A proposed Comet Nucleus Penetrator for the Comet Rendezvous Asteroid Flyby mission

Among the major objectives of NASA's program of space exploration is a better understanding of the origin and evolution of the solar system. Crucial to this objective is the study of comets, which are thought to be the most primitive, pristine bodies remaining in the solar system. The importance of the study of comets has led NASA to plan a mission to rendezvous with comet Tempel 2 in 1997. Critical to the understanding of comets will be measurements of the nucleus material to determine its elemental and isotopic composition, its mechanical properties, and its thermal state and properties. This paper describes a proposal for a Comet Nucleus Penetrator to accomplish these measurement goals. The Comet Nucleus Penetrator will implant instruments into the comet's nucleus beneath a probable volatile-depleted surface mantle into material more representative of the bulk composition of the nucleus.     

The putative mechanical strength of comet surface material applied to landing on a comet

The comet lander PHILAE (part of the ESA mission ROSETTA) is going to touch down on comet 67P/Churyumov–Gerasimenko in 2014. Landing dynamics depend on the mechanical strength of the surface material: in an extremely soft material, the lander (100 kg, 1 m/s touch-down velocity) may sink in too deep for successful operation while on a very hard surface the probability for bouncing and overturning increases. It is shown that direct knowledge on the strength of cometary surface material is very limited. In our view, even the Deep Impact experiment could not provide a reliable value of the mechanical strength of comet Tempel 1. We discuss the definition of “strength” and revise the ideas on cometary surface strength and theories that describe the low-velocity (≈1 m/s) impact of blunt bodies into dust-rich, fluffy cometary materials. Available direct and indirect measurements and data are critically reviewed. Lessons learnt from laboratory measurements to verify our equations of motion are presented as well. Conclusions for Philae are drawn: most likely, the soft landing will lead to a typical penetration of the lander's feet of up to 20 cm.     

Analysis and pre-development of an imaging spectrometer for in-situ cometary soil analysis on-board the esa rosetta mission

The CIVA-M instrument, a highly integrated infrared/visible microscope for the Rosetta mission (ESA — 2003) is presented. It will enable scientists to study in great detail the composition of the Wirtanen Comet: minerals, organic compounds and ices. A monochromator will illuminate a cometary sample, drilled from the comet sub-surface (≈40cm). An infrared detector will give an image of the sample for each wavelength, from 1 to 4μm with a spectral resolution of 6nm and a spatial resolution of 50 μm. In order to analyze accurately spectra a signal to noise ratio of 50 is needed (for ALBEDO = 0.04). We will use a 128×128 elements photovoltaic mercury cadmium telluride bi-dimensional array working at intermediate temperature (110K to 150K), from the French company SOFRADIR. At such relatively high temperature the critical parameter is the dark current: it limits the exposure time, preventing a high signal to noise ratio. I am in charge of the electronic board, which is the interface between the detector and the on-board processor. Some preliminary results obtained with this board, on a test detector, are then discussed.     

Rosetta: The ESA comet rendezvous mission

Rosetta was selected in November 1993 for the ESA Cornerstone 3 mission, to be launched in 2003, dedicated to the exploration of the small bodies of the solar system (asteroids and comets). Following this selection, the Rosetta mission and its spacecraft have been completely reviewed: this paper presents the studies performed the proposed mission and the resulting spacecraft design.

Three mission opportunities have been identified in 2003–2004, allowing rendezvous with a comet. From a single Ariane 5 launch, the transfer to the comet orbit will be supported by planetary gravity assists (two from Earth, one from Venus or Mars); during the transfer sequence, two asteroid fly-bys will occur, allowing first mission science phases. The comet rendezvous will occur 8–9 years after launch; Rosetta will orbit around the comet and the main science mission phase will take place up to the comet perihelion (1–2 years duration).

The spacecraft design is driven (i) by the communication scenario with the Earth and its equipment, (ii) by the autonomy requirements for the long cruise phases which are not supported by the ground stations, (iii) by the solar cells solar array for the electrical power supply and (iv) by the navigation scenario and sensors for cruise, target approach and rendezvous phases. These requirements will be developed and the satellite design will be presented.     

一种三元结构的火星采样返回任务方案分析

介绍了目前国外提出的一种三元结构的火星采样返回任务方案,整个方案分3次发射,分别发射漫游车、着陆器和轨道器,每次发射间隔为4年,最终目的是将火星样品带回地球。该方案的优势在于,通过3次发射分别完成漫游车巡视勘察、着陆器现场探测、轨道器数据中继和在轨探测,最终综合完成火星采样返回,能够极大地缓解项目进度和资金压力,充分利用每次发射窗口分步骤完成探测任务。文章重点对方案涉及的关键技术进行了分析,包括样品获取与封装、行星保护、精准着陆、漫游车的危险规避能力和移动性、火星上升器、交会与样品捕获、地球再入器技术等;对方案的前景和优势进行了探讨,并给出几点启示,如精准着陆或成为今后行星探测着陆方式的新趋势,火星采样返回任务将是人类火星探测的里程碑,今后的深空探测任务趋向国际合作模式等。     

Fourth John V. Breakwell memorial lecture the use of earth-return trajectories for missions to comets

The concept of using Earth-return trajectories in connection with missions to comets was originally proposed in 1972. Papers published in the 1970's and 1980's showed that by using multiple Earth-to-Earth transfers, it was possible to construct a trajectory that would encounter several comets. This technique was used for the first time by ESA's Giotto spacecraft. Following its encounter with Halley's comet in March 1986, Giotto used a single Earth gravity-assist maneuver to intercept comet Grigg-Skjellerup in July 1992. Japan's Sakigake spacecraft tried to use Earth gravity-assist maneuvers to reach comet Honda-Mrkos-Pajdusakova in 1996, but was not successful. Earth-return trajectories are essential elements of two Discovery-class missions to comets; Stardust, and the Comet Nucleus Tour (CONTOUR). The Stardust mission will be launched in February 1999, and will return dust samples collected from comet Wild-2 to the Earth in 2006. CONTOUR is scheduled for a launch in June 2002, and will use six Earth gravity-assist maneuvers to carry out three comet encounters: Encke in 2003; Schwassmann-Wachmann-3 in 2006; and d'Arrest in 2008. An extended-mission scenario would allow CONTOUR to accomplish two additional encounters: Tempel-2 in 2015, and Encke for a second time in 2023.     

Landing on small bodies: From the Rosetta Lander to MASCOT and beyond

Recent planning for science and exploration missions has emphasized the high interest in the close investigation of small bodies in the Solar System. In particular in-situ observations of asteroids and comets play an important role in this field and will contribute substantially to our understanding of the formation and history of the Solar System.The first dedicated comet Lander is Philae, an element of ESA's Rosetta mission to comet 67/P Churyumov–Gerasimenko. Rosetta was launched in 2004. After more than 7 years of cruise (including three Earth and one Mars swing-by as well as two asteroid flybys) the spacecraft has gone into a deep space hibernation in June 2011. When approaching the target comet in early 2014, Rosetta will be re-activated. The cometary nucleus will be characterized remotely to prepare for Lander delivery, currently foreseen for November 2014.The Rosetta Lander was developed and manufactured, similar to a scientific instrument, by a consortium consisting of international partners. Project management is located at DLR in Cologne/Germany, with co-project managers at CNES (France) and ASI (Italy). The scientific lead is at the Max Planck Institute for Solar System Science (Lindau, Germany) and the Institut d'Astrophysique Spatiale (Paris).Mainly scientific institutes provided the subsystems, instruments and the complete, qualified lander system. Operations are performed in two dedicated centers, the Lander Control Center (LCC) at DLR-MUSC and the Science Operations and Navigation Center (SONC) at CNES. This concept was adopted to reduce overall cost of the project and is foreseen also to be applied for development and operations of future small bodies landers.A mission profiting from experience gained during Philae development and operations is MASCOT, a surface package for the Japanese Hayabusa 2 mission. MASCOT is a small (∼10 kg) mobile device, delivered to the surface of asteroid 1999JU3. There it will operate for about 16 h. During this time a camera, a magnetometer, a thermal monitor and an IR analytical instrument will provide ground truth and thus will even be able to support the selection of possible sampling sites for the main spacecraft.MASCOT is a flexible design that can be adapted to a wide range of missions and possible target bodies. Also the payload is flexible to some extent (with an overall mass in the 3 kg range). For example, the surface package is part of the optional strawman payload for MarcoPolo-R, a European asteroid sample return mission, proposed for ESA Cosmic Vision M-class.     

Some novel aspects of cometary research

In spite of numerous observations and intense theoretical work already accomplished, many important questions concerning comets remain unsolved. The origin of comets is far from being elucidated. The nature of comets, of their nuclei seems to be reasonably described by the model of Whipple, yet their very structure and constitution remain hypothetical. The complex internal dynamics of active comets awaits a detailed explanation. One of the outstanding problems pertains to the very nature of the residual material remaining after the outgasing of the cometary nucleus. The problem is connected with the presence of organic matter, of their constituents as well as aggregates important to the development of life and to the hypothetical influence of such ingredients on the evolution of its forms already existing on some celestial bodies.It is obvious that irrespective to the recently devised methods and instruments new developments are needed. The paper attempts to show some novel ways of exploration of comets by the use of astronautical means. Recommendations for the realization of such future cometary missions are presented.     

Introduction to Japanese exploration study to the moon

The Japan Aerospace Exploration Agency (JAXA) views the lunar lander SELENE-2 as the successor to the SELENE mission. In this presentation, the mission objectives of SELENE-2 are shown together with the present design status of the spacecraft. JAXA launched the Kaguya (SELENE) lunar orbiter in September 2007, and the spacecraft observed the Moon and a couple of small satellites using 15 instruments. As the next step in lunar exploration, the lunar lander SELENE-2 is being considered. SELENE-2 will land on the lunar surface and perform in-situ scientific observations, environmental investigations, and research for future lunar utilization including human activity. At the same time, it will demonstrate key technologies for lunar and planetary exploration such as precise and safe landing, surface mobility, and overnight survival. The lander will carry laser altimeters, image sensors, and landing radars for precise and safe landing. Landing legs and a precisely controlled propulsion system will also be developed. A rover is being designed to be able to travel over a wide area and observe featured terrain using scientific instruments. Since some of the instruments require long-term observation on the lunar surface, technology for night survival over more than 2 weeks needs to be considered. The SELENE-2 technologies are expected to be one of the stepping stones towards future Japanese human activities on the moon and to expand the possibilities for deep space science.     

COSAC onboard Rosetta: a bioastronomy experiment for the short-period comet 67P/Churyumov-Gerasimenko

The COSAC (Cometary Sampling and Composition Experiment) onboard the Rosetta mission is a combined gas chromatograph (GC)-mass spectrometer (MS). It is situated on Philae, the lander of the mission, which is intended to land on the nucleus of comet 67P/Churyumov- Gerasimenko. The purpose of the experiment is to analyze the volatile fraction of soil samples retrieved by a drill. For investigation, the samples will be pyrolysed, and the emanating gases fed into a GC, into an MS, or the combination of both. In the first part of this paper, the bioastronomical relevance of such measurements is outlined. In the second part the details of the hardware and its performance are described.     

利用搜索法对嫦娥三号着陆器和巡视器定位

针对嫦娥三号巡视器相对定位时同波束甚长基线干涉测量（VLBI）差分相位时延存在纳秒量级模糊度的问题,提出利用搜索法对巡视器和着陆器的相对位置进行确定,并将该方法应用于着陆器的绝对位置的确定。首先介绍对嫦娥三号着陆器和巡视器测量的模式以及定位的原理,然后进行相应定位计算。利用该方法对着陆器定位结果与统计定位法结果比较,位置差100m左右,与月球勘测轨道飞行器（LRO）航拍定位结果差异在75m;该方法对巡视器在各停泊点的相对定位结果,与统计定位结果比较,位置差小于1m。     

Concept study on Deep Space Orbit Transfer Vehicle

In this paper, the concept of Orbit Transfer Vehicle for Deep Space Exploration (Deep Space OTV) is proposed, and its effectiveness and feasibility are discussed. Basic concept is the separation of two functions required for the deep space exploration, the transportation to the destination, and the exploration at the destination. Deep Space OTV is a spacecraft specialized for the transportation to the deep space destination. It is an expendable spacecraft propelled by solar electric propulsion. The payload of Deep Space OTV is Explorer, which is a spacecraft specialized for the exploration at the deep space destination. The effectiveness of the concept is discussed qualitatively, focused on the merits of the separations of two functions. The feasibility of Deep Space OTV is discussed based on the conceptual design of the spacecraft and its applicability to deep space missions. Several deep space missions are modeled and the payload capacity of Deep Space OTV is estimated. The missions include Asteroid rendezvous, Mars orbiter, Lunar lander, and so on.     

Concept study on Deep Space Orbit Transfer Vehicle

In this paper, the concept of Orbit Transfer Vehicle for Deep Space Exploration (Deep Space OTV) is proposed, and its effectiveness and feasibility are discussed. Basic concept is the separation of two functions required for the deep space exploration, the transportation to the destination, and the exploration at the destination. Deep Space OTV is a spacecraft specialized for the transportation to the deep space destination. It is an expendable spacecraft propelled by solar electric propulsion. The payload of Deep Space OTV is Explorer, which is a spacecraft specialized for the exploration at the deep space destination. The effectiveness of the concept is discussed qualitatively, focused on the merits of the separations of two functions. The feasibility of Deep Space OTV is discussed based on the conceptual design of the spacecraft and its applicability to deep space missions. Several deep space missions are modeled and the payload capacity of Deep Space OTV is estimated. The missions include Asteroid rendezvous, Mars orbiter, Lunar lander, and so on.     

Microbial influences on local carbon isotopic ratios and their preservation in carbonate

Analysis of the carbon isotopic composition of carbonates is a valuable tool for studying microbial processes and looking for evidence of life. Microbial fixation of CO2 and conversion of organic carbon to CO2 can produce measurable delta 13C shifts in a microbial mat environment. Diffusion modeling demonstrates that substantial isotopic shifts can develop within the mat and in the diffusion boundary layer in the fluid when CO2 fixation is rapid and prolonged for several hours. Carbonates that precipitate during rapid CO2 fixation can preserve these microbially produced isotopic shifts. However, continued precipitation during intervals when respiration dominates or after the cessation of active microbial growth commonly dilutes autotrophic isotopic signatures. Thus, preserved isotopic signatures rarely reflect the magnitude of isotopic shifts within the mat. Interpretation of observed isotopic shifts in microbial mat carbonate depends on fully characterizing ambient delta 13C and eliminating other origins for isotopic shifts. The carbon isotopic composition of reservoirs can vary substantially, both on Earth and on other planets. Characterizing the reservoir composition and any changes through time is critical to evaluating microbially induced shifts. In addition, careful evaluation of non-microbial causes for shifts in isotopic composition is essential for a reliable interpretation. Complicating processes include recrystallization, calcite precipitation over extended periods of time, variable precipitation rates and water chemistry, and mixing of carbonates having different isotopic signatures.     

Clathrate hydrates of oxidants in the ice shell of Europa

Europa's icy surface is radiolytically modified by high-energy electrons and ions, and photolytically modified by solar ultraviolet photons. Observations from the Galileo Near Infrared Mapping Spectrometer, ground-based telescopes, the International Ultraviolet Explorer, and the Hubble Space Telescope, along with laboratory experiment results, indicate that the production of oxidants, such as H2O2, O2, CO2, and SO2, is a consequence of the surface radiolytic chemistry. Once created, some of the products may be entrained deeper into the ice shell through impact gardening or other resurfacing processes. The temperature and pressure environments of regions within the europan hydrosphere are expected to permit the formation of mixed clathrate compounds. The formation of carbon dioxide and sulfur dioxide clathrates has been examined in some detail. Here we add to this analysis by considering oxidants produced radiolytically on the surface of Europa. Our results indicate that the bulk ice shell could have a approximately 1.7-7.6% by number contamination of oxidants resulting from radiolysis at the surface. Oxidant-hosting clathrates would consequently make up approximately 12-53% of the ice shell by number relative to ice, if oxidants were entrained throughout. We examine, in brief, the consequences of such contamination on bulk ice shell thickness and find that clathrate formation could lead to substantially thinner ice shells on Europa than otherwise expected. Finally, we propose that double occupancy of clathrate cages by O2 molecules could serve as an explanation for the observation of condensed-phase O2 on Europa. Clathrate-sealed, gas-filled bubbles in the near surface ice could also provide an effective trapping mechanism, though they cannot explain the 5771 A (O2)2 absorption.     

Results of impact simulation for the GIOTTO mission

The European Space Agency (ESA) has decided to carry out a fly-by mission to the comet Halley. The spacecraft will be launched by an ARIANE II and intercept the retrograde Halley orbit on 13 March, 1986. One group of experiments is designed to obtain data on size, mass and composition of the dust in the cometary tail. Because of the very high relative velocity during fly-by (69 km/s) laboratory experiments are necessary to develop and calibrate the experiments. These experiments are presently under way in the laboratory of the Lehrstuhl für Raumfahrttechnik of the Technische Universität München. First results have been obtained for both the Dust Impact Detection System (DIDSY) and the P?articulate Impact Analyzer (PIA). These results are compared with the theoretical models for hypervelocity impact craters. The agreement is good at impact velocities around 15 km/s.     

The Suess-Urey mission (return of solar matter to Earth)

The Suess-Urey (S-U) mission has been proposed as a NASA Discovery mission to return samples of matter from the Sun to the Earth for isotopic and chemical analyses in terrestrial laboratories to provide a major improvement in our knowledge of the average chemical and isotopic composition of the solar system. The S-U spacecraft and sample return capsule will be placed in a halo orbit around the L1 Sun-Earth libration point for two years to collect solar wind ions which implant into large passive collectors made of ultra-pure materials. Constant Spacecraft-Sun-Earth geometries enable simple spin stabilized attitude control, simple passive thermal control, and a fixed medium gain antenna. Low data requirements and the safety of a Sun-pointed spinner, result in extremely low mission operations costs.     

基于脉冲子结构的探测器结构动力学优化设计

针对传统结构优化设计中，精细化模型求解复杂结构动响应过于耗时的问题，引入保精度、高效的脉冲子结构方法，提出一种考虑结构动力学响应的优化设计流程，并对月球探测器太阳翼结构进行优化分析，获得了太阳翼结构设计参数，有效地提高了太阳翼动力学特性指标，改善了月球探测器关键位置处的动力学环境。结果表明，脉冲子结构方法可以有效应用于航天器结构动力学优化设计，提高优化设计效率，所得优化结果对实际结构设计具有一定指导意义。     

月球探测器软着陆机构

综述了月球探测器软着陆机构的应用与发展现状。介绍了软着陆机构的性能要求和组成,并根据着陆腿结构和缓冲器种类对软着陆机构进行了分类。讨论了着陆器主体设计、着陆腿结构和缓冲器的模块化设计。阐述了着陆器发射、在轨飞行、着陆和着陆后阶段的动力学研究内容。分析了缓冲器设计、着陆机构基本构型设计,以及缓冲器与基本构型主要参数配置等关键技术,对月球探测器软着陆机构设计有一定的参考意义。     

Nucleobases and prebiotic molecules in organic residues produced from the ultraviolet photo-irradiation of pyrimidine in NH(3) and H(2)O+NH(3) ices

Although not yet identified in the interstellar medium (ISM), N-heterocycles including nucleobases-the information subunits of DNA and RNA-are present in carbonaceous chondrites, which indicates that molecules of biological interest can be formed in non-terrestrial environments via abiotic pathways. Recent laboratory experiments and ab initio calculations have already shown that the irradiation of pyrimidine in pure H(2)O ices leads to the formation of a suite of oxidized pyrimidine derivatives, including the nucleobase uracil. In the present work, NH(3):pyrimidine and H(2)O:NH(3):pyrimidine ice mixtures with different relative proportions were irradiated with UV photons under astrophysically relevant conditions. Liquid- and gas-chromatography analysis of the resulting organic residues has led to the detection of the nucleobases uracil and cytosine, as well as other species of prebiotic interest such as urea and small amino acids. The presence of these molecules in organic residues formed under abiotic conditions supports scenarios in which extraterrestrial organics that formed in space and were subsequently delivered to telluric planets via comets and meteorites could have contributed to the inventory of molecules that triggered the first biological reactions on their surfaces.