Radio Science最新文献_第9页

Cross-Polarization Gain Calibration of Linearly Polarized VLBI Antennas by Observations of 4C 39.25 通过观测 4C 39.25 校准线性极化 VLBI 天线的跨极化增益

IF 1.6 4区地球科学

Radio Science Pub Date : 2024-03-28 DOI: 10.1029/2023rs007892

F. Jaron, I. Martí-Vidal, M. Schartner, J. González-García, E. Albentosa-Ruiz, S. Bernhart, J. Böhm, J. Gruber, S. Modiri, A. Nothnagel, V. Pérez-Díez, T. Savolainen, B. Soja, E. Varenius, M. H. Xu

{"title":"Cross-Polarization Gain Calibration of Linearly Polarized VLBI Antennas by Observations of 4C 39.25","authors":"F. Jaron, I. Martí-Vidal, M. Schartner, J. González-García, E. Albentosa-Ruiz, S. Bernhart, J. Böhm, J. Gruber, S. Modiri, A. Nothnagel, V. Pérez-Díez, T. Savolainen, B. Soja, E. Varenius, M. H. Xu","doi":"10.1029/2023rs007892","DOIUrl":"https://doi.org/10.1029/2023rs007892","url":null,"abstract":"Radio telescopes with dual linearly polarized feeds regularly participate in Very Long Baseline Interferometry. One example is the VLBI Global Observing System (VGOS), which is employed for high-precision geodesy and astrometry. In order to achieve the maximum signal-to-noise ratio, the visibilities of all four polarization products are combined to Stokes <i>I</i> before fringe-fitting. Our aim is to improve cross-polarization bandpass calibration, which is an essential processing step in this context. Here we investigate the shapes of these station-specific quantities as a function of frequency and time. We observed the extra-galactic source 4C 39.25 for 6 hours with a VGOS network. We correlated the data with the DiFX software and analyzed the visibilities with PolConvert to determine the complex cross-bandpasses with high accuracy. Their frequency-dependent shape is to first order characterized by a group delay between the two orthogonal polarizations, in the order of several hundred picoseconds. We find that this group delay shows systematic variability in the range of a few picoseconds, but can remain stable within this range for several years, as evident from earlier sessions. On top of the linear phase-frequency relationship there are systematic deviations of several tens of degrees, which in addition are subject to smooth temporal evolution. The antenna cross-bandpasses are variable on time scales of ∼1 hr, which defines the frequency of necessary calibrator scans. The source 4C 39.25 is confirmed as an excellent cross-bandpass calibrator. Dedicated surveys are highly encouraged to search for more calibrators of similar quality.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"34 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140325684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Spectroscopic evaluation of epidermis-equivalent phantom in terahertz-frequency region 太赫兹频率区域表皮等效模型的光谱评估

IF 1.6 4区地球科学

Radio Science Pub Date : 2024-03-01 DOI: 10.1029/2023RS007809

Maya Mizuno;Shota Yamazaki;Tomoaki Nagaoka

引用次数: 0

Variation in the reflection height of VLF/LF transmitter signals in the D-region ionosphere and the possible source: A 2018 meteoroid in Hokkaido, Japan D 区电离层中 VLF/LF 发射机信号反射高度的变化及其可能来源：2018 年日本北海道的一颗流星体

IF 1.6 4区地球科学

Radio Science Pub Date : 2024-03-01 DOI: 10.1029/2023RS007801

H. Ohya;T. Suzuki;F. Tsuchiya;H. Nakata;K. Shiokawa

{"title":"Variation in the reflection height of VLF/LF transmitter signals in the D-region ionosphere and the possible source: A 2018 meteoroid in Hokkaido, Japan","authors":"H. Ohya;T. Suzuki;F. Tsuchiya;H. Nakata;K. Shiokawa","doi":"10.1029/2023RS007801","DOIUrl":"10.1029/2023RS007801","url":null,"abstract":"Several studies have examined ionospheric variation associated with meteorites, meteoroids, or meteors based on Global Satellite Navigation System total electron content observations. However, there have been few quantitative studies of the D-region of the ionosphere (60–90 km), which is associated with meteoroids. We investigated variation in the D-region during the passage of a meteoroid over northeastern Hokkaido, Japan, at 11:55:55 UT on 18 October 2018, using very low-frequency (VLF, 3–30 kHz) and low-frequency (LF, 30–300 kHz) signals observed by three transmitters [JJY (40 kHz), JJY (60 kHz), and JJI (22.2 kHz)], at Rikubetsu, Japan. Periodic variation of 100–200 s was observed in the VLF and LF amplitudes upon arrival of the acoustic wave. The vertical seismic velocity of Hi-net and F-net data also showed acoustic waves. Although the main period of the acoustic wave was 0.1–0.5 s in the seismic data, a longer period component (100–200 s) remained during propagation up to the D-region ionosphere. The estimated velocity of the acoustic waves was ∼340 m/s on the ground according to the Hi-net seismic data. The acoustic wave originated near the endpoint (25 km altitude) of the meteoroid trajectory. Based on the observed propagation time of the acoustic waves and ray tracing results, the acoustic waves propagated obliquely from near the endpoint of the meteoroid trajectory up to a D-region height (about ∼90 km altitude), south of the Rikubetsu receiver.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 3","pages":"1-10"},"PeriodicalIF":1.6,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139968763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A cryogenic wideband (2.5–14 GHz) receiver system for the Arecibo Observatory 12 m telescope 阿雷西博天文台 12 米望远镜低温宽带（2.5-14 千兆赫）接收器系统

IF 1.6 4区地球科学

Radio Science Pub Date : 2024-03-01 DOI: 10.1029/2023RS007839

D. Anish Roshi;Phil Perillat;Felix Fernandez;Hamdi Mani;Benetge Perera;Periasamy K. Manoharan;Luis Quintero;Arun Venkataraman

{"title":"A cryogenic wideband (2.5–14 GHz) receiver system for the Arecibo Observatory 12 m telescope","authors":"D. Anish Roshi;Phil Perillat;Felix Fernandez;Hamdi Mani;Benetge Perera;Periasamy K. Manoharan;Luis Quintero;Arun Venkataraman","doi":"10.1029/2023RS007839","DOIUrl":"10.1029/2023RS007839","url":null,"abstract":"In this paper we present details of the construction of a wideband, cryogenic receiver and its successful commissioning on the Arecibo Observatory 12m telescope. The cryogenic receiver works in the 2.5–14 GHz frequency range. We upgraded the current narrow band, room temperature receivers of the telescope with the new wideband receiver. The current receiver is built around a Quadruple-Ridged Flared Horn (QRFH) developed by Akgiray et al. (2013, https://doi.org/10.1109/tap.2012.2229953). To mitigate strong radio frequency interference (RFI) below 2.7 GHz, we installed a highpass filter before the first stage low noise amplifier (LNA). The QRFH, highpass filter, noise coupler and LNA are located inside a cryostat and are cooled to 15 K. The measured receiver temperature is 25 K (median value) over 2.5–14 GHz. The system temperature measured at zenith is about 40 K near 3.1 and 8.6 GHz and the zenith antenna gains are 0.025 and 0.018 K/Jy at the two frequencies respectively. We recommend the following improvements to the telescope system: (a) Upgrade the highpass filter to achieve better RFI rejection near 2.5 GHz; (b) Improve aperture efficiency at 8.6 GHz; (c) Upgrade the intermediate frequency system to increase the upper frequency of operation from 12 to 14 GHz.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 3","pages":"1-11"},"PeriodicalIF":1.6,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140277606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Front matter 首页

IF 1.6 4区地球科学

Radio Science Pub Date : 2024-03-01 DOI: 10.1002/rds.21239

引用次数: 0

Measurement and calibration of EMF: A study using phone and GBDT for mobile communication signals 电磁场的测量和校准：使用手机和 GBDT 测量移动通信信号的研究

IF 1.6 4区地球科学

Radio Science Pub Date : 2024-02-01 DOI: 10.1029/2023RS007890

Sheng Zeng;Weiwei Chen;Yuhang Ji;Liping Yan;Xiang Zhao

{"title":"Measurement and calibration of EMF: A study using phone and GBDT for mobile communication signals","authors":"Sheng Zeng;Weiwei Chen;Yuhang Ji;Liping Yan;Xiang Zhao","doi":"10.1029/2023RS007890","DOIUrl":"10.1029/2023RS007890","url":null,"abstract":"Electromagnetic exposure caused by mobile communication signals has always been a cause of concern. Due to the cost and inconvenience of professional measurement equipment, researchers have turned to smartphone APPs to study and assess the electric field strength caused by mobile communication signals. However, existing cell phone-based measurements have two weaknesses. First, no system architecture suitable for large-scale crowdsourced testing has been proposed. Second, since smartphone sensors cannot measure electric field strength directly, existing methods for converting the received signal power of the phone and electric field strength have errors of more than 5 dB. This paper proposes a measurement and calibration method for electric field strength of mobile communication signals based on a smartphone app and gradient boosting decision tree (GBDT). This method consists of a downlink signal acquisition system based on an APP and a calibration model based on GBDT to convert received signal power into electric field strength. The experimental results show that the proposed model achieves a R\u0000<sup>2</sup>\u0000 score of 0.93 and a MAE of 0.97 dB. Compared with the existing methods, our method improves the calibration accuracy by 4 dB, enabling large-scale, low-cost, and high-precision direct measurement of the electric field strength of mobile communication signals.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 2","pages":"1-13"},"PeriodicalIF":1.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139918642","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Granite Exposure Mapping Through Sentinel‐2 Visible and Short Wave Infrared Bands 通过哨兵-2 可见光和短波红外波段绘制花岗岩暴露图

IF 1.6 4区地球科学

Radio Science Pub Date : 2024-02-01 DOI: 10.1029/2023rs007864

Nazir Jan, N. Minallah, Neelam Gohar, Naveed Jan, Shahid Khan, Salahuddin Khan, Mohammad Alibakhshikenari

{"title":"Granite Exposure Mapping Through Sentinel‐2 Visible and Short Wave Infrared Bands","authors":"Nazir Jan, N. Minallah, Neelam Gohar, Naveed Jan, Shahid Khan, Salahuddin Khan, Mohammad Alibakhshikenari","doi":"10.1029/2023rs007864","DOIUrl":"https://doi.org/10.1029/2023rs007864","url":null,"abstract":"Nonmetallic minerals like granite and limestone have calcite and biotitic ingredients as their major part which exhibit wonderful absorption features in the visible and short wave range of the electromagnetic spectrum. This research puts emphasis on delineating granite and limestone deposits of the Mardan district through the latest multispectral Landsat‐9 and Sentinel‐2 sensors of which the latter provided 94% mapping accuracy in delineating granites (biotitic bearing minerals) and limestone (calcite‐bearing minerals). The Image processing techniques of minimum noise fraction, which is double cascaded principal components analysis and pixel purity index algorithms proved helpful to bring significant improvements in classification results and in the reduction of noise and data size. The outcomes of the research study show that supervised machine learning algorithms are impactful to map such minerals provided that the data must be well organized and limited in size. The results achieved were verified through validation steps like, (a) Independent reference data of high‐resolution Google Earth maps and (b) Ground survey reports. Arc GIS 10.2 and Envi 5.3 software suite were used to create (a) ground truth points at random for accuracy assessment (b) portraying study area maps (c) Image Processing and Preprocessing tools and (d) implementation of machine learning algorithms. Access to the data and software suite is being provided for open research work.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"40 13","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139814145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Micro Rain Radar and Radiometric Measurements to Unravel Contrasting Features of Rain Microstructure Below and Above the Boundary Layer 微雨雷达和辐射测量揭示边界层以下和边界层以上雨微观结构的对比特征

IF 1.6 4区地球科学

Radio Science Pub Date : 2024-02-01 DOI: 10.1029/2023rs007875

G. Rakshit, R. Chakraborty, A. Maitra

{"title":"Micro Rain Radar and Radiometric Measurements to Unravel Contrasting Features of Rain Microstructure Below and Above the Boundary Layer","authors":"G. Rakshit, R. Chakraborty, A. Maitra","doi":"10.1029/2023rs007875","DOIUrl":"https://doi.org/10.1029/2023rs007875","url":null,"abstract":"Ka‐band Micro rain Doppler radar is an effective tool to investigate the profiles of precipitation microstructure in terms of the raindrop size distribution (DSD). The DSD parameters that vary appreciably with height are indicative of the associated atmospheric phenomena. Hence the present investigation endeavors to put light on the underlying physical processes responsible for the evolution of varied rain microstructure profiles using micro rain radar (MRR), and radiometric measurements complemented with re‐analysis outputs over an urban tropical location, Kolkata (22.57°N, 88.37°E), India. MRR unravels the prevalence of significant biases in the typical power law relationship (Dm = aRb) between rain rate (R) and mass‐weighted mean drop diameter (Dm) along the rain height, especially during intense convective rain events, above the atmospheric boundary layer (ABL). Consequently, an alternative empirical relation appropriate to account for the R‐Dm variability above the ABL is proposed. Further, radiometric measurements and re‐analysis outputs reveal that the presence of atmospheric instabilities coupled with wind shear impacts above the ABL contributes to the enhanced breakup of raindrops and the deviations in the usual R‐Dm relationship. Thus, the present study intends to highlight the applicability of ground‐based radar measurements over the tropics to devise quantitative precipitation algorithms for reliable rain estimates.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"12 4-5","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139871966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Electron density specification in the inner magnetosphere from the narrow band receiver onboard DSX 从 DSX 星载窄带接收器获取内磁层的电子密度规格

IF 1.6 4区地球科学

Radio Science Pub Date : 2024-02-01 DOI: 10.1029/2023RS007907

Yi-Jiun Su;John A. Carilli;J. Brent Parham;Xiangning Chu;Ivan A. Galkin;Gregory P. Ginet

引用次数: 0

Processing of VLF amplitude measurements: Deduction of a quiet time seasonal variation 处理甚低频振幅测量：静默时间季节性变化的推导

IF 1.6 4区地球科学

Radio Science Pub Date : 2024-02-01 DOI: 10.1029/2023RS007834

H. Schneider;V. Wendt;D. Banys;M. Clilverd;T. Raita

{"title":"Processing of VLF amplitude measurements: Deduction of a quiet time seasonal variation","authors":"H. Schneider;V. Wendt;D. Banys;M. Clilverd;T. Raita","doi":"10.1029/2023RS007834","DOIUrl":"10.1029/2023RS007834","url":null,"abstract":"The amplitude of Very Low Frequency (VLF) transmissions propagating from transmitter to receiver between the Earth's surface and the ionospheric D-region is a useful measurement to detect changes in the ionization within the D-region ranging from 60 to 90 km. The VLF signal amplitude is disturbed by geomagnetic, solar, and atmospheric phenomena. To be able to identify perturbations in the VLF signal amplitude, we determine its averaged seasonal variation under quiet solar and geomagnetic conditions. Here it is challenging, that long time series of the VLF signal amplitude show significant jumps and outliers, which are caused artificially by technical adjustments/maintenance work. This paper presents a new approach for processing long VLF data time series over multiple years resulting in level 2 data. The new level 2 data enables the consideration of time series with artificial jumps since the jumps are leveled. Moreover, the outliers are removed by a robust and systematic 2-step outlier filtering. The average seasonal and diurnal variation for different transmitter-receiver combinations can be computed with the new level 2 data by applying a composite analysis. A subsequently applied polynomial fit obtains the quiet time lines for daytime and nighttime, representing the typical seasonal variation under undisturbed conditions of the VLF signal amplitude for each considered link. The developed quiet time lines may serve as a tool to determine perturbations of the VLF signal amplitude with solar and geomagnetic as well as atmospheric origin. Also, they allow comparison of the VLF signal amplitude variation for different transmitter-receiver links.","PeriodicalId":49638,"journal":{"name":"Radio Science","volume":"59 2","pages":"1-12"},"PeriodicalIF":1.6,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139753205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0