用于小Re数流动显示研究的水平式肥皂膜水洞

介绍了一种用于小如数流动显示研究的水平式肥皂膜水洞。该装置试验段流速稳定,流速范围为0．2～1．5m／s。采用了几种模型在该水洞中进行试验,试验结果表明,水平式肥皂膜水洞在研究小胁数流动显示方面具有独特优势,能够反映出物体在小胁数下的微细流动特征。     

绳系微小卫星的旋转编队飞行

针对三星编队飞行问题,提出一种绳系控制方法,在自旋刚体卫星的平衡分析的基础上,建立了Thomson和Likins Pringle平衡构形的绳系三星编队模型,通过对编队系统的稳定性分析得到了两种构形下的稳定条件,并给出了三种控制策略用以解决Likins-Pringle构形不能满足平衡条件的问题。最后经过仿真验证了理论分析的正确性,并对三种控制策略进行了检验,结果表明Thomson构形无须辅助手段,在满足特定条件下可以稳定运行,Likins-Pringle构形采用弹簧系统和喷气辅助绳系控制时满足特定条件也可以稳定运行。     

A series of small scientific satellite with flexible standard bus

Japan Aerospace Exploration Agency has a plan to develop the small satellite standard bus for various scientific missions and disaster monitoring missions. The satellite bus is a class of 250–400 kg mass with three-axis control capability of 0.02 accuracy. The science missions include X-ray astronomy missions, planetary telescope missions, and magnetosphere atmosphere missions. In order to adapt the wide range of mission requirements, the satellite bus has to be provided with flexibility. The concepts of modularization, reusability, and product line are applied to the standard bus system. This paper describes the characteristics of the small satellite standard bus which will be firstly launched in 2011.     

Autonomous navigation of formation flying spacecrafts in deep space exploration and communication by hybrid navigation utilizing neural network filter

Autonomous navigation of spacecrafts is a difficult task, however, which is a must in future deep space exploration. With multiple spacecrafts flying in space, this aim can be achieved by formation flying spacecraft (FFS) utilizing inverse time difference of arrival (ITDOA) and inverse difference Doppler (IDD) methods, which can locate the position of earth-station from one-way uplink signals in the FFS coordinate, and by way of conversion of coordinates, the position of FFS is achieved in earth-centered earth-fixed (ECEF) coordinate. The ability of neural network (NN) filter in navigation to extract position of spacecrafts from random measuring noise of signal arrival time and Doppler shift is studied with different radius of FFS and surveying parameters. The NN filter used by spacecraft group is new way of unidirectional autonomous navigation and is of high precision of hybrid navigation.     

Nusselt number for convection driven by tidal and radiogenic heating

The ‘traditional’ formulas giving the Nusselt number Nu as a function of Rayleigh number Ra cannot be used for low and moderate values of Ra. Moreover, the recent progress in 3D numerical modeling makes possible to determine the Nusselt number Nu as a function of Rayleigh number Ra for convection driven by radiogenic and tidal heating. We found that for low and moderate Ra: Nu(Ra) = ε(Ra+ξ)^λ where λ depends on rheology and boundary conditions, ε depends only on the mode of heating, and ξ = ε^−1/λ · Nu(Ra) makes possible to develop a parameterized theory of convection in medium size icy satellites. We also indicate some differences between convection driven by tidal and radiogenic heating and convection driven exclusively by radiogenic heating.     

The origin of sulfur-bearing species on the surfaces of icy satellites

We present experimental results in order to understand the physico-chemical effects induced by fast ions irradiating sulfur bearing molecules. The experiments are relevant both to Solar System objects (icy satellites, comets, TNOs) and icy mantles on grains in the interstellar medium. Here we concentrate on the application to the Galilean moons that are exposed to high energetic particle fluxes in the jovian magnetosphere.     

Tomographic reconstruction of the ionospheric electron density as a function of space and time

Electron density distribution is the major determining parameter of the ionosphere. Computerized Ionospheric Tomography (CIT) is a method to reconstruct ionospheric electron density image by computing Total Electron Content (TEC) values from the recorded Global Positioning Satellite System (GPS) signals. Due to the multi-scale variability of the ionosphere and inherent biases and errors in the computation of TEC, CIT constitutes an underdetermined ill-posed inverse problem. In this study, a novel Singular Value Decomposition (SVD) based CIT reconstruction technique is proposed for the imaging of electron density in both space (latitude, longitude, altitude) and time. The underlying model is obtained from International Reference Ionosphere (IRI) and the necessary measurements are obtained from earth based and satellite based GPS recordings. Based on the IRI-2007 model, a basis is formed by SVD for the required location and the time of interest. Selecting the first few basis vectors corresponding to the most significant singular values, the 3-D CIT is formulated as a weighted least squares estimation problem of the basis coefficients. By providing significant regularization to the tomographic inversion problem with limited projections, the proposed technique provides robust and reliable 3-D reconstructions of ionospheric electron density.     

防空导弹拦截编队目标制导精度建模研究

随着现代战争中空袭模式的发展变化,防空导弹拦截的目标已由单机目标逐渐演变为编队目标.因此,研究拦截多机种、多架次编队目标情况下的武器系统性能,具有极其重要的实战意义.基于单个目标的制导误差平面的定义已经不能够适应这种形势发展的需要,本文对拦截双目标及多目标编队情况下的制导误差平面定义进行了拓展,实现了在接近实战条件下的制导精度的数学建模和仿真研究,使研究武器系统拦截编队目标的制导性能成为可能.     

小卫星临近作业轨道和姿态联合控制

建立了小卫星相对轨道和姿态的误差动力学模型,根据作业任务和姿态指向要求确定了小卫星相对轨道和姿态的期望运动;采用相对轨道和姿态联合控制策略,并考虑小卫星作业过程中质量和转动惯量的不确定性,设计了自适应全状态反馈控制律;数值仿真结果表明该控制律具有较强的自适应性。     

编队飞行卫星群描述及摄动分析

定义了一组新的编队飞行卫星群相对运动描述参数 ,以及基于此的构型设计方法 ;并分析了地球非球形摄动对这组参数的影响 ,给出了为消除摄动长期影响所需的速度脉冲量 ,并对部分参数给出了减少摄动影响的设计方法