“Beautiful and cantankerous instruments”: telescopes, technology, and astronomy’s changing practice

Between the dedication of the 200” Hale Telescope in 1948 and the completion of today’s 8–10 m behemoths, astronomers’ most iconic symbol, the telescope itself—its design, its technology, and its use—was transformed as a research tool. The importance of this is deceptively simple: in astronomy, technological innovations have often led to new discoveries. Driven by the need to get as much observing time as possible and the desire to take advantage of the best observing conditions, modern observatories have experimented with new technologies and modes of collecting images and spectra. This entailed a re-casting of the telescope by astronomers and science managers as a factory of scientific data. At the same time, contemporary astronomers express considerable unease and apprehension about how these technological changes have altered, in ways subtle and profound, the nature of astronomical observing and what it meant to be an astronomer. This short essay addresses the issues associated with these recent changes in astronomical practice and their connections to astronomers’ desire for ever larger and more complex telescopes.     

Serendipitous UV source catalogues for 10 years of XMM and 5 years of Swift

Two UV serendipitous source catalogues are presented which were compiled based on the observations with two similar UV telescopes, one being on-board the ESA’s XMM Newton observatory and another—on-board the NASA’s Swift satellite. Both telescopes have similar optical and registration systems providing photometry in three ultraviolet and three visible bands. After processing a 10 years long series of observations from XMM and 5 years from Swift, we have compiled two source catalogues containing more than 4 million sources for XMM and 6 million sources for Swift. We describe the processing algorithms and present catalogue characteristics in comparison with each other.     

AGN at very high energies: Cosmic accelerators and probes of space-time

During the last decade, very high energy astrophysics emerged as a new branch of astronomy with major discoveries achieved by the present ground-based gamma-ray Cherenkov telescopes. The sample of cosmic sources firmly detected at very high energy (VHE) now exceeds two hundred objects, including active galactic nuclei (AGN), pulsar wind nebulae, and several other types of sources of which a significant number are unidentified ones. The scientific return from recent VHE data is particularly interesting for AGN science, shedding new light on particle acceleration and emission processes around supermassive black holes, and probing the intergalactic space by the analysis of VHE photons propagating from bright remote sources to the Earth. The perspectives of this research field are promising with new generation VHE instruments such as CTA, a project of open observatory at extreme energies at the horizon 2023, allowing a deep analysis of the sky in the highest part of the electromagnetic spectrum, from 20 GeV to 300 TeV.     

POlarization Emission of Millimeter Activity at the Sun (POEMAS): New Circular Polarization Solar Telescopes at Two Millimeter Wavelength Ranges

We present a new system of two circular polarization solar radio telescopes, POEMAS, for observations of the Sun at 45 and 90 GHz. The novel characteristic of these instruments is the capability to measure circular right- and left-hand polarizations at these high frequencies. The two frequencies were chosen so as to bridge the gap at radio frequencies between 20 and 200 GHz of solar flare spectra. The telescopes, installed at CASLEO Observatory (Argentina), observe the full disk of the Sun with a half power beam width of 1.4^°, a time resolution of 10 ms at both frequencies, a sensitivity of 2?–?4 K that corresponds to 4 and 20 solar flux unit (=10⁴ Jy), considering aperture efficiencies of 50±5 % and 75±8 % at 45 and 90 GHz, respectively. The telescope system saw first light in November 2011 and is satisfactorily operating daily since then. A few flares were observed and are presented here. The millimeter spectra of some flares are seen to rise toward higher frequencies, indicating the presence of a new spectral component distinct from the microwave one.     

The Gaia Mission: Expected Applications to Asteroid Science

According to current plans of the European space agency, Gaia will be launched in 2011. By performing a systematic survey of the whole sky down to magnitude V = 20, this mission will provide a fundamental contribution in practically all branches of modern Astrophysics. Gaia will be able to survey with repeated observations spanning over 5 years several 100,000 s asteroids. It will directly measure sizes of about 1,000 objects, obtain the masses of about 100 of them, derive spin properties and overall shapes of more than 10,000 objects, yield much improved orbits and taxonomic classification for most of the observed sources. The final harvest will very likely include new discoveries of objects orbiting at heliocentric distances less than 1 AU. At the end of the mission, we will know average densities of about 100 objects belonging to all the major taxonomic classes, have a much more precise knowledge of the inventory and size and spin distributions of the population, of the distribution of taxonomic classes as a function of heliocentric distance, and of the dynamical and physical properties of dynamical families.     

The Thirty Meter Telescope (TMT): An International Observatory

The Thirty Meter Telescope (TMT) will be the first truly global ground-based optical/infrared observatory. It will initiate the era of extremely large (30-meter class) telescopes with diffraction limited performance from its vantage point in the northern hemisphere on Mauna Kea, Hawaii, USA. The astronomy communities of India, Canada, China, Japan and the USA are shaping its science goals, suite of instrumentation and the system design of the TMT observatory. With large and open Nasmyth-focus platforms for generations of science instruments, TMT will have the versatility and flexibility for its envisioned 50 years of forefront astronomy. The TMT design employs the filled-aperture finely-segmented primary mirror technology pioneered with the W.M. Keck 10-meter telescopes. With TMT’s 492 segments optically phased, and by employing laser guide star assisted multi-conjugate adaptive optics, TMT will achieve the full diffraction limited performance of its 30-meter aperture, enabling unprecedented wide field imaging and multi-object spectroscopy. The TMT project is a global effort of its partners with all partners contributing to the design, technology development, construction and scientific use of the observatory. TMT will extend astronomy with extremely large telescopes to all of its global communities.     

Absorption spectroscopy of gamma‐ray burst afterglows: Probing the GRB line of sight

GRB absorption spectroscopy opened up a new window in the study of the high redshift Universe, especially with the launch of the Swift satellite and the quick and precise localization of the afterglow. Eight‐meter class telescopes can be repointed within a few hours from the GRB, enabling the acquisition of high signal‐to‐noise ratio and high resolution afterglow spectra. In this paper I will give a short review of what we learned through this technique, and I will present some of the first results obtained with the X‐shooter spectrograph (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spectroscopic Observations of the Star Formation Regions in Nearby Galaxies

In recent years the number of worldwide 8∼10 m-class ground-based telescopes is continually increased, the 4 m-diameter or smaller telescopes have become the small and medium-sized telescopes. In order to obtain some noticeable scientific results by using these existing small and medium-sized telescopes, we have to consider very carefully what we can do, and what we can not. For this reason, the Time Allocation Committee of the 2.16 m telescope of the National Astronomical observatories of China (NAOC) has decided to support some key projects since 2013. The long-term project “Spectroscopic Observations of the Star Formation Regions in Nearby Galaxies” proposed by us is one of three key projects, it is supported by the committee with 30 dark/grey nights in each of three years.     

History of X-ray telescopes and astronomy

The development of X-ray telescopes over the last 45 years is briefly summarized. The first applications to the study of solar X-ray emission are described up to the 1973 Skylab mission. The rather convoluted path that led to the first stellar X-ray orbiting telescope Einstein (1978) and later to Chandra (1999) are discussed. During this 45 years period the angular resolution improved from 20 to 0.5 arc sec and the sensitivity by ten billions. X-ray observations have discovered new types of stellar systems (binary X-ray sources containing neutron stars and black holes) and intergalactic high temperature plasmas containing most of the baryonic mass of the universe. They have become an indispensable tool to study the role of energetic phenomena in the creation and dynamic evolution of cosmic structures. The methodology introduced by X-ray astronomy has influenced all of astronomy.     

Super resolution for astronomical observations

In order to obtain detailed information from multiple telescope observations a general blind super-resolution (SR) reconstruction approach for astronomical images is proposed in this paper. A pixel-reliability-based SR reconstruction algorithm is described and implemented, where the developed process incorporates flat field correction, automatic star searching and centering, iterative star matching, and sub-pixel image registration. Images captured by the 1-m telescope at Yunnan Observatory are used to test the proposed technique. The results of these experiments indicate that, following SR reconstruction, faint stars are more distinct, bright stars have sharper profiles, and the backgrounds have higher details; thus these results benefit from the high-precision star centering and image registration provided by the developed method. Application of the proposed approach not only provides more opportunities for new discoveries from astronomical image sequences, but will also contribute to enhancing the capabilities of most spatial or ground-based telescopes.     

Investigating Sub-Pixel 45-Second Periodic Wobble in SDO/AIA Data from January to August 2012

Artifacts could mislead interpretations in astrophysical observations. A thorough understanding of an instrument will help in distinguishing physical processes from artifacts. In this article, we investigate an artifact of the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory. Time-series data and wavelet spectra revealed periodic intensity perturbations in small regions over the entire image in certain AIA extreme ultraviolet (EUV) passbands at a period of about 45 seconds. These artificial intensity variations are prominently detected in regions with sharp intensity contrast, such as sunspot light bridges. This artifact was caused by a periodic pointing wobble of the two AIA telescopes ATA 2 (193 and 211 Å channels) and ATA 3 (171 Å and UV channels), to a lesser extent, while the other two telescopes were not found to be affected. The peak-to-peak amplitude of the wobble was about 0.2 pixel in ATA 2 and 0.1 pixel in ATA 3. This artifact was intermittent and affected the data of seven months from 18 January to 28 August 2012, as a result of a thermal adjustment to the telescopes. We recommend that standard pointing-correction techniques, such as local correlation tracking, should be applied before any detailed scientific analysis that requires sub-pixel pointing accuracy. Specifically, this artificial 45-second periodicity was falsely interpreted as abnormal sub-minute oscillations in a light bridge of a sunspot (Yuan and Walsh in Astron. Astrophys.594, A101, 2016).     

近地小行星发现数目与发现场景的统计分析

近地小行星是一类可能对地球安全造成潜在威胁的太阳系小天体, 目前绝大部分的近地小行星是由地基望远镜发现的, 且数目仍在不断增加. 为了对我国未来开展近地小行星发现监测提供参考和借鉴, 利用国际小行星中心公开的数据库对所有近地小行星首次发现时刻的观测资料开展了多维度统计分析. 发现望远镜探测能力的限制会对近地小行星的发现造成选择效应, 导致不同轨道类型近地小行星发现的相对比例逐年变化且与直径有关. 另外, 结合数值模拟获得的轨道数据, 对近地小行星首次发现时的观测场景进行了还原, 获得了发现时刻近地小行星位置在不同天球坐标系的分布, 分析了其分布特征与季节、测站纬度和小行星直径的依赖关系. 最后, 通过分析数据定量考察了太阳、月球和银道面对近地小行星发现的影响, 发现地基望远镜一般难以发现来自太阳方向90$^\circ$范围内直径140m以下的近地小行星, 并且随着小行星直径的减小该限制范围也将变大; 月光污染对近地小行星发现的影响也非常显著, 望月前后几天的观测限制可导致约29%的目标无法被发现, 而且分析表明农历上半月发现的目标一般比下半月发现的更难以被跟踪观测; 银道面特别是银心方向会对近地小行星发现产生影响, 使得黄道面附近存在与季节相关的观测``盲区''.     

Photometry: New techniques,an introduction

In most fields of observational astronomy, the new techniques we have now and are developing offer great potentials for more and better data, and thus to increased understanding of the universe about us. Photometry, as perhaps the most fundamental of all the observational tools, is no exception. The next years will be most exciting, but we must always be aware of the potential pitfalls involved with new technology. In fact, the new technologies must be handled with great care in order to insure that our data is really first class. New generation small telescopes can be a great asset, offering great complementarity to the new large telescopes and to space astronomy.Operated by AURA, Inc. under cooperative agreement with the National Science Foundation, Washington D.C.     

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．     

Past and future of ESO

In 1964, the European Southern Observatory (ESO) came into being as a response to the need of European astronomers for access to large telescopes in good observing conditions. The original plan called for a 3.6 m telescope in addition to a number of smaller instruments. The 3.6 m telescope took some 12 years to build, while ESO headquarters moved from Hamburg to CERN to Garching near Munich, and during the times of office of three Directors General, and it was built on La Silla in Chile, where superior sites had been found. After 1982, when Italy and Switzerland joined the original six member countries, ESO was able to expand by building the 3.5 m New Technology Telescope, and ultimately planning and constructing the VLT on Paranal. At present ESO is a stable organization that has been successful in its original aims, and in view of new plans can look forward in confidence.     

Astronomical spectroscopy in the last four decades: survival of the fittest

Spectroscopic astronomical instrumentation has much evolved in the last 40 years. Long-slit grating spectrographs with a photographic plate as the detector working in the 0.3–1 μm range were prevalent up to the early 1970s. The replacement of photographic plates by two-dimensional digital detectors provided gains in sensitivity of two orders of magnitude and much better photometric and radial velocity precision, and opened the 1 to 25 μm infrared domain. Another gain in speed by up to two orders of magnitude was then obtained through the development of various spectroscopic systems, each optimized for a subset of astronomical objects. This development was underpinned by a number of technological advances, in particular the development of automatic data reduction pipelines using sophisticated algorithms. With ever larger and more complex instrument systems for the present 8–10 m diameter telescopes—and soon even more for the next generation of Extremely Large Telescopes, the development of an instrument is now a big enterprise, ranging all the way from long-term enabling technology efforts to management of large teams for construction and deployment over typically 7–8 years.     

Grid integration of robotic telescopes

Robotic telescopes and grid technology have made significant progress in recent years. Both innovations offer important advantages over conventional technologies, particularly in combination with one another. Here, we introduce robotic telescopes used by the Astrophysical Institute Potsdam as ideal instruments for building a robotic telescope network. We also discuss the grid architecture and protocols facilitating the network integration that is being developed by the German AstroGrid‐D project. Finally, we present three user interfaces employed for this purpose. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The UVIT telescopes on the Astrosat observatory

The UVIT telescopes are a payload package on the ISRO Astrosat observatory. They are co-aligned with three X-ray telescopes, and will operate simultaneously with them. The overall observatory is summarized, and details are given of the design, performance, and operation of the UVIT telescopes. These will offer close to arcsecond resolution over half-degree fields, simultaneously in FUV, NUV, and blue-visible bands. All bands have several filters and the UV bands have low-dispersion objective gratings.     

High-energy cosmology

Our knowledge of the high-energy universe is undergoing a period of rapid change as new astronomical detectors of high-energy radiation start to operate at their design sensitivities. Now is a boomtime for high-energy astrophysics, with new discoveries from Swift and HESS, results from MAGIC and VERITAS starting to be reported, the upcoming launches of the γ-ray space telescopes GLAST and AGILE, and anticipated data releases from IceCube and Auger. A formalism for calculating statistical properties of cosmological γ-ray sources is presented. Application is made to model calculations of the statistical distributions of γ-ray and neutrino emission from (i) beamed sources, specifically, long-duration GRBs, blazars, and extragalactic microquasars, and (ii) unbeamed sources, including normal galaxies, starburst galaxies and clusters. Expressions for the integrated intensities of faint beamed and unbeamed high-energy radiation sources are also derived. A toy model for the background intensity of radiation from dark-matter annihilation taking place in the early universe is constructed. Estimates for the γ-ray fluxes of local group galaxies, starburst, and infrared luminous galaxies are briefly reviewed. Because the brightest extragalactic γ-ray sources are flaring sources, and these are the best targets for sources of PeV–EeV neutrinos and ultra-high energy cosmic rays, rapidly slewing all-sky telescopes like MAGIC and an all-sky γ-ray observatory beyond Milagro will be crucial for optimal science return in the multi-messenger age.     

Unusual Solar Radio Burst Observed at Decameter Wavelengths

An unusual solar burst was observed simultaneously by two decameter radio telescopes UTR-2 (Kharkov, Ukraine) and URAN-2 (Poltava, Ukraine) on 3 June 2011 in the frequency range of 16?–?28 MHz. The observed radio burst had some unusual properties, which are not typical for the other types of solar radio bursts. Its frequency drift rate was positive (about 500 kHz?s^?1) at frequencies higher than 22 MHz and negative (100 kHz?s^?1) at lower frequencies. The full duration of this event varied from 50 s up to 80 s, depending on the frequency. The maximum radio flux of the unusual burst reached ≈10³ s.f.u. and its polarization did not exceed 10 %. This burst had a fine frequency-time structure of unusual appearance. It consisted of stripes with the frequency bandwidth 300?–?400 kHz. We consider that several accompanied radio and optical events observed by SOHO and STEREO spacecraft were possibly associated with the reported radio burst. A model that may interpret the observed unusual solar radio burst is proposed.