The New Horizons Pluto Kuiper Belt Mission: An Overview with Historical Context

NASA’s New Horizons (NH) Pluto–Kuiper Belt (PKB) mission was selected for development on 29 November 2001 following a competitive selection resulting from a NASA mission Announcement of Opportunity. New Horizons is the first mission to the Pluto system and the Kuiper belt, and will complete the reconnaissance of the classical planets. New Horizons was launched on 19 January 2006 on a Jupiter Gravity Assist (JGA) trajectory toward the Pluto system, for a 14 July 2015 closest approach to Pluto; Jupiter closest approach occurred on 28 February 2007. The ～400 kg spacecraft carries seven scientific instruments, including imagers, spectrometers, radio science, a plasma and particles suite, and a dust counter built by university students. NH will study the Pluto system over an 8-month period beginning in early 2015. Following its exploration of the Pluto system, NH will go on to reconnoiter one or two 30–50 kilometer diameter Kuiper Belt Objects (KBOs) if the spacecraft is in good health and NASA approves an extended mission. New Horizons has already demonstrated the ability of Principal Investigator (PI) led missions to use nuclear power sources and to be launched to the outer solar system. As well, the mission has demonstrated the ability of non-traditional entities, like the Johns Hopkins Applied Physics Laboratory (JHU/APL) and the Southwest Research Institute (SwRI) to explore the outer solar system, giving NASA new programmatic flexibility and enhancing the competitive options when selecting outer planet missions. If successful, NH will represent a watershed development in the scientific exploration of a new class of bodies in the solar system—dwarf planets, of worlds with exotic volatiles on their surfaces, of rapidly (possibly hydrodynamically) escaping atmospheres, and of giant impact derived satellite systems. It will also provide other valuable contributions to planetary science, including: the first dust density measurements beyond 18 AU, cratering records that shed light on both the ancient and present-day KBO impactor population down to tens of meters, and a key comparator to the puzzlingly active, former dwarf planet (now satellite of Neptune) called Triton which is in the same size class as the small planets Eris and Pluto.     

The Geology of Mercury: The View Prior to the MESSENGER Mission

Mariner 10 and Earth-based observations have revealed Mercury, the innermost of the terrestrial planetary bodies, to be an exciting laboratory for the study of Solar System geological processes. Mercury is characterized by a lunar-like surface, a global magnetic field, and an interior dominated by an iron core having a radius at least three-quarters of the radius of the planet. The 45% of the surface imaged by Mariner 10 reveals some distinctive differences from the Moon, however, with major contractional fault scarps and huge expanses of moderate-albedo Cayley-like smooth plains of uncertain origin. Our current image coverage of Mercury is comparable to that of telescopic photographs of the Earth’s Moon prior to the launch of Sputnik in 1957. We have no photographic images of one-half of the surface, the resolution of the images we do have is generally poor (∼1 km), and as with many lunar telescopic photographs, much of the available surface of Mercury is distorted by foreshortening due to viewing geometry, or poorly suited for geological analysis and impact-crater counting for age determinations because of high-Sun illumination conditions. Currently available topographic information is also very limited. Nonetheless, Mercury is a geological laboratory that represents (1) a planet where the presence of a huge iron core may be due to impact stripping of the crust and upper mantle, or alternatively, where formation of a huge core may have resulted in a residual mantle and crust of potentially unusual composition and structure; (2) a planet with an internal chemical and mechanical structure that provides new insights into planetary thermal history and the relative roles of conduction and convection in planetary heat loss; (3) a one-tectonic-plate planet where constraints on major interior processes can be deduced from the geology of the global tectonic system; (4) a planet where volcanic resurfacing may not have played a significant role in planetary history and internally generated volcanic resurfacing may have ceased at ∼3.8 Ga; (5) a planet where impact craters can be used to disentangle the fundamental roles of gravity and mean impactor velocity in determining impact crater morphology and morphometry; (6) an environment where global impact crater counts can test fundamental concepts of the distribution of impactor populations in space and time; (7) an extreme environment in which highly radar-reflective polar deposits, much more extensive than those on the Moon, can be better understood; (8) an extreme environment in which the basic processes of space weathering can be further deduced; and (9) a potential end-member in terrestrial planetary body geological evolution in which the relationships of internal and surface evolution can be clearly assessed from both a tectonic and volcanic point of view. In the half-century since the launch of Sputnik, more than 30 spacecraft have been sent to the Moon, yet only now is a second spacecraft en route to Mercury. The MESSENGER mission will address key questions about the geologic evolution of Mercury; the depth and breadth of the MESSENGER data will permit the confident reconstruction of the geological history and thermal evolution of Mercury using new imaging, topography, chemistry, mineralogy, gravity, magnetic, and environmental data.     

Impact Cratering Theory and Modeling for the Deep Impact Mission: From Mission Planning to Data Analysis

The cratering event produced by the Deep Impact mission is a unique experimental opportunity, beyond the capability of Earth-based laboratories with regard to the impacting energy, target material, space environment, and extremely low-gravity field. Consequently, impact cratering theory and modeling play an important role in this mission, from initial inception to final data analysis. Experimentally derived impact cratering scaling laws provide us with our best estimates for the crater diameter, depth, and formation time: critical in the mission planning stage for producing the flight plan and instrument specifications. Cratering theory has strongly influenced the impactor design, producing a probe that should produce the largest possible crater on the surface of Tempel 1 under a wide range of scenarios. Numerical hydrocode modeling allows us to estimate the volume and thermodynamic characteristics of the material vaporized in the early stages of the impact. Hydrocode modeling will also aid us in understanding the observed crater excavation process, especially in the area of impacts into porous materials. Finally, experimentally derived ejecta scaling laws and modeling provide us with a means to predict and analyze the observed behavior of the material launched from the comet during crater excavation, and may provide us with a unique means of estimating the magnitude of the comet’s gravity field and by extension the mass and density of comet Tempel 1.     

The Geophysics of Mercury: Current Status and Anticipated Insights from the MESSENGER Mission

Current geophysical knowledge of the planet Mercury is based upon observations from ground-based astronomy and flybys of the Mariner 10 spacecraft, along with theoretical and computational studies. Mercury has the highest uncompressed density of the terrestrial planets and by implication has a metallic core with a radius approximately 75% of the planetary radius. Mercury’s spin rate is stably locked at 1.5 times the orbital mean motion. Capture into this state is the natural result of tidal evolution if this is the only dissipative process affecting the spin, but the capture probability is enhanced if Mercury’s core were molten at the time of capture. The discovery of Mercury’s magnetic field by Mariner 10 suggests the possibility that the core is partially molten to the present, a result that is surprising given the planet’s size and a surface crater density indicative of early cessation of significant volcanic activity. A present-day liquid outer core within Mercury would require either a core sulfur content of at least several weight percent or an unusual history of heat loss from the planet’s core and silicate fraction. A crustal remanent contribution to Mercury’s observed magnetic field cannot be ruled out on the basis of current knowledge. Measurements from the MESSENGER orbiter, in combination with continued ground-based observations, hold the promise of setting on a firmer basis our understanding of the structure and evolution of Mercury’s interior and the relationship of that evolution to the planet’s geological history.     

Mercury: A post-Mariner 10 assessment

Our knowledge of Mercury has improved dramatically since the flight of Mariner 10. The planet is probably differentiated into a large iron-rich core (75% of the total radius) and a relatively thin (600 km) silicate mantle. Although the surface of Mercury superficially resembles the Moon, there are three main differences: (1) large areas of relatively old intercrater plains, (2) a widespread (probably global) distribution of lobate scarps, and (3) a similar albedo between young smooth plains and the older mercurian highlands. The origin of Mercury's plains units is still uncertain but a volcanic origin is favored for at least large tracts of the younger smooth plains. The older intercrater plains seem to span a range of ages, large tracts of which appear to have been implaced during the period of intense bombardment. The widespread distribution of lobate scarps probably resulted from a period of global contraction relatively late in Mercury's history. This period of contraction probably resulted primarily from cooling of the lithosphere and/or core following core formation. The crater diameter density distribution on the Moon, Mars and Mercury indicates that all the terrestrial planets experienced a period of intense bombardment early in their histories and that the objects responsible for this bombardment probably belonged to the same population(s).     

复合材料在飞机上的新应用

简要介绍了复合材料在A380、波音787以及A350上的应用情况,重点介绍了波音787大型整体机身筒形件的研制。     

Mercury’s Atmosphere: A Surface-Bounded Exosphere

The existence of a surface-bounded exosphere about Mercury was discovered through the Mariner 10 airglow and occultation experiments. Most of what is currently known or understood about this very tenuous atmosphere, however, comes from ground-based telescopic observations. It is likely that only a subset of the exospheric constituents have been identified, but their variable abundance with location, time, and space weather events demonstrate that Mercury’s exosphere is part of a complex system involving the planet’s surface, magnetosphere, and the surrounding space environment (the solar wind and interplanetary magnetic field). This paper reviews the current hypotheses and supporting observations concerning the processes that form and support the exosphere. The outstanding questions and issues regarding Mercury’s exosphere stem from our current lack of knowledge concerning the surface composition, the magnetic field behavior within the local space environment, and the character of the local space environment.     

Correction to: Mission to Planet Earth: The First Two Billion Years

Space Science Reviews - The Ionospheric Connection Explorer (ICON) mission makes measurements in near-Earth space that provide knowledge of the state of the ionosphere. From the vantage of...     

A Unified Approach to Model-Reference Adaptive Systems Part I: Theory

A unified approach to model-reference adaptive control systems is presented. A linearized error equation for each adaptive system is derived about some operating point and converted into the standard form for plotting root loci. The contribution made here is to convert the selection of an adaptive technique and the choosing of adaptive coefficients for some desired system performance from a "mystical art" to standard control techniquess.     

复杂深孔的高效加工方法

当孔深超过10倍孔径时,加工出的孔一般很深。孔深达300倍径时就需要专门的技术,并采用单管钻头或双管钻头进行钻削。在加工至这些孔底部的漫长过程中,需要使用正确的运动机构、刀具配置以及合适的切削刃才能完成内腔、凹槽、螺纹和型腔的加工。支撑板技术是另一重要领域,在深孔钻削中也至关重要,现在它作为深孔加工技术的一部分也发展很快,其中就包括在该领域能实现更高性能的高质刀具的开发。     

复杂深孔的高效加工方法

复杂的深孔加工变得越来越富有挑战性。零件通常需要具有更多的特征,例如非常小的孔、内腔、不同的孔径、轮廓、凹槽、螺纹及不同的孔方向。要高效地完成此类公差很小的孔的加工,不仅需要具备丰富的经验和研发资源,而且需要良好的研发能力和应用设备,并要实质性地参与到客户的加工过程中去。     

Radar ECCM: A European Approach

The radar designer must optimize parameters for performance in electronic countermeasures (ECM) and avoid any constraints which could be exploited by ECM. ECM/electronic counter-counter measures (ECCM) strategy must take into account electromagnetic compatibility (EMC) including enemy EMC. Electronic scanning improves search performance, but also reduces ECCM performance in other ways. While electronic scanning avoids some constraints, it imposes others, particularly in the frequency domain. It is argued that simple radars of good performance may be as cost effective in ECM as more complex systems. Some examples of recent developments are given.     

To Fly to the Sun: Solar Probe Mission & Technology Challenges

To fly close to the Sun (to a perihelion of 4 solar radii) represents many unique challenges to a mission and spacecraft design. The solar probe design is a result of over two decades of studies that have allowed the evolution of both the mission and trajectory design, as well as the spacecraft configurations. During these studies some of the most significant design challenges have been the trajectory design, the spacecraft shield design, the spacecraft configuration, the telecommunications near perihelion, science instrument accommodations, and minimizing mission cost. This latter challenge (minimum cost) permeates all other design issues suggesting specific solutions consistent with this constraint. This presents the evolution and rationale that have taken place to arrive at the current design for this challenging mission.     

Managing: From Invention to Hardware

A definition of the five categories of technical effort in the Air Force; an establishment of a new subcategorization of basic research (unbounded and guided); and a discussion in detail of the following, with cross-references to like problems in industrial concerns: 1) basic research, 2) exploratory development, 3) advanced development, 4) the role of the manager, 5) the manager's desirable and undesirable traits, 6) the role of the scientist and engineer, 7) the organization, and 8) future trends.     

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.     

一种测试导弹挂飞载荷的新方法

针对导弹研制过程中挂飞载荷难以确定的现状,提出导弹挂飞载荷的一种新的测试方法.挂飞测力试验方法以天平测量技术为依托,可直接测出导弹在挂飞过程中的吊挂载荷、舵面气动载荷等,同时可对风洞试验结果和理论计算结果进行有效评估,为确定吊挂强度和舵面气动载荷等问题提供了一种直接、准确的解决方法.     

Phase-Locked Demodulator Threshold: A New Approach

In this paper the dependence of the threshold CNR of a simple phaselocked demodulator on the frequency deviation of an FM signal has been evaluated by the concept of quasi-stationary approximation. Experimental findings have been presented in support of the theoretical conclusion.     

研究Ramsey问题的计算机方法

本文阐述了一个构造Ｒａｍｓｅｙ图的算法，它可以作为寻找Ｒａｍｓｅｙ数的一个辅助工具，算法采用回溯方法，搜索极大独立集组成的堆栈。并给出了寻找Ｒａｍｓｅｙ数的一种具体的步骤。