Pub Date : 2019-05-29DOI: 10.1142/S225117171950003X
G. Schoonderbeek, A. Szomoru, A. Gunst, L. Hiemstra, J. Hargreaves
With the ever-increasing data rates in radio astronomy, a universal Field Programmable Gate Array (FPGA)-based hardware platform which can be used at different locations in the signal processing chain, like a beamformer, data router or correlator, would reduce development time significantly. In this paper, we present the design of such a platform, the UniBoard2. With UniBoard2, both large rack-based and single-board systems can be made. Standard Quad Small Form-factor Pluggable (QSFP) input and output (IO) interfaces on the front side make it easy to interface UniBoard2 to standard 40 Gigabit Ethernet (GbE) network equipment. Hardware design challenges, like transceiver links, power supplies, power dissipation and cooling are described. The paper concludes with some examples of systems (like beamformers and correlators) that can be built using the UniBoard2 hardware platform.
{"title":"UniBoard2, A Generic Scalable High-Performance Computing Platform for Radio Astronomy","authors":"G. Schoonderbeek, A. Szomoru, A. Gunst, L. Hiemstra, J. Hargreaves","doi":"10.1142/S225117171950003X","DOIUrl":"https://doi.org/10.1142/S225117171950003X","url":null,"abstract":"With the ever-increasing data rates in radio astronomy, a universal Field Programmable Gate Array (FPGA)-based hardware platform which can be used at different locations in the signal processing chain, like a beamformer, data router or correlator, would reduce development time significantly. In this paper, we present the design of such a platform, the UniBoard2. With UniBoard2, both large rack-based and single-board systems can be made. Standard Quad Small Form-factor Pluggable (QSFP) input and output (IO) interfaces on the front side make it easy to interface UniBoard2 to standard 40 Gigabit Ethernet (GbE) network equipment. Hardware design challenges, like transceiver links, power supplies, power dissipation and cooling are described. The paper concludes with some examples of systems (like beamformers and correlators) that can be built using the UniBoard2 hardware platform.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S225117171950003X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48337444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-05-29DOI: 10.1142/S2251171719920016
K. Buch, A. Boonstra, G. Hellbourg, J. Kocz, U. Rau, L. Greenhill
{"title":"Erratum: Preface: “Interference Mitigation Techniques in Radio Astronomy”","authors":"K. Buch, A. Boonstra, G. Hellbourg, J. Kocz, U. Rau, L. Greenhill","doi":"10.1142/S2251171719920016","DOIUrl":"https://doi.org/10.1142/S2251171719920016","url":null,"abstract":"","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171719920016","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46361432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-05-29DOI: 10.1142/S2251171719500053
D. Mozurkewich, A. Jorgensen, G. V. van Belle
Ground-based long-baseline astronomical interferometry operates in a regime where short integration exposures are demanded by working in the presence of a turbulent atmosphere. To reduce piston noise to less than one radian per aperture, these exposure times are on order 10 milliseconds or less in the visible. It has long been recognized that, in the low signal-to-noise ratio (SNR) regime, the visibility SNR is improved by co-adding frames, each rotated by an estimate of its phase. However, implementation of this technique is challenging. Where it is most needed, on low SNR baselines and when combining multiple phases to estimate the phase for a lower SNR baseline, phase errors reduce the amplitude by a large amount and in a way that has proven difficult to calibrate. In this paper, an improved coherent integration algorithm is presented. A parameterized model for the phase as a function of time and wavelength is fit to the entire data set. This framework is used to build a performance model which can be used in two ways. First, it can be used to test the algorithm; by comparing its performance to theory, one can test how well the parameter fitting has worked. Also, when designing future systems, this model provides a simple way to predict performance and compare it to alternative techniques such as hierarchical fringe tracking. This technique has been applied to both simulated and stellar data.
{"title":"Coherent Integration in Astronomical Interferometry: Theory and Practice","authors":"D. Mozurkewich, A. Jorgensen, G. V. van Belle","doi":"10.1142/S2251171719500053","DOIUrl":"https://doi.org/10.1142/S2251171719500053","url":null,"abstract":"Ground-based long-baseline astronomical interferometry operates in a regime where short integration exposures are demanded by working in the presence of a turbulent atmosphere. To reduce piston noise to less than one radian per aperture, these exposure times are on order 10 milliseconds or less in the visible. It has long been recognized that, in the low signal-to-noise ratio (SNR) regime, the visibility SNR is improved by co-adding frames, each rotated by an estimate of its phase. However, implementation of this technique is challenging. Where it is most needed, on low SNR baselines and when combining multiple phases to estimate the phase for a lower SNR baseline, phase errors reduce the amplitude by a large amount and in a way that has proven difficult to calibrate. In this paper, an improved coherent integration algorithm is presented. A parameterized model for the phase as a function of time and wavelength is fit to the entire data set. This framework is used to build a performance model which can be used in two ways. First, it can be used to test the algorithm; by comparing its performance to theory, one can test how well the parameter fitting has worked. Also, when designing future systems, this model provides a simple way to predict performance and compare it to alternative techniques such as hierarchical fringe tracking. This technique has been applied to both simulated and stellar data.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171719500053","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47824922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-18DOI: 10.1142/S2251171719400075
W. Baan, A. Jessner, Jaap Steenge
This paper presents an observing methodology for calibrated measurements of radio interference levels and compares these with threshold interference limits that have been established for interference entering the bands allocated to the Radio Astronomy Service. The measurement time and bandwidth intervals for these observations may be commensurate with the time and frequency variability characteristic of the interfering signals and the threshold levels may be appropriately scaled from the values presented in ITU-R RA.769 using a 2000[Formula: see text]s reference time interval. The data loss for astronomical instruments may be measured as a percentage of occupancy in the time–frequency domain both for short and long measurement intervals. The observed time–frequency occupancy characteristics for non-geostationary satellite systems and earth stations in the mobile–satellite service may be incorporated into an effective power flux density simulation to obtain the effective data loss and sky blockage due to these services.
{"title":"Measuring Data Loss Resulting from Interference","authors":"W. Baan, A. Jessner, Jaap Steenge","doi":"10.1142/S2251171719400075","DOIUrl":"https://doi.org/10.1142/S2251171719400075","url":null,"abstract":"This paper presents an observing methodology for calibrated measurements of radio interference levels and compares these with threshold interference limits that have been established for interference entering the bands allocated to the Radio Astronomy Service. The measurement time and bandwidth intervals for these observations may be commensurate with the time and frequency variability characteristic of the interfering signals and the threshold levels may be appropriately scaled from the values presented in ITU-R RA.769 using a 2000[Formula: see text]s reference time interval. The data loss for astronomical instruments may be measured as a percentage of occupancy in the time–frequency domain both for short and long measurement intervals. The observed time–frequency occupancy characteristics for non-geostationary satellite systems and earth stations in the mobile–satellite service may be incorporated into an effective power flux density simulation to obtain the effective data loss and sky blockage due to these services.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171719400075","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49578523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-04-18DOI: 10.1142/S2251171719400063
K. Buch, K. Naik, Swapnil Nalawade, Shruti Bhatporia, Y. Gupta, B. Ajithkumar
Radio Frequency Interference (RFI) excision in wideband radio telescope receivers is gaining significance due to increasing levels of manmade RFI and operation outside the protected radio astronomy bands. The effect of RFI on astronomical data can be significantly reduced through real-time excision. In this paper, Median Absolute Deviation (MAD) is used for excising signals corrupted by strong impulsive interference. MAD estimation requires recursive median calculation which is a computationally challenging problem for real-time excision. This challenge is addressed by implementation of a histogram-based technique for MAD computation. The architecture is developed and optimized for Field Programmable Gate Array (FPGA) implementation. The design of a more robust variant of MAD called Median-of-MAD (MoM) is described. The architecture of MAD and MoM techniques and subsequent optimization allows for four RFI excision blocks on a single Xilinx Virtex-5 FPGA. These techniques have been tested on the GMRT wideband backend (GWB) processing a maximum of 400[Formula: see text]MHz bandwidth and the results show significant improvement in the signal-to-noise ratio (SNR).
{"title":"Real-Time Implementation of MAD-Based RFI Excision on FPGA","authors":"K. Buch, K. Naik, Swapnil Nalawade, Shruti Bhatporia, Y. Gupta, B. Ajithkumar","doi":"10.1142/S2251171719400063","DOIUrl":"https://doi.org/10.1142/S2251171719400063","url":null,"abstract":"Radio Frequency Interference (RFI) excision in wideband radio telescope receivers is gaining significance due to increasing levels of manmade RFI and operation outside the protected radio astronomy bands. The effect of RFI on astronomical data can be significantly reduced through real-time excision. In this paper, Median Absolute Deviation (MAD) is used for excising signals corrupted by strong impulsive interference. MAD estimation requires recursive median calculation which is a computationally challenging problem for real-time excision. This challenge is addressed by implementation of a histogram-based technique for MAD computation. The architecture is developed and optimized for Field Programmable Gate Array (FPGA) implementation. The design of a more robust variant of MAD called Median-of-MAD (MoM) is described. The architecture of MAD and MoM techniques and subsequent optimization allows for four RFI excision blocks on a single Xilinx Virtex-5 FPGA. These techniques have been tested on the GMRT wideband backend (GWB) processing a maximum of 400[Formula: see text]MHz bandwidth and the results show significant improvement in the signal-to-noise ratio (SNR).","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171719400063","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41850278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-03-22DOI: 10.1142/S2251171719500119
P. Nagler, B. Edwards, B. Kilpatrick, N. Lewis, P. Maxted, C. Netterfield, V. Parmentier, E. Pascale, Subhajit Sarkar, G. Tucker, I. Waldmann
Although there exists a large sample of known exoplanets, little data exists that can be used to study their global atmospheric properties. This deficiency can be addressed by performing phase-resolved spectroscopy — continuous spectroscopic observations of a planet’s entire orbit about its host star — of transiting exoplanets. Planets with characteristics suitable for atmospheric characterization have orbits of several days, thus phase curve observations are highly resource intensive, especially for shared use facilities. In this work, we show that an infrared spectrograph operating from a high altitude balloon platform can perform phase-resolved spectroscopy of hot Jupiter-type exoplanets with performance comparable to a space-based telescope. Using the EXoplanet Climate Infrared TElescope (EXCITE) experiment as an example, we quantify the impact of the most important systematic effects that we expect to encounter from a balloon platform. We show an instrument like EXCITE will have the stability and sensitivity to significantly advance our understanding of exoplanet atmospheres. Such an instrument will both complement and serve as a critical bridge between current and future space-based near-infrared spectroscopic instruments.
{"title":"Observing Exoplanets in the Near-Infrared from a High Altitude Balloon Platform","authors":"P. Nagler, B. Edwards, B. Kilpatrick, N. Lewis, P. Maxted, C. Netterfield, V. Parmentier, E. Pascale, Subhajit Sarkar, G. Tucker, I. Waldmann","doi":"10.1142/S2251171719500119","DOIUrl":"https://doi.org/10.1142/S2251171719500119","url":null,"abstract":"Although there exists a large sample of known exoplanets, little data exists that can be used to study their global atmospheric properties. This deficiency can be addressed by performing phase-resolved spectroscopy — continuous spectroscopic observations of a planet’s entire orbit about its host star — of transiting exoplanets. Planets with characteristics suitable for atmospheric characterization have orbits of several days, thus phase curve observations are highly resource intensive, especially for shared use facilities. In this work, we show that an infrared spectrograph operating from a high altitude balloon platform can perform phase-resolved spectroscopy of hot Jupiter-type exoplanets with performance comparable to a space-based telescope. Using the EXoplanet Climate Infrared TElescope (EXCITE) experiment as an example, we quantify the impact of the most important systematic effects that we expect to encounter from a balloon platform. We show an instrument like EXCITE will have the stability and sensitivity to significantly advance our understanding of exoplanet atmospheres. Such an instrument will both complement and serve as a critical bridge between current and future space-based near-infrared spectroscopic instruments.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171719500119","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49178364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-03-01DOI: 10.1142/S2251171719400038
R. Black, B. Jeffs, K. Warnick
Radio frequency interference (RFI) is rapidly becoming a major issue for many applications. It is especially problematic for radio astronomy, where signal-to-noise ratios (SNRs) are less than unity. Antenna array systems such as phased array feeds (PAFs) and interferometric imaging arrays are able to cancel RFI through adaptive projection-based spatial notch filtering techniques. Current methods for formulating these projection operators suffer from an unfortunate trade-off. They must sacrifice integration time when calculating the sample spatial correlation matrix in order to track RFI motion, but this consequently increases sample estimation error and reduces null depth. In this work, we propose a new way to process spatial correlation matrices to form a broad null that reliably cancels moving RFI without increasing sample estimation error due to insufficient integration. Additionally, when assisted by an RFI-tracking auxiliary antenna, this approach also reduces the total data rate coming out of a spatial correlator, thus making broad-null-based RFI cancelation more computationally efficient and practical for real-time active array-based RFI mitigation systems.
{"title":"Deep, Broad Null Formation for Canceling Moving RFI in Radio Astronomical Arrays","authors":"R. Black, B. Jeffs, K. Warnick","doi":"10.1142/S2251171719400038","DOIUrl":"https://doi.org/10.1142/S2251171719400038","url":null,"abstract":"Radio frequency interference (RFI) is rapidly becoming a major issue for many applications. It is especially problematic for radio astronomy, where signal-to-noise ratios (SNRs) are less than unity. Antenna array systems such as phased array feeds (PAFs) and interferometric imaging arrays are able to cancel RFI through adaptive projection-based spatial notch filtering techniques. Current methods for formulating these projection operators suffer from an unfortunate trade-off. They must sacrifice integration time when calculating the sample spatial correlation matrix in order to track RFI motion, but this consequently increases sample estimation error and reduces null depth. In this work, we propose a new way to process spatial correlation matrices to form a broad null that reliably cancels moving RFI without increasing sample estimation error due to insufficient integration. Additionally, when assisted by an RFI-tracking auxiliary antenna, this approach also reduces the total data rate coming out of a spatial correlator, thus making broad-null-based RFI cancelation more computationally efficient and practical for real-time active array-based RFI mitigation systems.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":"1 1","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171719400038","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41491952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-03-01DOI: 10.1142/s225117171902001x
K. Buch, A. Boonstra, G. Hellbourg, J. Kocz, U. Rau, L. Greenhill
{"title":"Preface: “Interference Mitigation Techniques in Radio Astronomy”","authors":"K. Buch, A. Boonstra, G. Hellbourg, J. Kocz, U. Rau, L. Greenhill","doi":"10.1142/s225117171902001x","DOIUrl":"https://doi.org/10.1142/s225117171902001x","url":null,"abstract":"","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/s225117171902001x","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42087625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-03-01DOI: 10.1142/S2251171719400105
W. Baan
This paper presents an overview of methods for mitigating radio frequency interference (RFI) in radio science data. The primary purpose of mitigation is to assist observatories to take useful data outside frequency bands allocated to the Science Services (Radio Astronomy Service (RAS) and Earth Exploration Service (EESS)): mitigation should not be needed within passive bands. Mitigation methods may be introduced at a variety of points within the data acquisition system in order to lessen the RFI intensity and to limit the damage it causes. These methods range from proactive methods to changing the local RFI environment by means of regulatory manners, to pre- and post-detection methods, to various pre-processing methods, and to methods applied at or post-processing.
{"title":"Implementing RFI Mitigation in Radio Science","authors":"W. Baan","doi":"10.1142/S2251171719400105","DOIUrl":"https://doi.org/10.1142/S2251171719400105","url":null,"abstract":"This paper presents an overview of methods for mitigating radio frequency interference (RFI) in radio science data. The primary purpose of mitigation is to assist observatories to take useful data outside frequency bands allocated to the Science Services (Radio Astronomy Service (RAS) and Earth Exploration Service (EESS)): mitigation should not be needed within passive bands. Mitigation methods may be introduced at a variety of points within the data acquisition system in order to lessen the RFI intensity and to limit the damage it causes. These methods range from proactive methods to changing the local RFI environment by means of regulatory manners, to pre- and post-detection methods, to various pre-processing methods, and to methods applied at or post-processing.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S2251171719400105","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47465829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-03-01DOI: 10.1142/S225117171940009
A. Deshpande, B. M. Lewis
Several post-detection approaches to the mitigation of radio-frequency interference (RFI) are compared by applying them to the strong RFI from the Iridium satellites. These provide estimates for the desired signal in the presence of RFI, by exploiting distinguishing characteristics of the RFI, such as its polarization, statistics, and periodicity. Our data are dynamic spectra with full Stokes parameters and 1[Formula: see text]ms time resolution. Moreover, since most man-made RFI is strongly polarized, we use the data to compare its unpolarized component with its Stokes I. This approach on its own reduces the RFI intensity by many tens of dBs. A comprehensive approach that also recognizes non-Gaussian statistics, and the time and frequency structure inherent in the RFI, permits exceedingly effective post-detection excision provided full Stokes intensity data are available.
{"title":"Iridium Satellite Signals: A Case Study in Interference Characterization and Mitigation for Radio Astronomy Observations","authors":"A. Deshpande, B. M. Lewis","doi":"10.1142/S225117171940009","DOIUrl":"https://doi.org/10.1142/S225117171940009","url":null,"abstract":"Several post-detection approaches to the mitigation of radio-frequency interference (RFI) are compared by applying them to the strong RFI from the Iridium satellites. These provide estimates for the desired signal in the presence of RFI, by exploiting distinguishing characteristics of the RFI, such as its polarization, statistics, and periodicity. Our data are dynamic spectra with full Stokes parameters and 1[Formula: see text]ms time resolution. Moreover, since most man-made RFI is strongly polarized, we use the data to compare its unpolarized component with its Stokes I. This approach on its own reduces the RFI intensity by many tens of dBs. A comprehensive approach that also recognizes non-Gaussian statistics, and the time and frequency structure inherent in the RFI, permits exceedingly effective post-detection excision provided full Stokes intensity data are available.","PeriodicalId":45132,"journal":{"name":"Journal of Astronomical Instrumentation","volume":" ","pages":""},"PeriodicalIF":1.3,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42452468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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