Detection and Classification of Astronomical Targets with Deep Neural Networks in Wide Field Small Aperture Telescopes
Taiyuan University of Technology（太原理工大学）
Peng Jia, Qiang Liu, Yongyang Sun
备注：
Accepted by Astronomical Journal. The complete code can be downloaded from https://doi.org/10.12149/101016. This code can be directly used to process images obtained by WFSATs. Images obtained by ordinary sky survey telescopes can also be processed with this code, however more annotated images are required to train the neural network
Wide field small aperture telescopes are widely used for optical transient observations. Detection and classification of astronomical targets in observed images are the most important and basic step. In this paper, we propose an astronomical targets detection and classification framework based on deep neural networks. Our framework adopts the concept of the Faster R-CNN and uses a modified Resnet-50 as backbone network and a Feature Pyramid Network to extract features from images of different astronomical targets. To increase the generalization ability of our framework, we use both simulated and real observation images to train the neural network. After training, the neural network could detect and classify astronomical targets automatically. We test the performance of our framework with simulated data and find that our framework has almost the same detection ability as that of the traditional method for bright and isolated sources and our framework has 2 times better detection ability for dim targets, albeit all celestial objects detected by the traditional method can be classified correctly. We also use our framework to process real observation data and find that our framework can improve 25 % detection ability than that of the traditional method when the threshold of our framework is 0.6. Rapid discovery of transient targets is quite important and we further propose to install our framework in embedded devices such as the Nvidia Jetson Xavier to achieve real-time astronomical targets detection and classification abilities.
Radio interferometry is the current method of choice for deep space astronomy, but in the past few decades optical techniques have become increasingly common. This research seeks to characterize the performance of aperture masking interferometry in the near-infrared at small scales. A mask containing six pairs of apertures at varying diameters and separations was constructed for use with a 24-inch telescope at the MIT Wallace Astrophysical Observatory. Test images of Spica and Jupiter were captured for 28 different telescope configurations, varying aperture separation, aperture diameter, colle…
Taiyuan University of Technology（太原理工大学）；Durham University（杜伦大学）
Wide field small aperture telescopes (WFSATs) are commonly used for fast sky survey. Telescope arrays composed by several WFSATs are capable to scan sky several times per night. Huge amount of data would be obtained by them and these data need to be processed immediately. In this paper, we propose ARGUS (Astronomical taRGets detection framework for Unified telescopes) for real-time transit detection. The ARGUS uses a deep learning based astronomical detection algorithm implemented in embedded devices in each WFSATs to detect astronomical targets. The position and probability of a detection bei…
Speckle Imaging based on triple correlation is a very efficient image reconstruction technique which is used to retrieve Fourier phase information of the object in presence of atmospheric turbulence. We have developed both Direct Bispectrum and Radon transform based Tomographic speckle masking algorithms to retrieve atmospherically distorted astronomical images. The latter is a much computationally efficient technique because it works with one dimensional image projections. Tomographic speckle imaging provides good image recovery like direct bispectrum but with a large improvement in computati…
The Wide Aperture Exoplanet Telescope (WAET) is a ground-based optical telescope layout in which one dimension of a filled aperture can be made very, very large (beyond 100 m) at low cost and complexity. With an unusual beam path but an otherwise-conventional optics, we obtain a fully-steerable telescope on a low-rise mount with a fixed gravity vector on key components. Numerous design considerations and scaling laws suggest that WAET can be far less expensive than other giant segmented mirror telescopes.
Cost data for ground-based telescopes of the last century are analyzed for trends in the relationship between aperture size and cost. We find that for apertures built prior to 1980, costs scaled as aperture size to the 2.8 power, which is consistent with the previous finding of Meinel (1978). After 1980, `traditional' monolithic mirror telescope costs have scaled as aperture to the 2.5 power. The large multiple mirror telescopes built or in construction during this time period (Keck, LBT, GTC) appear to deviate from this relationship with significant cost savings as a result, although it is un…
Focal plane wavefront sensing is an appealing technique to cophase multiple aperture telescopes. Phase diversity, operable with any aperture configuration or source extension, generally suffers from high computing load. In this Letter, we introduce, characterize and experimentally validate the LAPD algorithm, based on a fast linearized phase diversity algorithm \rev{with a capture range comparable to classic phase diversity.} We demonstrate that a typical performance of lambda/75 RMS wavefront error can be reached.
The Australian Astronomical Observatory operates the Anglo-Australian Telescope and the United Kingdom Schmidt Telescope in Australia, as well as coordinating access for the Australian community to the Gemini, Magellan, and other international telescope facilities. We review here the processes involved within the AAO related to allocating observing time on these facilities, as well as the impact on telescope use of both the Large Program projects and the AAO's instrument program.
Segmented telescopes are a possibility to enable large-aperture space telescopes for the direct imaging and spectroscopy of habitable worlds. However, the complexity of their aperture geometry, due to the central obstruction, support structures and segment gaps, makes high-contrast imaging challenging. The High-contrast Imager for Complex Aperture Telescopes (HiCAT) testbed was designed to study and develop solutions for such telescope pupils using wavefront control and coronagraphic starlight suppression. The testbed design has the flexibility to enable studies with increasing complexity for …
Using the convolution of seeing and diffraction, the relation between seeing and aperture in the visibility of sunspots is explored. It is shown that even telescopes with apertures smaller than 5 centimetres are significantly affected by seeing. Although larger aperture instruments suffer more from seeing than smaller ones, their level of detail always remains better under the same atmospheric conditions.
Telescope arrays allow high-performance wide-field imaging systems to be built more quickly and at lower cost than conventional telescopes. Distributed aperture telescopes (the premier example of which is the Dragonfly Telephoto Array) are a special type of array in which all telescopes point at roughly the same position in the sky. In this configuration the array performs like a large and optically very fast single telescope with unusually good control over systematic errors. In a few key areas, such as low surface brightness imaging over wide fields of view, distributed aperture telescopes o…
Two high performance coronagraphic approaches compatible with segmented and obstructed telescope pupils are described. Both concepts use entrance pupil amplitude apodization and a combined phase and amplitude focal plane mask to achieve full coronagraphic extinction of an on-axis point source. While the first concept, named Apodized Pupil Complex Mask Lyot Coronagraph (APCMLC), relies on a transmission mask to perform the pupil apodization, the second concept, named Phase-Induced Amplitude Apodization complex mask coronagraph (PIAACMC), uses beam remapping for lossless apodization. Both concep…
Wide-field (> 100 deg$^2$) hard X-ray coded-aperture telescopes with high angular resolution (< 2') will enable a wide range of time domain astrophysics. For instance, transient sources such as gamma-ray bursts can be precisely localized without assistance of secondary focusing X-ray telescopes to enable rapid followup studies. On the other hand, high angular resolution in coded-aperture imaging introduces a new challenge in handling the systematic uncertainty: average photon count per pixel is often too small to establish a proper background pattern or model the systematic uncertainty in a ti…
The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese mega-science project funded by the National Development and Reform Commission (NDRC) of the People's Republic of China. The National Astronomical Observatories of China (NAOC) is in charge of its construction and subsequent operation. Upon its expected completion in September 2016, FAST will surpass the 300-meter Arecibo Telescope and the 100-meter Green Bank Telescope in terms of absolute sensitivity in the 70 MHz to 3 GHz bands. In this paper, we report on the project, its current status, the key science goals, and…
In this paper, we are going to introduce the Kottamia Astronomical Observatory, KAO, to the astronomical community. The current status of the telescope together with the available instrumentations is described. An upgrade stage including a new optical system and a computer controlling of both the telescope and dome are achieved. The specifications of a set of CCD cameras for direct imaging and spectroscopy are given. A grating spectrograph is recently gifted to KAO from Okayama Astrophysical Observatory, OAO, of the National Astronomical Observatories in Japan. This spectrograph is successfull…
Current state-of-the-art high contrast imaging instruments take advantage of a number of elegant coronagraph designs to suppress starlight and image nearby faint objects, such as exoplanets and circumstellar disks. The ideal performance and complexity of the optical systems depends strongly on the shape of the telescope aperture. Unfortunately, large primary mirrors tend to be segmented and have various obstructions, which limit the performance of most conventional coronagraph designs. We present a new family of vortex coronagraphs with numerically-optimized gray-scale apodizers that provide t…
The last half-century has seen dramatic developments in gamma-ray telescopes, from their initial conception and development through to their blossoming into full maturity as a potent research tool in astronomy. Gamma-ray telescopes are leading research in diverse areas such as gamma-ray bursts, blazars, Galactic transients, and the Galactic distribution of aluminum-26.
The Five-hundred-meter Aperture Spherical radio Telescope (FAST), the largest single dish radio telescope in the world, has implemented an innovative technology for its huge reflector, which changes the shape of the primary reflector from spherical to that of a paraboloid of 300 m aperture. Here we explore how the current FAST sensitivity can potentially be further improved by increasing the illuminated area (i.e., the aperture of the paraboloid embedded in the spherical surface). Alternatively, the maximum zenith angle can be increased to give greater sky coverage by decreasing the illuminate…
The National Astronomical Observatories, Chinese Academy of Science (NAOC), has started building the largest antenna in the world. Known as FAST, the Five-hundred-meter Aperture Spherical radio Telescope is a Chinese mega-science project funded by the National Development and Reform Commission (NDRC). FAST also represents part of Chinese contribution to the international efforts to build the square kilometer array (SKA). Upon its finishing around September of 2016, FAST will be the most sensitive single-dish radio telescope in the low frequency radio bands between 70 MHz and 3 GHz. The design …
The Simons Observatory (SO) is a ground-based cosmic microwave background (CMB) survey experiment that consists of three 0.5 m small-aperture telescopes (SATs) and one 6 m large-aperture telescope (LAT), sited at an elevation of 5200 m in the Atacama Desert in Chile. In order to meet the sensitivity requirements set for next-generation CMB telescopes, the LAT will deploy 30,000 transition edge sensor (TES) detectors at 100 mK across 7 optics tubes (OT), all within the Large Aperture Telescope Receiver (LATR). Additionally, the LATR has the capability to expand to 62,000 TES across 13 OTs. The …
A novel method nicknamed ELASTIC is proposed for the alignment of multiple-aperture telescopes, in particular segmented telescopes. It only needs the acquisition of two diversity images of an unresolved source, and is based on the computation of a modified, frequency-shifted, cross-spectrum. It provides a polychromatic large range tip/tilt estimation with the existing hardware and an inexpensive noniterative unsupervised algorithm. Its performance is studied and optimized by means of simulations. They show that with 5000 photo-electrons/sub-aperture/frame and 1024x1024 pixel images, residues a…
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The Atacama Large Aperture Submillimeter Telescope (AtLAST) is a concept for a 50m class single-dish telescope that will provide high sensitivity, fast mapping of the (sub-)millimeter sky. Expected to be powered by renewable energy sources, and to be constructed in the Atacama desert in the 2030s, AtLAST's suite of up to six state-of-the-art instruments will take advantage of its large field of view and high throughput to deliver efficient continuum and spectroscopic observations of the faint, large-scale emission that eludes current facilities. Here we present the key science drivers for the …
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The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is by far the largest telescope of any kind ever built. FAST produced its first light in September 2016 and it is now under commissioning, with normal operation to commence in late 2019. During testing and early science operation, FAST has started making astronomical discoveries, particularly pulsars of various kinds, including millisecond pulsars, binaries, gamma-ray pulsars, etc. The papers in this mini-volume propose ambitious observational projects to advance our knowledge of astronomy, astrophysics and fundamental physics in…
The Advanced Technology Large Aperture Space Telescope (ATLAST) is a set of mission concepts for the next generation UV-Optical-Near Infrared space telescope with an aperture size of 8 to 16 meters. ATLAST, using an internal coronagraph or an external occulter, can characterize the atmosphere and surface of an Earth-sized exoplanet in the Habitable Zone of long-lived stars at distances up to ~45 pc, including its rotation rate, climate, and habitability. ATLAST will also allow us to glean information on the nature of the dominant surface features, changes in cloud cover and climate, and, poten…
Point spread function modelling for astronomical telescopes: a review focused on weak gravitational lensing studies
CEA（法国原子能和替代能源委员会）；CNRS（法国国家科学研究中心）；AIM（天体物理与宇宙学研究所）；University College London (UCL)（伦敦大学学院）；Mullard Space Science Laboratory（穆拉德空间科学实验室）；Institute of Astrophysics（天体物理研究所）
The Virtual Observatory (VO) is becoming the de-facto standard for astronomical data publication. However, the number of radio astronomical archives is still low in general, and even lower is the number of radio astronomical data available through the VO. In order to facilitate the building of new radio astronomical archives, easing at the same time their interoperability with VO framework, we have developed a VO-compliant data model which provides interoperable data semantics for radio data. That model, which we call the Radio Astronomical DAta Model for Single-dish (RADAMS) has been built us…
Precision wavefront control on future segmented-aperture space telescopes presents significant challenges, particularly in the context of high-contrast exoplanet direct imaging. We present a new wavefront control architecture that translates the ground-based artificial guide star concept to space with a laser source aboard a second spacecraft, formation flying within the telescope field-of-view. We describe the motivating problem of mirror segment motion and develop wavefront sensing requirements as a function of guide star magnitude and segment motion power spectrum. Several sample cases with…
VST--Tube is a new software package designed to process optical astronomical images. It is an automated pipeline to go from the raw exposures to fully calibrated co-added images, and to extract catalogs with aperture and PSF photometry. A set of tools allow the data administration and the quality check of the intermediate and final products. VST-Tube comes with a Graphical User Interface to facilitate the interaction between data and user. We outline here the VST--Tube architecture and show some applications enlightening some of the characteristics of the pipeline.
The Earth-skimming $ν_τ$ method allows for huge target mass and detection volume simultaneously. In part motivated by IceCube PeV astro-neutrino events, the planned NTA observatory has three site stations watching the air mass surrounded by Mauna Loa, Mauna Kea, and Hualalai on Hawaii Island, plus a site station at the center watching the lower night sky. Sensitivities equivalent to $> 100$ km$^3$ water and pointing accuracy of $< 0.2^\circ$ can be achieved with Cherenkov-fluorescence stereoscopic observation for PeV-EeV neutrinos that is almost background-free. With design based on experience…
We describe a new concept to correct for scintillation noise on high-precision photometry in large and extremely large telescopes using telemetry data from adaptive optics (AO) systems. Most wide-field AO systems designed for the current era of very large telescopes and the next generation of extremely large telescopes require several guide stars to probe the turbulent atmosphere in the volume above the telescope. These data can be used to tomographically reconstruct the atmospheric turbulence profile and phase aberrations of the wavefront in order to assist wide-field AO correction. If the wa…
The Five-hundred-metre Aperture Spherical Telescope (FAST) uses adaptive spherical panels to achieve a huge collecting area for radio waves. In this paper, we try to explore the optimal parameters for the curvature radius of spherical panels and the focal distance by comparison of the calculated beam patterns. We show that to get the best beam shape and maximum gain, the optimal curvature radius of panels is around 300 m, and a small shift in the focal distance of a few cm is needed. The aperture efficiency can be improved by ~10% at 3 GHz by this small shift. We also try to optimise the panel…
The Astronomical Telescope of the University of Stuttgart (ATUS): Development, Optimization, and Lessons Learned
Institute of Space Systems, Universität Stuttgart（斯图加特大学空间系统研究所）；The German SOFIA Institute (Deutsches SOFIA Institut, DSI)（德国SOFIA研究所）；SOFIA Science Center, NASA Ames Research Center（NASA艾姆斯研究中心SOFIA科学中心）
Aryabhatta Research Institute of Observational Sciences (acronym ARIES) operates a 1-m aperture optical telescope at Manora Peak, Nainital since 1972. Considering the need and potential of establishing moderate size optical telescope with spectroscopic capability at the geographical longitude of India, the ARIES plans to establish a 3.6m new technology optical telescope at a new site called Devasthal. This telescope will have instruments providing high resolution spectral and seeing-limited imaging capabilities at visible and near-infrared bands. A few other observing facilities with very spec…
We present A-PHOT, a new publicly available code for performing aperture photometry on astronomical images, that is particularly well suited for multi-band extragalactic surveys. A-PHOT estimates the fluxes emitted by astronomical objects within a chosen set of circular or elliptical apertures. Unlike other widely used codes, it runs on predefined lists of positions, allowing for repeated measurements on the same list of objects on different images. This can be very useful when forced photometric measurement on a given position is needed. A-PHOT can also estimate morphological parameters and a…
Antenna efficiency is one of the most important figures-of-merit of a radio telescope for observations especially at millimeter wavelengths or shorter wavelengths, even for a multibeam radio telescope. To analyze a system with a beam waveguide, a lossless antenna consisting of two apertures in series is considered in the frame of the scalar wave approximation. We found that the antenna efficiency can be evaluated with the field distribution over the second aperture, and that the antenna efficiency is factorized into three factors: efficiencies of beam coupling, transmission spillover, and rece…
Our team at the INAF-Astronomical Observatory of Padova and the University of Padova is engaged in the design, construction and operations of instruments with very high time accuracy in the optical band for applications to High Time Resolution Astrophysics and Quantum Astronomy. Two instruments were built to perform photon counting with sub-nanosecond temporal accuracy, Aqueye+ and Iqueye. Aqueye+ is regularly mounted at the 1.8m Copernicus telescope in Asiago, while Iqueye was mounted at several 4m class telescopes around the world and is now attached through the Iqueye Fiber Interface at the…
Among present-day observatories, the Arecibo Radio Telescope represents an extension of Galileo's vision to its logical extreme. With a diameter of 305 metres and state-of-the-art instrumentation, Arecibo continues to build on its legacy of world-class scientific achievement in radio astronomy. This paper highlights milestones in the remarkable history of this telescope, and also discusses current surveys that are imaging the hydrogen content of our Milky Way Galaxy, and far beyond, in unprecedented detail.
The first observations with the 25 cm telescope of the Shumen Astronomical Observatory led to the following conclusions: (a) Intra-night observations of variable stars with an amplitude larger than 0.1 mag are possible down to 14 mag with an acceptable quality with this setup; (b) The equipment is suitable for observations of bright extended objects with sizes up to 30 arcmin (planets, comets, clusters, nebulae, galaxies) with resolution 0.88 arcsec/pix; (c) The guiding of telescope is very good which makes the equipment appropriate for prolonged patrols; (d) The observations with the 25 cm ar…
Current large-aperture cosmic microwave background (CMB) telescopes have nearly maximized the number of detectors that can be illuminated while maintaining diffraction-limited image quality. The polarization-sensitive detector arrays being deployed in these telescopes in the next few years will have roughly $10^4$ detectors. Increasing the mapping speed of future instruments by at least an order of magnitude is important to enable precise probes of the inflationary paradigm in the first fraction of a second after the big bang and provide strong constraints on cosmological parameters. The CMB c…
We present a comprehensive methodology for the simulation of astronomical images from optical survey telescopes. We use a photon Monte Carlo approach to construct images by sampling photons from models of astronomical source populations, and then simulating those photons through the system as they interact with the atmosphere, telescope, and camera. We demonstrate that all physical effects for optical light that determine the shapes, locations, and brightnesses of individual stars and galaxies can be accurately represented in this formalism. By using large scale grid computing, modern processo…
The American Astronomical Society's WorldWide Telescope (WWT) project enables terabytes of astronomical images, data, and stories to be viewed and shared among researchers, exhibited in science museums, projected into full-dome immersive planetariums and virtual reality headsets, and taught in classrooms from middle school to college levels. We review the WWT ecosystem, how WWT has been used in the astronomical community, and comment on future directions.
Astronomical images are essential for exploring and understanding the universe. Optical telescopes capable of deep observations, such as the Hubble Space Telescope, are heavily oversubscribed in the Astronomical Community. Images also often contain additive noise, which makes de-noising a mandatory step in post-processing the data before further data analysis. In order to maximise the efficiency and information gain in the post-processing of astronomical imaging, we turn to machine learning. We propose Astro U-net, a convolutional neural network for image de-noising and enhancement. For a proo…
In less than a year, the James Webb Space Telescope (JWST) will inherit the mantle of being the world's pre-eminent infrared observatory. JWST will carry with it an Aperture Masking Interferometer (AMI) as one of the supported operational modes of the Near-InfraRed Imager and Slitless Spectrograph (NIRISS) instrument. Aboard such a powerful platform, the AMI mode will deliver the most advanced and scientifically capable interferometer ever launched into space, exceeding anything that has gone before it by orders of magnitude in sensitivity. Here we present key aspects of the design and commiss…
Direct imaging of exoplanets or circumstellar disk material requires extreme contrast at the 10-6 to 10-12 levels at < 100 mas angular separation from the star. Focal-plane mask (FPM) coronagraphic imaging has played a key role in this field, taking advantage of progress in Adaptive Optics on ground-based 8+m class telescopes. However, large telescope entrance pupils usually consist of complex, sometimes segmented, non-ideal apertures, which include a central obstruction for the secondary mirror and its support structure. In practice, this negatively impacts wavefront quality and coronagraphic…
We present methods for optimizing pupil and focal plane optical elements that improve the performance of vortex coronagraphs on telescopes with obstructed or segmented apertures. Phase-only and complex masks are designed for the entrance pupil, focal plane, and the plane of the Lyot stop. Optimal masks are obtained using both analytical and numerical methods. The latter makes use of an iterative error reduction algorithm to calculate "correcting" optics that mitigate unwanted diffraction from aperture obstructions. We analyze the achieved performance in terms of starlight suppression, contrast…
In optical astronomical telescopes, the primary baffle is a tube-like structure centering in the hole of the primary mirror and the vanes usually locate inside the baffle, improving the suppression of stray light. They are the most common methods of stray light control. To characterize the performance of primary baffle and vanes, an empirical comparison based on astronomical observations has been made with Xinglong 50cm telescope. Considering the convenience of switching, an independent vanes structure is designed, which can also improve the process of the primary mirror cooling and the air ci…
Next generation radio telescopes will be much larger, more sensitive, have much larger observation bandwidth and will be capable of pointing multiple beams simultaneously. Obtaining the sensitivity, resolution and dynamic range supported by the receivers requires the development of new signal processing techniques for array and atmospheric calibration as well as new imaging techniques that are both more accurate and computationally efficient since data volumes will be much larger. This paper provides a tutorial overview of existing image formation techniques and outlines some of the future dir…
Xinglong Observatory of the National Astronomical Observatories, Chinese Academy of Sciences (NAOC), is one of the major optical observatories in China, which hosts nine optical telescopes including the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and the 2.16 m reflector. Scientific research from these telescopes is focused on stars, galaxies, and exoplanets using multicolor photometry and spectroscopic observations. Therefore, it is important to provide the observing conditions of the site, in detail, to the astronomers for an efficient use of these facilities. In this …
Intelligent scheduling of the sequence of scientific exposures taken at ground-based astronomical observatories is massively challenging. Observing time is over-subscribed and atmospheric conditions are constantly changing. We propose to guide observatory scheduling using machine learning. Leveraging a 15-year archive of exposures, environmental, and operating conditions logged by the Canada-France-Hawaii Telescope, we construct a probabilistic data-driven model that accurately predicts image quality. We demonstrate that, by optimizing the opening and closing of twelve vents placed on the dome…
The Xinglong 2.16-m reflector is the first 2-meter class astronomical telescope in China. It was jointly designed and built by the Nanjing Astronomical Instruments Factory (NAIF), Beijing Astronomical Observatory (now National Astronomical Observatories, Chinese Academy of Sciences, NAOC) and Institute of Automation, Chinese Academy of Sciences in 1989. It is Ritchey-Chrétien (R-C) reflector on an English equatorial mount and the effective aperture is 2.16 meters. It had been the largest optical telescope in China for $\sim18$ years until the Guoshoujing Telescope (also called Large Sky Area M…
