Machine learning-based analysis has become essential to efficiently handle the increasing massive data from modern astronomical instruments in recent years. Churchwell et al. (2006, 2007) identified infrared ring structures, which are believed to relate to the formation of massive stars, with the human eye. Recently, Ueda et al. (2020) showed that Convolutional Neural Networks (CNN) can detect objects with indistinct boundaries such as infrared rings with comparable accuracy as the human eye. However, such a classification-based object detector requires a long processing time, making it impractical to apply to existing all-sky 12 μm and 22 μm data captured by WISE. We introduced the Single Shot MultiBox Detector (SSD, Liu W. et al. 2016), which directly outputs the locations and confidences of targets, to significantly reduce the time for identification. We applied an SSD model to the rings toward the 6 deg2 region in the Galactic plane which is the same region used in Ueda et al. (2020), and confirmed that the time for identification was reduced by about 1/80 with maintaining almost the same accuracy. Since detecting small rings is still difficult by even this model, an input image should be cropped
into small images, which increases the number of applications of the model. There is still room for reducing the
processing time. In the future, we will try to solve this problem and detect the rings faster.
Photogrammetry technique is widely used for the initial alignment of main-reflector panels of millimeter/ submillimeter-wave telescopes by analyzing a great number of photos of the reflector at the rest state taken from different angles and distances. In this study, we investigated a possibility that the photogrammetry can be applied for real-time surface measurements which is important to realize active surface controls that improve reflector surface accuracy during scientific observations. The technique is important especially for realizing larger aperture and higher frequency telescopes. We developed a simulator to investigate the accuracy of the surface measurements with photos taken with fixed cameras mounted on the stays of the sub-reflector. As a result, we found that the accuracy of surface measurement is roughly inversely proportional to square-root of the number of fixed cameras, and the calculation time roughly proportional to the product of the numbers of cameras and measurement points. For the case of Nobeyama 45-m telescope, the accuracy of 1 mm (rms) was achieved for 164 surface points by 10 cameras with a calculation time of ∼2 sec by a developed python code using a single-core Xeon processor. In order to improve the accuracy with a minimum number of cameras, more various camera positions (e.g., surrounding the vertex hole of the main reflector and surrounding the main reflector) should be investigated, and their combination should be optimized. Applying high-performing technologies such as multiprocessors and/or GPUs, faster calculation is to be considered.
We report the current status of the NASCO (NAnten2 Super CO survey as legacy) project which aims to provide all-sky CO data cube of southern hemisphere using the NANTEN2 4-m submillimeter telescope installed at the Atacama Desert through developing a new multi-beam receiver and a new telescope control system. The receiver consists of 5 beams. The four beams, located at the four corners of a square with the beam separation of 720′′, are installed with a 100 GHz band SIS receiver having 2-polarization sideband-separation filter. The other beam, located at the optical axis, is installed with a 200 GHz band SIS receiver having 2-polarization sideband-separation filter. The cooled component is modularized for each beam, and cooled mirrors are used. The IF bandwidths are 8 and 4 GHz for 100 and 200 GHz bands, respectively. Using XFFTS spectrometers with a bandwidth of 2 GHz, the lines of 12CO, 13CO, and C18O of J=1−0 or J=2−1 can be observed simultaneously for each beam. The control system is reconstructed on the ROS architecture, which is an open source framework for robot control, to enable a flexible observation mode and to handle a large amount of data. The framework is commonly used and maintained in a robotic field, and thereby reliability, flexibility, expandability, and efficiency in development are improved as compared with the system previously used. The receiver and control system are installed on the NANTEN2 telescope in December 2019, and its commissioning and science verification are on-going. We are planning to start science operation in early 2021.
Owing to recent performance improvement and lower pricing of computers, built-in computers are equipped in virtually all measurement/control hardware, and small computers (e.g., Raspberry-Pi) can be obtained inexpensively to monitor the environment and/or hardware status. Those devices are able to communicate via network. The system having flexibility adaptable with the rapidly changing trend of hardware is desired in order to provide powerful functions quickly for the telescope control. Software developed for robot operations could be used for this purpose that controlling distributed and network-linked hardware. The Robot Operating System (ROS) is an open source software platform and one of the most used frameworks for robot operations. It has a number of libraries and tools to help us create robot applications. Under this background, we are developing NECST (NEw Control System for Telescope) using ROS framework. In NECST, each atomic operation (such as device operation and arithmetic operation) is divided into a node which is an elemental object in ROS. Nodes are grouped and packaged by their functionalities for convenience. The control systems of telescope and receiver are built by combining those packages. Since there are about ∼100 nodes even in the telescope control part, we also developed utilities to manage nodes that visualizes sent/received data in real time. Currently, NECST is installed and operated mainly for receiver control and antenna control of 1.85-m mm-submm wave telescope.
We present a concept of a millimeter wavefront sensor that allows real-time sensing of the surface of a groundbased millimeter/submillimeter telescope. It is becoming important for ground-based millimeter/submillimeter astronomy to make telescopes larger with keeping their surface accurate. To establish `millimetric adaptive optics (MAO)' that instantaneously corrects the wavefront degradation induced by deformation of telescope optics, our wavefront sensor based on radio interferometry measures changes in excess path lengths from characteristic positions on the primary mirror surface to the focal plane. This plays a fundamental role in planed 50-m class submillimeter telescopes such as LST and AtLAST.
We are promoting the Hybrid Installation Project in Nobeyama, Triple-band Oriented (HINOTORI), a project aiming at triple-band simultaneous single-dish and VLBI observation in the 22-, 43- and 86-GHz bands using the Nobeyama 45-m Telescope. The triple-band simultaneous observation becomes possible by developing two perforated plates and mounting them in the Nobeyama 45-m Telescope optics. One is a 22/43-GHz-band perforated plate, which transmits the higher frequency (43-GHz) band and reflects the lower frequency (22-GHz) band, and the other is a 43/86-GHz-band perforated plate, which transmits the 86-GHz band and reflects the 43-GHz band or lower. Both plates are designed to be installed in the large telescope optics with a beam diameter as large as 50 cm and insertion/reflection losses are both 0.22 dB (5%) or less in the design. The receivers used in triple-band simultaneous observation system are the H22 and H40 receivers, which are already installed in the Nobeyama 45-m Telescope, and the TZ receiver, which is a 100-GHz-band receiver including the 86-GHz band and reinstalled in the Nobeyama 45-m Telescope. A system of simultaneous observations in the 22- and 43-GHz bands of the Nobeyama 45-m Telescope with the 22/43- GHz-band perforated plate has been completed and commissioned for scientific observations. Also VLBI fringes between the Nobeyama 45-m telescope with the dual-band observation system and the VERA 20-m telescopes at 22 and 43 GHz was detected successfully.
The 1.85-m mm-submm telescope has been operated at Nobeyama Radio Observatory to observe molecular clouds in the nearby Galactic Plane based on the molecular lines of 12CO, 13CO, C18O(J = 2–1). We are planning to relocate the telescope to a site (∼2,500 m) at the Atacama Desert in Chile and to newly install a dual-band receiver for simultaneous observations of lines of CO isotopes with the transitions of J = 2–1 and J = 3–2. In order to achieve this goal, we have developed a wideband diplexer to separate radio frequency (RF) 211–275 GHz (ALMA Band 6) and 275–373 GHz (ALMA Band 7). We adopted a waveguide type FrequencySeparation Filters (FSF) as the basic concept of the wideband diplexer in 210–375 GHz. The wideband diplexer (α) has already been fabricated and measured as the prototype, and we thus obtained reasonable performance in the CO lines band. On the other hand, the measurement result indicates the return loss is relatively worse in 280–300 GHz, although it doesn’t affect the simultaneous observations of 230 GHz and 345 GHz band. We carried out 3D shape measurement with an optical microscope, and then, found that there are machining errors in the parts of the resonator in High Pass Filter. The analysis based on electromagnetic simulation reveals that the errors significantly affect return loss around cut-off frequency. In this paper, we describes the design of the waveguide diplexer, S-parameter measurement, and detailed analysis to verify the discrepancy between simulation and measurement.
We report the current status of the 1.85-m mm-submm telescope installed at the Nobeyama Radio Observatory (altitude 1400 m) and the future plan. The scientific goal is to reveal the physical/chemical properties of molecular clouds in the Galaxy by obtaining large-scale distributions of molecular gas with an angular resolution of several arcminutes. A semi-automatic observation system created mainly in Python on Linux-PCs enables effective operations. A large-scale CO J =2–1 survey of the molecular clouds (e.g., Orion-A/B, Cygnus-X/OB7, Taurus- California-Perseus complex, and Galactic Plane), and a pilot survey of emission lines from minor molecular species toward Orion clouds have been conducted so far. The telescope also is providing the opportunities for technical demonstrations of new devices and ideas. For example, the practical realizations of PLM (Path Length Modulator) and waveguide-based sideband separating filter, installation of the newly designed waveguide-based circular polarizer and OMT (Orthomode Transducer), and so on. As the next step, we are now planning to relocate the telescope to San Pedro de Atacama in Chile (altitude 2500 m), and are developing very wideband receiver covering 210–375 GHz (corresponding to Bands 6–7 of ALMA) and full-automatic observation system. The new telescope system will provide large-scale data in the spatial and frequency domain of molecular clouds of Galactic plane and Large/Small Magellanic Clouds at the southern hemisphere. The data will be precious for the comparison with those of extra-galactic ones that will be obtained with ALMA as the Bands 6/7 are the most efficient frequency bands for the surveys in extra-galaxies for ALMA.
Currently, we are performing a large-scale survey of molecular clouds toward the Galactic Plane in 12CO, 13CO, and C18O(J = 2–1) with the 1.85-m mm-submm telescope from Nobeyama Radio Observatory. In addition, we are proceeding with the preparation of a new project to observe several additional molecular lines including higher transitions of CO isotopes, such as 12CO, 13CO, and C18O(J = 2–1, 3–2) simultaneously with a wideband receiver (210–375 GHz). The optics has a Cassegrain reflector antenna with Nasmyth beam-waveguide feed and is composed of Main-reflector, Sub-reflector, ellipsoidal mirrors, and plane mirrors. New wideband optics will be required to achieve this goal. In order to accomplish the optics, we have designed a corrugated horn with a fractional bandwidth of ∼56 %, and frequency independent optics to couple the beam from the telescope onto the horn. The corrugated horn has a conical profile and the variable corrugation depth. It has been optimized by using CHAMP, our targeting return loss of better than −20 dB, cross-polarization loss of better than −25 dB, and far-field good radiation pattern. The simulation of the corrugated horn results in low return loss, low crosspolarization, and symmetric beam pattern in that frequency band. The simulated aperture efficiency of the designed receiver optics on the 1.85-m telescope is above 0.76 at all frequencies by using GRASP. Recently, we have succeeded in simultaneous observation of 12CO, 13CO, and C18O(J = 2–1 and 3–2) toward Orion KL with the optics for the first time.
Recently, the amount of data obtained from astronomical instruments has been increasing explosively, and data science methods such as Machine Learning/Deep Learning gain attention on the back of the growth in demand for automatic analysis. Using these methods, the number of applications to the target sources that have clear boundaries with the background i.e., stars, planets, and galaxies is increasing year by year. However, there are a few studies which applied the data science methods to the interstellar medium (ISM) distributed in the Galactic plane, which have complicated and ambiguous silhouettes. We aim to develop classifiers to automatically extract various structures of the ISM by Convolutional Neural Network (CNN) that is strong in image recognition even in deep learning. In this study, we focus on the infra-red (IR) ring structures distributed in the Galactic plane. Based on the catalog of Churchwell et al. (2006, 2007), we created a “Ring” dataset from the Spitzer/GLIMPSE 8 μm and Spitzer/MIPSGAL 24 μm data and optimized the parameters of the CNN model. We applied the developed model to a range of 16.5° ≤ l ≤ 19.5°, |b| ≤ 1° . As a result, 234 “Ring” candidates are detected. The “Ring” candidates were matched with 75% Milky Way Project (MWP, Simpson et al. 2012) “Ring” and 65% WISE Hii region catalog (Anderson et al. 2014). In addition, new“Ring”and Hii region candidate objects were also found. For these results, we conclude that the CNN model may have a recognition accuracy equal to or better than that of human eyes.
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