利用GOCE卫星数据确定全球重力场模型

利用GOCE卫星观测数据确定全球静态重力场是当前大地测量学的研究热点.本文联合2011-02-28至2012-03-05共12个月的GOCE卫星轨道和梯度数据采用直接法恢复了210阶次的重力场模型SWJTUGO01S,利用零相位的有限脉冲带通数字滤波器对GOCE梯度数据进行滤波处理,直接在梯度仪坐标系中建立梯度观测方程,避免了坐标转换过程中高精度梯度观测分量精度的损失;采用短弧积分法处理轨道数据,并利用方差分量估计确定联合解的最优权,Kuala正则化方法用于处理数据极空白问题.基于EGM2008模型和北美地区的GPS水准观测数据,对SWJTU-GO01S模型进行内外符合精度分析,结果表明:SWJTU-GO01S模型在210阶次的大地水准面误差和累计误差分别为2.1 cm和13.7 cm,整体上优于欧空局公布的第二代时域法和空域法模型的精度,在150阶以后优于ITG-GRACE2010S的精度;本文的研究为进一步联合多类卫星观测数据恢复重力场模型提供参考.     

Resources scheduling for data relay satellite with microwave and optical hybrid links based on improved niche genetic algorithm

The formation of the Space-based Information System with the technology of high performance optical inter-satellite communication and the realization of global seamless coverage and mobile terminal accessing are the necessary trend of the development of optical and microwave hybrid communication. Considering the resources, missions and restraints of data relay satellite optical and microwave hybrid links system, a model of hybrid links resources scheduling is established and a scheduling algorithm based on an improved niche genetic algorithm is put forwarded. According to the multi-user-satellite, multi-time-window, multi-class-antenna and a number of missions with priority weight, the scheduling schemes are generated randomly to begin with and evaluated with the fitness functions. To obtain an optimal scheduling result, an improved niche genetic algorithm is adopted to optimize the scheduling schemes. The simulation result reveals that a satisfactory result is obtained and the improved niche genetic algorithm has advantages in both efficiency and performance in a scenario including a relay satellite with 2 optical antennas and 1 microwave antenna for user satellites connection, 8 user satellites with 64 missions. The simulation indicates that the model and the optimization algorithm are suitable for multi-user, multi-mission and multi-class-antenna hybrid communication recourses scheduling problem.     

TDICCD相机的卫星姿态稳定度确定

为解决卫星平台振动造成的图像质量下降问题,提高TDI CCD相机成像质量,分析了卫星姿态稳定度的范围及影响。讨论了卫星平台振动与TDI CCD成像质量的相关性,推导了卫星平台姿态稳定度和像移的关系公式,得出TDI CCD相机对卫星姿态稳定度的要求与轨道高度以及积分级数有关。实验验证了公式推导,结果显示：轨道高度越高,积分级数越大,对卫星姿态稳定度的要求就越严格。数据表明：轨道高度在200～1000 km变化时,对卫星姿态稳定度的要求从0.0377 rad/s提升至0.00635 rad/s;TDI CCD 相机的积分级数在1～100间变化时,对卫星姿态稳定度的要求从0.014 rad/s提升到0.00014 rad/s。本文工作确定了卫星姿态稳定度和轨道高度以及积分级数的关系,有助于TDI CCD成像质量的提升。     

Satellite laser ranging experiment with sub-centimeter single-shot ranging precision at Shanghai Observatory

The Shanghai Astronomical Observatory, Chinese Academy of Sciences, incollaboration with the Czech Technical University, carried out the experiment of satellite laser ranging with sub-centimeter precision in Shanghai in August 2001. A pico-second event timer was used for the measurement of the time interval between the transmitted and returned laser pulses for Lageos 1, 2, Starlette, Stella, Topex/Poseiden and ERS-2 in coordination with the existing laser transmitting and receiving system at the Shanghai Observatory. The analysis of the measurement showed that the single-shot ranging precision with these satellites is 7-8 mm. In order to compare ranging precision, the existing ranging system has tracked simultaneously these satellites and obtained the ranging precision of 12-15 mm. It means that the ranging precision with the new system is 80% better thanthe existing system. The systematic biases with the existing system have also been checked in the experiment.     

A Future Millimeter/Sub–Millimeter Radiometer for Satellite Observation of Ice Clouds

The instrument concept of a future spaceborne millimeter/sub-millimeter radiometer is proposed in this paper for the remote sensing of ice clouds from satellite. The proposed radiometer is expected to operate at a series of frequencies within the millimeter and sub-millimeter wave range from 150 to about 900 GHz. Five frequencies are selected in the atmospheric windows, i.e., 150, 220, 463, 683, 874 GHz, and at each frequency there are two orthogonally polarized channels. Three water vapor channels located close to 183.31 GHz are also included in this instrument, since they can provide water vapor information, which is needed for ice cloud parameter retrieval. To simplify system design and test, a modular design philosophy is followed in the receiver frontend design and two antennas are used separately for the millimeter and sub-millimeter channels. Overall, the instrument requirements can be met with today's technology, except for the channels at the highest frequencies, where the radiometric sensitivity can be larger than the required 1.0 K for the 10 km spatial resolution (2.5 ms integration time). However, this situation can be improved by averaging neighboring pixels in data processing if certain compromise in the spatial resolution can be made at these frequencies.     

余弦BOC信号伪相关函数无模糊跟踪方法

二进制偏移载波 (binary offset carrier,BOC) 调制方式实现了频谱分离和频段共享,被应用于全球导航卫星系统中;但由于BOC信号自相关函数的主峰和副峰幅度差异较小,容易引起捕获和跟踪模糊,导致较大的测距误差;余弦相位BOC(Cosine-phased BOC,CosBOC)信号自相关函数形式相对复杂,给其无模糊处理带来了挑战;基于伪相关函数法(pseudo correlation function, PCF)思想,针对CosBOC信号设计本地参考信号的特殊码片波形,与接收信号相关后经过非线性组合可获得单峰无模糊相关函数,消除了跟踪模糊性;仿真结果表明:参数取值合适时该方法的跟踪和抗多径性能均优于同等条件下的BPSK-like方法。     

Colloidal Core–Satellite Supraparticles via Preprogramed Burst of Nanostructured Micro‐Raspberry Particles

Colloidal molecules, or more general supraparticles, i.e., particles which are themselves assembled of smaller nanoparticles in a defined way, are known to be synthesizable via bottom‐up assembly techniques in colloidal dispersion. The amount of synthesizable particles is mostly limited to milligrams. Herein, a bottom‐up‐programed, triggerable top‐down process is reported to obtain core–satellite supraparticles, i.e., particles composed of a larger core particle surrounded by smaller satellite particles. The key is to prepare a nanostructured, microparticulate powder into which defined burst behavior is preprogramed. Once the system is mechanically triggered, it bursts into well‐defined nanosized core–satellite supraparticles. Scale‐up is easily feasible and several hundred grams per batch can be demonstrated. The product is a ready‐to‐use and flexibly processible powder. Upon simple mixing with a polymer, it disintegrates into the preprogramed core–satellite supraparticles, thus forming a highly sophisticated nanocomposite with the polymer matrix. A pure silica nanoparticle system and a silica–iron oxide nanoparticle hybrid system are presented to demonstrate the versatility of the approach. Enhanced mechanical and unexpected magneto‐optical properties with the particle system are found. The disintegration of the microparticles into individual core–satellite colloidal supraparticles is confirmed via in situ liquid cell transmission electron microscopy.     

空间环境对卫星光通信系统性能的影响分析

分析了空间环境对卫星光通信系统的主要影响因素,包括高能带电粒子辐射、太阳辐射、等离子体辐射等环境。分析结果表明,为了有效减小卫星光通信器件的单粒子翻转率,需要对轨道倾角和轨道高度进行优化设计;为了有效抑制太阳辐射,对日俯仰角需要限制在一个很小的变化范围;增大信号发射功率和减小系统跟瞄误差都是提高卫星光通信系统可靠性的有效途径;对等离子体辐射环境来说,300eV以上的中等能量等离子体会严重干扰卫星的正常工作。