altitude 4630 m) close to Huancayo and Cerro Verde Tellolo (16°33′17.6″ S, 71°39′59.4″ W, altitude 2272 m) close to Arequipa. 3D maps of the layer surface were retrieved and compared with pseudo-relief intensity maps of the same region. The mean altitude of the emission barycenter is located at 86.3 km on July 26. Comparable relief wavy features appear in the 3D and intensity maps. It is shown that the vertical amplitude of the wave system varies as exp (Δz/2H) within the altitude range Δz = 83.5–88.0 km, H being the scale height. The oscillatory kinetic energy at the altitude of the OH layer is comprised between 3 × 10−4 and 5.4 × 10−4 J/m3, which is 2–3 times smaller than the values derived from partial radio wave at 52°N latitude. 相似文献
913.
K. Gustafsson L. Sihver D. Mancusi T. Sato G. Reitz T. Berger 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
The radiation environment in space is very different from the one encountered on Earth. In addition to the sparsely ionizing radiation, there are particles of different Z with energies ranging from keV up to hundreds of GeV which can cause severe damage to both electronics and humans. It is therefore important to understand the interactions of these highly ionizing particles with different materials such as the hull of space vehicles, human organs and electronics. We have used the Particle and Heavy-Ion Transport code System (PHITS), which is a three-dimensional Monte Carlo code able to calculate interactions and transport of particles and heavy ions with energies up to 100 GeV/nucleon in most matter. PHITS is developed and maintained by a collaboration between RIST (Research Organization for Information Science & Technology), JAEA (Japan Atomic Energy Agency), KEK (High Energy Accelerator Research Organization), Japan and Chalmers University of Technology, Sweden. For the purpose of examining the applicability of PHITS to the shielding design we have simulated the ESA facility Matroshka (MTR) designed and lead by the German Aerospace Center (DLR). Preliminary results are presented and discussed in this paper. 相似文献
914.
Gabriele Giorgi Peter J.G. Teunissen Sandra Verhagen Peter J. Buist 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
GNSS (Global Navigation Satellite Systems)-based attitude determination is an important field of study, since it is a valuable technique for the orientation estimation of remote sensing platforms. To achieve highly accurate angular estimates, the precise GNSS carrier phase observables must be employed. However, in order to take full advantage of the high precision, the unknown integer ambiguities of the carrier phase observables need to be resolved. This contribution presents a GNSS carrier phase-based attitude determination method that determines the integer ambiguities and attitude in an integral manner, thereby fully exploiting the known body geometry of the multi-antennae configuration. It is shown that this integral approach aids the ambiguity resolution process tremendously and strongly improves the capacity of fixing the correct set of integer ambiguities. In this contribution, the challenging scenario of single-epoch, single-frequency attitude determination is addressed. This guarantees a total independence from carrier phase slips and losses of lock, and it also does not require any a priori motion model for the platform. The method presented is a multivariate constrained version of the popular LAMBDA method and it is tested on data collected during an airborne remote sensing campaign. 相似文献
915.
J.R. Fernandez C.J. Mertens D. Bilitza X. Xu J.M. Russell III M.G. Mlynczak 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
We present a new technique for improving ionospheric models of nighttime E-region electron densities under geomagnetic storm conditions using TIMED/SABER measurements of broadband 4.3 μm limb radiance. The response of E-region electron densities to geomagnetic activity is characterized by SABER-derived NO+(v) 4.3 μm Volume Emission Rates (VER). A storm-time E-region electron density correction factor is defined as the ratio of storm-enhanced NO+(v) VER to a quiet-time climatological average NO+(v) VER, which will be fit to a geomagnetic activity index in a future work. The purpose of this paper is to demonstrate the feasibility of our technique in two ways. One, we compare storm-to-quiet ratios of SABER-derived NO+(v) VER with storm-to-quiet ratios of electron densities measured by Incoherent Scatter Radar. Two, we demonstrate that NO+(v) VER can be parameterized by widely available geomagnetic activity indices. The storm-time correction derived from NO+(v) VER is applicable at high-latitudes. 相似文献
916.
O.G. Morales-Olivares R.A. Caballero-Lopez 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
Our understanding of galactic cosmic ray (GCR) modulation has advanced greatly in the last three decades. However, we still need an appropriate knowledge of the GCR intensity gradient. Numerical simulations of the transport particle equation allow interpretation of cosmic ray intensities in the heliosphere. We use the numerical solution of the GCR transport equation during solar maximum epoch to compute the radial and latitudinal gradients. Our analysis indicates that adiabatic energy loss plays an important role in the radial distribution of GCR in the inner heliosphere, while in the outer region the diffusion and convection are the relevant processes. The latitudinal gradient is small. 相似文献
917.
G. Zimbardo S. Perri P. Pommois P. Veltri 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
The transport of energetic particles in the presence of magnetic turbulence can exhibit a variety of regimes different from the standard quasilinear diffusion. Here we discuss a number of solar and space problems where nonquasilinear diffusion is found, and then we illustrate anomalous transport regimes, for which the mean square deviation grows nonlinearly with time. In particular, we concentrate on superdiffusive regimes, and show what is the theoretical framework which is to be used to describe superdiffusion. We discuss the results of numerical simulations which show that superdiffusive and subdiffusive regimes are possible, and describe data analyses which allow to single out the superdiffusive transport from the observation of energetic particle profiles upstream of interplanetary shocks. The implications of superdiffusion on the efficiency of wave particle interactions are also discussed. 相似文献
918.
G.D. Aburjania K.Z. Chargazia O.A. Kharshiladze 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
The linear mechanism of generation, intensification and further nonlinear dynamics of internal gravity waves (IGW) in stably stratified dissipative ionosphere with non-uniform zonal wind (shear flow) is studied. In case of the shear flows the operators of linear problem are non-selfadjoint, and the corresponding Eigen functions – nonorthogonal. Thus, canonical – modal approach is of less use studying such motions. Non-modal mathematical analysis becomes more adequate for such problems. On the basis of non-modal approach, the equations of dynamics and the energy transfer of IGW disturbances in the ionosphere with a shear flow is obtained. Exact analytical solutions of the linear as well as the nonlinear dynamic equations of the problem are built. The increment of shear instability of IGW is defined. It is revealed that the transient amplification of IGW disturbances due time does not flow exponentially, but in algebraic – power law manner. The effectiveness of the linear amplification mechanism of IGW at interaction with non-uniform zonal wind is analyzed. It is shown that at initial linear stage of evolution IGW effectively temporarily draws energy from the shear flow significantly increasing (by an order of magnitude) own amplitude and energy. With amplitude growth the nonlinear mechanism turns on and the process ends with self-organization of nonlinear solitary, strongly localized IGW vortex structures (the monopole vortex, the transverse vortex chain or the longitudinal vortex street). Accumulation of these vortices in the ionospheric medium can create the strongly turbulent state. 相似文献
919.
V. S. Moiseev D. S. Gushchina A. N. Kozar G. E. Borzov 《Russian Aeronautics (Iz VUZ)》2009,52(2):221-227
Using formalism of the queueing theory, we propose two-objective models for optimizing the number of unmanned aerial vehicles (UAV) designed for remote monitoring (reconnaissance) of certain regions. A model that takes into account the UAV failure in performing a flight mission is considered. The numerical method and examples of solving problems stated are presented. 相似文献
920.
An optimization method for composite lattice shell structures under axially compressive loads is proposed aiming at the preliminary design. The method implements and improves some previous results of the fully analytical approach which is currently adopted at the state-of-the-art. The fully analytical approach provides the minimum mass solution under buckling and strength constraints, irrespective of other possible design limitations, such as, shell stiffness constraints. As a consequence, the minimum mass solution turns out to be satisfactory whereas other requirements are absent or automatically achieved but, on the contrary, it can drive the final preliminary configuration far from the real optimum.The proposed method implements numerical minimization allowing the designer to easily handle suboptimal configurations which are located in the vicinity of the minimum mass solution. When stiffness requirement is present (as in most cases) the benefit of this approach – in terms of weight saving with respect to the analytical design – is finally shown with a practical example. 相似文献