基于双框架控制力矩陀螺的航天器动量管理

为减小维持大型航天器的姿态稳定和降低能量消耗的动量管理中的扰动力矩对姿态稳定的干扰,设计了周期性抑制滤波器。姿态控制的执行机构采用双框架控制力矩陀螺群（DGCMGs）,应用KENNEL操纵率,使航天器执行机构的角动量在本体系的x轴分量和偏航角可达稳定,同时角动量在本体系的z轴分量和滚转角可在较小的范围内振荡。数值仿真结果验证了方案的可行性。     

Vertical motions in Thailand after the 2004 Sumatra–Andaman Earthquake from GPS observations and its geophysical modelling

Following previous findings from ongoing GPS research in Thailand since 2004 we continue to exploit the GPS technique to monitor and model land motions induced by the Sumatra–Andaman Earthquake. Our latest results show that up to the end of 2010, Thailand has been co-seismically displaced and is subsequently undergoing a post-seismic horizontal deformation with total displacements (co-seismic plus post-seismic) ranging from 10.5 to 74.7 cm. We observed the largest horizontal displacements in the southern part of Thailand and moderate and small displacements in the central and northern parts. In addition to horizontal displacements throughout Thailand, continuous GPS measurements show that large parts of Thailand are subsiding at rates up to 1 cm/yr. It is the first time that such vertical post-seismic deformations at large distances (650–1500 km away from the Earthquake’s epicentre) have been recorded. We have investigated the physical processes leading to the observed subsidence. While after-slip on the subduction interface induces negligible or even slightly positive vertical motions, relaxation in the asthenosphere is associated with a sizable subsidence. Predictions from a 3D finite element model feature an asthenosphere with an effective viscosity of the order of 3 * 10¹⁸ Pas, fit the horizontal post-seismic data and the observed subsidence well. This model is then used to predict the subsidence over the whole seismic cycle. The subsidence should go on with a diminishing rate through the next two decades and its final magnitude should not exceed 10 cm in the Bangkok area.     

The effect of geocenter motion on Jason-2 orbits and the mean sea level

We compute a series of Jason-2 GPS and SLR/DORIS-based orbits using ITRF2005 and the std0905 standards ( Lemoine et al., 2010). Our GPS and SLR/DORIS orbit data sets span a period of 2 years from cycle 3 (July 2008) to cycle 74 (July 2010). We extract the Jason-2 orbit frame translational parameters per cycle by the means of a Helmert transformation between a set of reference orbits and a set of test orbits. We compare the annual terms of these time-series to the annual terms of two different geocenter motion models where biases and trends have been removed. Subsequently, we include the annual terms of the modeled geocenter motion as a degree-1 loading displacement correction to the GPS and SLR/DORIS tracking network of the POD process. Although the annual geocenter motion correction would reflect a stationary signal in time, under ideal conditions, the whole geocenter motion is a non-stationary process that includes secular trends. Our results suggest that our GSFC Jason-2 GPS-based orbits are closely tied to the center of mass (CM) of the Earth consistent with our current force modeling, whereas GSFC’s SLR/DORIS-based orbits are tied to the origin of ITRF2005, which is the center of figure (CF) for sub-secular scales. We quantify the GPS and SLR/DORIS orbit centering and how this impacts the orbit radial error over the globe, which is assimilated into mean sea level (MSL) error, from the omission of the annual term of the geocenter correction. We find that for the SLR/DORIS std0905 orbits, currently used by the oceanographic community, only the negligence of the annual term of the geocenter motion correction results in a – 4.67 ± 3.40 mm error in the Z-component of the orbit frame which creates 1.06 ± 2.66 mm of systematic error in the MSL estimates, mainly due to the uneven distribution of the oceans between the North and South hemisphere.     

Noise analysis of continuous GPS coordinate time series for CMONOC

The Crustal Movement Observation Network of China (CMONOC) is one of the major scientific infrastructures, mainly using Global Positioning System (GPS) measurements, to monitor crustal deformation in the Chinese mainland. In this paper, decade-long coordinate time series of 26 continuous GPS sites of CMONOC are analyzed for their noise content using maximum likelihood estimation (MLE). We study the noise properties of continuous GPS time series of CMONOC for the unfiltered, filtered solutions and also the common mode signals in terms of power law plus white noise model. In the spatial filtering, we remove for every time series a common mode error that was estimated from a modified stacking of position residuals from other sites within ∼1000 km of the selected site. We find that the common mode signal in our network has a combination of spatially correlated flicker noise and a common white noise with large spatial extent. We demonstrate that for the unfiltered solutions of CMONOC continuous GPS sites the main colored noise is a flicker process, with a mean spectral index of ∼1. For the filtered solutions, the main colored noise is a general power law process, indicating that a major number of the filtered regional solutions have a combination of noise sources or local effects. The velocity uncertainties from CMONOC continuous GPS coordinate time series may be underestimated by factors of 8–16 if a pure white noise model is assumed. In addition, using a white plus flicker noise model, the median values of velocity errors for the unfiltered solutions are 0.16 (north), 0.17 (east) and 0.58 (vertical) mm/yr, and the median values for the filtered solutions are 0.09 (north), 0.10 (east) and 0.40 (vertical) mm/yr.     

有磁场时电子在航天器光电子鞘层中的漂移运动

采用二级漂移近似理论，研究了在航天器光电子鞘层中与电流收集有关的电子在磁场中的运动轨道和收集电子有关的磁瓶结构，结果表明当磁场越强，航天器表面电势越弱，磁瓶在无穷远处横截面积就越小。在光电子鞘层中，势垒对电流收集影响较大，磁瓶的横截面积在略远于垫垒处有极大值，磁瓶在无穷远处的横截面积并非随着势垒距航天器距离的远近而单调变化。     

飞机稳定尾旋的改出规律研究

研究稳定尾旋的改出方法，即寻求一种操纵规律，可以使飞机从一种稳定状态（稳定尾旋）跳到另一处非失速稳定状态。从系统的全局稳定性观点出发，构造了李雅普诺夫函数，根据输入操纵第一时刻该函数增长速度最大条件，保证尾旋改出过程中飞机振荡状态的频率接近其固有频率，从而救是飞机稳定尾旋的改出规律－－振荡型改了操纵规律。本文静放求解飞机运动的六自由度的方法计算出尾旋改出的时间历程，验证了用简单的三舵面回中难改出稳     

幂律过程拟合优度检验的功效比较

幂律过程常被用于描述复杂系统的可靠性增长模型和可修系统的可靠性分析。本文考虑定数截尾场合幂律过程的７种拟合优度检验统计量，在备选假设为对数幂律过程时，比较了这７种检验法的功效。大量随机模拟计算表明，当ｒ在较宽的范围内，Ｆ检验法的功效比其余６种检验法都要高。     

关于我国飞机租赁立法的构想

阐述了我国租赁立法及我国飞机租赁立法的现状、从理论上论述我国建立"以民航法八条为主，辅之以专门行政法规"的飞机租赁法律体制的立法构想。同时，对我国飞机租赁立法中所面J］占的问题，提出自己的看法和建议。     

IDS contribution to ITRF2008

For the first time, the International DORIS Service (IDS) has produced a technique level combination based on the contributions of seven analysis centers (ACs), including the European Space Operations Center (ESOC), Geodetic Observatory Pecny (GOP), Geoscience Australia (GAU), the NASA Goddard Space Flight Center (GSFC), the Institut Géographique National (IGN), the Institute of Astronomy, Russian Academy of Sciences (INASAN, named as INA), and CNES/CLS (named as LCA). The ACs used five different software packages to process the DORIS data from 1992 to 2008, including NAPEOS (ESA), Bernese (GOP), GEODYN (GAU, GSC), GIPSY/OASIS (INA), and GINS (LCA). The data from seven DORIS satellites, TOPEX/Poseidon, SPOT-2, SPOT-3, SPOT-4, SPOT-5, Envisat and Jason-1 were processed and all the analysis centers produced weekly SINEX files in either variance–covariance or normal equation format. The processing by the analysis centers used the latest GRACE-derived gravity models, forward modelling of atmospheric gravity, updates to the radiation pressure modelling to improve the DORIS geocenter solutions, denser parameterization of empirically determined drag coefficients to improve station and EOP solutions, especially near the solar maximum in 2001–2002, updated troposphere mapping functions, and an ITRF2005-derived station set for orbit determination, DPOD2005. The CATREF software was used to process the weekly AC solutions, and produce three iterations of an IDS global weekly combination. Between the development of the initial solution IDS-1, and the final solution, IDS-3, the ACs improved their analysis strategies and submitted updated solutions to eliminate troposphere-derived biases in the solution scale, to reduce drag-related degradations in station positioning, and to refine the estimation strategy to improve the combination geocenter solution. An analysis of the frequency content of the individual AC geocenter and scale solutions was used as the basis to define the scale and geocenter of the IDS-3 combination. The final IDS-3 combination has an internal position consistency (WRMS) that is 15 to 20 mm before 2002 and 8 to 10 mm after 2002, when 4 or 5 satellites contribute to the weekly solutions. The final IDS-3 combination includes solutions for 130 DORIS stations on 67 different sites of which 35 have occupations over 16 years (1993.0–2009.0). The EOPs from the IDS-3 combination were compared with the IERS 05 C04 time series and the RMS agreement was 0.24 mas and 0.35 mas for the X and Y components of polar motion. The comparison to ITRF2005 in station position shows an agreement of 6 to 8 mm RMS in horizontal and 10.3 mm in height. The RMS comparison to ITRF2005 in station velocity is at 1.8 mm/year on the East component, to 1.2 mm/year in North component and 1.6 mm/year in height.     

基于空间两点的视觉自主着陆导引算法设计

为提高无人机着陆效率,从着陆速度向量场和导引律设计两方面研究改进。首先,基于椭圆设计速度向量场,实现飞行路程更短、机动性能要求更低的着陆轨迹。然后,基于像素坐标系与机体坐标系的关系,设计无人机的航迹方位角指令;以椭圆切线方向为参考,结合合作矢量特征,设计航迹倾斜角指令;利用图像信息,设计速度大小指令。最后,理论比较了传统轨迹与提出轨迹对方向机动性性能的要求,给出了轨迹参数与无人机方向机动性性能的关系。利用Simulink搭建系统仿真平台,计算满足要求的合作矢量特征。结果表明,无人机以曲线轨迹准确软着陆到目标,满足实际运用的需要。