FY-2卫星星载扫描辐射计午夜杂散光的分析

“风云二号”(FY-2C)的主要载荷是自旋稳定平台上的多通道扫描辐射计。卫星进入午夜工作时,太阳光线将会入射到辐射计的R-C光学系统中,并且经过各种器件及框架结构反射或者漫反射,从而产生影响成像的杂散光。针对气象部门提供的FY-2C卫星云图中午夜杂散光较严重的情况,分析了特定噪声区域的产生原因,并为同型号卫星星载扫描辐射计的改进提供参考性建议。     

基于四叉树复小波变换的卫星图像去噪

小波变换方法被广泛应用于图像处理,但由于其不具有平移不变性以及较少的方向选择,因而限制了它的应用范围。四叉树复小波变换,是对Malla算法的一种改进,通过奇偶滤波器的对称使用,在四棵数上分别实现分解和重构。与一般复小波一样,四叉树复小波算法具有较好的方向选择性和平移不变性,并且容易实现完全重构。采用四叉树复小波变换和基于子带噪声的自适应阈值方法,对一幅卫星图像进行了去噪处理,仿真实验表明该方法具有较好的去噪效果。     

高分辨率遥感影像融合处理技术的对比分析研究

随着遥感技术的发展,获取遥感数据的手段越来越丰富。由各种不同的传感器获取的影像数据与日俱增,在同一地区形成了多时相、多分辨率的影像序列。如何综合各种类型的遥感影像信息,提高遥感数据的利用效益已成为遥感应用的瓶颈问题。多源遥感数据融合技术是解决这一问题的有效手段。高空间分辨率影像数据的多样性和复杂性对遥感信息融合处理技术提出了新的更高的要求。以IKONOS卫星数据为例对其进行了空间分辨率的影像融合。研究中引入了多种融合方法,如IHS变换、主成分分析、小波变换以及基于区域特征的自适应小波包算法。从光谱质量和空间信息的角度出发对融合方法进行了比较研究,分析出了比较适合于IKONOS卫星的高分辨率影像融合的处理方法。     

基于感兴趣区域的海洋卫星遥感图像压缩算法

针对海洋监视卫星遥感图像的特点,提出了一种基于感兴趣区域的自适应遥感图像近无损压缩算法。该算法利用红-黑小波提升方法检测出目标的边缘,采用阈值法将目标和背景分割,使用外接矩形来描述目标,从而自动确定感兴趣区域。感兴趣区域采用Rice无损熵编码方法,背景区域采用比特平面编码的有损压缩方法。实验结果表明,该算法能有效地划分感兴趣区域,其压缩比较无损压缩有了很大提高,目标无失真,整幅图像的峰值信噪比都在40dB以上。算法的计算复杂度较低,易于硬件实现,而且还具有自适应性和数据包独立的优点,适合于海洋监视卫星遥感图像近无损压缩应用。     

Impact dynamics analysis of free-floating space manipulator capturingsatellite on orbit and robust adaptive compound controlalgorithm design for suppressing motion

The impact dynamics, impact effect, and post-impact unstable motion sup- pression of free-floating space manipulator capturing a satellite on orbit are analyzed. Firstly, the dynamics equation of free-floating space manipulator is derived using the sec- ond Lagrangian equation. Combining the momentum conservation principle, the impact dynamics and effect between the space manipulator end-effector and satellite of the cap- ture process are analyzed with the momentum impulse method. Focusing on the unstable motion of space manipulator due to the above impact effect, a robust adaptive compound control algorithm is designed to suppress the above unstable motion. There is no need to control the free-floating base position to save the jet fuel. Finally, the simulation is proposed to show the impact effect and verify the validity of the control algorithm.     

基于卫星观测数据的预测模型及其应用

在战争中为了避开敌方军事卫星的侦查,需要对其过顶时间进行预警.对于参数公开的卫星,可以通过根数来进行准确的预报.而对于参数未知的卫星,提出了一种根据过往观测数据来对卫星过顶时间进行预测的思路:将卫星与地球之间复杂的三维耦合运动进行降维,并且以地面为参考系,发现卫星星下点运动轨迹具有高度的周期性·根据这种思路,可以通过获取的过往观测数据来对卫星未来的过顶时间进行准确预测.而对于战时地面运动单位躲避卫星的问题,可以根据所面对的不同侦查卫星通过设置一个固定的路线,让地面单位在该路线中有计划的行驶,能够躲避多种卫星的侦查.     

Stability analysis of relative equilibria of mechanical systems with cyclic coordinates: a direct approach

Nonlinear stability of relative equilibria of mechanical systems has been investigated during the past two decades by notable authors and has resulted in the so-called energy momentum method. Although it has numerous important engineering applications, this theory involves subtle mathematical methods such as group theory with which engineers usually are not familiar. This paper develops a simple and natural approach to the problem for the case of cyclic coordinates in the Lagrangian since many practical examples can be easily formulated in terms of cyclic coordinates. Referring to standard algebraic operations, a stability criterion for relative equilibria is derived. As a computational benefit the presented approach does not require knowledge of a system's complete kinetic energy, either for formulating steady-state equations or for checking stability. The application of the method, which is closely related to Routh's method, will be demonstrated using the example of a dumbell satellite.     

Proton loss of inner radiation belt during geomagnetic storm of 2018 based on CSES satellite observation

The proton distribution in inner radiation belt is often affected by strong geomagnetic storm disturbance. Based on the data of the sun-synchronous CSES satellite, which carries with several high energy particle payloads and was launched in February 2018, we analyzed the extensive proton variations in the inner radiation belt in a wide energy range of 2 MeV-220 MeV during 2018 major geomagnetic storm. The result indicates that the loss mechanism of protons was energy dependence which is consistent with some previous studies. For protons at low energy 2 MeV-20 MeV, the fluxes were decreased during main phase of the storm and did not come back quickly during the recovery phase, which is likely to be caused by Coulomb collision due to neutral atmosphere density variation. At higher energy 30 MeV-100 MeV, it was confirmed that the magnetic field line curvature scattering plays a significant role in the proton loss phenomenon during this storm. At highest energies > 100 MeV, the fluxes of protons kept a stable level and did not exhibit a significant loss during this storm.     

Hohmann转移释放绳系卫星的方法研究

借助Ｈｏｈｍａｎｎ轨道转移的思想，研究一种绳系卫星释放方法并进行动力学分析．从轨道方程和Ｋｅ ｐｌｅｒ方程导出轨道转移条件．由数值计算对此方法加以说明．