月面环境三维激光SLAM技术

同步建图与定位（SLAM）可实现月球车在未知复杂月面环境下的定位与导航,月球表面由陨坑、石头等起伏地形构成,缺乏树木、建筑物等地面存有的显著特征,大量特征不显著的点云数据会对月球车定位精度和实时性造成影响。本文提出了一种针对月面环境的显著特征点云提取方法以及基于曲面定位能力估计的增量式优化算法,通过Fisher信息矩阵计算曲面定位能力指标,获取机器人位姿估计的不确定性测量,利用增量式的SLAM方案进行优化,用于提高定位精度与实时性。通过在Gazebo （物理仿真平台）仿真场景下的测试,验证了算法性能。     

The Scientific Measurement System of the Gravity Recovery and Interior Laboratory (GRAIL) Mission

The Gravity Recovery and Interior Laboratory (GRAIL) mission to the Moon utilized an integrated scientific measurement system comprised of flight, ground, mission, and data system elements in order to meet the end-to-end performance required to achieve its scientific objectives. Modeling and simulation efforts were carried out early in the mission that influenced and optimized the design, implementation, and testing of these elements. Because the two prime scientific observables, range between the two spacecraft and range rates between each spacecraft and ground stations, can be affected by the performance of any element of the mission, we treated every element as part of an extended science instrument, a science system. All simulations and modeling took into account the design and configuration of each element to compute the expected performance and error budgets. In the process, scientific requirements were converted to engineering specifications that became the primary drivers for development and testing. Extensive simulations demonstrated that the scientific objectives could in most cases be met with significant margin. Errors are grouped into dynamic or kinematic sources and the largest source of non-gravitational error comes from spacecraft thermal radiation. With all error models included, the baseline solution shows that estimation of the lunar gravity field is robust against both dynamic and kinematic errors and a nominal field of degree 300 or better could be achieved according to the scaled Kaula rule for the Moon. The core signature is more sensitive to modeling errors and can be recovered with a small margin.     

Soft landing stability analysis of a Mars lander under uncertain terrain

Safe soft landing of the lander is vital to the Mars surface exploration mission. Analysis and verification of the landing stability under uncertain terrain play an important role in lander design. However, the effect of uncertain terrain is ignored in most existing studies, making the analysis incomprehensive and increasing the risk of landing failure in practice. In this paper, a Mars lander with 10 attitude control thrusters is introduced and its dynamics model is then established considering plastic deformation parts and nonlinear contact forces. The effectiveness and accuracy of the dynamics modeling method are verified by experiments with an average relative error of 10%. In order to carry out the dynamics simulation with high-fidelity terrain, a terrain generation method based on statistical data is proposed. Through Monte Carlo simulation under a 50 m × 50 m randomly generated landing terrain, the stability of the lander and the effects of attitude control thrusters are analyzed. The results show that the failure rate is 5.5%, in which the primary failure forms are overturning and abnormal attitude. When the landing simulations are repeated without thrusters, the stable ratio decreases from 94.5% to 90.7%, suggesting the positive effects of attitude control thrusters in improving landing stability under rough terrain.     

月球巡视探测器自主定向算法研究

月球巡视探测器自主导航是其能在月面执行探测任务的关键,而定向又是月球巡视探测器自主导航的一个重要组成部分,其定向精度将直接影响到月球巡视探测器定位性能。将CCD(ChargeCoupleDevice)太阳敏感器应用到月球巡视探测器上,用太阳敏感器测量太阳位置矢量,结合加速度计测量的重力矢量,利用QUEST算法推算了月球巡视探测器的姿态和航向,为月球巡视探测器构建了一套适用于长时间、长距离导航的绝对定向方案,通过理论分析和实际推算描述了该定向方案的具体实现过程,最后以仿真结果验证了该方案的可行性,为下一步月球巡视探测器定位研究提供了技术参考。     

Solar power system options for the Radiation and TechnologyDemonstration spacecraft

The Radiation and Technology Demonstration (RTD) Mission has the primary objective of demonstrating high-power (10 kilowatts) electric thruster technologies in Earth orbit. This paper discusses the conceptual design of the RTD spacecraft photovoltaic (PV) power system and mission performance analyses. These power system studies assessed multiple options for PV arrays, battery technologies and bus voltage levels. To quantify performance attributes of these power system options, a dedicated Fortran code was developed to predict power system performance and estimate system mass. The low-thrust mission trajectory was analyzed and important Earth orbital environments were modeled. Baseline power system design options are recommended on the basis of performance, mass and risk/complexity. Important findings from parametric studies are discussed and the resulting impacts to the spacecraft design and cost     

嫦娥探测器分段渐倾转移机构设计

巡视探测器转移机构是在地外空间环境执行巡视探测器转移释放任务的空间机构。与美国、苏联转移任务不同，中国探月工程（CLEP）二期着陆器采用腿式着陆缓冲机构及巡视器顶部搭载方式，转移任务沿着陆器周向展开距离及巡视器释放高度增加，转移难度增大。在设计阶段，转移机构是否符合探测任务严苛的工程约束及设计指标；在执行阶段，转移机构能否在月面非确知环境下正常展开、转移过程是否稳定可靠，是嫦娥探测器顺利完成探测任务的关键。为保障月球后续任务及火星探测任务中转移机构的设计需要，根据巡视器转移系统特点，以探月二期工程中首次探索并成功自主设计定型的嫦娥分段渐倾转移机构为例，对巡视器转移系统的组成、任务需求及设计约束予以阐述，并结合参研人员经验，对机构研制方案的选取、关键环节设计、工程状态及任务验证情况进行说明，以为后续工作及相关工程提供参考。     

Selection of the Mars Science Laboratory Landing Site

The selection of Gale crater as the Mars Science Laboratory landing site took over five years, involved broad participation of the science community via five open workshops, and narrowed an initial >50 sites (25 by 20?km) to four finalists (Eberswalde, Gale, Holden and Mawrth) based on science and safety. Engineering constraints important to the selection included: (1)?latitude (±30°) for thermal management of the rover and instruments, (2)?elevation (<?1?km) for sufficient atmosphere to slow the spacecraft, (3)?relief of <100–130?m at baselines of 1–1000?m for control authority and sufficient fuel during powered descent, (4)?slopes of <30° at baselines of 2–5?m for rover stability at touchdown, (5)?moderate rock abundance to avoid impacting the belly pan during touchdown, and (6)?a?radar-reflective, load-bearing, and trafficable surface that is safe for landing and roving and not dominated by fine-grained dust. Science criteria important for the selection include the ability to assess past habitable environments, which include diversity, context, and biosignature (including organics) preservation. Sites were evaluated in detail using targeted data from instruments on all active orbiters, and especially Mars Reconnaissance Orbiter. All of the final four sites have layered sedimentary rocks with spectral evidence for phyllosilicates that clearly address the science objectives of the mission. Sophisticated entry, descent and landing simulations that include detailed information on all of the engineering constraints indicate all of the final four sites are safe for landing. Evaluation of the traversabilty of the landing sites and target “go to” areas outside of the ellipse using slope and material properties information indicates that all are trafficable and “go to” sites can be accessed within the lifetime of the mission. In the final selection, Gale crater was favored over Eberswalde based on its greater diversity and potential habitability.     

Radar Image Processing with Clusters of Computers

Some radar image processing algorithms such as shape-from-shading are particularly compute-intensive and time-consuming. If, in addition, a data set to be processed is large, then it may make sense to perform the processing of images on multiple workstations or parallel processing systems. We have implemented shape-from-shading, stereo matching, resampling, gridding, and visualization of terrain models in such a manner that they execute either on parallel machines or on clusters of workstations. We were motivated by the large image data set from NASA's Magellan mission to planet Venus, but received additional inspiration from the European Union's Center for Earth Observation program (CEO) and Austria's MISSION initiative for distributed processing of remote sensing images on remote workstations, using publicly-accessible algorithms. We developed a multi-processor approach that we denote as CDIP for Concurrent and Distributed Image Processing. The speedup for image processing tasks increases nearly linearly with the number of processors, be they on a parallel machine or arranged in a cluster of distributed workstations. Our approach adds benefits for users of complex image processing algorithms: the efforts for code porting and code maintenance are reduced and the necessity for specialized parallel processing hardware is eliminated.     

月球车释放对着陆器稳定性的影响

因基于摇臂式月球车释放机构在月球车释放时对着陆器的倾翻力矩较大,易使着陆器倾翻而导致整个探测任务失败,所以对月球车着陆释放时着陆器稳定性的研究尤为重要.将着陆器腿不等量压缩、月面坡度、低重力环境、释放加速度等因素进行参数化处理;应用D-H坐标法得到基于各参量的支撑多边形坐标以及着陆器和月球车的位姿方程,进而建立了月球车...     

Geochemical Constraints on the Origin of the Moon and Preservation of Ancient Terrestrial Heterogeneities

Space Science Reviews - Chang’E 4 is the first mission to the far side of the Moon and consists of a lander, a&nbsp;rover, and a relay spacecraft. Lander and rover were launched at 18:23...     

Mission segment division of the whole aeroengine loading spectrum based on flight actions

This paper studies on a division method of the whole aeroengine loading spectrum flight mission segment and rotor speed mission segment, which is based on the actual flight actions and related to the flight operations of aeroengine and is suitable for the variable-speed aeroengines such as turbojet and turbofan. Through the research, the aeroengine loading spectrum operation-related mission segments can be divided, which can provide important data basis for the life research on the structures wh...     

REMS: The Environmental Sensor Suite for the Mars Science Laboratory Rover

The Rover Environmental Monitoring Station (REMS) will investigate environmental factors directly tied to current habitability at the Martian surface during the Mars Science Laboratory (MSL) mission. Three major habitability factors are addressed by REMS: the thermal environment, ultraviolet irradiation, and water cycling. The thermal environment is determined by a mixture of processes, chief amongst these being the meteorological. Accordingly, the REMS sensors have been designed to record air and ground temperatures, pressure, relative humidity, wind speed in the horizontal and vertical directions, as well as ultraviolet radiation in different bands. These sensors are distributed over the rover in four places: two booms located on the MSL Remote Sensing Mast, the ultraviolet sensor on the rover deck, and the pressure sensor inside the rover body. Typical daily REMS observations will collect 180 minutes of data from all sensors simultaneously (arranged in 5 minute hourly samples plus 60 additional minutes taken at times to be decided during the course of the mission). REMS will add significantly to the environmental record collected by prior missions through the range of simultaneous observations including water vapor; the ability to take measurements routinely through the night; the intended minimum of one Martian year of observations; and the first measurement of surface UV irradiation. In this paper, we describe the scientific potential of REMS measurements and describe in detail the sensors that constitute REMS and the calibration procedures.     

Risk-based technology portfolio optimization for early space mission design

The successful design, development, and operation of space missions requires informed decisions to be made across a vast array of investment, scientific, technological, and operational issues. In the work reported in this paper, we address the problem of determining optimal technology investment portfolios that minimize mission risk and maximize the expected science return of the mission. We model several relationships that explicitly link investment in technologies to mission risk and expected science return. To represent and compute these causal and computational dependencies, we introduce a generalization of influence diagrams that we call inference nets. To illustrate the approach, we present results from its application to a technology portfolio investment trade study done for a specific scenario for the projected 2009 Mars MSL mission. This case study examines the impact of investments in precision landing and long-range roving technologies on the mission capability, and the associated risk, of visiting a set of preselected science sites. We show how an optimal investment strategy can be found that minimizes the mission risk given a fixed total technology investment budget, or alternatively how to determine the minimum budget required to achieve a given acceptable mission risk.     

Mars Science Laboratory Mission and Science Investigation

Scheduled to land in August of 2012, the Mars Science Laboratory (MSL) Mission was initiated to explore the habitability of Mars. This includes both modern environments as well as ancient environments recorded by the stratigraphic rock record preserved at the Gale crater landing site. The Curiosity rover has a designed lifetime of at least one Mars year (～23?months), and drive capability of at least 20?km. Curiosity’s science payload was specifically assembled to assess habitability and includes a gas chromatograph-mass spectrometer and gas analyzer that will search for organic carbon in rocks, regolith fines, and the atmosphere (SAM instrument); an x-ray diffractometer that will determine mineralogical diversity (CheMin instrument); focusable cameras that can image landscapes and rock/regolith textures in natural color (MAHLI, MARDI, and Mastcam instruments); an alpha-particle x-ray spectrometer for in situ determination of rock and soil chemistry (APXS instrument); a?laser-induced breakdown spectrometer to remotely sense the chemical composition of rocks and minerals (ChemCam instrument); an active neutron spectrometer designed to search for water in rocks/regolith (DAN instrument); a weather station to measure modern-day environmental variables (REMS instrument); and a sensor designed for continuous monitoring of background solar and cosmic radiation (RAD instrument). The various payload elements will work together to detect and study potential sampling targets with remote and in situ measurements; to acquire samples of rock, soil, and atmosphere and analyze them in onboard analytical instruments; and to observe the environment around the rover. The 155-km diameter Gale crater was chosen as Curiosity’s field site based on several attributes: an interior mountain of ancient flat-lying strata extending almost 5?km above the elevation of the landing site; the lower few hundred meters of the mountain show a progression with relative age from clay-bearing to sulfate-bearing strata, separated by an unconformity from overlying likely anhydrous strata; the landing ellipse is characterized by a mixture of alluvial fan and high thermal inertia/high albedo stratified deposits; and a number of stratigraphically/geomorphically distinct fluvial features. Samples of the crater wall and rim rock, and more recent to currently active surface materials also may be studied. Gale has a well-defined regional context and strong evidence for a progression through multiple potentially habitable environments. These environments are represented by a stratigraphic record of extraordinary extent, and insure preservation of a rich record of the environmental history of early Mars. The interior mountain of Gale Crater has been informally designated at Mount Sharp, in honor of the pioneering planetary scientist Robert Sharp. The major subsystems of the MSL Project consist of a single rover (with science payload), a Multi-Mission Radioisotope Thermoelectric Generator, an Earth-Mars cruise stage, an entry, descent, and landing system, a launch vehicle, and the mission operations and ground data systems. The primary communication path for downlink is relay through the Mars Reconnaissance Orbiter. The primary path for uplink to the rover is Direct-from-Earth. The secondary paths for downlink are Direct-to-Earth and relay through the Mars Odyssey orbiter. Curiosity is a scaled version of the 6-wheel drive, 4-wheel steering, rocker bogie system from the Mars Exploration Rovers (MER) Spirit and Opportunity and the Mars Pathfinder Sojourner. Like Spirit and Opportunity, Curiosity offers three primary modes of navigation: blind-drive, visual odometry, and visual odometry with hazard avoidance. Creation of terrain maps based on HiRISE (High Resolution Imaging Science Experiment) and other remote sensing data were used to conduct simulated driving with Curiosity in these various modes, and allowed selection of the Gale crater landing site which requires climbing the base of a mountain to achieve its primary science goals. The Sample Acquisition, Processing, and Handling (SA/SPaH) subsystem is responsible for the acquisition of rock and soil samples from the Martian surface and the processing of these samples into fine particles that are then distributed to the analytical science instruments. The SA/SPaH subsystem is also responsible for the placement of the two contact instruments (APXS, MAHLI) on rock and soil targets. SA/SPaH consists of a robotic arm and turret-mounted devices on the end of the arm, which include a drill, brush, soil scoop, sample processing device, and the mechanical and electrical interfaces to the two contact science instruments. SA/SPaH also includes drill bit boxes, the organic check material, and an observation tray, which are all mounted on the front of the rover, and inlet cover mechanisms that are placed over the SAM and CheMin solid sample inlet tubes on the rover top deck.     

Exploration of the Habitability of Mars: Development of Analytical Protocols for Measurement of Organic Carbon on the 2009 Mars Science Laboratory

The mission goal of the 2009 Mars Science Laboratory is to assess the habitability of a region on Mars. This large rover incorporates an Analytical Laboratory that contributes to this mission objective by means of a detailed characterization of mineralogy and chemistry. The Sample Analysis at Mars instrument suite in the Analytical Laboratory provides the capability to analyze volatiles released from rocks and soils and gases directly sample from the atmosphere. A primary focus of this suite is the detection and identification of organic molecules. The protocols for the extraction and analysis of organics under development for this mission are described as are experiments carried out on Mars analog samples to evaluate these methods.     

玉兔号巡视器导航定位中的多目标管理方法

基于多目标管理方法,阐述了玉兔号巡视器定位多目标管理的概念。兼顾技术成熟度、定位效率、冗余验证和阶段化分层管理等原则,对玉兔号巡视器着陆点和导航点的定位方法进行建模及分析比较,给出对应的定位方案。最后,将基于此多目标管理方法制定的方案,应用于玉兔号巡视器的定位任务,定位精度优于亚像素级,相对定位精度优于4％。     

Robotic Air Vehicle: A Pilot's Perspective

This paper focuses on concepts and technologies required to develop a robotic air vehicle (RAV). A vehicle of this type has the capability to be a launch and forget weapon system. The authors are engineers and pilots so they view both the technical approach and piloting issues with equal importance. RAV must have the machine intelligence to make decisions within the mission and battlefield constraints. This requires a piloting expert system and route planner to perform passive terrain following, terrain avoidance, obstacle avoidance, and autonomous navigation based on low cost sensor inputs such as a multifunction FLIR, digital terrain map, and directional reference systems. RAV is a cost effective way to fight in a threat environment where aircrew loss rates would be unacceptable. RAV provides the Air Force a means to expand its combat capabilities.     

High-adaption locomotion with stable robot body for planetary exploration robot carrying potential instruments on unstructured terrain

There is a strong demand for Planetary Exploration Mobile robots (PEMRs) that have the capability of the traversability, stability, efficiency and high load while tackling the specialized tasks on planet surface. In this paper, an electric parallel wheel-legged hexapod robot which has high-adaption locomotion on the unstructured terrain is presented. Also, the hybrid control framework, which enables robot to stably carry the heavy loads as well as to traverse the uneven terrain by utilizing both legged and wheeled locomotion, is also proposed. Based on this framework, robot controls the multiple DOF leg for performing high-adaption locomotion to negotiate obstacles via Gait Generator (GG). Additionally, by using Whole-Body Control (WBC) of framework, robot has the capability of flexibly accommodating the uneven terrain by Attitude Control (AC) kinematically adjusting the length of legs like an active suspension system, and by Force/torque Balance Control (FBC) equally distributing the Ground Reaction Force (GRF) to maintain a stable body. The simulation and experiment are employed to validate the proposed framework with the physical system in the planetary analog environments. Particularly, to smoothly demonstrate the performance of robot transporting heavy loads, the experiment of carrying 3-person load of about 240 kg is deployed.     

Terrain database integrity monitoring for synthetic vision systems

A real-time terrain database integrity monitor for synthetic vision systems (SVS) that are to be used in civil aviation is presented. SVS provides pilots with advanced display technology including terrain information as well as other information about the external environment such as obstacles and traffic. The use of SVS to support strategic and tactical decision-making and the compelling nature of the terrain depiction may require terrain database server certification at the essential and flight-critical levels. SVS and terrain database characteristics are discussed and a failure model is identified. Real-time integrity monitors are proposed that check the consistency between terrain profiles described by the database and terrain profiles that are sensed in flight by either a downward-looking (DWL) sensor or a forward-looking (FWL) season A DWL sensor scheme is discussed in detail and it is shown that this scheme can provide the necessary integrity required for an essential certification of a terrain database server.