Modelling of the MICROSCOPE Mission

The French space mission MICROSCOPE aims at testing the Equivalence Principle (EP) up to an accuracy of 10^?15. The experiment will be carried out on a satellite which is developed and produced within the CNES Myriade series. The measuring accuracy will be achieved by means of two high-precision capacitive differential accelerometers that are built by the French institute ONERA, see Touboul and Rodrigues (Class. Quantum Gravity 18:2487–2498, 2001). At ZARM, which is a member of the science team, the data evaluation process is prepared. Therefore, a comprehensive simulation of the real system including the science signal and all error sources is built for the development and testing of data reduction and data analysis algorithms to extract the EP violation signal. Currently, the ZARM Drag-Free simulator, a tool to support mission modelling, is adapted for the MICROSCOPE mission in order to simulate test mass and satellite dynamics. Models of environmental disturbances like solar radiation pressure are considered, also. Additionally, detailed modelling of the on-board capacitive sensors is done. The actual status of the mission modelling will be presented. Particularly, the modelling of disturbances forces will be discussed in detail.     

MICROSCOPE On-ground and In-orbit Calibration

The MICROSCOPE mission, to be launched in 2011, will perform the test of the universality of free fall (Equivalence Principle) to an accuracy of 10^?15. The payload consists of two sensors, each controlling the free fall of a pair of test masses: the first for the test of the Equivalence Principle (titanium/platinum), the second for performance verification (platinum/platinum). The capability to detect a faint violation signal of the EP test is conditioned upon the rejection of disturbances arising from the coupling and misalignments of the instrument vectorial outputs. Therefore the performance of the mission depends on the success of the series of calibration operations which are planned during the satellite life in orbit. These operations involve forced motion of the masses with respect to the satellite. Specific data processing tools and simulations are integral parts of the calibration and performance enhancement process, as are the tests operated on ground at the ZARM drop tower. The presentation will focus on the current status of the MICROSCOPE payload, the rationale for the in-orbit calibrations, the data processing operations and the tests performed at the ZARM drop tower.     

Microscope Instrument Development,Lessons for GOCE

Two space missions are presently under development with payload based on ultra-sensitive electrostatic accelerometers. The GOCE mission takes advantage of a three axis gradiometer accommodated in a very stable thermal case on board a drag-free satellite orbiting at a very low altitude of 250 km. This ESA mission will perform the very highly accurate mapping of the Earth gravity field with a geographical resolution of 100 km. The MICROSCOPE mission is devoted to the test of the “Universality of free fall” in view of the verification of the Einstein Equivalence Principle (EP) and of the search of a new interaction. The MICROSCOPE instrument is composed of two pairs of differential electrostatic accelerometers and the accelerometer proof-masses are the bodies of the EP test. The satellite is also a drag-free satellite exhibiting a fine attitude control and in a certain way, each differential accelerometer is a one axis gradiometer with an arm of quite null length. The development of this instrument much interests the definition and the evaluation of the sensor cores of the gradiometer. The in flight calibration process of both instruments is also very similar. Lessons form these parallel developments are presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

Challenges in the Measurement and Data-Processing Chain of the LISA Mission

The LISA Mission (Laser Interferometer Space Antenna) is currently under mission formulation with a launch date planned in 2020. The purpose of the mission is the observation of gravitational waves at frequencies between 0.1 mHz and 1 Hz by measuring distance fluctuations between inertial reference points, represented by cubic proof masses. In order to provide a sufficient sensitivity of the instrument, distance fluctuations between two inertial reference points must be measured with a strain accuracy of around 10^?20 Hz^?1/2. This is achieved by setting up a laser interferometer with a base-length of 5?10⁶ km and a path-length measurement noise in the order of 10 pm?Hz^?1/2. For a correct evaluation of the data on the ground, it is essential that the science data telemetry preserves all required frequency domain information. That is, any on-board data-processing and down-sampling must be done with great care in order not to introduce aliasing or other artifacts into the data stream. As an additional complication, most of the optical metrology data is dominated by laser phase noise which is about eight orders of magnitude larger than the required instrument sensitivity. However, by applying a method called “time-delayed interferometry” during the ground data processing, this laser phase noise can be eliminated from the data. This method has already been demonstrated in a detailed simulation environment, but it requires a very careful filtering, synchronization, and interpolation of the individual data streams. Last but not least, a calibration of system parameters is necessary in many areas of the LISA measurement system. The system design must therefore ensure that all data required for these calibrations is available on-ground in a quality that allows a successful computation of the calibration coefficients within a reasonable time-frame. The data streams do not only include data from the optical metrology system, but also from the drag-free and attitude control system which are used to derive other information, such as the charge state of the proof mass. This yields a strong coupling between the different disciplines since data that is only used for housekeeping purposes in other missions becomes an essential part of the science data stream for the LISA mission. This paper gives an overview of the LISA measurement and data-processing chain. It highlights the most challenging areas that have been identified so far and describes the intended solution methods.     

Potential Effects of Surface Temperature Variations and Disturbances and Thermal Convection on the Mars InSight HP<Superscript>3</Superscript> Heat-Flow Determination

The HP³ instrument on the InSight lander mission will measure subsurface temperatures and thermal conductivities from which heat flow in the upper few meters of the regolith at the landing site will be calculated. The parameter to be determined is steady-state conductive heat flow, but temperatures may have transient perturbations resulting from surface temperature changes and there could be a component of thermal convection associated with heat transport by vertical flow of atmospheric gases over the depth interval of measurement. The experiment is designed so that it should penetrate to a depth below which surface temperature perturbations are smaller than the required measurement precision by the time the measurements are made. However, if the measurements are delayed after landing, and/or the probe does not penetrate to the desired depth, corrections may be necessary for the transient perturbations. Thermal convection is calculated to be negligible, but these calculations are based on unknown physical properties of the Mars regolith. The effects of thermal convection should be apparent at shallow depths where transient thermal perturbations would be observed to deviate from conductive theory. These calculations were required during proposal review and their probability of predicting a successful measurement a prerequisite for mission approval. However, their uncertainties lies in unmeasured physical parameters of the Mars regolith.     

The Galileo Dust Detector

The Galileo Dust Detector is intended to provide direct observations of dust grains with masses between 10^-19 and 10^-9 kg in interplanetary space and in the Jovian system, to investigate their physical and dynamical properties as functions of the distances to the Sun, to Jupiter and to its satellites, to study its interaction with the Galilean satellites and the Jovian magnetosphere. Surface phenomena of the satellites (like albedo variations), which might be effects of meteoroid impacts will be compared with the dust environment. Electric charges of particulate matter in the magnetosphere and its consequences will be studied; e.g., the effects of the magnetic field on the trajectories of dust particles and fragmentation of particles due to electrostatic disruption. The investigation is performed with an instrument that measures the mass, speed, flight direction and electric charge of individual dust particles. It is a multicoincidence detector with a mass sensitivity 10⁶ times higher than that of previous in-situ experiments which measured dust in the outer solar system. The instrument weighs 4.2 kg, consumes 2.4 W, and has a normal data transmission rate of 24 bits s^-1 in nominal spacecraft tracking mode. On December 29, 1989 the instrument was switched-on. After the instrument had been configured to flight conditions cruise science data collection started immediately. In the period to May 18, 1990 at least 168 dust impacts have been recorded. For 81 of these dust grains masses and impact speeds have been determined. First flux values are given.     

The Student Dust Counter on the New Horizons Mission

The Student Dust Counter (SDC) experiment of the New Horizons Mission is an impact dust detector to map the spatial and size distribution of dust along the trajectory of the spacecraft across the solar system. The sensors are thin, permanently polarized polyvinylidene fluoride (PVDF) plastic films that generate an electrical signal when dust particles penetrate their surface. SDC is capable of detecting particles with masses m>10^?12 g, and it has a total sensitive surface area of about 0.1 m², pointing most of the time close to the ram direction of the spacecraft. SDC is part of the Education and Public Outreach (EPO) effort of this mission. The instrument was designed, built, tested, integrated, and now is operated by students.     

Precession–nutation correction for star tracker attitude measurement of STECE satellite

Space Technology Experiment and Climate Exploration(STECE) is a small satellite mission of China for space technology experiment and climate exploration. A new test star tracker and one ASTRO 10 star tracker have been loaded on the STECE satellite to test the new star tracker's measurement performance. However,there is no autonomous precession–nutation correction function for the test star tracker,which causes an apparent periodic deflection in the inter-boresight angle between the two star trackers with respect to each other of up to ±500 arcsec,so the precession and nutation effect needs to be considered while assessing the test star tracker. This paper researches on the precession–nutation correction for the test star tracker's attitude measurement and presents a precession–nutation correction method based on attitude quaternion data. The periodic deflection of the inter-boresight angle between the two star trackers has been greatly eliminated after the precession and nutation of the test star tracker's attitude data have been corrected by the proposed method and the validity of the proposed algorithm has been demonstrated. The in-flight accuracy of the test star tracker has been assessed like attitude noise and low-frequency errors after the precession–nutation correction.     

多级轴流压气机不同工况下失速／喘振试验研究

通过试验的形式，开展了多级轴流压气机在静叶优化角度及中间级引气情况下的失速／喘振试验研究。采用高精度、高频响的动态压力传感器，高速同步采集板、快速A／D采集板和高速处理机相结合，借助于频谱分析的方法来找出失速／喘振频率，并且找出对应该频率的各通道之间的相位差，分析出失速／喘振首发级。利用DASP6．61数据大容量自动采集与信号处理系统对喘振信号进行数学处理。试验结果表明：测量手段及数学处理模型是可行的。在压气机静叶优化条件下，不同的引气量对失速／喘振有影响。     

Extended Pile Driving Model to Predict the Penetration of the Insight/HP<Superscript>3</Superscript> Mole into the Martian Soil

The NASA InSight mission will provide an opportunity for soil investigations using the penetration data of the heat flow probe built by the German Aerospace Center DLR. The Heat flow and Physical Properties Probe (HP³) will penetrate 3 to 5 meter into the Martian subsurface to investigate the planetary heat flow. The measurement of the penetration rate during the insertion of the HP³ will be used to determine the physical properties of the soil at the landing site. For this purpose, numerical simulations of the penetration process were performed to get a better understanding of the soil properties influencing the penetration performance of HP³. A pile driving model has been developed considering all masses of the hammering mechanism of HP³. By cumulative application of individual stroke cycles it is now able to describe the penetration of the Mole into the Martian soil as a function of time, assuming that the soil parameters of the material through which it penetrates are known. We are using calibrated materials similar to those expected to be encountered by the InSight/HP³ Mole when it will be operated on the surface of Mars after the landing of the InSight spacecraft. We consider various possible scenarios, among them a more or less homogeneous material down to a depth of 3–5 m as well as a layered ground, consisting of layers with different soil parameters. Finally we describe some experimental tests performed with the latest prototype of the InSight Mole at DLR Bremen and compare the measured penetration performance in sand with our modeling results. Furthermore, results from a 3D DEM simulation are presented to get a better understanding of the soil response.     

Measurements of quasi-static electric fields between 3 and 7 Earth radii on GEOS-1

Quasi-static electric fields have been measured with two spherical probes supported by cable booms providing a baseline of 42 m for the measurement. The performance of the experiment is outlined to demonstrate that electric fields can be measured with accuracies of ±0.7 mV m^-1 and ±1.0 mV m^-1 in the dawn-dusk and satellite-sun directions respectively. These uncertainties can be considerably reduced under favourable plasma conditions. Examples of typical observations are described.

1. The average electric field is always characterized by an irregular structure with time scales 0.5–5 min and with amplitudes of a few mV m^-1.
2. During substorms dawn-dusk electric fields up to 20–30 mV m^-1 have been observed over intervals of 30–60 s.
3. Oscillating electric fields with peak-to-peak amplitudes up to 10 mV m^-1 and periods of 3–10 min have been observed following magnetospheric disturbances.

The observations are discussed in terms of plasma motions and possible spatial scale sizes of the phenomena, standing magnetospheric wave modes and electrostatic potentials.     

某型航空涡扇发动机静电传感器机载化监测实验

计了一种特定尺寸的静电传感器,并将其装配在涡扇发动机低压涡轮出口附近的尾喷管管壁,以民用涡扇发动机为静电传感器载体及监测对象开展静电监测实验.以一个完整性能试车过程为周期,采集周期内的尾气静电信号.进一步对静电信号和发动机性能参数进行数据对比分析,同时对测试过程中异常状态下活动率水平（AL）和负事件率（NER）进行计算.实验验证了航空发动机静电监测技术具备机载化的可行性,实验结果表明:正常状态下静电信号电压幅值大小约为5mV,静电水平跟随运行功率变化并呈正相关性;静电传感器对尾气中存在的异常颗粒具有良好的监测效果,在发动机富油状态下静电信号的活动率水平和负事件率分别达到14pC及8%.      

时统信号数字信道传输误差分析与研究

通过对时统信号的理论分析和实际测试验证,准确地分析出时统信号经数字信道传输产生的误差来源于信道的群时延失真和增益频率特性的影响,同时提出了克服传输误差的三种方法：第一种是改善时统信号特性的发送补偿法,已在现有设备上通过修改编码软件方法实现;第二种是改善信道传输特性的信道拓宽法,已在现有设备的伴音信道上验证;第三种是改善时统设备接收适应能力的接收均衡法。完成了均衡器的设计和制作。并通过了实际测试验证。最后对三种方法进行了对比分析。     

基于CPLD的频率响应特性测试卡设计

提出了一种基于CPLD的频率响应特性测试卡设计方案,分析了DDS原理的CPLD实现方法,给出了数据处理算法流程,并进行了设计验证实验,结果表明在逐点单频测试状态下,相位和幅值测量与标准仪器相比相位差小于0.5°,幅值差小于0.1dB。     

Wave particle interactions as an energy transfer mechanism between different particle species

Recent improvements in experimental techniques and cooperative data analysis efforts have brought a lot of information on the basic mechanisms by which energy can be exchanged between different particle species in the collisionless magnetospheric or solar wind plasmas. Some of these mechanisms are reviewed. A particular emphasis is put on interactions which occur in the equatorial magnetosphere between energetic protons and electromagnetic ultra low frequency (ULF) waves and which are linked with He⁺ ion trapping and heating as well as with field-aligned suprathermal electron beam generation. The process by which ion conic distributions are produced by electrostatic ion cyclotron waves generated at high altitude along auroral field lines by drifting electrons is also discussed.     

基于压缩感知的信源个数与信号参数估计算法

信源个数与信号参数估计是盲信号处理的关键环节，对后续信号的侦察处理意义重大。针对当前盲信号信源个数与信源参数估计研究割裂的问题，提出了一种联合估计算法。通过分析信号的稀疏系数在不同测量矩阵相同稀疏字典下位置相同的特点，提高了信源个数和信号参数的估计精度，实现算法的自适应控制；通过数理分析确定了多级搜索策略的最优级次，大大降低了稀疏字典的原子数目。仿真结果表明：算法在一定信噪比下能够实现信源个数和信号参数的有效估计；信源个数和信号参数的估计精度随着压缩比的降低而逐渐提高，随着信噪比的提高而逐步增强；噪声对信源个数和信号参数估计精度的影响很大，尤其是低信噪比下；第2个信源载波频率和调频斜率的估计误差明显高于第1个信源参数的估计误差。     

Science Objectives and Rationale for the Radiation Belt Storm Probes Mission

The NASA Radiation Belt Storm Probes (RBSP) mission addresses how populations of high energy charged particles are created, vary, and evolve in space environments, and specifically within Earth’s magnetically trapped radiation belts. RBSP, with a nominal launch date of August 2012, comprises two spacecraft making in situ measurements for at least 2 years in nearly the same highly elliptical, low inclination orbits (1.1×5.8 RE, 10^°). The orbits are slightly different so that 1 spacecraft laps the other spacecraft about every 2.5 months, allowing separation of spatial from temporal effects over spatial scales ranging from ～0.1 to 5 RE. The uniquely comprehensive suite of instruments, identical on the two spacecraft, measures all of the particle (electrons, ions, ion composition), fields (E and B), and wave distributions (d E and d B) that are needed to resolve the most critical science questions. Here we summarize the high level science objectives for the RBSP mission, provide historical background on studies of Earth and planetary radiation belts, present examples of the most compelling scientific mysteries of the radiation belts, present the mission design of the RBSP mission that targets these mysteries and objectives, present the observation and measurement requirements for the mission, and introduce the instrumentation that will deliver these measurements. This paper references and is followed by a number of companion papers that describe the details of the RBSP mission, spacecraft, and instruments.     

光学头罩超声速绕流流场光学传输效应风洞试验研究

在Ma=3连续超声速风洞中,开展了光学头罩绕流流场光学传输效应的风洞模拟试验方法研究,进行了现场振动测量与隔离,研制了专用试验装置,采用哈特曼传感器和剪切干涉仪两种手段进行了光学传输效应的试验测量。试验中,针对试验装置各部分的不同组合状态,进行了大量的测试,研究了试验装置有效性以及试验数据重复性,着重分析了探测光束的PV值与RMS值。结果表明：导流板可明显抑制风洞洞壁边界层干扰,试验装置与方法可行,对于连续式风洞中模型绕流流场光学传输效应测试有一定参考价值。     

某型飞机铝合金LY11螺旋桨腐蚀损伤试验

在疲劳试验机及电磁激振试验台上,对不同腐蚀情况的某型飞机螺旋桨桨叶模拟试件进行试验,分别得到了腐蚀损伤面积比随低周循环数N的变化规律,振动频率随损伤深度比、损伤长度比及损伤面积比的变化规律.试验表明,在载荷、温度相同条件下,材料性能、喷丸强化措施和使用环境是影响螺旋桨腐蚀损伤的重要因素;腐蚀损伤的面积比、腐蚀深度比对螺旋桨桨叶振动频率影响较大并获得最大深度比为0.14,模拟试件损伤深度最大允许值为0.7 mm,损伤面积比为0.015,损伤面积最大允许值为3.006 mm2.      

The Lunar Gravity Ranging System for the Gravity Recovery and Interior Laboratory (GRAIL) Mission

The Lunar Gravity Ranging System (LGRS) flying on NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission measures fluctuations in the separation between the two GRAIL orbiters with sensitivity below 0.6 microns/Hz^1/2. GRAIL adapts the mission design and instrumentation from the Gravity Recovery and Climate Experiment (GRACE) to a make a precise gravitational map of Earth’s Moon. Phase measurements of Ka-band carrier signals transmitted between spacecraft with line-of-sight separations between 50 km to 225 km provide the primary observable. Measurements of time offsets between the orbiters, frequency calibrations, and precise orbit determination provided by the Global Positioning System on GRACE are replaced by an S-band time-transfer cross link and Deep Space Network Doppler tracking of an X-band radioscience beacon and the spacecraft telecommunications link. Lack of an atmosphere at the Moon allows use of a single-frequency link and elimination of the accelerometer compared to the GRACE instrumentation. This paper describes the implementation, testing and performance of the instrument complement flown on the two GRAIL orbiters.