Retrieval and validation of aerosol optical depth using GF-1 WFV cameras data

Conventional AOD (Aerosol Optical Depth) retrieval is restricted to the global and regional scale due to the limited spatial resolution of satellites. This does not allow for aerosol monitoring at the city level. The Chinese GF-1 Wide Field of View (WFV) sensors have sufficiently fine resolution as a data source for AOD retrieval with fine spatial resolution and a 4-day revisit time. In this study, principles similar to those in the Deep Blue (DB) and Dark Target (DT) algorithms were used to retrieve AOD at 100 m spatial resolution from GF-1 WFV images supported by Moderate Resolution Imaging Spectraradiometer (MODIS) surface reflectance (SR) products (MOD09A1). The derived GF-1 WFV AOD were compared with a combination of MOD04_3K DT AOD and MOD04_L2 DB AOD (MODIS AOD) to find that they yield reasonable Spearman correlations (R_S > 0.82) over Taiwan and Beijing. The derived GF-1 WFV AOD were also validated against Aerosol Robotic Network (AERONET) AOD; the Spearman correlation values were R_S = 0.911 in Beijing and R_S = 0.858 in Taiwan.     

0-1线性规划的连续化求解方法

针对0-1线性规划的优化问题,提出一种惩罚函数方法。考虑到0-1线性规划的最优值特征,通过在目标函数中加上惩罚函数,将0-1离散线性规划模型连续化成非线性规划模型,并使用Matlab的Fmincon函数进行求解。经对多个算例的计算,并和其他算法比较,结果表明惩罚函数法的可行性和有效性。将该方法应用于实际的飞机排班问题上,取得比较满意的结果。     

简析一起飞机转弯航向误差大的故障原因及预防措施

某型飞机装有两套HZX-1航向姿态系统，飞行中同时出现转弯航向误差大现象，本文通过分析故障原因，找出了引起故障的关键产品，并针对故障制定了预防措施。     

Physical properties and long-term evolution of the debris clouds produced by two catastrophic collisions in Earth orbit

The population of cataloged orbital debris increased by approximately 40% in just a couple of years, from January 2007 to February 2009. This was due to two collisions in space, which involved the catastrophic destruction of three intact satellites (Fengyun 1C, Cosmos 2251 and Iridium 33) in high inclination orbits. Both events occurred in the altitude range already most affected by previous launch activity and breakup events, thus boosting the cataloged population in low Earth orbit by more than 60%.     

Latitudinal features of Total Electron Content over the African and European longitude sector following the St. Patrick’s day storm of 2015

GNSS TEC values have been obtained from 18 stations distributed from the magnetic equator to nearly 80°N magnetic dip in the African and west-European longitude sector corresponding to the March 17–18, 2015 geomagnetic storm. Significantly depleted ionosphere have been observed at stations north of 50°N geographic on March 18, 2015 following the above storm over a longitude swath 11.9°–21°E covering the Eastern Africa and Western European longitude sector. High ROTI values were noted on March 17^th at locations around 80°N magnetic dip. Two prominent peaks in PCN were noted around 09:00 UT and 14:00 UT on March 17, 2015 and around 15:00 UT on March 18, 2015. Daytime thermospheric (O/N₂) ratio was markedly less on March 18th at latitudes above 60°N geographic which is suggested to be the major driver behind depleted high latitude ionosphere during the recovery phase of the storm on March 18, 2015.     

Upgrade of the GOCE Level 1b gradiometer processor

This paper describes the upgrade of the GOCE Level 1b gradiometer processing as part of ESA’s Payload Data Segment (PDS). Four processing steps have been identified which can be improved: 1. The optimal determination of the angular rates of the satellite, based on a combination of star sensor and gradiometer data. This is the so-called angular rate reconstruction. 2. The optimal determination of the spacecraft’s attitude, again based on a combination of star sensor and gradiometer data. 3. The combination of data of all simultaneously available star sensors. And, 4. the calibration of the measured accelerations is improved by taking the time dependence of selected calibration parameters into account.     

基于变步长CFD/RBD方法的旋转弹轨迹仿真

采用变步长方法实现非定常Navier-Stokes方程和刚体六自由度运动方程的耦合求解,并对美国ARL旋转弹试验模型的飞行轨迹进行了仿真。旋转弹自由飞行过程中受到空气阻力作用,转速下降,气动力变化趋缓。因此轨迹仿真时先选取较小的时间步长,随着转速的下降逐渐增大步长,这样可以减少计算时间。刚体六自由度运动方程的数值求解采用变步长Adams预估校正法。将定步长和变步长两种方法应用于旋转弹实验模型轨迹仿真,并将计算得到的旋转弹空间位置、姿态角与试验结果进行了对比,结果显示:方法能较精确地仿真旋转弹飞行轨迹。在相同初始步长条件下,变步长方法较定步长方法计算时间减半;在相同计算时间条件下,变步长方法较定步长方法精度更高。     

月球主要构造特征：嫦娥一号月球影像初步研究

月球在31亿年前已基本停止地质活动,从而保留了其形成初期的信息．这些信息对于认识月球、地球乃至太阳系的形成演化具有重要意义．在已有研究成果的基础上,结合嫦娥一号探月卫星CCD影像数据,从月海穹窿、撞击坑、月岭、断裂、月坑链、月溪及月谷等方面介绍了月球主要构造形式的地质特征、形貌特征及遥感影像特征,对其成因以及所隐含的地质意义进行了分析．结果表明,嫦娥一号CCD影像信息丰富,影像清晰,利用其CCD影像数据进一步研究月球的构造现象是可行的．