Strategies for detection of putative life on Europa

Planned future exploration missions to the Jovian satellite Europa have a strong astrobiological motivation. Characterization of the potential habitability of the liquid water environments, and searching for life signals are the main astrobiological objectives of these missions. To meet these objectives specific strategies and instrumentation are required. Here we discuss some scenarios for the development of Europa potential biospheres. These scenarios are based on assumptions of the life similarity concept and knowledge about terrestrial life in extreme environments. Since the potential habitable environments on Europa are in the interior of the satellite it is not possibly to directly detect life. However, there are processes that link aqueous sub-surface environments with the near-surface environment, such as tectonism or magmatism. Therefore, by analysing endogenous materials that arise from the interior it is possible to make predictions about what is in the sub-surface. We propose some measurements and instrumentation for future missions to detect biosignatures on the upper layers of Europa, including the simple physico-chemical traces of metabolism to complex biomolecules or biostructures. Raman spectroscopy or biosensor technologies are the future for in situ exploration of the Solar System.     

Confocal microscopy in microgravity research.

We have studied the application and the feasibility of confocal scanning laser microscopy (CSLM) in microgravity research. Its superior spatial resolution and 3D imaging capabilities and its use of light as a probe, render this instrument ideally suited for the study of living biological material on a (sub-)cellular level. In this paper a number of pertinent biological microgravity experiments is listed, concentrating on the direct observation of developing cells and cellular structures under microgravity condition. A conceptual instrument design is also presented, aimed at sounding rocket application followed by Biorack/Biolab application at a later stage.     

Commercialization of space activities: Legal requirements constituting a basic incentive for private enterprise involvement

Commercialization of space activities requires a legal framework for private investors and entrepreneurs in order to promote and develop this sector of industry into a fully-fledged commercial enterprise. Apart from the already existing international public legal framework of space law, rules should be created to provide a level playing field for all interested parties. These rules should point to transparency of risks and liabilities and liberalization of the various space market segments. Another legal instrument will be that of dispute resolution among participants in the arena of space activities. For the more distant future the Moon Agreement should be reassessed in the light of resources exploration, management and exploitation against the background of private enterprise involvement.     

The first results from the Herschel-HIFI mission

This paper contains a summary of the results from the first years of observations with the HIFI instrument onboard ESA’s Herschel space observatory. The paper starts by outlining the goals and possibilities of far-infrared and submillimeter astronomy, the limitations of the Earth’s atmosphere, and the scientific scope of the Herschel-HIFI mission. The presentation of science results from the mission follows the life cycle of gas in galaxies as grouped into five themes: Structure of the interstellar medium, First steps in interstellar chemistry, Formation of stars and planets, Solar system results and Evolved stellar envelopes. The HIFI observations paint a picture where the interstellar medium in galaxies has a mixed, rather than a layered structure; the same conclusion may hold for protoplanetary disks. In addition, the HIFI data show that exchange of matter between comets and asteroids with planets and moons plays a large role. The paper concludes with an outlook to future instrumentation in the far-infrared and submillimeter wavelength ranges.     

Geometric problem solving with strings and pins

Humans solve spatial and abstract problems more easily if these can be visualized and/or physically manipulated. We analyze the domain of geometric problem solving from a cognitive perspective and identify several levels of domain abstraction that interact in the problem solving process. We discuss the roles of physical manifestations of spatial configurations, their manipulation, and their perception for understanding problem solving processes. We propose an extension of the classical problem solving repertoire of constructive geometry to approach certain problems more directly than under the compass-and-straightedge paradigm. Specifically, we introduce strings and pins as helpful metaphors for a generalization of the constructive geometry approach. We present classical problems from spatial problem solving to illustrate the ‘strings and pins’ paradigm. Three case studies are discussed: strings-and-pins solutions to (i) the ellipse construction problem; (ii) the shortest path problem; and (iii) the angle trisection problem. Comparisons to formal solutions are drawn. Differences and similarities between the compass-and-straightedge paradigm and the strings-and-pins paradigm are analyzed. Features and limitations of constructive and depictive geometry as well as implications for computational approaches are discussed. The strings-and-pins domain is shown to be more general and less restrictive than the compass-and-straightedge domain.     

Review of state of the art in smart rotor control research for wind turbines

This article presents a review of the state of the art and present status of active aeroelastic rotor control research for wind turbines. Using advanced control concepts to reduce loads on the rotor can offer great reduction to the total cost of wind turbines. With the increasing size of wind turbine blades, the need for more sophisticated load control techniques has induced the interest for locally distributed aerodynamic control systems with build-in intelligence on the blades. Such concepts are often named in popular terms ‘smart structures’ or ‘smart rotor control’. The review covers the full span of the subject, starting from the need for more advanced control systems emerging from the operating conditions of modern wind turbines and current load reduction control capabilities. An overview of available knowledge and up-to date progress in application of active aerodynamic control is provided, starting from concepts, methods and achieved results in aerospace and helicopter research. Moreover, a thorough analysis on different concepts for smart rotor control applications for wind turbines is performed, evaluating available options for aerodynamic control surfaces, actuators (including smart materials), sensors and control techniques. Next, feasibility studies for wind turbine applications, preliminary performance evaluation and novel computational and experimental research approaches are reviewed. The potential of load reduction using smart rotor control concepts is shown and key issues are discussed. Finally, existing knowledge and future requirements on modeling issues of smart wind turbine rotors are discussed. This study provides an overview of smart rotor control for wind turbines, discusses feasibility of future implementation, quantifies key parameters and shows the challenges associated with such an approach.     

一种基于不确定性全寿命周期仿真的分离模块航天器评估方法(英文)

为了对新概念分离模块航天器进行全面评估,本文提出了一种基于不确定性全寿命周期仿真的评估方法。首先,对分离模块航天器术语和体系结构进行了阐述,对评价准则进行了定义,确定以风险调节全寿命周期成本和净收益现值的期望值和方差作为评价指标。其次,对分离模块航天器概念设计阶段学科模型进行了介绍,以此为基础对全寿命周期成本模型和净收益现值模型进行了详细讨论。再次,对全寿命周期不确定性因素进行了分析,并采用概率论进行了数学建模。然后,对全寿命周期仿真过程时序进行了分析,采用面向对象建模的方法对仿真模型进行了建模;仿真模型集成了仿真对象的不确定性模型,能够随着全寿命周期仿真演进对仿真对象的不确定性状态进行动态演化,以此为基础构建了基于不确定性全寿命周期仿真评估平台。最后,基于该评估方法对虚拟对地遥感分离模块航天器方案进行讨论,结果表明在考虑不确定性因素影响下,模块分离方案和分批发射方案对成本与收益有很大影响,且分离模块航天器比其对应传统单颗航天器更有优势。     

Nitrogen incorporation in CH(4)-N(2) photochemical aerosol produced by far ultraviolet irradiation

Nitrile incorporation into Titan aerosol accompanying hydrocarbon chemistry is thought to be driven by extreme UV wavelengths (λ<120?nm) or magnetospheric electrons in the outer reaches of the atmosphere. Far UV radiation (120-200?nm), which is transmitted down to the stratosphere of Titan, is expected to affect hydrocarbon chemistry only and not initiate the formation of nitrogenated species. We examined the chemical properties of photochemical aerosol produced at far UV wavelengths, using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), which allows for elemental analysis of particle-phase products. Our results show that aerosol formed from CH(4)/N(2) photochemistry contains a surprising amount of nitrogen, up to 16% by mass, a result of photolysis in the far UV. The proportion of nitrogenated organics to hydrocarbon species is shown to be correlated with that of N(2) in the irradiated gas. The aerosol mass greatly decreases when N(2) is removed, which indicates that N(2) plays a major role in aerosol production. Because direct dissociation of N(2) is highly improbable given the immeasurably low cross section at the wavelengths studied, the chemical activation of N(2) must occur via another pathway. Any chemical activation of N(2) at wavelengths >120?nm is presently unaccounted for in atmospheric photochemical models. We suggest that reaction with CH radicals produced from CH(4) photolysis may provide a mechanism for incorporating N into the molecular structure of the aerosol. Further work is needed to understand the chemistry involved, as these processes may have significant implications for how we view prebiotic chemistry on early Earth and similar planets.     

On the Detectability and Use of Normal Modes for Determining Interior Structure of Mars

The InSight mission to Mars is well underway and will be the first mission to acquire seismic data from a planet other than Earth. In order to maximise the science return of the InSight data, a multifaceted approach will be needed that seeks to investigate the seismic data from a series of different frequency windows, including body waves, surface waves, and normal modes. Here, we present a methodology based on globally-averaged models that employs the long-period information encoded in the seismic data by looking for fundamental-mode spheroidal oscillations. From a preliminary analysis of the expected signal-to-noise ratio, we find that normal modes should be detectable during nighttime in the frequency range 5–15 mHz. For improved picking of (fundamental) normal modes, we show first that those are equally spaced between 5–15 mHz and then show how this spectral spacing, obtained through autocorrelation of the Fourier-transformed time series can be further employed to select normal mode peaks more consistently. Based on this set of normal-mode spectral frequencies, we proceed to show how this data set can be inverted for globally-averaged models of interior structure (to a depth of \(\sim 250~\mbox{km}\)), while simultaneously using the resultant synthetically-approximated normal mode peaks to verify the initial peak selection. This procedure can be applied iteratively to produce a “cleaned-up” set of spectral peaks that are ultimately inverted for a “final” interior-structure model. To investigate the effect of three-dimensional (3D) structure on normal mode spectra, we constructed a 3D model of Mars that includes variations in surface and Moho topography and lateral variations in mantle structure and employed this model to compute full 3D waveforms. The resultant time series are converted to spectra and the inter-station variation hereof is compared to the variation in spectra computed using different 1D models. The comparison shows that 3D effects are less significant than the variation incurred by the difference in radial models, which suggests that our 1D approach represents an adequate approximation of the global average structure of Mars.