航天器星敏感器自主定位方法及精度分析

用星敏感器和地平仪测量星光与地平之间的“星光抑角”为观测量，利用推广卡尔曼滤波方法实时估计航天器的最佳位置，使航天器在失去地面遥控的情况下，能够自主准确地确定运行轨道。由于航天器自主定位系统在工作期间会受到硬、软件等诸多因素的影响，因而使其定位精度达不到预计要求。在此我们通过大量仿真计算，指出一些对自主定位系统精度影响较大的因素，并对它们进行了比较分析。     

基于CMOS APS的星敏感器光学系统参数确定

基于CMOS APS图象传感器的星敏感器是适应航天技术的发展而产生的新一代姿态敏感器。确定光斑形状和大小、光学系统有效通光孔径、视场和焦距等参数是进行星敏感器光学设计的前提。本文基于选定的CMOS APS图象传感器分别对这些参数进行了分析和计算。确定光斑形状和大小的依据是，减小由于探测器像元对光斑能量分布的采样导致点扩散函数变形，从而引起的利用亚像元技术求星像中心的计算误差。光学系统的有效通光孔径与星敏感器所能探测到的极限星等有关，通过从目标辐射特性直到探测器响应的能量计算可以确定孔径的大小。确定视场和焦距首先要满足星敏感器实现全天自主星图识别所需的导航星捕获概率，其次要考虑与之相关的误差。     

Lunar lander's three-dimensional translation and yaw rotation motion estimation during a descent phase using optical navigation

Optical navigation for a lunar lander consists of estimating a lander's 3-dimensional (3-D) relative dynamic motion with respect to a preselected landing site using a passive 2-dimensional (2-D) video image sequence. Lunar landing missions require a lander to perform an autonomous accurate landing with simple mechanical structure, easy operation and low cost. These requirements have motivated the need to develop an advanced navigation system. Existing navigation systems trade-off simplicity, accuracy and cost. High accuracy navigation systems typically imply complexity and high cost. In this paper, we consider a scenario where the descending phase starts from an initial altitude of 10 km with a time-of-descent of 100 s. The navigation camera is an off-the-shelf optical instrument used to take the video image sequence of the landing site during the landing phase. It is fed into the motion estimation algorithm to be processed. The continuous wavelet transform (CWT) is used to analyse each image frame of the input digital video image sequence. The output is a 2-D video image motion trajectory map, which represents the projection motion of the landing site. The 2-D video image motion is projected back to the 3-D lander's relative motion based on a geometric analysis. The outputs of this estimation algorithm are the 3-D attitude motion parameters of the lander at a time corresponding to an image being taken. The attitude determination and control system (ADCS) of the lander uses these data to perform the lander's attitude control task. In this article, we provide the motion modelling for a lunar lander during the descending phase. The projection of a 3-D planar to 2-D image plane is analysed which build the correspondence between the 3-D lander's motion and the 2-D image motion. This link provides the evidence for the geometry analysis. CWT is reviewed and CWT for video image sequence analysis is also introduced. Numerical simulation of the estimated 2-D video image sequence under the lander performing a 3-D translation and yaw rotation during the terminal descent are shown to verify the proposed concepts. The analysis of the results show that the proposed method achieves highly accurate 2-D video image motion estimation of less then 1% error with significant savings of cost, mass and volume. It leads to the accurate estimation of the lander's 3-D relative motion with respect to the landing site.     

Study of the mode of angular velocity damping for a spacecraft at non-standard situation

Non-standard situation on a spacecraft (Earth’s satellite) is considered, when there are no measurements of the spacecraft’s angular velocity component relative to one of its body axes. Angular velocity measurements are used in controlling spacecraft’s attitude motion by means of flywheels. The arising problem is to study the operation of standard control algorithms in the absence of some necessary measurements. In this work this problem is solved for the algorithm ensuring the damping of spacecraft’s angular velocity. Such a damping is shown to be possible not for all initial conditions of motion. In the general case one of two possible final modes is realized, each described by stable steady-state solutions of the equations of motion. In one of them, the spacecraft’s angular velocity component relative to the axis, for which the measurements are absent, is nonzero. The estimates of the regions of attraction are obtained for these steady-state solutions by numerical calculations. A simple technique is suggested that allows one to eliminate the initial conditions of the angular velocity damping mode from the attraction region of an undesirable solution. Several realizations of this mode that have taken place are reconstructed. This reconstruction was carried out using approximations of telemetry values of the angular velocity components and the total angular momentum of flywheels, obtained at the non-standard situation, by solutions of the equations of spacecraft’s rotational motion.     

A simplified technique for determining the rotational motion of a satellite based on the onboard measurements of the angular velocity and magnetic field of the Earth

The mathematical model, which allowed us to reconstruct the rotational motion of the Bion M-1 and Foton M-4 satellites by processing the measurements of onboard magnetometers and the angular velocity sensor, is sufficiently detailed and accurate. If we slightly lower the requirements for accuracy and transfer to a rougher model, i.e., we will not update the biases in measurements of the angular velocity component, then the measurement processing technique can be significantly simplified. The volume of calculations in minimizing the functional of the least-square technique is reduced; the most complicated part of calculations is performed using the standard procedure of computational linear algebra. This simplified technique is described below, and the examples of its application for reconstructing the rotational motion of the Foton M-4 satellite are presented. A noticeable distinction in the reconstructions of motion, constructed by simplified and more exact techniques, is revealed in processing the measurements over time intervals longer than 4 hours.     

A procedure for calculating the damping in multi-element space structures

A procedure is outlined for estimating the damping in a multi-element space structure by incorporating distributed material damping and discrete nonlinear joint properties into a linear analysis. Tests have been conducted in which the transient response of a truss member is measured in free fall in a vacuum in order to obtain precise material damping characteristics. The force-state mapping technique is then used to identify the localized nonlinearities in joints by mapping the force transmitted through the joint as a function of the full mechanical state of the joint. The identified nonlinear joint parameters are then linearized using an equivalent energy approach which finds the equivalent linear stiffness and linear viscous damping by equating the integrated work done and energy dissipated by the nonlinearity to those of a spring and damper undergoing sinusoidal motion. The distributed material damping and localized nonlinear effects are then incorporated to form a linearized damped finite element model. Finally, an eigenvalue perturbation analysis is developed to explore the effect of introducing damping at the joints on the overall dynamics of the truss, and to obtain design guidance on where supplemental joint damping might optimally be added.     

Mass determination of a small body in solar system by using a test-mass during a fly-by

The mass estimation of small bodies in the solar system—such as comets or minor planets—with an accuracy sufficient to get scientific information is difficult. The ground-based range-rate measurements are not practicable for bodies smaller than 100 km diameter.A proof mass, ejected from the spacecraft before the flyby and whose relative trajectory is determined with onboard measurements can give very good results even for small bodies. This paper presents the expected accuracy of mass determination depending on ballistic conditions (relative velocity and closest approach), type and accuracy of measurements (range, optical).     

A method for determination of gamma-ray direction in space

Gamma-ray bursts (GRBs) are short and most intense bursts of gamma-rays that come from random direction in space. Their origins are still unknown and they originate likely from cosmological distances, probably after birth of a new black hole or death of a giant star. In this work, Geant simulations of a detector array aiming identification of gamma-ray directions in space were performed and a method was used for this identification. The array consists of three quadratic NaI(Tl) scintillators which are facing different directions. The method is based on the difference of the counts registered in these three detectors. This form of the array which can scan three dimensions in space is crucial to pinpoint origin of the GRBs. The array would also be applicable in various fields where identifications of the gamma-ray directions are necessary.     

Non-intrusive,three-dimensional temperature and composition measurements inside fluid cells in microgravity using a confocal holography microscope

Application of a confocal scanning laser holography (CSLH) microscope to the study of fluid flow in a microgravity environment is described herein. This microscope offers a new, non-intrusive means to determine three-dimensional density gradients within solid objects, fluids, and plasmas, including flames. The index-of-refraction is determined from the phase measurements of the microscope, which is a function of the object temperature and composition. The object being studied is a fluid-cell chamber, which is heated and cooled on opposing walls to produce a steady-state fluid flow due to convection and heat transfer. The holograms are created from the interference of a “known” reference beam with an “unknown” object beam. A three-dimensional amplitude and phase image of the object is produced by the reconstruction of many holograms, where each hologram represents a scanned point inside the object.     

空间超高速撞击碎片云前端速度的预测模型

文章利用一组二级轻气炮发射2017-T4 铝质球形弹丸撞击6061-T6单层铝板的地面试验数据,通过选择适当的函数模型,采用多元函数拟合的方法,得到了碎片云前端速度与靶板厚度、弹丸直径和弹丸速度关系的三元二阶多项式模型。再用另外一组数据对该模型进行检验,验证了其对碎片云前端速度具有较好的预测效果。将以上两组数据同样用于建立“无量纲化”模型进行碎片云前端速度预测,并与前述多项式模型的预测结果进行比较发现,该多项式模型预测的方均根误差及平均相对误差均明显优于“无量纲化”模型。该多项式模型可用于预测空间碎片撞击航天器产生的碎片云的前端速度,有助于航天器的空间碎片防护设计。     

SRAM单元的单粒子效应三维敏感区形状参数模拟仿真方法

为揭示静态随机存储器（SRAM）辐射效应以及内部电荷收集变化规律,从而为器件辐射效应及加固提供有效的仿真数据支撑,针对器件在轨单粒子翻转（SEU）,提出一种SRAM单元的三维敏感区形状参数模拟仿真方法。首先通过器件级和电路级仿真相结合的手段,利用计算机辅助设计（TCAD）构建三维模型;然后通过仿真获得重离子从不同方向入射后的单粒子瞬态电流,将此电流作为故障注入到65 nm SRAM单元的电路级模型中仿真SEU;最终得到65 nm SRAM单元的单粒子效应（SEE）三维敏感区形状参数。     

SOLID3: a multiplex antibody microarray-based optical sensor instrument for in situ life detection in planetary exploration

The search for unequivocal signs of life on other planetary bodies is one of the major challenges for astrobiology. The failure to detect organic molecules on the surface of Mars by measuring volatile compounds after sample heating, together with the new knowledge of martian soil chemistry, has prompted the astrobiological community to develop new methods and technologies. Based on protein microarray technology, we have designed and built a series of instruments called SOLID (for "Signs Of LIfe Detector") for automatic in situ detection and identification of substances or analytes from liquid and solid samples (soil, sediments, or powder). Here, we present the SOLID3 instrument, which is able to perform both sandwich and competitive immunoassays and consists of two separate functional units: a Sample Preparation Unit (SPU) for 10 different extractions by ultrasonication and a Sample Analysis Unit (SAU) for fluorescent immunoassays. The SAU consists of five different flow cells, with an antibody microarray in each one (2000 spots). It is also equipped with an exclusive optical package and a charge-coupled device (CCD) for fluorescent detection. We demonstrated the performance of SOLID3 in the detection of a broad range of molecular-sized compounds, which range from peptides and proteins to whole cells and spores, with sensitivities at 1-2?ppb (ng?mL?1) for biomolecules and 10? to 103 spores per milliliter. We report its application in the detection of acidophilic microorganisms in the Río Tinto Mars analogue and report the absence of substantial negative effects on the immunoassay in the presence of 50?mM perchlorate (20 times higher than that found at the Phoenix landing site). Our SOLID instrument concept is an excellent option with which to detect biomolecules because it avoids the high-temperature treatments that may destroy organic matter in the presence of martian oxidants.     

Microscope in orbit calibration procedure for a test of the equivalence principle at 10(-15)

The scientific objectives of the MICROSCOPE space mission impose a very fine calibration of the on-board accelerometers. However the required performance cannot be achieved on ground because of the presence of high disturbing sources. On-board the CHAMP satellite, accelerometers similar in the concept to the MICROSCOPE instrument, have already flown and analysis of the provided data then allowed to characterise the vibration environment at low altitude as well as the fluctuation of the drag. The requirements of the in-orbit calibration procedure for the MICROSCOPE instrument are demonstrated by modelling the expected applied acceleration signals with the developed analytic model of the mission. The proposed approach exploits the drag-free system of the satellite and the sensitivity of the accelerometers. A specific simulator of the attitude control system of the satellite has been developed and tests of the proposed solution are performed using nominal conditions or disturbing conditions as observed during the CHAMP mission.     

A method for determination of internal gravity wave parameters from a vertical temperature or density profile measurement in the Earth’s atmosphere

A method for determination of internal gravity wave (IGW) parameters from a single vertical temperature or density profile measurement in the Earth’s atmosphere has been developed. This method may be used for the analysis of profiles measured by any techniques in which the accuracy is enough to measure small (∼1%) amplitudes of the temperature or density fluctuations in the atmosphere. The criterion for the IGW identification has been formulated and argued. In the case when this criterion is satisfied then analyzed fluctuations can be considered as wave-induced. The method is based upon the analysis of relative amplitude thresholds of the temperature or density wave field and upon linear IGW saturation theory in which amplitude thresholds are restricted by dynamical instability processes in the atmosphere. In order to approbate the method we have used data of simultaneous radiosonde measurements of the temperature and wind velocity in the Earth’s stratosphere where the saturated IGW propagation has been detected. It is shown that the application of the method to radio occultation temperature data gives the possibility to identify IGWs in the Earth’s lower stratosphere and to determine values of key wave parameters.     

A residual based adaptive unscented Kalman filter for fault recovery in attitude determination system of microsatellites

This paper presents an adaptive unscented Kalman filter (AUKF) to recover the satellite attitude in a fault detection and diagnosis (FDD) subsystem of microsatellites. The FDD subsystem includes a filter and an estimator with residual generators, hypothesis tests for fault detections and a reference logic table for fault isolations and fault recovery. The recovery process is based on the monitoring of mean and variance values of each attitude sensor behaviors from residual vectors. In the case of normal work, the residual vectors should be in the form of Gaussian white noise with zero mean and fixed variance. When the hypothesis tests for the residual vectors detect something unusual by comparing the mean and variance values with dynamic thresholds, the AUKF with real-time updated measurement noise covariance matrix will be used to recover the sensor faults. The scheme developed in this paper resolves the problem of the heavy and complex calculations during residual generations and therefore the delay in the isolation process is reduced. The numerical simulations for TSUBAME, a demonstration microsatellite of Tokyo Institute of Technology, are conducted and analyzed to demonstrate the working of the AUKF and FDD subsystem.     

Multibeam array designed for use in a maritime system using an OTS platform

The study, based on actual hardware specifically developed for a multibeam array, has been concerned with the definition of a payload compatible with the requirements of a second generation maritime system. The proposed payload designed to operate in an OTS spacecraft has the following performance. 19 beam global coverage, give 70 Maritime channels having 52.4 dB Hz quality in deep fades. Mass of payload incl. antenna, 112 kg; d.c. power consumption, 334 W; Operational life time, 7 yr.     

空间非合作机动目标跟踪相对导航方法研究

就基于雷达测量的空间非合作机动目标跟踪相对导航问题进行了研究,提出了一套 既能够处理测量粗差,又能使滤波器在存在未知输入情况下快速收敛的相对导航算法。本文 将强跟踪滤波器的思想引入到二阶分离插值滤波算法（DDF2）,设计DDF2\|STF滤波器;另 外,本文将DDF2与Huber滤波算法相结合,设计DDF2\|Huber滤波器;最后,本文设计了相应 的滤波器切换准则,根据不同情况选用DDF2\|Huber和DDF2\|STF滤波器,从而得到一套 完整的相对导航算法。数学仿真证实了所提出相对导航算法的有效性。本文的研究成果为工 程设计提供了理论参考。
     

The need for a new Franco-German partnership in space: A joint policy memorandum

France and Germany have long been partners in space. However, new attitudes and directions in their respective space programmes are affecting the nature of traditional Franco-German space relations in an evolving European space context. The long-standing partnership is at a juncture and there is a need for a new dialogue to define what future directions the partnership should take. With this in mind, a joint memorandum was initiated by the European Space Policy Institute (ESPI), who prepared it together with the Paris-based Fondation pour la Recherche Stratégique (FRS) and the Institut Français des Relations Internationales (IFRI), as well as the Berlin-based German Stiftung Wissenschaft und Politik (SWP). It reflects on the state of current Franco-German space relations and lays out the issues to be considered by decision makers in both countries to provide a new impetus to the Franco-German partnership.     

PANIC – A surface science package for the in situ characterization of a near-Earth asteroid

This paper presents the results of a mission concept study for an autonomous micro-scale surface lander also referred to as PANIC – the Pico Autonomous Near-Earth Asteroid In Situ Characterizer. The lander is based on the shape of a regular tetrahedron with an edge length of 35 cm, has a total mass of approximately 12 kg and utilizes hopping as a locomotion mechanism in microgravity. PANIC houses four scientific instruments in its proposed baseline configuration which enable the in situ characterization of an asteroid. It is carried by an interplanetary probe to its target and released to the surface after rendezvous. Detailed estimates of all critical subsystem parameters were derived to demonstrate the feasibility of this concept. The study illustrates that a small, simple landing element is a viable alternative to complex traditional lander concepts, adding a significant science return to any near-Earth asteroid (NEA) mission while meeting tight mass budget constraints.     

A microbial oasis in the hypersaline Atacama subsurface discovered by a life detector chip: implications for the search for life on Mars

The Atacama Desert has long been considered a good Mars analogue for testing instrumentation for planetary exploration, but very few data (if any) have been reported about the geomicrobiology of its salt-rich subsurface. We performed a Mars analogue drilling campaign next to the Salar Grande (Atacama, Chile) in July 2009, and several cores and powder samples from up to 5?m deep were analyzed in situ with LDChip300 (a Life Detector Chip containing 300 antibodies). Here, we show the discovery of a hypersaline subsurface microbial habitat associated with halite-, nitrate-, and perchlorate-containing salts at 2?m deep. LDChip300 detected bacteria, archaea, and other biological material (DNA, exopolysaccharides, some peptides) from the analysis of less than 0.5?g of ground core sample. The results were supported by oligonucleotide microarray hybridization in the field and finally confirmed by molecular phylogenetic analysis and direct visualization of microbial cells bound to halite crystals in the laboratory. Geochemical analyses revealed a habitat with abundant hygroscopic salts like halite (up to 260?g kg(-1)) and perchlorate (41.13?μg g(-1) maximum), which allow deliquescence events at low relative humidity. Thin liquid water films would permit microbes to proliferate by using detected organic acids like acetate (19.14?μg g(-1)) or formate (76.06?μg g(-1)) as electron donors, and sulfate (15875?μg g(-1)), nitrate (13490?μg g(-1)), or perchlorate as acceptors. Our results correlate with the discovery of similar hygroscopic salts and possible deliquescence processes on Mars, and open new search strategies for subsurface martian biota. The performance demonstrated by our LDChip300 validates this technology for planetary exploration, particularly for the search for life on Mars.