弹道导弹中段机动突防制导误差修正方法

针对弹道导弹中段反拦截实时机动突防带来的参数偏差问题,给出了在地球非球形摄动影响下的位置和速度偏差量的计算方法,采用改进的fg级数和预测制导方法获得了机动推力的作用方向及发动机的开启时间,并对再入点误差进行了修正。仿真结果表明,采用该方法可有效地修正因机动突防与地球扁率而引起的再入点参数误差,为末制导系统的工作提供了良...     

长波授时附加二次相位因子修正方法

附加二次相位因子（ASF）是影响长波授时精度的主要因素,而其理论计算复杂、实测成本太高,不便于工程推广。本文选取华北平原区域为研究范围,提出一种简单高效的ASF修正方法———建立对应的ASF数据网格,采用插值算法进行ASF修正研究。通过对ASF数据网格的验证和分析,得到了和预期效果相一致的实验结果。实验结果表明：建立区域性的ASF数据网格有利于快速地修正ASF误差,便于实际工程应用。     

基于纠删码的遥测链路丢帧恢复技术

针对遥测系统在恶劣天气条件、航天器姿态调整、天线指向偏离、脉冲干扰等各种因素影响下出现的遥测信号闪断以至接收机丢帧问题,提出一种适用于闪断信道的纠删码技术,用于恢复丢失的数据帧.首先介绍LDPC（低密度奇偶校验）纠删码的编译码算法,然后构造一种以短码长的随机码为外码、IRA（不规则重复累积）LDPC码为内码的级联纠删码,最后给出纠删码的应用策略和实现纠删码所需的CCSDS（空间数据系统咨询委员会）协议扩展.通过仿真实验和分析,得到了LDPC纠删码和级联纠删码的纠删性能,得出级联纠删码与LDPC纠删码均可获得接近理想的纠删性能的结论,且级联纠删码的构造更为灵活,可适应不同的应用环境,对CCSDS协议进行适当扩展后即可支持纠删码在CCSDS遥测链路中的应用.     

光照处理中改进的Gamma矫正方法

在图像处理中，光照始终是影响图像质量的重要因素。为了有效弱化光照对图像质量的影响，利用非线性函数叠加的方法构造了一个合理的Gamma值变化曲线，使Gamma矫正方法充分适应了图像中光照变化的实际情况，并有效防止了Gamma矫正可能产生的图像失真。实验证明该方法在改善图像光照条件、提高图像质量方面具有良好的性能。     

基于OEM的差分GPS基准站的设计

介绍了差分GPS(DGPS)的定位模型以及RTCM SC-104数据格式及其电文编码,提出了利用廉价的GPS-OEM(原始设备制造商)建立基准站的设计方案,方法是利用GPS-OEM和微处理器构成硬件系统,利用GPS-OEM输出的二进制差分修正数据,将其编码为RTCM SC-104电文来进行设计.实验结果表明这种DGPS基准站同样可以达到1~5?m的水平平面定位精度,因此具有性能价格比高,实用灵活的优点.     

一种超声速射流计算方法与实验验证

高温射流流场计算是尾焰辐射目标特性计算的前提,然而由于缺少可靠实验数据,针对湍流超声速射流的数值模拟多集中于低温射流,高温射流计算与实验的对比工作还很少见。利用k-ωSST双方程湍流模型,模拟了多个典型超声速射流实验的流场速度与温度分布,通过与实验结果进行对比,建立了一种超声速射流计算方法。首先,通过对比多个低温射流的实验与计算结果,探索了湍流模型中可压缩修正以及来流湍动粘性比对超声速射流计算结果的影响;进而,针对火箭发动机尾焰实验,计算尾焰流场与流场红外辐射,流场辐射计算结果与实验观测结果符合较好,进一步验证了计算方法。最终认为经过可压缩修正的k-ωSST双方程湍流模型结合湍动粘性比取值30可以作为超声射流计算中较为典型的湍流计算方法。     

An improved approach to model ionospheric delays for single-frequency Precise Point Positioning

PPP with low-cost, single-frequency receivers has been receiving increasing interest in recent years because of its large amount of possible users. One crucial issue in single-frequency PPP is the mitigation of ionospheric delays which cannot be removed by combining observations on different frequencies. For this purpose, several approaches have been developed, such as, the approach using ionospheric model corrections with proper weight, the GRAPHIC (Group and Phase Ionosphere Calibration) approach, and the method to model ionospheric delays over a station with a low polynomial or stochastic process. From our investigation on the stochastic characteristics of the ionospheric delay over a station, it cannot be precisely represented by either a deterministic model in the form of a low-order polynomial or a stochastic process for each satellite, because of its strong irregular spatial and temporal variations. Therefore, a novel approach is developed accordingly in which the deterministic representation is further refined by a stochastic process for each satellite with an empirical model for its power density. Furthermore, ionospheric delay corrections from a constructed model using GNSS data are also included as pseudo-observations for a better solution. A large data set collected from about 200 IGS stations over one month in 2010 is processed with the new approach and several commonly adopted approaches for validation. The results show its significant improvements in terms of positioning accuracy and convergence time with a negligible extra processing time, which is also demonstrated by data collected with a low-cost, handheld, single-frequency receiver.     

Improvement of the ADEOS-II/GLI sun-glint algorithm using concomitant microwave scatterometer-derived wind data

The tendency of over-estimation of sun-glint reflectance was found in GLI satellite ocean color data, after applying the traditional sun-glint model of Cox and Munk together with objective analysis wind data. ADEOS-II has provided a good opportunity to improve the glint model using data measured by GLI and SeaWinds, both onboard the satellite. With the help of simultaneous wind measurements achieved by SeaWinds, the Cox and Munk model is re-evaluated using GLI measurements to obtain a new relationship between the surface mean square slope and wind. The new model was found to be very close to the Cox and Munk under moderate wind speed but is much different under calm condition, where it shows similarity to the result reported by Ebuchi and Kizu. It also improves the ocean color data availability and the precision of sun-glint reflectance, based on the evaluation result of the generated Level 3 data products.     

GPS VEHICLE NAVIGATION SYSTEM

介绍了一种ＧＰＳ智能导航系统。本系统可以广泛应用于城市、省际的交通运输领域。作为智能交通系统的一部分,将在很大程度上改善司机在复杂交通状态下的驾驶条件。文中详细讨论了系统所采用的两项关键技术：地理信息库系统、车辆位置的实时修正。     

热膜温度效应研究

用热膜测模型表面摩擦应力,在风洞试验中已得到广泛的应用,但在飞行试验中,由于大气温度与地面温度有很大差异,因此传统的校准方法无法应用。本文通过对热膜的传热机理进行分析,找到一种温度修正方法。此方法用于飞行试验中,得到较好的结果。