Characteristics and formation of amino acids and hydroxy acids of the Murchison meteorite.

Eight characteristics of the unique suite of amino acids and hydroxy acids found in the Murchison meteorite can be recognized on the basis of detailed molecular and isotopic analyses. The marked structural correspondence between the alpha-amino acids and alpha-hydroxy acids and the high deuterium/hydrogen ratio argue persuasively for their formation by aqueous phase Strecker reactions in the meteorite parent body from presolar, i.e., interstellar, aldehydes, ketones, ammonia, and hydrogen cyanide. The characteristics of the meteoritic suite of amino acids and hydroxy acids are briefly enumerated and discussed with regard to their consonance with this interstellar-parent body formation hypothesis. The hypothesis has interesting implications for the organic composition of both the primitive parent body and the presolar nebula.     

对于动态目标的航天器鲁棒PD+快速跟踪控制方法

摘要：针对卫星对于空间动态目标快速、稳定地跟踪、控制目标，同时考虑平台模型的不确定性、外部随机干扰、系统控制力矩与角速度约束等因素，设计PD+控制器实现对于动态目标的快速、稳定跟踪；在经典PD控制器的基础上设计控制添加项使得系统能够按照既定轨迹运动；采用变结构的手段实现系统收敛速度的提升；合理设计Lyapunov函数的结构，引出角速度、四元数的耦合项对V函数进行改良，简化系统稳定性证明与分析的过程；讨论系统最极端情形，通过对V函数上下界的讨论分析系统该情形下的稳定性；最后通过数值仿真验证所提出算法的有效性与优越性.     

Encouraging space exploration through a new application of space property rights

Two major treaties define the legal framework of space, the Outer Space and Moon Treaties. The former prevents conflict and ensures free access in space, in part by preventing property claims in space, while the latter in part established the need for sharing space resources between the developed and less developed nations. Several groups argue that this has unintentionally restrained space commerce. Discussions supporting or expanding the current legal regime are contrasted with allowing individual property rights. A normative solution is suggested for establishing property rights and establishing equity between the developed and less developed nations.     

The loneliness of the long-duration astronaut

This paper investigates the psychological implications of long duration spaceflight. Initial psychological problems associated with a heavy workload were identified during Skylab missions. Since then, most of our knowledge of psychological problems has come from experience onboard Russian spacecraft. Noted problems include anxiety, boredom, crew interactions, problems associated with isolation and confinement, and others. Efforts to alleviate or prevent these problems are discussed, as well as comparisons to similar environments such as arctic regions or submarines. As the U.S. participates in longer space missions, it will be wise to study psychological issues and to learn from our Russian counterparts.     

A Clutter Reduction Technique for Random Signal Radars

The performance of certain radars is degraded in environments with significant clutter returns, and since the clutter is signal-generated, increasing the transmitted power does not improve the situation. However, changing the pulse width and pulse period of the transmitted signal can increase the input signal-to-interference ratio. In this correspondence, the transmitted signal is made up of pulses of random waveforms and the receiver is a correlator where the reference signal extends over many pulses. An expression for input signal-to-interference ratio as a function of pulse width and period is obtained for the case of a distributed target. This expression could be maximized by any of several methods, but to further elucidate the clutter reduction technique, contour plots of the input signal-to-interference ratio are presented.     

Polar rain entry of galactic electrons into the inner heliosphere?

The understanding of the relative intensity variations in cosmic ray ions and electrons with respect to solar modulation is a grand challenge for cosmic ray modulation theory. Although effects of the heliospheric neutral sheet, gradient-curvature drifts, and merged interaction regions provide qualitative explanations for observed solar cycle variations of high energy protons and ions, these effects do not account for the anomalously high intensities of high energy galactic electrons at 22-year intervals of the solar magnetic solar cycle. From the similar modulation responses of protons and heavy ions it does not appear that cosmic ray pressure effects, dominated by protons, can account for the chargesign asymmetry of cosmic ray modulation. External factors including modulation in the heliosheath and polar linkage to the interstellar magnetic field are examined as potential causes of symmetry breaking for electron modulation with respect to the solar magnetic polarity at solar minimum.     

From Mercury to Pluto: A Common Approach to Mission Timekeeping

The successful launch of the New Horizons spacecraft for a rendezvous with Pluto and Charon and the continuing progress of the MESSENGER spacecraft toward Mercury now positions mankind to unlock mysteries of our solar system from Mercury to Pluto and beyond. Both missions, though very different in concept, use the same generic timekeeping system design. This paper explores how we maintain time on these spacecraft and how we establish on the ground the correlation between spacecraft time and Earth time. It further reviews the sub-millisecond correlation accuracy that has been demonstrated for the MESSENGER mission and the time accuracy we expect to achieve for that mission at Mercury and for the New Horizons mission at Pluto-Charon