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大气湍流极大限制了地基大口径望远镜观测天文目标图像的空间分辨率.根据最大似然估计原理,提出了用实际光学带宽约束的可有效减小天文观测图像中大气湍流影响的盲反卷积方法,通过共轭梯度优化算法使卷积误差函数趋向最小.建立了望远镜光学系统参数和图像频域带宽的关系,采用变量正性约束、点扩散函数带宽有限约束,提高算法的收敛性.为避免图像处理中有效傅立叶变换频率超出截止频率,要求采集望远镜焦面图像时单个成像单元(如CCD像素单元)应小于四分之一衍射斑直径.算法中未用目标支持域约束,所提出的方法适用于全视场天文图像恢复.用计算机模拟和对实际天文目标双鱼座图像数据的恢复结果验证了所提出方法的有效性. 相似文献
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相位差法波前探测是利用焦面和已知像差函数及像差尺度的离焦位置上同时采集的一对短曝光图像,通过最优化方法使代价函数最小化,从而得到目标和波前相位估计值的渡前探测方法.本文通过计算机模拟了像差函数为离焦像差的情况下,经相位差法波前探测成像系统后在焦面和离焦面上采集得到的图像强度分布,采用有限内存拟牛顿法(LFBGS)对模拟图像进行数值求解,实现了渡前相位的重构和对面源目标的重建;由于在实际应用中测量误差和机械加工带来的离焦量偏差是不可避免的,因此在模拟实验中就离焦量尺度不精确的情况进行了分析. 相似文献
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斑点干涉成像技术是克服大气湍流影响,提高地面大口径望远镜分辨本领的有效途径之一。该技术利用斑点相机拍摄一系列的短曝光像,使得大气湍流冻结,再经过图像处理获得高分辨率重建像。该技术设备简单,易于实现,很快在观测天文学中得到了广泛的应用,尤其是对双星的研究。首先回顾了天文高分辨率重建技术的发展,并介绍了相关研究成果。描述了几种典型的斑点干涉成像处理方法及其优缺点。对图像噪声类型及滤波方法进行了分析。在上海天文台1.56m望远镜上开展了双星斑点干涉观测实验,目标星等4~7mag,双星目标星等差小于2。分别采用斑点干涉术和迭代位移叠加法成功实现了双星目标的高分辨率成像,初步证明了在1.56m望远镜上进行斑点干涉成像实验,能够达到接近望远镜衍射极限的分辨率水平。 相似文献
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基于帧选择和多帧降质图像盲解卷积的自适应光学图像恢复 总被引:1,自引:0,他引:1
自适应光学系统受观测条件与自身条件的限制,通常只能对受大气湍流影响的降质图像进行部分校正.提出一种基于帧选择与多帧降质图像盲解卷积的事后处理方法进行自适应光学图像高分辨力恢复.该方法通过帧选择技术筛选出合适的多帧降质图像参与迭代盲解卷积运算,不需要除正性限制外的任何先验知识,并已应用于云南天文台1.2m望远镜61单元自适应光学系统所观测到的星体目标图像恢复中.实验结果表明:该方法可以有效补偿自适应光学系统校正残差对图像的影响,恢复出达到衍射极限的图像. 相似文献
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大气湍流理论的进展及其天文学意义(英) 总被引:2,自引:0,他引:2
传统的大气湍流理论始于大约30年前.湍流理论的发展使得天文学家对大气湍流对天文观测的影响有了很好的认识,尤其是它为天文台选址和天文高分辨率技术提供了基础.近年来新的天文观测已对传统的大气湍流理论提出了挑战,并可能给地面天文观测带来一场革命.在回顾了大气湍流理论的发展历史后对传统大气湍流理论的基本特性及其应用作了系统的综述,并介绍了新的天文观测事实以及为此而提出的新的大气湍流理论模型. 相似文献
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幸运成像技术是用于消除天文图像中大气湍流影响的高分辨率图像重建技术,传统的基于中央处理器的幸运成像算法难于实时化。利用现场可编程门阵列并行处理的优势,设计了一种基于现场可编程门阵列的幸运成像算法并构建了一个实验系统。该系统用现场可编程门阵列完成了选图、配准、叠加的全部幸运成像算法流程,所得高分辨率图像与基于传统中央处理器算法处理的结果完全相同,但幸运成像算法的处理速度比传统中央处理器的处理速度快19倍。该算法在现场可编程门阵列上的实现,为幸运成像技术的实时或准实时化提供了一种可行的方案。 相似文献
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Solar System Research - Finding and studying possible collisions of asteroids approaching the Earth requires a significant amount of computation. This paper describes the R0 program created to... 相似文献
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Magnetars are the neutron stars with the highest magnetic fields up to 1015–1016 G. It has been proposed that they are also responsible for a variety of extra-galactic phenomena, ranging from giant flares in nearby galaxies to fast radio bursts. Utilizing a relativistic mean field model and a variable magnetic field configuration, we investigate the effects of strong magnetic fields on the equation of state and anisotropy of pressure of magnetars. It is found that the mass and radius of low-mass magnetars are weakly enhanced under the action of the strong magnetic field, and the anisotropy of pressure can be ignored. Unlike other previous investigations, the magnetic field is unable to violate the mass limit of the neutron stars. 相似文献
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P. Maltby 《Solar physics》1972,26(1):76-82
Observations of the penumbral intensity of sunspots in 13 wavelength regions are presented. In 4 wavelength regions 54 sunspots are measured. In the other wavelength regions the number of sunspots considered ranges from 3–19.The penumbral intensity alters with position within the spot. This intensity variation is found to be comparable with the change in intensity from one spot to another. The penumbral intensity is found to be independent of spot size in the sample considered.The penumbra model of Kjeldseth Moe and Maltby (1969) with = 0.055 is supported by the measurements. 相似文献
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Many asteroids with a semimajor axis close to that of Mars have been discovered in the last several years. Potentially some of these could be in 1:1 resonance with Mars, much as are the classic Trojan asteroids with Jupiter, and its lesser-known horseshoe companions with Earth. In the 1990s, two Trojan companions of Mars, 5261 Eureka and 1998 VF31, were discovered, librating about the L5 Lagrange point, 60° behind Mars in its orbit. Although several other potential Mars Trojans have been identified, our orbital calculations show only one other known asteroid, 1999 UJ7, to be a Trojan, associated with the L4 Lagrange point, 60° ahead of Mars in its orbit. We further find that asteroid 36017 (1999 ND43) is a horseshoe librator, alternating with periods of Trojan motion. This asteroid makes repeated close approaches to Earth and has a chaotic orbit whose behavior can be confidently predicted for less than 3000 years. We identify two objects, 2001 HW15 and 2000 TG2, within the resonant region capable of undergoing what we designate “circulation transition”, in which objects can pass between circulation outside the orbit of Mars and circulation inside it, or vice versa. The eccentricity of the orbit of Mars appears to play an important role in circulation transition and in horseshoe motion. Based on the orbits and on spectroscopic data, the Trojan asteroids of Mars may be primordial bodies, while some co-orbital bodies may be in a temporary state of motion. 相似文献
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In the text-books of astronomy, sections generally related to the Moon deal with the orbital elements of the Earth-Moon system such asa, e, i, ,
and the time of perigee passage. While the MEAN of the first of the three elements do not vary, mean longitude of the ascending node-mean longitude of the lunar perigee and the time of perigee passage undergoes secular as well as periodic changes due predominantly to the action of the Sun's gravitational attraction. While to a certain degree, explanations related to the calculation of the lunar orbit parameters are given, not a single graphical representation of these short- or long-periodic changes are presented. We allow the number of data related to these periodic changes must cover a large span of time; and if regression of the line of nodes or advances of the line of apses are to be graphically seen, data covering 18.61 and 8.85 yr, respectively, are needed. In this work we particularly aim at the graphical representation of the periodic changes of the line of nodes. 相似文献
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