近代天文圆顶发展概况

综述了国内外天文圆顶的各种设计方案，比较了各种方案的性能，并介绍了为改善圆顶性能，降低造价进行的相关研究，以及为下一代巨型地面望远镜圆顶进行的预研究．结合目前正在研制的大天区多目标光纤光谱望远镜——LAMOST，简述了我国LAMOST望远镜圆顶的设计方案及其相关研究的概况。     

一种基于AS-Ⅰ总线的圆顶随动系统

介绍了一种采用AS-Ⅰ现场总线技术进行位置检测的望远镜圆顶随动方法.该方法采用断续跟踪的方式,不但安装和维护简单,而且具有运行时震动小等特点.给出了由望远镜转动中心与圆顶球心不重合引起的偏差的计算公式,并对其进行了分析.     

兴隆2.16米望远镜圆顶吊装通道通风研究

圆顶引起望远镜附近的大气湍流,造成望远镜成像质量与观测精度下降,较差的圆顶视宁度浪费了优秀台址的观测条件。圆顶通风是大型望远镜圆顶设计中必不可少的部分,可以有效解决圆顶视宁度问题。为了减小兴隆2.16 m望远镜圆顶视宁度对观测的影响,将圆顶吊装通道改造为通风口,并使用计算流体动力学软件对通风效果进行分析。分析结果表明,将圆顶吊装通道改造为通风口可以提高圆顶内外热平衡速率,使圆顶内空气更稳定,从而降低圆顶视宁度对观测的影响。根据通风效果模拟结果,可对通风策略进行优化设计。圆顶通风的研究可为2.16 m望远镜圆顶通风改造提供参考依据,以提高望远镜成像质量和观测效率。     

丽江2.4米望远镜的圆顶侧窗自动化控制系统

丽江2.4 m望远镜的圆顶采用方位随动和滑动式天窗的超半球结构,起初为改善因圆顶和望远镜终端电子设备引起的内外大气湍流,设计了大面积的多组机械式侧窗。但由于高平台手动操作危险、缓慢、不精确且易损坏,为实现侧窗稳定的多组自动控制,开发了基于STM32板的嵌入式圆顶侧窗自动控制系统,利用WiFi模块、串口模块和手柄实现侧窗的远程和多通道控制。同时结合气象数据、圆顶位置信息等使系统能根据气象阈值进行预警、自动开合,并尽量减小风对望远镜振动的影响。侧窗控制系统的设计可满足上层系统集成的需要。该系统稳定可靠,能满足侧窗的自主运行与人为控制。     

基于ASCOM及PLC的随动天文圆顶控制

四川稻城县无名山址点是云南天文台新近选定的天文台址。为实现在无名山50 cm光学望远镜开展远程自动观测,需要对圆顶进行远程自动控制驱动开发。基于天文公共对象模型(Astronomy Common Object Model, ASCOM)标准,采用Modbus/TCP协议连接可编程控制器(Programable Logical Controller, PLC),实现了圆顶的自动控制。重点介绍了圆顶控制原理和实现方法,结果表明,圆顶控制系统具有融合度高、使用方便的特点,满足远程自动观测的需求,对于中小型观测系统具有一定的借鉴意义。     

用于测量圆顶视宁度的微温脉动仪的研制

为评价云南天文台丽江2.4m望远镜的圆顶视宁度,研制了一种能测量温度、气压和微温脉动的仪器。在天文圆顶附近,望远镜前方光路上,放置几组微温传感器,可以测得圆顶附近影响天文观测的湍流强度的分布情况。介绍了这套仪器的基本原理,电路设计,程序设计,实验定标以及一个简单的测试。     

1.56m望远镜CCD照相机平场检验初步结果

利用1.56m望远镜圆顶平场和天空平场和天空平场的资料，通过对各种滤光片得到的平场内各区域的统计，研究了圆顶平场之间、天空平场之间以及天空平和圆顶平场之间的差异。观测资料分析结果表明，圆顶平场之间相互一致，天空平场之间也相互一致。误差小于1％，除B渡光片之外，在一定范围内圆顶平场和天空平场之间最大差异均小于1％。还给出了一些做好圆顶平场和天空平场的建议。     

阻导风板及其在NVST上的测试结果

太阳望远镜采用全开式圆顶有许多好处,但是此时风对望远镜产生比较大的扰动。为了减少风对望远镜的影响,设计了阻导风板,并在实际应用中得到了很好的结果。全面介绍了阻导风板的原理、结构,并给出了设计要点及在1m红外太阳望远镜（NewVacuum Solar Telescope,NVST）上的实测结果。     

基于ASCOM和Modbus/TCP协议的天文圆顶控制系统

圆顶是天文望远镜系统的重要外围设备,随着望远镜技术的发展,圆顶控制技术得到不断进步。为实现云南天文台自动差分像运动大气视宁度监测仪完全自动化,开发了一套基于ASCOM和Modbus/TCP协议的圆顶控制系统。结合ASCOM天文技术标准和Modbus/TCP协议规范,详细介绍了系统的结构原理和实现方法。实测结果表明,系统具有较好的稳定性和兼容性,完全满足自动观测的需求,为中小型天文望远镜圆顶设计提供了经验和方法。     

云南天文台1.2米望远镜的圆顶自动化控制系统

圆顶的自动化控制对提高观测数据质量和减轻观测人员工作量具有重要意义。针对云南天文台1.2 m望远镜的圆顶特殊结构——两个半球向两侧平移打开、胶轮摩擦驱动旋转,采用嵌入式控制板现场控制、有线以太网远程通讯的架构,研制了圆顶自动化控制系统,嵌入式控制板采用运行Linux系统的FL2440,圆顶位置检测采用8个霍尔探头、3个磁钢相结合的方式,达到了15°的位置分辨率,列出较详细的控制指令集。经过两个月的试运行,结果表明:系统安全、稳定、可靠,满足日常观测的需求。     

Impact tectonics in the core of the Vredefort dome,South Africa: Implications for central uplift formation in very large impact structures

Abstract— The 80 km wide Vredefort dome presents a unique opportunity to investigate the deep levels of the central uplift of a very large impact structure. Exposure of progressively older strata in the collar of the dome and of progressively higher‐grade metamorphic rocks toward its center is consistent with differential uplift; however, the deepest levels exposed correspond to pre‐impact midcrust, rather than lower crust, as has been suggested previously. Pre‐impact Archean gneissic fabrics in the core of the dome are differentially rotated, with the angle of rotation increasing sharply at a distance of ?16–19 km from the center. The present asymmetric dips of the collar strata, with layering dipping outward at moderate angles in the southeastern sector but being overturned and dipping inward in the northwestern sector, and the eccentric distribution of the pre‐impact metamorphic isograds around the core of the dome can be reconciled with symmetric rotation of an initially obliquely NW‐dipping target sequence during central uplift formation. The rocks in the core of the dome lack distinctive megablocks or large‐slip‐magnitude faults such as have been described in other central uplifts. We suggest that the large‐scale coherent response of these rocks to the central uplift formation could have been accommodated by small‐scale shear and/or rotation along pervasive pseudotachylitic breccia vein‐fractures.     

GPS接收机天线相位中心偏差的检测

GPS接收机天线相位中心偏差是指GPS天线接收卫星信号的电气中心与基机械几何中心之差。在高精度测量中，这是不容忽视的。讨论了采用基线测量相对测定法确定天线相位中心在水平和垂直方向上的偏差的原理和方法，并给出了测量结果及建议。     

Parametric excitation of a high altitude gravity gradient satellite

Attitude dynamics of a gravity oriented satellite in the presence of solar radiation pressure is examined. It is shown that even with a small offset between the satellite center of mass and center of pressure, significant pointing errors may result from the parametric excitation of the attitude motion by the radiation pressure. The phenomenon is illustrated through the analysis of a simple configuration involving a spherical shaped satellite possessing a nonspherical but axisymmetric mass distribution.     

Identification,distribution and significance of lunar volcanic domes

Over 300 previously unrecognized volcanic domes were identified on Lunar Orbiter photographs using the following criteria: (1) the recognition of land forms on the Moon similar in morphology to terrestrial volcanic domes, (2) structural control, (3) geomorphic discordance, and (4) the recognition of land forms modified by dome-like swellings. Many terrestrial volcanic domes are similar in morphology to lunar domes. This analogy suggests that some lunar hills are in fact extrusive volcanic domes. Many of the domes identified in this paper seem to be related to basins and craters, and with the exception of local tectonic grid control few domes are related to any observable Moon-wide pattern. Domes are not uniquely found on maria. Dome formation probably spans a wide range of lunar time and activity in areas where domes are located may be continuing to the present as revealed by the close correlation of dome distribution with the distribution of lunar transient events. The overall morphology of a lunar dome is a poor indicator of the composition of the rock that forms the dome. Contribution No. 33 Planetary Geology Group, University of New Mexico.     

Morphology and origin of an evaporitic dome in the eastern Tithonium Chasma, Mars

A 3.4 km-high, dome-shaped upland in eastern Tithonium Chasma (TC) coincides with areas containing abundant surface signatures of the sulphate mineral kiersite, as identified by the OMEGA image spectrometer. The dome has surface features on its summit, flanks, and at its base that were apparently formed by liquid water released from melting ice. These features include a variety of karst landforms as well as erosive and depositional landforms. The surface of the dome has few impact craters, which suggests a relatively young age for the dome. Rock layers in the dome are laterally continuous but are visibly deformed in some places. The mineralogical and structural characteristics of the dome suggest that it was emplaced as a diapir, similar to many salt diapirs on Earth.     

Random processes as a cause of the lunar asymmetry

The offset of the center of mass of the Moon from its center of figure together with moment of inertia differences are explainable by a lunar crust of randomly varying thickness. The necessity of postulating a method of preferential material transport into a particular lunar hemisphere to explain the lunar asymmetry is eliminated.This paper represents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS 7-100, sponsored by the National Aeronautics and Space Administration.     

Contribution of the mantle to the lunar asymmetry

Evidence of three kinds indicates a lunar compositional asymmetry: (1) mare basalts are much more abundant on the near side; (2) the incompatible rich KREEP component is mainly observed in near-side soils; and (3) materials on the far side are less dense than those of the near side, as indicated by the 2-km offset between the center of mass and center of figure. Recent models to explain the 2-km offset are based on near-side-far-side differences in the thickness of crustal units. The most widely discussed model calls for a thickness of anorthosite ～ 24 km greater on the far side than on the near side, but no satisfactory method of generating such a large difference has been proposed. We suggest that much of the offset reflects longitudinal differences in mantle composition primarily resulting from earlier (or more rapid) crystallization of the magma ocean on what is now the far-side hemisphere. As a result, the far-side mantle would be more magnesian and thus less dense than the near-side mantle. Differences in the amount of anorthosite or the amount of crustal porosity probably make relatively small contributions to the offset. We have evaluated four scenarios: (a) If the anorthositic crust initially formed a floating continent over what is now the near side, this would have provided thermal insulation that would have reduced the near-side cooling rate. (b) Crystallization of the magma ocean while the Moon was near the Earth would have resulted in heating by earthshine, thus reducing the near-side cooling rate. (c) An asymmetric bombardment could have preferentially heated the near side. (d) A suggestion by D. Stevenson, collection of metal from the magma ocean in one hemisphere would have pushed the unmelted “core” into an asymmetric position, and resulted in earlier magma ocean crystallization in the deeper hemisphere. Our assessment is that the asymmetric “core” hypothesis is the most plausible, that the floating continent mechanism is possible, and that the Earthshine and symmetric bombardment mechanisms are not viable. An attractive feature of the asymmetric- mantle model is that it also accounts for the asymmetries in the distribution of KREEP and mare basalts. More rapid crystallization of the far side would leave urKREEP, the last dregs of the magma ocean, concentrated under the near-side crust, thus leading to the observed tendency for KREEP to be found on the near side surface. Further, the concentration of urKREEP-associated radiactive elements on the near side would result in a much lower rate of conductive cooling of the near-side mantle and thus a much longer period of basalt extrusion on the near side. The formation of basalts would also be enhanced by the presence of more fusible materials in the near-side mantle.     

Open‐foldable domes with high‐tension textile membranes: The GREGOR dome

Double layers of high‐tensioned textile membranes were applied to the completely open‐foldable dome for the GREGOR telescope for the first time. Simultaneous climate measurements inside and outside the dome have proven the thermalinsulating capability of this double‐layer construction. The GREGOR dome is the result of the continuation of the ESO research on open‐foldable domes with textile structures, followed by the research for the DOT dome with high‐tensioned textile membranes. It cleared the way to extreme stability required for astronomical practice on high mountain sites with heavy storms and ice formation. The storm Delta with 245 km/h 1‐minute mean maximum at the location of the GREGOR caused no problems, nor did other storms afterwards. Opening and closing experiences up to wind speeds of 90 km/h were without problems. New technical developments were implemented and tested at the GREGOR dome, opening the way for application to much larger domes up to the 30 m diameter‐class range (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of density inhomogeneity on YORP: The case of Itokawa

The effect of density inhomogeneity on the YORP effect for a given shape model is investigated. A density inhomogeneity will cause an offset between the center of figure and the center of mass and a re-orientation of the principal axes away from those associated with the shape alone. Both of these effects can alter the predicted YORP rate of change in angular velocity and obliquity. We apply these corrections to the Itokawa shape model and find that its YORP angular velocity rate is sensitive to offsets between its center of mass and center of figure, with a shift on the order of 15 m being able to change the sign of the YORP effect for that asteroid. Given the non-detection of YORP for Itokawa as of 2008, this can shed light on the density distribution within that body. The theory supports a shift of the asteroid center of mass towards Itokawa's neck region, where there is an accumulation of finer gravels, or towards the asteroid's “Head” region. Detection of the YORP effect for Itokawa should provide some strong constraints on its density distribution. This theory could also be applied to asteroids visited by future spacecraft to constrain density inhomogeneities.     

Evidence for convection in planetary interiors from first-order topography

Center of mass-center of figure offsets are known for the Earth, Moon, Mars and Venus. Such an offset requires a density distribution asymmetric about the center of mass. Observational evidence indicates that the terrestrial, lunar and Martian offsets result from crusts of variable thickness rather than lateral density inhomogeneities and that the thickness variations are more likely caused by internal convection than impact.Paper dedicated to Professor Harold C. Urey on the occasion of his 80th birthday on 29 April, 1973.