面向世纪之交的射电天文

立足于无线电电子科学技术和其它技术的发展，而诞生和成长起来的射电天文学已经走过了６２年成果累累的历程，面临２１世纪人类神经和自然技术包括天文学发展的挑战，射电天文学将迈出的新的步伐。本文拟在射电天文现状和讨论中计划的基础上对此给予评述和预测。     

射电天文站电磁环境测量方法及分析

射电天文业务是接收来自遥远宇宙天体的射电信号进行研究的科学.由于来自宇宙天体的射电天文信号非常微弱,比通信系统的信号暗弱百万倍,使射电天文望远镜对周围电磁环境的要求极其严格.射电天文站址要选在电磁环境良好的地区,并在以后的运行中得到电磁环境的保护.建立一套测试射电天文站址电磁环境的设备和方法,对射电天文站址的电磁环境进行实际测试,并对实测数据进行科学合理地分析、评价,作为以后射电天文观测和保护电磁环境研究的依据都是非常重要的.     

射电天文业务干扰评价和电磁环境保护探讨(上)

射电天文业务负责接收源于宇宙的电磁波，是当代天文学研究最重要的手段之一，受到ITU《无线电规则》的重点保护。近年来，我国无线电通信快速发展的同时，射电天文业务受到干扰的概率越来越大。国家无线电监测中心乌鲁木齐站2005年承担了信息产业部无线电管理局下达的软科学研究课题——“射电天文业务干扰评价和电磁环境保护研究”，课题小组在一年多的研究工作中查阅了大量相关资料、咨询了多位射电天文专家，并对乌鲁木齐天文站25米射电望远镜进行了实测试验，该研究课题于2007年元月顺利通过了部无线电管理局的评审验收。本文以课题报告和专家评审意见为基础，与大家共同交流探讨射电天文业务干扰评价，以及射电天文站电磁环境保护问题。[编者按]     

天体射电蒙气差的一种计算方法

本文主要讨论利用射电进行对测天体确定天体在天球上的位置,或通过观测射电天体进行天文定位时,需要考虑大气折射的影响,并给出了观测天体射电的蒙气差ρ理论计算和修正方法。     

黑体辐射的外差探测

为了将射电天文学所用的一些干涉计量法扩展到红外波段,巳完成了 10.6米黑体非相干辐射的外差探测,并研究了探测到的信号之间的关系。     

曲靖非相干散射雷达月球探测初步结果

非相干散射雷达是目前地面监测电离层最强大的设备,在月球等天体目标探测方面也具有潜在价值。本文介绍了曲靖非相干散射雷达技术特点与月球探测数据处理方法,分析了月球探测初步结果以及目前存在的不足与下一步工作计划。结果表明,曲靖非相干散射雷达目前可探测月球单极化回波（右旋圆极化）、反演月表反射系数和粗糙度、进行初步成像等,探测结果与现有研究结果基本一致。本文工作对我国地基雷达天文探测具有重要意义。     

我国红外天文学发展的十年

回顾了十年来我国红外天文学的进展,介绍了各种红外天文仪器在我国的研制与应用,列举了我国红外天文观测的主要成果,并探讨了今后我国进一步发展用于天文目的的红外探测器及红外天文仪器的必要性。     

太赫兹混频器技术研究进展

太赫兹混频器可通过本征信号与原信号混合，经频率变换，实现频谱探测、超分辨成像和天文信号高灵敏探测，在太赫兹频谱识别、太赫兹安检、射电天文探测等领域具有重要应用前景。本文首先介绍了太赫兹混频器的基本原理、分类、主流技术方案；其次针对太赫兹混频器超灵敏化、高频化、中频宽带化和小型化集成的应用需求，分析了国内外太赫兹混频器设计与制作技术的发展动态；最后归纳了太赫兹混频器的应用状况、技术挑战和可能的解决方案，以便阐明三类太赫兹混频器的技术特点和技术发展趋势。     

现代天文导航及其关键技术

分析导航技术的地位、作用及其局限性,综述天文导航技术现状及国内外对天文导航技术的认识,指出天文导航技术的优点,在此基础上,重点论述天文导航关键技术,提出基于自然天体及人造天体射电测量、消除水平基准制约和可见光观测限制的天文导航技术发展思路.     

THz 遥感技术的应用进展

近年来,在射电天文学、大气科学发展的推动作用下,THz 时域光谱技术发展迅速,被广泛地应用于遥感领域。介绍了与THz 遥感相关的技术和应用,包括地球观测系统和射电天文学,突出了THz 遥感技术与其他学科之间的紧密联系,显示出了巨大的应用前景。美国、欧洲、日本在THz 遥感领域起步较早,拥有一些成熟的技术和设备;中国起步较晚,技术上和国际先进水平还有一定差距。     

Synthetic aperture radiometer systems

Aperture synthesis is an emerging technology for passive microwave remote sensing from space. It is an interferometric technique similar to earth rotation synthesis employed in radio astronomy in which pairs of small antennas and signal processing are used to obtain the resolution of a single large antenna. The technique has the potential to overcome the barriers that antenna size has plated on passive microwave remote sensing from space. The technique has been demonstrated successfully for remote sensing at L-band with the aircraft prototype ESTAR. New aircraft instruments are under development and proposals have been submitted for instruments to demonstrate this technology in space     

The Challenge of Astronomy to Millimeter-Wave Technology

The inseparability of pure and applied science, or the synergy between scientific discovery and technological advance, has already been well illustrated in the field of radio astronomy. Recent astronomical discoveries in the millimeter range, and what can he expected to emerge from the far-infrared region, make further technological developments in these relatively unexploited areas of great interest to astronomy as well as technologically challenging. The nature of problems and the goals of astronomy in this area are discussed with particular reference to technological needs and developments.     

Radio telescopes

A radio telescope is used in radio astronomy to measure the intensity of the radiation received from various parts of the sky. Such a telescope must be able both to detect and to locate faint radio sources of small angular size, and also to measure the brightness distribution across extended radio sources or over large sky areas. Ideally the telescope should be capable of making such measurements over a wide frequency range and for different types of polarization of the incoming waves. The noise powers available in radio astronomy are very small, and some of the radio sources have angular sizes or angular structure of, perhaps, only one second of arc, so that a radio telescope needs both high gain and good resolving power. The paper describes various types of radio telescopes which have been built and tested, and outlines the astronomical needs which they fulfill. The parabolic reflector antenna is first described, with particular reference to the fully steerable 210-foot telescope at the Australian National Radio Astronomy Observatory and to the 300-foot transit telescope at the U. S. National Radio Astronomy Observatory. Of the telescopes which use fixed or partly fixed reflector surfaces, those at the University of Illinois, at the Nançay station of the Paris Observatory, and at the Arecibo Ionospheric Observatory in Puerto Rico are described in some detail. Instruments in which the resolution is improved without a corresponding increase of collecting area, such as the cross-type antennas, are briefly described. The future progress of radio telescope design is certain to follow the development of parabolic dishes to still greater sizes, and the exploitation of synthetic antenna systems; the article concludes with a survey of both developments.     

A subspace-tracking approach to interference nulling for phasedarray-based radio telescopes

Several next-generation radio telescopes, now in the planning stages, are based on phased-array technology. One reason for this is to make use of adaptive nulling techniques to combat radio frequency interference, which is a growing problem for radio astronomy. This paper presents a low-complexity approach to interference nulling which is suitable for use in such systems. The approach uses subspace-tracking to identify interference, followed by spatial projections to place deep nulls in the directions of interferers. This technique overcomes two limitations of power-minimization algorithms (e.g., "minimum variance"), namely power inversion and pattern rumble, which create serious problems for radio astronomy. Furthermore, this technique imposes a lower computational burden and provides side information which is useful in later stages of data processing. Performance results from a phased array demonstrator system and a simulation are presented     

Digital signal processing based on the generalized Kravchenko-Kotel’nikov-Levitan sampling theorems

New low- and high-frequency digital filters, which relies on atomic functions and have good frequency-time properties and rapid convergence, have been proposed. Their efficiency is investigated via digital signal processing as applied to the problem of interferometry and synthesis in radio astronomy.     

太空美术与科学普及

太空美术,也是天文美术和航天美术。它体现了天文、航天,以及太空技术方面的探索发现的成果。在天文学教育、天文学普及和太空探索领域内,太空美术占有非常重要的位置。近20年来,中国的报纸、杂志和电视节目在传播太空美术成就方面做出了不少努力。     

"生物医学仪器"课程改革的实践

目前在"生物医学仪器"课程中讲述的内容主要为常见的医学电子仪器,随着技术的迅速发展,仪器逐渐实现了微型化、智能化、网络化和多功能化.本文针对目前"生物医学仪器"课程教学中存在的不足及不能完全满足当前教学发展需要的状况,从教学内容、实践教学、教学方法和手段等方面对该课程的教学改革进行了实践探索.     

NLMS算法在射电天文中的应用

射电天文被动接收宇宙中极其微弱的射电信号,很容易受到人们有源业务活动的影响。为了抑制和消除射电望远镜观测过程中出现的电视信号干扰,采取了通常用在通信雷达领域的自适应抗干扰措施,利用两个辅助天线,极大地抑制了电视信号干扰,改善了信噪比,从而能够检测出微弱的射电天文信号。