In situ analysis of Europa ices by short-range melting probes

A key aspect for understanding the astrobiological potential of planets and moons in the Solar system is the analysis of material embedded in or underneath icy layers on the surface. In particular in case of the icy crust of Jupiters moon Europa such investigation would be of greatest interest. For a Europa lander to be launched in the 2020–2030 timeframe, we propose to use a simplified instrumented melting probe which is able to access and sample depths of a few meters without the necessity of heavy and complicated drilling equipment.     

美国新型载人火星探测技术方案

文章概括介绍了＂发现号＂宇宙飞船的布局结构。然后详细介绍了飞船用于火星探测的两种着陆舱的具体设计方案以及载人火星探测的任务剖面。最后分析了＂发现号＂宇宙飞船火星探测方案的关键可行技术和诸多设计优点。     

“凤凰号”火星探测器着陆过程

文章主要介绍了＂凤凰号＂火星着陆器的着陆过程、着陆点选择方法原则、巡航阶段工作任务,对进入（Entry）、下降（Descent）和着陆（Landing）即EDL阶段的蒙特卡罗分析结果和飞行器重建数值结果进行了总结比较。并对＂凤凰号＂相关的经验和教训进行了比较总结,这对中国未来的火星探测以及其他深空探测具有一定的借鉴作用。     

嫦娥三号巡视器-着陆器释放分离过程关键力学问题分析

针对嫦娥三号探测器两器释放分离过程几个关键力学问题,给出两器释放分离过程的主要风险点与影响参数,应用ADAMS建立两器释放分离全过程仿真模型,开展了全过程动力学仿真与相关试验。分析得到可适应安全释放分离要求的着陆器最大着陆姿态边界与关键性能参数,为两器释放分离提供了理论支撑与依据。     

Surface elements and landing strategies for small bodies missions – Philae and beyond

The investigation of small bodies, comets and asteroids, can contribute substantially to our understanding of the formation and history of the Solar System. In-situ observations by Landers play a prominent role in this field.The Rosetta Lander – Philae – is currently on its way to comet 67P/Churyumov–Gerasimenko. It will land in November 2014 and perform numerous experiments with a suite of 10 scientific instruments.Philae has been designed to cope with a wide range of possible comet properties. The considerations taken during its development are relevant for future Lander missions to small bodies in the Solar System.In addition the paper provides a review of alternative concepts, studied or developed for various missions like Phobos, Hayabusa/Minerva or Géocroiseur/Leonard.Various missions to small bodies in the Solar System, including Landers, are currently studied (e.g., Marco Polo). The paper will address the mission options and compare applicable technologies with the solutions chosen for Philae.     

Methods and measurements to assess physical and geochemical conditions at the surface of Europa

An international effort dedicated to the science exploration of Jupiter system planned by ESA and NASA in the beginning of the next decade includes in-depth science investigation of Europa. In parallel to EJSM (Europa-Jupiter System Mission) Russia plans a Laplace-Europa Lander mission, which will include another orbiter and the surface element: Europa Lander. In-situ methods on the lander provide the only direct way to assess environmental conditions, and to perform the search for signatures of life. A critical advantage of such in situ analysis is the possibility to enhance concentration and detection limits and to provide ground truth for orbital measurements. The science mission of the lander is biological, geophysical, chemical, and environmental characterizations of the Europa surface. This review is dedicated to methods and strategies of geophysical and environmental measurements to be performed at the surface of Europa, and their significance for the biological assessment, basing on the concept of a relatively large softly landed module, allowing to probe a shallow subsurface. Many of the discussed methods were presented on the workshop “Europa Lander: Science Goals and Experiments” held in Moscow in February 2009. Methods and instruments are grouped into geophysical package, means of access to the subsurface, methods of chemical and structural characterization, and methods to assess physical conditions on the surface.     

双月球探测器相对定位的同波束VLBI技术研究

针对着陆器和月球车数传信号无法在同一通道内记录的问题,提出利用射电源观测修正不同通道装置内部时延的同波束甚长基线干涉测量（VLBI）方法,解算含微小偏移量的差分相时延。利用嫦娥二号两个X波段VLBI信号观测数据和上海、昆明、乌鲁木齐三个台站的同波束VLBI器地对接数据验证了提出的方法。结果表明解算的含微小偏移量差分相时延形式误差在皮秒量级,系统误差在0.5ns(纳秒)左右,有望把月球车的相对定位精度提高至数十米。     

Effects of restitution,friction, and attitude on 2D low-velocity rigid-body impacts

The impact of nonspherical bodies is complex, even at low velocities where contacting bodies are assumed to be rigid. Models of varying complexity (e.g. finite element methods) can be used to evaluate such impacts, but it is advantageous to use impulsive models such as that by Stronge, which are computationally inexpensive and governed by (fixed) material interaction coefficients. Stronge’s model parameterizes nonspherical rigid-body impacts with energetic restitution and Coulomb friction coefficients. This model was successfully used in large-scale simulations of ballistic lander deployment to asteroids and comets, whose trajectories involve dozens of chaotic bounces. To better understand the complex dynamics of these bouncing trajectories, this paper performs a dedicated study of idealized bouncing in two dimensions and on a flat plane, in order to limit the involved degrees of freedom. Using a numerical implementation of Stronge’s model, the motion of a bouncing square is simulated with different impact conditions: the square’s impact attitude, velocity, and mass distribution as well as the surface restitution and friction coefficients. The simulation results are used to investigate how these conditions affect the bouncing motion of the square, with a distinction between first impacts with zero angular velocity and successive impacts in which the square is spinning. This reveals how a single “macroscopic” bounce that separates two ballistic arcs may often consist of multiple micro-impacts that occur in quick succession. For the different impact conditions, we show how the number of micro-impacts per macro-bounce varies, as well as the normal, tangential, and total kinematic restitution coefficients. These are different from the energetic material restitution coefficient that parameterizes the impact. Finally, we examine how the settling time and distance of the bouncing trajectories change. These trends provide insight into the bouncing motion of ballistic lander spacecraft in small-body microgravity.     

The Rosetta Lander (“Philae”) Investigations

The paper describes the Rosetta Lander named Philae and introduces its complement of scientific instruments. Philae was launched aboard the European Space Agency Rosetta spacecraft on 02 March 2004 and is expected to land and operate on the nucleus of 67P/Churyumov-Gerasimenko at a distance of about 3 AU from the Sun. Its overall mass is ~98 kg (plus the support systems remaining on the Orbiter), including its scientific payload of ~27 kg. It will operate autonomously, using the Rosetta Orbiter as a communication relay to Earth. The scientific goals of its experiments focus on elemental, isotopic, molecular and mineralogical composition of the cometary material, the characterization of physical properties of the surface and subsurface material, the large-scale structure and the magnetic and plasma environment of the nucleus. In particular, surface and sub-surface samples will be acquired and sequentially analyzed by a suite of instruments. Measurements will be performed primarily during descent and along the first five days following touch-down. Philae is designed to also operate on a long time-scale, to monitor the evolution of the nucleus properties. Philae is a very integrated project at system, science and management levels, provided by an international consortium. The Philae experiments have the potential of providing unique scientific outcomes, complementing by in situ ground truth the Rosetta Orbiter investigations. Philae team members are listed in the acknowledgements