共查询到20条相似文献，搜索用时 203 毫秒
1.
相控阵馈源(Phased array feeds, PAFs)接收机作为下一代微波接收机, 为大口径射电天文望远镜的射电干扰(Radio Frequency Interference, RFI)缓解工作带来了新的解决方法. PAFs接收机对射电望远镜焦平面的电磁波进行空域采样, 返回时域阵列信号, 使用最小方差无失真响应(Minimum Variance Distortionless Response, MVDR)波束合成器可以自适应地识别RFI的方向, 同时抑制RFI在输出信号中的功率, 从而达到提升射电望远镜灵敏度的效果. 仿真结果表明MVDR波束合成器对有源高能量的射电干扰有很强的识别能力和一定程度的缓解能力, 同时, 该波束合成器对各阵元信道中加性噪声累积引起的无源干扰有很强的抑制能力, 因此, PAFs接收机的MVDR波束合成器可以增强日益复杂电磁波环境下射电望远镜的抗干扰能力. 相似文献
2.
3.
《天文学报》2017,(5)
一直以来,射电天文装备不断得到升级和发展,以使其具有更好的观测性能,包括提高数据记录的时间和频率分辨率以及获得更高的接收和记录带宽等.然而与之形成矛盾的是:国际电信联盟(International Telecommunication Union,ITU)仅为射电天文分配了非常有限的频谱资源,导致的后果是射电观测设备不可避免地受到日益增强的非天文信号的影响,后者的来源主要是人类的通信活动和日常生活,这就构成了通常射电天文中所说的射频干扰(Radio Frequency Interference,RFI).射频干扰会降低数据质量甚至导致数据无效,对科学结果的影响越来越严重.对RFI消减的需求进行分析,总结了RFI的特性、抑制和消减的技术和方案,并介绍了一些有代表性的射电望远镜(或阵列)中采用的RFI消减方法;还分析比较了4种常用方案,即预防、预检测、预相关和后相关的优势和不足.对RFI进行准确的识别和标记是减少数据损失从而有效提高数据质量的关键,也是发展RFI消减技术的最终目的.通过研究不难发现,上述4种方案的组合运用将具有更高的实用价值.近几年来,随着高速数字信号处理和高性能计算的迅速发展,依赖大量计算的实时模式下的预检测以及离线模式下从大型望远镜阵列所产生的大规模干涉相关数据中检测RFI已经成为可能. 相似文献
4.
在射电天文观测中,射频干扰(Radio Frequency Interference, RFI)会以多种形式混入望远镜接收系统,给观测带来误判或者降低观测信噪比.近年来国内国际射电天文快速发展,国内国际大型射电望远镜和阵列先后建设,观测灵敏度大为提高,射频干扰的影响尤为突出.随着科技发展和人类活动的加剧,射频干扰日益严重且不可逆转.提出利用2维离散小波变换的方法分析射电天文观测的数据,对望远镜系统输出的时间频率序列进行小波变换,根据小波系数分离出原始信号中各分量,每个分量统计得到相应的阈值,将各分量与阈值相比较识别干扰成分并标记去除.利用该方法对实际观测数据进行了处理,结果表明该方法能够很好地标记并消减干扰信号,且提高了观测的信噪比. 相似文献
5.
6.
从海量的天文观测数据中快速搜寻罕见的快速射电暴(Fast Radio Burst, FRB)事件, 干扰缓解是其中一项关键而具有挑战的工作. 射频干扰(Radio Frequency Interference, RFI)会淹没真实的天文事件, 还会导致搜寻管线输出大量的假阳性候选体. 由于干扰来源及其种类的复杂性, 目前并没有一种通用的方法可以解决这个问题. 为了降低干扰对FRB观测搜寻的影响, 分析和研究了南山26m射电望远镜L波段观测数据中的干扰情况, 针对主要的窄带干扰和宽带干扰建立了3层次的干扰缓解处理流程, 从而有效缓解了观测数据的干扰污染情况. 将该流程嵌入到FRB色散动态谱搜寻(Dispersed Dynamic Spectra Search, DDSS)管线中, 实验结果表明, 搜寻管线的检测率和检测精度得到了进一步的提高. 该方法为FRB观测数据干扰缓解处理提供了有价值的参考. 相似文献
7.
随着频率使用率的提高, 射电天文台址地面或空间存在强电磁干扰致使望远镜接收机系统处于非线性状态. 为减少强电磁干扰的影响、提高天文观测效率, 提出了一种基于望远镜远场区域的强干扰源规避方法. 首先, 通过仿真分析确定的射电望远镜远场方向图, 结合望远镜与干扰源之间的位置关系, 分析了强电磁干扰到达射电望远镜焦点处的功率响应, 并依据接收机第2阶中频放大器性能参数, 确定射电望远镜处于非饱和状态的规避角度计算方法. 其次, 采用该方法计算分析了民航飞机对射电望远镜的影响, 若民航飞机上有主动发射的干扰源, 且不经过反射等传播现象, 当射电望远镜主波束轴偏开一定方向后, 可有效降低对射电望远镜的干扰强度. 相似文献
8.
9.
《天文研究与技术》2020,(1)
射电天文中,射频干扰问题多样而复杂,面对不同的射频干扰问题,针对不同的干扰机制,采取针对性的方法。从器件阶段消减射频干扰,可以预防射频干扰进入望远镜内部。介绍了德令哈毫米波望远镜9波束边带分离型超导接收机, 1个本振链路系统分配18路本振信号方案,针对本振链路中信号发生器的谐波信号引起的中频窄带干扰,设计了注入模拟谐波信号的测试方案,确认了干扰产生机制并得出谐波信号频率与干扰信号频率和功率的对应关系,分析并验证了谐波干扰的传输路径。为了消减谐波干扰,利用YIG滤波器可变频段的带通特性,在本振链路上滤除谐波信号,防止谐波信号耦合到接收机系统,完成了谐波干扰的消减。 相似文献
10.
11.
《Chinese Astronomy and Astrophysics》2023,47(2):335-352
Thanks to the excellent performance of FAST (Five-hundred-meter Aperture Spherical radio Telescope), the number of pulsars has increased rapidly. It is very important to analyze the physical parameters of known pulsars. The overall properties of pulsars are studied by analyzing the related physical parameters such as spatial position, period, surface magnetic flux density and so on. A large number of pulsars were detected by FAST near the galactic disk, which reflect the superiority of its detection ability. The diagram of the relationship between the period and the time derivative of period of pulsars has been updated. At present, 57 pulsars have crossed the classical “death line”, and five were discovered by FAST. Finally, the physical parameters of the binary pulsar systems are statistically analyzed, the binary pulsar systems are evolving towards the direction of low eccentricity and the decrease mass of the companion star. Moreover, 9 are located above the “spin-up line”. FAST is making China into the golden age of pulsar discovery, which will further promote the rapid development of pulsar physics. 相似文献
12.
P. C. Freire M. Kramer A. G. Lyne 《Monthly notices of the Royal Astronomical Society》2001,322(4):885-890
We present a simple, novel method for determining the orbital parameters of binary pulsars. This method works with any sort of orbital sampling, no matter how sparse, provided that information on the period derivatives is available with each measurement of the rotational period of the pulsar, and it is applicable to binary systems with nearly circular orbits. We use the technique to estimate precisely the hitherto unknown orbital parameters of two binary millisecond pulsars in the globular cluster 47 Tucanae, 47 Tuc S and T. The method can also be used more generally to make first-order estimates of the orbital parameters of binary systems using a minimal number of data. 相似文献
13.
G. Miniutti D. R. Ballantyne S. W. Allen A. C. Fabian R. R. Ross 《Monthly notices of the Royal Astronomical Society》2006,371(1):283-292
The Parkes High-Latitude pulsar survey covers a region of the sky enclosed by Galactic longitudes 220° < l < 260° and Galactic latitudes | b | < 60°. The observations have been performed using the 20-cm multibeam receiver on the Parkes 64-m radio telescope. A total of 6456 pointings of 265 s each have been collected. The system adopted provided a sensitivity limit, for long-period pulsars with 5 per cent duty cycles, of ∼0.5 mJy. Data analysis resulted in the detection of 42 pulsars of which 18 were new discoveries. Four of these belong to the class of the millisecond – or recycled – pulsars; three of these four are in binary systems. The double pulsar system J0737−3039 is among those and has been presented elsewhere. Here, we discuss the other discoveries and provide timing parameters for the objects for which we have a phase-connected solution. 相似文献
14.
Paul D. Kiel Jarrod R. Hurley Matthew Bailes James R. Murray 《Monthly notices of the Royal Astronomical Society》2008,388(1):393-415
The computation of theoretical pulsar populations has been a major component of pulsar studies since the 1970s. However, the majority of pulsar population synthesis has only regarded isolated pulsar evolution. Those that have examined pulsar evolution within binary systems tend to either treat binary evolution poorly or evolve the pulsar population in an ad hoc manner. Thus, no complete and direct comparison with observations of the pulsar population within the Galactic disc has been possible to date. Described here is the first component of what will be a complete synthetic pulsar population survey code. This component is used to evolve both isolated and binary pulsars. Synthetic observational surveys can then be performed on this population for a variety of radio telescopes. The final tool used for completing this work will be a code comprised of three components: stellar/binary evolution, Galactic kinematics and survey selection effects. Results provided here support the need for further (apparent) pulsar magnetic field decay during accretion, while they conversely suggest the need for a re-evaluation of the assumed typical millisecond pulsar formation process. Results also focus on reproducing the observed diagram for Galactic pulsars and how this precludes short time-scales for standard pulsar exponential magnetic field decay. Finally, comparisons of bulk pulsar population characteristics are made to observations displaying the predictive power of this code, while we also show that under standard binary evolutionary assumption binary pulsars may accrete much mass. 相似文献
15.
We use a new self-consistent model to derive the conversion efficiency from rotation power to γ-ray power for pulsars (εth ). Our result indicates that εth ∝τ6/7 P 2 , where τ and P are the characteristic age and period of the pulsar, which shows that although the efficiency increases with the characteristic age of the pulsar, it also depends on the pulsar period. We test our model results with the survey of high-energy γ-rays from pulsars by EGRET. Our model not only successfully explains the efficiency of the confirmed γ-ray pulsars but also explains why the γ-ray efficiency of millisecond pulsars is so low. 相似文献
16.
Xiaohu Yang H. J. Mo Frank C. van den Bosch Simone M. Weinmann Cheng Li Y. P. Jing 《Monthly notices of the Royal Astronomical Society》2005,362(2):711-726
Some massive binaries should contain energetic pulsars which inject relativistic leptons from their inner magnetospheres and/or pulsar wind regions. If the binary system is compact enough, then these leptons can initiate inverse Compton (IC) e± pair cascades in the anisotropic radiation field of a massive star. γ-rays can be produced in the IC cascade during its development in a pulsar wind region and above a shock in a massive star wind region where the propagation of leptons is determined by the structure of a magnetic field around the massive star. For a binary system with specific parameters, we calculate phase-dependent spectra and fluxes of γ-rays escaping as a function of the inclination angle of the system and for different assumptions on injection conditions of the primary leptons (their initial spectra and location of the shock inside the binary). We conclude that the features of γ-ray emission from such massive binaries containing energetic pulsars should allow us to obtain important information on the acceleration of particles by the pulsars, and on interactions of a compact object with the massive star wind. Predicted γ-ray light curves and spectra in the GeV and TeV energy ranges from such binary systems within our Galaxy and Magellanic Clouds should be observed by future AGILE and GLAST satellites and low-threshold Cherenkov telescopes, such as MAGIC, HESS, VERITAS or CANGAROO III. 相似文献
17.
脉冲星数据比对分析和可视化系统(PSRDB,URL:http://www.psrdb.net/),由FAST(Five-hundred-meter Aperture Spherical Radio Telescope)早期科学数据中心团队为快速开展脉冲星候选体比对分析和数据管理研发.通过前端数据提交页面,接收和维护来自FAST及其他研究机构的候选体数据.目前,PSRDB已收录自1967年人类发现第1颗脉冲星以来所有公开文献发表的2811颗脉冲星样本,并采集了当前主要巡天项目尚未正式发表的源和候选体,如FAST多科学目标同时扫描巡天(CRAFTS)候选体数据.基于入库基础数据,利用位置、周期、色散等参数进行比对分析,辅助科研工作者在线检索匹配已知星表数据,最后将检索匹配、比对分析结果生成图表供进一步分析.目前,PSRDB已被应用于FAST脉冲星搜寻和候选体数据管理.未来,PSRDB可在新源认证、后随观测、观测计划制定和原始数据处理流程设计等方面提供数据和工具支撑. 相似文献
18.
Simon Johnston Luciano Nicastro & Bärbel Koribalski 《Monthly notices of the Royal Astronomical Society》1998,297(1):108-116
We report on multi-epoch, multifrequency observations of 64 pulsars with high spectral and time resolution. Scintillation parameters were obtained for 49 pulsars, including 13 millisecond pulsars. Scintillation speeds were derived for all 49, which doubles the number of pulsars with speeds measured in this way. There is excellent agreement between the scintillation speed and proper motion for the millisecond pulsars in our sample using the simple assumption of a mid-placed scattering screen. This indicates that the scaleheight of scattering electrons is similar to that of the dispersing electrons. In addition, we present observations of the Vela pulsar at 14 and 23 GHz, and show that the scintillation bandwidth scales as ν3.93 over a factor of 100 in observing frequency. We show that for PSR J0742−2822, and perhaps PSR J0837−4135, the Gum nebula is responsible for the high level of turbulence along their lines of sight, contrary to previous indications. There is a significant correlation between the scintillation speeds and the product of the pulsar's period and period derivative for the 'normal' pulsars. However, we believe this to be caused by selection effects both in pulsar detection experiments and in the choice of pulsars used in scintillation studies. 相似文献
19.
Bhaswati Bhattacharyya Rajaram Nityananda 《Monthly notices of the Royal Astronomical Society》2008,387(1):273-278
We present a simple method for determination of the orbital parameters of binary pulsars, using data on the pulsar period at multiple observing epochs. This method uses the circular nature of the velocity space orbit of Keplerian motion and produces preliminary values based on two one-dimensional searches. Preliminary orbital parameter values are then refined using a computationally efficient linear least-squares fit. This method works for random and sparse sampling of the binary orbit. We demonstrate the technique on (i) the highly eccentric binary pulsar PSR J0514−4002 (the first known pulsar in the globular cluster NGC 1851) and (ii) 47 Tuc T, a binary pulsar with a nearly circular orbit. 相似文献
20.
D. R. Lorimer A. J. Faulkner A. G. Lyne R. N. Manchester M. Kramer M. A. McLaughlin G. Hobbs A. Possenti I. H. Stairs F. Camilo M. Burgay N. D'Amico A. Corongiu F. Crawford 《Monthly notices of the Royal Astronomical Society》2006,372(2):777-800
We present the discovery and follow-up observations of 142 pulsars found in the Parkes 20-cm multibeam pulsar survey of the Galactic plane. These new discoveries bring the total number of pulsars found by the survey to 742. In addition to tabulating spin and astrometric parameters, along with pulse width and flux density information, we present orbital characteristics for 13 binary pulsars which form part of the new sample. Combining these results from another recent Parkes multibeam survey at high Galactic latitudes, we have a sample of 1008 normal pulsars which we use to carry out a determination of their Galactic distribution and birth rate. We infer a total Galactic population of 30 000 ± 1100 potentially detectable pulsars (i.e. those beaming towards us) having 1.4-GHz luminosities above 0.1 mJy kpc2 . Adopting the Tauris & Manchester beaming model, this translates to a total of 155 000 ± 6000 active radio pulsars in the Galaxy above this luminosity limit. Using a pulsar current analysis, we derive the birth rate of this population to be 1.4 ± 0.2 pulsars per century. An important conclusion from our work is that the inferred radial density function of pulsars depends strongly on the assumed distribution of free electrons in the Galaxy. As a result, any analyses using the most recent electron model of Cordes & Lazio predict a dearth of pulsars in the inner Galaxy. We show that this model can also bias the inferred pulsar scaleheight with respect to the Galactic plane. Combining our results with other Parkes multibeam surveys we find that the population is best described by an exponential distribution with a scaleheight of 330 pc. Surveys underway at Parkes and Arecibo are expected to improve the knowledge of the radial distribution outside the solar circle, and to discover several hundred new pulsars in the inner Galaxy. 相似文献