总线通讯实验系统中矢量字的处理方法

研究了在1553B总线通讯实验系统远程终端（RT）仿真中矢量字的处理方法。设计了矢量字的手动单个设置、自动更新和使能RT中断更新三种处理方法。详细分析了各种方法中数据传输的执行过程。由于实验系统中能够灵活地设置矢量字,因此可以实现对采用更新机制传输消息的通讯过程的仿真。     

仿生四足六旋翼无人机自适应着陆性能分析

旋翼无人机在民用和军用领域被广泛应用,但传统撬式起落架在复杂地形下难以起降,为了扩大旋翼无人机的降落面积和应用范围,设计一种仿人腿式两级缓冲自适应起落架。通过对仿生腿的正逆运动学分析,提出一种自适应起落架姿态调整策略;建立仿生四足六旋翼无人机着陆动力学模型,基于多体动力学软件sim?center 3D 开展了着陆动力学仿真,并与传统撬式起落架进行着陆性能对比研究。结果表明：着陆腿式的两级缓冲自适应起落架及其姿态调整策略,能够使滚转角减小95.69%,过载系数降低34.06%,两级缓冲自适应起落架在面对复杂地形时具备主动调节姿态安全着陆的地形适应能力和极好的减震缓冲能力。     

Quantitative Assessments of the Martian Hydrosphere

In this paper, we review current estimates of the global water inventory of Mars, potential loss mechanisms, the thermophysical characteristics of the different reservoirs that water may be currently stored in, and assess how the planet’s hydrosphere and cryosphere evolved with time. First, we summarize the water inventory quantified from geological analyses of surface features related to both liquid water erosion, and ice-related landscapes. They indicate that, throughout most of Martian geologic history (and possibly continuing through to the present day), water was present to substantial depths, with a total inventory ranging from several 100 to as much as 1000 m Global Equivalent Layer (GEL). We then review the most recent estimates of water content based on subsurface detection by orbital and landed instruments, including deep penetrating radars such as SHARAD and MARSIS. We show that the total amount of water measured so far is about 30 m GEL, although a far larger amount of water may be stored below the sounding depths of currently operational instruments. Finally, a global picture of the current state of the subsurface water reservoirs and their evolution is discussed.     

Early analysis of precise orbit and clock offset determination for the satellites of the global BeiDou-3 system

Eight new-generation BeiDou satellites (BeiDou-3) have been launched into Medium Earth Orbit (MEO), allowing for global coverage since March 2018, and they are equipped with new hydrogen atomic clocks and updated rubidium clocks. Firstly, we analyzed the signals for the carrier-to-noise-density ratio (C/N0) and pseudorange multipath (MP) by using international GNSS (Global Navigation Satellite System) Monitoring and Assessment System (iGMAS) station data, and found that B1C has a lower C/N0, and B2a has the same level of C/N0 as the B1I and B3I signals. For pseudorange multipath, compared with the BeiDou-2 satellites, the obvious systematic variation of MP scatters related to the elevation angle is greatly improved for the BeiDou-3 and BeiDou-3e satellites signals. For the signals of the BeiDou-3 satellites, the order of the Root Mean Square (RMS) values of multipath and noise is B3I?<?B1I?<?B2a?<?B1C. Then, the comparison of the precise orbit determination and clock offset determination for the BeiDou-2, BeiDou-3, and BeiDou-3 experimental (BeiDou-3e) satellites was done by using 10 stations from iGMAS. The 3D precision of the 24?h orbit overlap is 24.55, 25.61, and 23.35?cm for the BeiDou-3, BeiDou-3e, and BeiDou-2 satellites, respectively. BeiDou-3 satellite has a comparable precision to that of the BeiDou-2 satellite. For the precision of clock offset estimation, the Standard Deviation (STD) of the BeiDou-3 MEO satellite is 0.350?ns, which is an improvement of 0.042?ns over that of the BeiDou-2 MEO satellite. The stabilities of the BeiDou-3 and BeiDou-3e onboard clocks are better than those of BeiDou-2 by factors of 2.84 and 1.61 at an averaging time of 1000 and 10,000?s, respectively.     

一种时间欠采样实时频率和二维角估计方法

提出了用均匀平行线阵和阵元输出信号的时间延迟估计时间欠采样来波频率、方位角和仰角的方法.该算法在DFT波束空间使用PRO-ESPRIT方法,实现频率无模糊估计,完成来波信号频率和角度的估计.频率间接估计算法是先估计数字频率,然后用数字频率求模拟频率,其估计方差比直接估计算法的方差要小几个数量级.仿真实验表明了算法的有效性.     

第2009卡林顿周太阳活动的初步分析

介绍了第 2 0 0 9卡林顿周大黑子群AR484,AR486和AR488产生的太阳活动以及这些太阳活动对地球空间环境造成的影响。依据对太阳活动的统计研究 ,简要分析了三个大黑子群活动的差异。分析结果指出 ,关注某一时期太阳活动的活动经度带以及太阳活动在某一半球的主次是解决太阳活动短期预报非常重要的思路     

Preparation of the Biochip experiment on the EXPOSE-R2 mission outside the International Space Station

Biochips might be suited for planetary exploration. Indeed, they present great potential for the search for biomarkers – molecules that are the sign of past or present life in space – thanks to their size (miniaturized devices) and sensitivity. Their detection principle is based on the recognition of a target molecule by affinity receptors fixed on a solid surface. Consequently, one of the main concerns when developing such a system is the behavior of the biological receptors in a space environment. In this paper, we describe the preparation of an experiment planned to be part of the EXPOSE-R2 mission, which will be conducted on the EXPOSE-R facility, outside the International Space Station (ISS), in order to study the resistance of biochip models to space constraints (especially cosmic radiation and thermal cycling). This experiment overcomes the limits of ground tests which do not reproduce exactly the space parameters. Indeed, contrary to ground experiments where constraints are applied individually and in a limited time, the biochip models on the ISS will be exposed to cumulated constraints during several months. Finally, this ISS experiment is a necessary step towards planetary exploration as it will help assessing whether a biochip can be used for future exploration missions.     

The Solar Sail Materials (SSM) project – Status of activities

SSM (Solar Sail Materials) is an on-going project for the European Space Agency (ESA) relying on past and recent European solar sail design projects. It aims at developing and testing future technologies suitable for large, operational solar sailcrafts.