多层打孔隔热材料空间应用热性能研究

在分析了空间多层打孔隔热材料中导热和辐射的复合传热问题的基础上,提出了空间多层打孔隔热材料反射屏温度计算的模型以及内部辐射数值分析模型.利用该模型对不同几何、物理参数下的对象进行模拟计算,通过对计算结果的分析,明确作为几何参数的层密度和层数以及作为表面特性参数的黑度和打孔率对材料热性能的影响.该热性能的研究对提高空间多层打孔隔热材料的隔热效果,实现材料的优化设计具有积极的指导意义.     

Integration of lessons from recent research for “Earth to Mars” life support systems

Development of reliable and robust strategies for long-term life support for planetary exploration must be built from real-time experimentation to verify and improve system components. Also critical is incorporating a range of viable options to handle potential short-term life system imbalances. This paper revisits some of the conceptual framework for a Mars base prototype which has been developed by the authors along with others previously advanced (“Mars on Earth^®”) in the light of three years of experimentation in the Laboratory Biosphere, further investigation of system alternatives and the advent of other innovative engineering and agri-ecosystem approaches. Several experiments with candidate space agriculture crops have demonstrated the higher productivity possible with elevated light levels and improved environmental controls. For example, crops of sweet potatoes exceeded original Mars base prototype projections by an average of 46% (53% for best crop) ultradwarf (Apogee) wheat by 9% (23% for best crop), pinto bean by 13% (31% for best crop). These production levels, although they may be increased with further optimization of lighting regimes, environmental parameters, crop density etc. offer evidence that a soil-based system can be as productive as the hydroponic systems which have dominated space life support scenarios and research. But soil also offers distinct advantages: the capability to be created on the Moon or Mars using in situ space resources, reduces long-term reliance on consumables and imported resources, and more readily recycling and incorporating crew and crop waste products. In addition, a living soil contains a complex microbial ecosystem which helps prevent the buildup of trace gases or compounds, and thus assist with air and water purification. The atmospheric dynamics of these crops were studied in the Laboratory Biosphere adding to the database necessary for managing the mixed stands of crops essential for supplying a nutritionally adequate diet in space. This paper explores some of the challenges of small bioregenerative life support: air-sealing and facility architecture/design, balance of short-term variations of carbon dioxide and oxygen through staggered plantings, options for additional atmospheric buffers and sinks, lighting/energy efficiency engineering, crop and waste product recycling approaches, and human factor considerations in the design and operation of a Mars base. An “Earth to Mars” project, forging the ability to live sustainably in space (as on Earth) requires continued research and testing of these components and integrated subsystems; and developing a step-by-step learning process.     

The possibilities of polar meteorology,environmental remote sensing,communications and space weather applications from Artificial Lagrange Orbit

The ability to observe meteorological events in the polar regions of the Earth from satellite celebrated an anniversary, with the launch of TIROS-I in a pseudo-polar orbit on 1 April 1960. Yet, after 50 years, polar orbiting satellites are still the best view of the polar regions of the Earth. The luxuries of geostationary satellite orbit including rapid scan operations, feature tracking, and atmospheric motion vectors (or cloud drift winds), are enjoyed only by the middle and tropical latitudes or perhaps only cover the deep polar regions in the case of satellite derived winds from polar orbit. The prospect of a solar sailing satellite system in an Artificial Lagrange Orbit (ALO, also known as “pole sitters”) offers the opportunity for polar environmental remote sensing, communications, forecasting and space weather monitoring. While there are other orbital possibilities to achieve this goal, an ALO satellite system offers one of the best analogs to the geostationary satellite system for routine polar latitude observations.     

CCSDS近地LDPC译码算法研究

针对CCSDS（空间数据系统咨询委员会）推荐的近地LDPC（低密度奇偶校验）码技术进行了研究,建立了和积译码算法、对数似然和积译码算法、最小和译码算法的数学模型,并对上述译码算法的译码复杂度和译码性能进行了仿真分析.分析结果表明,和积译码算法与对数似然和积译码算法的译码性能距离香农限1.2 dB,最小和译码算法的译码性能距离香农限1.45 dB.因此,提出基于最小和译码算法的改进算法——偏移最小和译码算法与归一化最小和译码算法,并分析了这2种译码算法的译码复杂度,同时进行了大量仿真实验.实验结果表明,当偏移因子β=0.15时,偏移最小和译码算法性能达到最优,译码性能距离香农限1.25 dB;当归一化因子α=0.741 2时,归一化译码算法的译码性能达到最优,译码性能距离香农限1.2 dB.归一化译码算法具有优异的译码性能和合理的复杂度,可以遴选作为CCSDSLDPC的译码算法用于工程实现.此外,还研究了迭代次数对译码性能的影响,结果表明,当迭代次数大于10次时,译码性能提升不再明显,故工程实现时迭代次数应设置为10次.     

科学实验卫星高速上行链路设计

为保障在卫星与地面之间开展空间量子科学实验的条件,必须为科学实验载荷建立一条星—地高速数据双向传输链路.通过跟踪CCSDS-SLS-NGU（空间数据系统咨询委员会-空间链路业务-下一代上行链路）工作组对NGU的研究进展,结合科学实验卫星有效载荷建立高速上行链路的需求,采用高带宽利用率调制技术、高效信道编码方式及适用的链路数据传输协议,设计了一种传输速率为1Mbit/s、误码率优于1×10-9的高速上行链路方案,并给出星载设备实现方案和地面初步测试结果.该方案在技术体制上兼容已有CCSDS规范,便于地面站及星载接收机实现,完全满足开展空间量子科学实验的需要.     

顾及频间偏差的GNSS多频非组合PPP变形监测

精密单点定位(PPP)技术有望解决长距离、大范围等监测场景难以找到稳定基准点的难题。现代化的全球卫星导航系统(GNSS)卫星纷纷开始播发多频信号,多频观测值融合理论上可提升PPP变形监测性能。为了充分利用多频冗余观测数据,详细研究了每个频点的差分码偏差(DCB)和全球定位系统(GPS)存在的相位频率间卫星钟偏差(PIFCB)的改正方法,扩展了多频数据处理的严密理论模型,能够灵活处理GPS三频、Galileo五频和BDS-3五频观测数据。多频PPP振动监测实验结果表明,GPS三频PPP、BDS-3五频PPP、Galileo五频PPP较各自双频PPP位移监测精度可分别提升12%、13%和14%,表明多频PPP技术有利于提升PPP位移监测精度与稳定性。     

面向北斗导航电文认证的符号级欺骗方法研究

导航电文认证(NMA)技术已成为抵御生成式欺骗、保护全球卫星导航系统(GNSS)民用信号的重要发展方向之一.针对NMA在不改变导航电文的情况下难以抵御欺骗的漏洞,提出了面向北斗NMA的符号级欺骗(SLA)方法,并设计了最大后验概率(MAP)符号估计改进算法,以历次MAP估计值的众数作为新估计量,实现导航电文的快速恢复.基于北斗B1C信号NMA方案开展了欺骗效果评估试验.结果表明,在载噪比大于45 dB·Hz和短估计时延(小于30 μs)条件下,SLA针对北斗B1C认证电文能够达到90％的序列欺骗成功率,与安全码估计-重放(SCER)相比,该方法能够显著降低符号误码率,缩短估计时延,具有更好的欺骗效果,也将为北斗NMA设计优化提供技术支撑.     

BDS-3不同频点双频组合伪距单点定位性能分析

北斗卫星导航系统(BDS)在进行双频单点定位时通常固定使用B1I和B3I频点组合.为充分探究BDS-3系统的定位潜力,针对BDS-3不同频点双频伪距单点定位(SPP)性能展开研究.推导了卫星差分码偏差(DCB)改正公式,并建立了 BDS-3任意双频组合SPP数学模型.利用全球35个多模GNSS实验(MGEX)跟踪站121 d的实测数据,采用改进的RTKLIB软件进行了全球范围内BDS-3双频无电离层组合SPP解算实验.首先,对BDS-3的6种频点信号质量进行了全面评估,包括信噪比、多路径效应和数据可用率等指标.其次,对基于DCB改正的14种BDS-3双频伪距组合进行了性能对比.研究发现,在多路径误差、信噪比及数据完整率等多项指标上,B2ab信号质量最高,B2b与B2a其次,B3I与B1C次之,B1I表现较差.在BDS-3的14种不同双频组合SPP性能比较中,基于DCB改正的定位精度明显优于未加DCB改正的情况.DCB改正相对未改正可以将三维精度由14.9～31.2 m显著减小到1.7～15.5 m.受无电离层双频组合模型噪声放大系数的影响,最优组合为B1C&B2a,最差组合为B2a&B2ab,两者数值分别为1.7 m与15.5 m.以上结论可以为BDS-3伪距定位在车载导航等方面的应用提供参考.     

高速数字设计及其在卫星定位接收机中的应用

高灵敏度卫星定位接收机的迅速发展是未来定位导航产业的必然趋势。本文主要介绍高灵敏度卫星导航接收机的组成和设计概要。分析了数字电路设计中常遇到的信号完整性问题。着重对高速数字系统定义和传输线阻抗进行了理论分析,运用Cadence公司的ALLEGROPCBSIGXL软件给出了层叠等的设置方法和一些重要信号的分析仿真。将高速数字设计的理论分析与实际应用相结合,在卫星定位接收机主板设计中得到了验证。     

美国用于空间站辐射器中的热控涂层

综述了六种美国可用于空间站辐射器中的热控涂层。从涂层的性能、价格、质量以及成熟性研究,对这六种热控涂层进行了评价。结果表明,Z－93型热控涂层最适合用于空间站的辐射器中,镀银F－46薄膜型热控涂层次之。