The history of radio telescopes, 1945–1990

Forged by the development of radar during World War II, radio astronomy revolutionized astronomy during the decade after the war. A new universe was revealed, centered not on stars and planets, but on the gas between the stars, on explosive sources of unprecedented luminosity, and on hundreds of mysterious discrete sources with no optical identifications. Using “radio telescopes” that looked nothing like traditional (optical) telescopes, radio astronomers were a very different breed from traditional (optical) astronomers. This pathbreaking of radio astronomy also made it much easier for later “astronomies” and their “telescopes” (X-ray, ultraviolet, infrared, gamma-ray) to become integrated into astronomy after the launch of the space age in the 1960s. This paper traces the history of radio telescopes from 1945 through about 1990, from the era of converted small-sized, military radar antennas to that of large interferometric arrays connected by complex electronics and computers; from the era of strip-chart recordings measured by rulers to powerful computers and display graphics; from the era of individuals and small groups building their own equipment to that of Big Science, large collaborations and national observatories.     

射电望远镜的发展和前景

在近代科学技术发展的基础上诞生和成长起来的射电天文学已经走过了66年的历程,作为射电天文学主要探测工具的射电望远镜有了长足的进步,面临21世纪人类社会和自然科学技术包括天文学发展的挑战,射电望远镜及射电天文学将迈出新的步伐．从射电天文学和射电望远镜发展的关系、射电望远镜几个主要发展方向和目前水平、自90年代以来逐步勾画而明确起来的未来发展方向等方面阐明了射电望远镜的发展和前景,以作为我国发展新一代射电望远镜的参考．     

Search for possible exomoons with the FAST telescope

Our knowledge of the solar system encourages us to believe that we might expect exomoons to be present around some known exoplanets. With present hardware and existing optical astronomy methods, we do not expect to be able to find exomoons for at least 10 years, and even then, it will be a hard task to detect them. Using data from the Exoplanet Orbit Database(EOD) we find stars with Jovian exoplanets within 50 light years. Most of them will be fully accessible by the new radio telescope, the Five-hundred-meter Aperture Spherical radio Telescope(FAST), under construction which is now in the test phase. We suggest radio astronomy based methods to search for possible exomoons around two exoplanets.     

VLT‐CRIRES: “Good Vibrations” Rotational‐vibrational molecular spectroscopy in astronomy

Near‐Infrared high spectral and spatial resolution spectroscopy offers new and innovative observing opportunities for astronomy. The “traditional” benefits of IR‐astronomy – strongly reduced extinction and availability of adaptive optics – more than offset for many applications the compared to CCD‐based astronomy strongly reduced sensitivity. Especially in high resolution spectroscopy interferences by telluric lines can be minimized. Moreover for abundance studies many important atomic lines can be accessed in the NIR. A novel spectral feature available for quantitative spectroscopy are the molecular rotational‐vibrational transitions which allow for fundamentally new studies of condensed objects and atmospheres. This is also an important complement to radio‐astronomy, especially with ALMA, where molecules are generally only observed in the vibrational ground state. Rot‐vib transitions also allow high precision abundance measurements – including isotopic ratios – fundamental to understand the thermo‐nuclear processes in stars beyond the main sequence. Quantitative modeling of atmospheres has progressed such that the unambiguous interpretation of IR‐spectra is now well established. In combination with adaptive optics spectro‐astrometry is even more powerful and with VLT‐CRIRES a spatial resolution of better than one milli‐arcsecond has been demonstrated. Some highlights and recent results will be presented: our solar system, extrasolar planets, star‐ and planet formation, stellar evolution and the formation of galactic bulges (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Asteroid Confusions with Extremely Large Telescopes

Asteroids can be considered as sources of contamination of point sources and also sources of confusion noise, depending whether their presence is detected in the image or their flux is under the detection limit. We estimate that at low ecliptic latitudes, ≈10,000–20,000 asteroids/sq. degree will be detected with an E-ELT like telescope, while by the end of Spitzer and Herschel missions, infrared space observatories will provide ≈100,000 serendipitous asteroid detections. The detection and identification of asteroids is therefore an important step in survey astronomy.     

Radio wavelength transients: Current and emerging prospects

Known classes of radio wavelength transients range from the nearby stellar flares and radio pulsars to the distant Universe γ‐ray burst afterglows. Hypothesized classes of radio transients include analogs of known objects, e.g., extrasolar planets emitting Jovian‐like radio bursts and giant‐pulse emitting pulsars in other galaxies, to the exotic, prompt emission from γ‐ray bursts, evaporating black holes, and transmitters from other civilizations. A number of instruments and facilities are either under construction or in early observational stages and are slated to become available in the next few years. With a combination of wide fields of view and wavelength agility, the detection and study of radio transients will improve immensely. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

云台射电频谱仪预研

简要介绍了用于研究分子夭文学的各种射电频谱仪及国内外发展状况,讨论了各种频谱仪的优缺点,最后提出了云台建立射电频谱仪的型式。     

The radio search for extrasolar planets with LOFAR

The Low Frequency Array (LOFAR) will come on line with unprecedented radio sensitivity and resolution between 10 and 240 MHz. Such a system will provide a factor of 10–30 improvement in sensitivity in the pursuit of the weak radio emission from extrasolar planets. To date, previous examinations of extrasolar planetary systems with the most advanced radio telescopes have yielded a negative result. However, the improvement in sensitivity by LOFAR over current systems will increase the likelihood of extrasolar planet detection in the radio. We apply radiometric models derived previously from the study of planets in our solar system to the known extrasolar planets, and demonstrate that approximately 3–5 of them should emit in the proper frequency range and with enough power to possibly become detectable at Earth with LOFAR.     

The faint radio sky: radio astronomy becomes mainstream

Radio astronomy has changed. For years it studied relatively rare sources, which emit mostly non-thermal radiation across the entire electromagnetic spectrum, i.e. radio quasars and radio galaxies. Now, it is reaching such faint flux densities that it detects mainly star-forming galaxies and the more common radio-quiet active galactic nuclei. These sources make up the bulk of the extragalactic sky, which has been studied for decades in the infrared, optical, and X-ray bands. I follow the transformation of radio astronomy by reviewing the main components of the radio sky at the bright and faint ends, the issue of their proper classification, their number counts, luminosity functions, and evolution. The overall “big picture” astrophysical implications of these results, and their relevance for a number of hot topics in extragalactic astronomy, are also discussed. The future prospects of the faint radio sky are very bright, as we will soon be flooded with survey data. This review should be useful to all extragalactic astronomers, irrespective of their favourite electromagnetic band(s), and even stellar astronomers might find it somewhat gratifying.     

Attempts by a theorist to work with Martin Ryle in the Cavendish, 1953–1955

The glorious years of discovery in radio astronomy in the Cavendish Laboratory, Cambridge were dominated by the personality of Martin Ryle. The contact to the theorists, in the Observatories only a short distance away, were occasionally strained. Personal experience from this era will be the subject of this contribution. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Antenna design and implementation for the future space Ultra-Long wavelength radio telescope

In radio astronomy, the Ultra-Long Wavelengths (ULW) regime of longer than 10 m (frequencies below 30 MHz), remains the last virtually unexplored window of the celestial electromagnetic spectrum. The strength of the science case for extending radio astronomy into the ULW window is growing. However, the opaqueness of the Earth’s ionosphere makes ULW observations by ground-based facilities practically impossible. Furthermore, the ULW spectrum is full of anthropogenic radio frequency interference (RFI). The only radical solution for both problems is in placing an ULW astronomy facility in space. We present a concept of a key element of a space-borne ULW array facility, an antenna that addresses radio astronomical specifications. A tripole–type antenna and amplifier are analysed as a solution for ULW implementation. A receiver system with a low power dissipation is discussed as well. The active antenna is optimized to operate at the noise level defined by the celestial emission in the frequency band 1 ? 30 MHz. Field experiments with a prototype tripole antenna enabled estimates of the system noise temperature. They indicated that the proposed concept meets the requirements of a space-borne ULW array facility.     

RATAN-600 radio telescope in the 24th solar-activity cycle. II. Multi-octave spectral and polarization high-resolution solar research system

Radio astronomy studies of the solar atmosphere possess a very important, not duplicated by other methods, place in the study of solar activity at all stages—from the birth of an active region until its collapse. A significant progress in these studies can be achieved in the implementation of new technical possibilities, such as an increase in the sensitivity of radio telescopes, a detailed spectral analysis over a wide frequency range, high temporal resolution and a broad coverage range in time. We report about the implementation of regular observations with a new spectral and polarization high-resolution system SPHRS, installed at the radio telescope RATAN-600.We describe the concept of the new system and the methods of its implementation.     

A real-time software backend for the GMRT

The new era of software signal processing has a large impact on radio astronomy instrumentation. Our design and implementation of a 32 antennae, 33 MHz, dual polarization, fully real-time software backend for the GMRT, using only off-the-shelf components, is an example of this. We have built a correlator and a beamformer, using PCI-based ADC cards and a Linux cluster of 48 nodes with dual gigabit inter-node connectivity for real-time data transfer requirements. The highly optimized compute pipeline uses cache efficient, multi-threaded parallel code, with the aid of vectorized processing. This backend allows flexibility in final time and frequency resolutions, and the ability to implement algorithms for radio frequency interference rejection. Our approach has allowed relatively rapid development of a fairly sophisticated and flexible backend receiver system for the GMRT, which will greatly enhance the productivity of the telescope. In this paper we describe some of the first lights using this software processing pipeline. We believe this is the first instance of such a real-time observatory backend for an intermediate sized array like the GMRT.     

Radio astronomy and very large telescopes

The current achievements of the observational abilities of radio astronomy is briefly reviewed putting emphasis on the imaging capability. The new projects in radio astronomy are discussed in connection with the new generation of optical/IR telescope projects.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 1988.     

高速同步数据采集系统性能测试方法研究

在射电天文观测中,天文信号十分微弱,在大部分情况下可以看成是噪声功率的微小增加,需要长的积分时间才能从噪声中显现,因此在进行射电天文数据采集时对采集系统的性能具有较高的要求.针对射电天文数据的特点,从噪声特性、频率特性和同步特性3方面给出了系统性能的衡量指标,围绕这些指标,分别研究了其测试方法,最后以某个实际射电天文数据采集系统为测试平台,进行了指标的测试.测试结果验证了所提指标的有效性和指标测试方法的合理性.     

大型射电望远镜主反射面调整方法研究

随着毫米波天文学和空间通信的重要性日益提高, 对天线性能提出了越来越高的要求, 而天线性能往往受到其反射器表面精度的限制. 微波全息技术是一种快速有效的检测反射面天线表面轮廓的测量技术. 通过微波全息测量得到天线口径场, 计算天马65m射电望远镜反射面与理想抛物面的偏差. 天马65m射电望远镜的主反射面板是放射状的, 有14圈. 面板的每个角都固定在面板下方促动器的螺栓上进行上下移动, 且相邻面板交点处的拐角共用一个促动器. 采用平面拟合的方法可以计算各块面板拐角处的调整值, 但是同一个促动器会得到4个不同的调整量. 通过平面拟合, 同时以天线照明函数为权重的平差计算方法得到相邻面板拐角的一个平差值, 即天马65m射电望远镜1104个促动器的最佳调整值. 通过多次调整和新算法的应用, 天马65m射电望远镜反射面的面形精度逐渐提高到了0.24mm.     

基于DBBC+Mark 5B记录系统的脉冲星观测

2009年11月,云南天文台射电天文研究团组采用40 m射电望远镜以及基于DBBC(Digital Base Band Conveter)和Mark 5B的VLBI记录系统对PSR J0835-4510和PSRJ0332+5434进行了观测。观测选用S波段右旋圆极化信号,起始频率为2 206.99 MHz,总带宽为32 MHz。对数据进行相干消色散和平均后,得到PSR J0332+5434的单脉冲图像和两颗脉冲星的平均脉冲轮廓。由平均轮廓的展宽随时间的变化关系,对脉冲星的视周期作了一定修正后,得到信噪比更高的平均轮廓图。最后对轮廓的信噪比随时间的变化作了初步分析,由此可了解整个系统在观测时的稳定性。     

The beginnings of decameter radio astronomy: pioneering works of Semen Ya. Braude and his followers in Ukraine

S.Ya. Braude (1911–2003) was the well‐known radio astronomer, one of the founders of low‐frequency astronomical research in the world, in particular in the former Soviet Union. He began to work in this field of science in 1957, in Kharkiv city (Ukraine), from the design and manufacturing small decameter interferometer ID‐1 and ID‐2. Since that time Braude and his team have developed more sophisticated radio decameter telescopes as UTR‐1 and UTR‐2 (the largest in the world till now) as well as the first decameter VLBI network URAN. They have obtained some important pioneering results about low‐frequency radio emission of objects in our Solar system, Galaxy and Metagalaxy by means of these telescopes. In this paper the key events of early history of decameter radio astronomy research in the former USSR are mentioned with emphasizing the role of S. Braude. For the period of 1957–1962, the quotations of Braude's Personal Diary (2003) are first laying open to the public. The most important results obtained by S.Ya. Braude and his followers as well as perspectives of decameter radio astronomy in Ukraine and in the world are highlighted briefly. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)