Which solar EUV indices are best for reconstructing the solar EUV irradiance?

The solar EUV irradiance is of key importance for space weather. Most of the time, however, surrogate quantities such as EUV indices have to be used by lack of continuous and spectrally resolved measurements of the irradiance. The ability of such proxies to reproduce the irradiance from different solar atmospheric layers is usually investigated by comparing patterns of temporal correlations. We consider instead a statistical approach. The TIMED/SEE experiment, which has been continuously operating since February 2002, allows for the first time to compare in a statistical manner the EUV spectral irradiance to five EUV proxies: the sunspot number, the f10.7, Ca K, and Mg II indices, and the He I equivalent width.     

The Emergence of Life

The Rosetta observations have greatly advanced our knowledge of the cometary nucleus and its immediate environment. However, constraints on the mission (both planned and unplanned), the only partially successful Philae lander, and other instrumental issues have inevitably resulted in open questions. Surprising results from the many successful Rosetta observations have also opened new questions, unimagined when Rosetta was first planned. We discuss these and introduce several mission concepts that might address these issues. It is apparent that a sample return mission as originally conceived in the 1980s during the genesis of Rosetta would provide many answers but it is arguable whether it is technically feasible even with today’s technology and knowledge. Less ambitious mission concepts are described to address the suggested main outstanding scientific goals.

     

Organic chemistry in Titan's atmosphere: new data from laboratory simulations at low temperature.

Many experiments have already been carried out to simulate organic chemistry on Titan, the largest satellite of Saturn. They can provide fruitful information on the nature of minor organic constituents likely to be present in Titan's atmosphere, both in gas and aerosol phases. Indeed, all the organic compounds but one already detected in Titan's atmosphere have been identified in simulation experiments. The exception, C4N2, as well as other compounds expected in Titan from theoretical modeling, such as other N-organics, and polyynes, first of all C6H2, have never been detected in experimental simulation thus far. All these compounds are thermally unstable, and the temperature conditions used during the simulation experiments were not appropriate. We have recently started a new program of simulation experiments with temperature conditions close to that of Titan's environment. It also uses dedicated analytical techniques and procedures compatible with the analysis of organics only stable at low temperatures, as well solid products of low stability in the presence of O2 and H2O. Spark discharge of N2-CH4 gas mixtures was carried out at low temperature in the range 100-150 K. Products were analysed by FTIR, GC and GC-MS techniques. GC-peaks were identified by their mass spectrum, and, in most cases, by comparison of the retention time and mass spectrum with standard ones. We report here the first detection in Titan simulation experiments of C6H2 and HC5N. Their abundance is a few percent relative to C4H2 and HC3N, respectively. Preliminary data on the solid products indicate an elemental composition corresponding to (H11C11N)n. These results open new prospects in the modeling of Titan's haze making.     

Regulative development of Xenopus laevis in microgravity.

To test whether gravity is required for normal amphibian development, Xenopus laevis females were induced to ovulate aboard the orbiting Space Shuttle. Eggs were fertilized in vitro, and although early embryonic stages showed some abnormalities, the embryos were able to regulate and produce nearly normal larvae. These results demonstrate for the first time that a vertebrate can ovulate in the virtual absence of gravity, and that the eggs can develop to a free-living stage.     

导航星座整网自主定轨的动力学短弧段伪逆平差法

针对传统静态自由网平差进行自主定轨存在的秩亏问题，提出一种卫星动力学短弧段定轨和自由网伪逆平差理论相结合的自主定轨算法。该算法以导航星座星间链路(ISL)双向测距为基础，利用伪逆平差法，解决整网位置解算起算数据不足带来的秩亏问题；同时，利用轨道动力学建立不同历元之间状态转移关系，解决单历元平差无法对速度分量进行有效估计的问题。仿真结果表明，自主运行90天，平均用户测距精度（URE）小于1 m（2σ），优于导航星座自主运行指标要求，验证了本文算法的有效性。     

Interstellar Mapping and Acceleration Probe (IMAP): A New NASA Mission

The Interstellar Mapping and Acceleration Probe (IMAP) is a revolutionary mission that simultaneously investigates two of the most important overarching issues in Heliophysics today: the acceleration of energetic particles and interaction of the solar wind with the local interstellar medium. While seemingly disparate, these are intimately coupled because particles accelerated in the inner heliosphere play critical roles in the outer heliospheric interaction. Selected by NASA in 2018, IMAP is planned to launch in 2024. The IMAP spacecraft is a simple sun-pointed spinner in orbit about the Sun-Earth L1 point. IMAP’s ten instruments provide a complete and synergistic set of observations to simultaneously dissect the particle injection and acceleration processes at 1 AU while remotely probing the global heliospheric interaction and its response to particle populations generated by these processes. In situ at 1 AU, IMAP provides detailed observations of solar wind electrons and ions; suprathermal, pickup, and energetic ions; and the interplanetary magnetic field. For the outer heliosphere interaction, IMAP provides advanced global observations of the remote plasma and energetic ions over a broad energy range via energetic neutral atom imaging, and precise observations of interstellar neutral atoms penetrating the heliosphere. Complementary observations of interstellar dust and the ultraviolet glow of interstellar neutrals further deepen the physical understanding from IMAP. IMAP also continuously broadcasts vital real-time space weather observations. Finally, IMAP engages the broader Heliophysics community through a variety of innovative opportunities. This paper summarizes the IMAP mission at the start of Phase A development.