Distributed satellite autonomous navigation using X-ray pulsars

Distributed X-ray pulsar-based navigation (DXNAV) is an effective method to realize earth-orbit satellite positioning under weak pulsar signal conditions. In this paper, we propose a new DXNAV method based on multiple information fusion. The DXNAV system principle and the pulse phase estimate Cramér-Rao lower bound are deduced. To suppress the calculation complexity and the error source, the X-ray pulsar photon time-of-arrival detected by each satellite is equivalently converted to the leading satellite directly using the inter-satellite link ranging and starlight angular distance measurement. A high precision estimate model of the pulse phase is built using pulsar standard profile, observed profile, and star-geocentric angular distance from distributed satellites. The estimated pulse phase is real-time supplied to the navigation system, which is established in the form of a deviation equation. The two-stage Kalman filter is designed to estimate the pulse phase in profile histogram bin step and the leader position in real-time step. Compared separately with the maximum likelihood phase estimate method and the celestial navigation method using only the star-geocentric angular distance, the simulation analysis shows that the estimation precisions of position and velocity are improved by 29% and 25%.     

A new approach for pulse amplitude measurement using Lagrange’s interpolation for radiation or particle detectors

In radiation detector signal processing, usually, the charge-sensitive preamplifier converts the small charge signal coming from the semiconductor-based detector into voltage form and then the signal is further amplified to measure the energy of the incoming radiation. The voltage pulse from a charge-sensitive preamplifier (CSPA) is amplified using a shaping amplifier which reduces the signal bandwidth. To achieve better energy resolution, precise measurement of the peak amplitude of shaping amplifier output is required. The signal processing methods are available in which the signal from the charge-sensitive preamplifier can be directly digitized using high-speed Analog to Digital Converters (ADC), and then further signal processing such as gain and shaping is carried out inside the Field Programmable Gate Arrays (FPGA). For multiple detector systems, digital signal processing methods are quite difficult to implement in Field Programmable Gate Arrays (FPGA). In this context, The development of an alternative technique is initiated that uses a charge-sensitive preamplifier, shaping amplifier, low sampling analog-to-digital converter, and FPGA, where LaGrange’s interpolation technique is implemented in FPGA to precisely measure the peak of the analog pulse. In this paper, the comparison of the proposed method with other pulse amplitude measurement techniques is discussed. Results show that the implemented technique gives similar energy resolution compared to digital pulse processing and standard peak detector-based techniques.     

大气环境监测卫星激光雷达技术

星载激光雷达是高精度测量全球大气CO2柱浓度和气溶胶垂直廓线的重要手段，大气环境监测卫星大气探测激光雷达(ACDL)在一套激光雷达中集成了2种探测体制，采用1 572 nm积分路径激光差分吸收方法测量全球CO2柱浓度，采用532 nm高光谱探测(HSRL)方法测量气溶胶和云的垂直廓线，均为国际首次在星载平台成功验证，是国际首个星载CO2探测激光雷达和国际首个高光谱气溶胶探测激光雷达。在国际已发射的星载激光雷达中，ACDL激光雷达是探测体制最全、波长最多、能量最高、频率最稳和精度最准的激光雷达，实现了创新跨越。大气探测激光雷达在轨连续工作，首次获得了全天时精度优于1 ppm的全球CO2柱浓度、精度优于20%的气溶胶廓线等遥感数据。本文介绍了ACDL激光雷达的工作原理、系统参数以及相关的定标测试结果。     

中远红外高功率量子级联激光技术研究进展

量子级联激光器具有体积小，重量轻，波长可调谐，以及光源能够覆盖中远红外和太赫兹波段等特点，使其在痕量气体检测、定向红外对抗、自由空间光通讯以及红外成像和光谱等领域有着广泛的应用。自从1994年第一个量子级联激光器问世以来，大功率、高电光效率以及室温下连续工作的量子级联激光器一直是人们追求的目标。首先介绍了量子级联激光器的有源层设计、波导设计和器件散热设计方面的研究进展；其次重点讨论了4 μm~5 μm 中波红外和 8 μm~12 μm长波红外高功率室温下连续量子级联激光器的发展和演变、以及大功率脉冲量子级联激光器研究情况；最后简要介绍了大功率量子级联激光器芯片的外延制备技术。     

标定脉宽对冲击传感器标定结果的影响

不同冲击脉宽在标定压电式冲击传感器过程产生不同的结果，主要原因是脉宽冲击频率处于传感器安 装频响的放大区，不同的脉宽作用于传感器后放大效应不同，导致标定结果差异。冲击传感器使用空气炮和霍普金 生杆进行单独标定，对标定结果进行了差异分析。对传感器安装频响曲线进行了定性分析，符合冲击脉宽差导致不 同标定结果的事实。对标定过程中标定脉宽控制提出了具体的措施，对于正确标定冲击传感器具有指导意义。     

脉冲爆震发动机中温度和组分浓度测量技术的发展

脉冲爆震发动机内部工作条件极其恶劣,测量爆震波温度和某组分浓度十分困难。本文回顾了近几年国内外在爆震温度场测量方面的技术发展,特别是应用激光诊断技术测量爆震波的温度和某些组分浓度。总结了国内外应用光学诊断技术测得的爆震波火焰温度,结果发现:对气体燃料/氧气而言,在化学恰当比下一般其爆震波温度大约为3900K,与CJ理论值非常接近;然而对液态燃料JP-10而言,当氧化剂为氧气时,爆震波温度为2500K;当氧化剂为空气时,爆震波温度仅仅约为1500K。     

基于可重构标定板的激光与视觉联合标定方法

目前,激光雷达与视觉传感器的联合标定方法包含动态在线标定与静态离线标定两大类.动态在线标定对标定的环境有较高的要求,且标定结果不稳定;静态离线标定通常采用标定板,因而对标定板的要求较高,手动选择与线拟合都易引入或放大误差,故提出了一种基于可重构标定板的激光雷达与视觉传感器的联合标定方法.首先,对传统的标定板进行拆分与重构,采用类条形码的方式自动识别激光雷达特征点,并添加相机校验机制以缓解标定过程中相机识别的不稳定性带来的误差.最后,通过与双目相机标定,采用重投影的方式对外参标定结果进行可视化主观评价与客观量化评价.实验表明,该标定方法的均方根误差(RMSE)为1.275cm,重投影后的误差为3.2个像素.