2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)最新文献_第6页

Radiothermal Emission model of Venus 金星的辐射热发射模型

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738414

Tinu Antony, C. SureshRaju, G. Swarup, N. Mohan

{"title":"Radiothermal Emission model of Venus","authors":"Tinu Antony, C. SureshRaju, G. Swarup, N. Mohan","doi":"10.23919/URSIAP-RASC.2019.8738414","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738414","url":null,"abstract":"The radio-thermal emission from Venus as observed by ground-based interferometric radio-telescopes shows a significant spectral variation, with a gradual increase in brightness temperature from 1 mm to 6 cm and a decrease thereafter at higher wavelengths. The first time GMRT observations beyond 70 cm wavelength also reconfirm this decreasing trend in Tb with the increase in wavelength [7]. Efforts have been made to model this spectral variation in Tb, [1], [10], but these models fail to explain the low-frequency radio-thermal emission from Venus (decrease in Tb with the increase in wavelength) and the problem still remains unresolved. The authors attempt to explain this problem using radiative transfer based model and radiometric observations of Venus focussing particularly on the higher wavelength Tb observations from the Giant meter radio telescope (GMRT). The GMRT brightness temperature (Tb) (at 0.21, 0.5, 0.9, 1.23 and 2 m) is observed to decrease with frequency. A radiative transfer model was developed and it is seen that a two layer Venusian surface model matches with the observations. Based on the simulation studies, the authors put forth a hypothesis that Venus may have an absorbing layer within the first few meter depth.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123816478","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}

引用次数: 0

Rheometry experiment of an electric field sensor for plasma wave observation 等离子体波观测用电场传感器流变实验

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738523

T. Imachi, S. Yagitani, M. Ozaki, R. Higashi, Y. Yokoyama

引用次数: 0

Time transfer via different GNSS systems 通过不同的GNSS系统进行时间传输

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738763

K. Liang

{"title":"Time transfer via different GNSS systems","authors":"K. Liang","doi":"10.23919/URSIAP-RASC.2019.8738763","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738763","url":null,"abstract":"GNSS time transfer is the most popular method for time transfer with good accuracy and precision on ultra long distance over the world. In TAI generation, time transfer by GPS (Global Positioning System) and GLONASS (GLObal NAvigation Satellite System), especially GPS, have been employed regularly for remote comparison links between PTB and other TAI laboratories. At present, BeiDou navigation satellite system (BDS) and Galileo system are developing fast. Time transfer via BDS and Galileo are becoming the important redundant comparison links and having the potential combination of multiple GNSS(Global Navigation Satellite System) links come true. A new multi-GNSS version of GNSS time transfer receiver NIM-TF-GNSS-3, has been under development by NIM (National Institute of Metrology, Beijing, China) since 2016. It is the third generation of GNSS time transfer receiver developed by NIM following NIM-TF-GNSS-1 [1] and NIM-TF-GNSS-2 [2]. The receiver provides the code and carrier phase measurements from BDS, GPS, GLONASS and Galileo for precise time transfer. The receiver can generate measurement data of both single frequency and dual frequencies in CGGTTS (CCTF Group on GNSS Time Transfer Standards) V2E, RINEX (Receiver Independent Exchange Format) V3 files. The experiments of time transfer via different GNSS systems on multiple links have been implemented for the evaluation on the long-term stability and accuracy. The combination method of multiple GNSS measurements for time transfer has been studied and discussed.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123969092","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}

引用次数: 0

Cylindrical Dielectric Resonator Antenna Array with Beam Steering Capability 具有波束导向能力的圆柱形介质谐振器天线阵列

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738470

N. Mishra, Soma Das

引用次数: 0

Capacity Analysis of Lattice reduction Aided Detection in Massive-MIMO systems 海量mimo系统中格约简辅助检测的容量分析

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738281

S. Sur, S. Bera, R. Bera, B. Maji

引用次数: 3

Challenges in design and development of Compressive Sensing based Single pixel optical Camera System for Spaceborne missions 基于压缩感知的星载单像素光学相机系统设计与开发中的挑战

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738598

J. Kumar, B. N. Sharma, K. A. Kumar, A. Sarkar

{"title":"Challenges in design and development of Compressive Sensing based Single pixel optical Camera System for Spaceborne missions","authors":"J. Kumar, B. N. Sharma, K. A. Kumar, A. Sarkar","doi":"10.23919/URSIAP-RASC.2019.8738598","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738598","url":null,"abstract":"Evolution of CCD and CMOS sensors as prime imaging technology has enabled development of efficient and compact remote sensing systems for spaceborne missions. These imaging systems typically sample the ground scenes by means of a linear or area array of photon detectors. The quest for resolving higher spatial frequencies over large ground area with better radiometric accuracies results in huge data volume constraining the transmission bandwidth. This necessitated the development of complex on-board compression systems in digital domain with power and weight constraints. Recently, compressive sensing (CS) has emerged as potential signal processing technique for efficiently acquiring and reconstructing the signals. The main advantage of this technique is that it compresses the signal during sensing process, thereby reducing burden on on-board processing electronics systems. Based on the CS concept, conceptual framework for single pixel optical camera systems have been extensively studied as it has potential to significantly revolutionize commercial digital camera systems. However, there has not been any systematic studies towards using the CS based single pixel camera systems for spaceborne missions.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"33 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113967540","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}

引用次数: 0

Theoretical modelling of the topside electron density distribution in the Indian equatorial and low latitude ionosphere using DU_LLTD Model 用DU_LLTD模式模拟印度赤道和低纬度电离层上层电子密度分布

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738607

Rimpy Kakoty, P. K. Bhuyan

引用次数: 0

Compact Conformal Multilayer Slot Antenna for Hyperthermia 用于热疗的紧凑型保形多层槽天线

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738242

Soni Singh, S. Singh, Dharmendra Singh

引用次数: 2

Role of the phase of Quasi-Biennial Oscillation in modulating the influence of SSW on Equatorial Ionosphere 准两年振荡的相位在调制SSW对赤道电离层的影响中的作用

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738274

S. Yadav, C. Vineeth, K. Kumar, R. Choudhary, T. Pant, S. Sunda

{"title":"Role of the phase of Quasi-Biennial Oscillation in modulating the influence of SSW on Equatorial Ionosphere","authors":"S. Yadav, C. Vineeth, K. Kumar, R. Choudhary, T. Pant, S. Sunda","doi":"10.23919/URSIAP-RASC.2019.8738274","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738274","url":null,"abstract":"Understanding the coupling of ionosphere-thermosphere (IT) system from the lower atmospheric forcing is one of the primary challenges for the space weather community. The present paper deals with the role of two lower atmospheric processes over the Indian region ionosphere i.e., stratospheric Quasi-Biennial Oscillation (QBO) and Sudden Stratospheric Warming (SSW). The role of QBO in modulating the response of equatorial/low latitude ionosphere over Indian sector to the major SSW events of 2009 and 2013 has been investigated by using combined measurements from meteor wind radar operating over Trivandrum, Global Positioning System (GPS) derived total electron content (TEC), and magnetic field data. The time variation of Equatorial Electrojet (EEJ)-induced surface magnetic field show that the response of EEJ is distinctly different during different phases of the QBO. The peaking time of EEJ and occurrence time of counter electrojet (CEJ) were found to be shifted towards morning/evening sector during the westward/eastward phase of the QBO during the SSW years. The TEC over both the equatorial and low-latitude ionosphere exhibit a similar feature. The tidal components derived from horizontal winds using a meteor wind radar revealed similar shift in their peaking time. These observations clearly vindicate that the phase of QBO plays a crucial role in structuring the equatorial electrodynamics and electron density distribution over low-latitudes during the SSW evens. These results are unique and achieves significance as we are heading towards solar minimum period where forcing from the lower atmosphere is an import aspect of ionospheric variability.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126435017","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}

引用次数: 1

On the nighttime enhancement in ionospheric electron density over the equatorial region 赤道地区电离层电子密度夜间增强的研究

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) Pub Date : 2019-03-01 DOI: 10.23919/URSIAP-RASC.2019.8738394

S. Yadav, R. Choudhary, P. R. Shreedevi, S. Sunda

{"title":"On the nighttime enhancement in ionospheric electron density over the equatorial region","authors":"S. Yadav, R. Choudhary, P. R. Shreedevi, S. Sunda","doi":"10.23919/URSIAP-RASC.2019.8738394","DOIUrl":"https://doi.org/10.23919/URSIAP-RASC.2019.8738394","url":null,"abstract":"Understanding the evolution of nighttime ionospheric electron density remains an elusive aspect in spite of the extensive research over the past several decades. At nighttime, during the absence of ionization, the ionospheric electron density is generally expected to decay gradually, but it does not behave as predicted by the simple notion and show enhancement occasionally. This phenomenon is called ionospheric nighttime enhancement (INE), and it depends strongly on location, season, and level of solar and geomagnetic activity. This paper focuses on the INE events over the equatorial region of the Indian sector. The Global Positioning System (GPS) derived total electron content (TEC) measurements obtained from two InSWIM (Indian network for Space Weather Impact monitoring) stations have been used. The collocated ionosonde has been used to obtain the information on the bottomside ionospheric parameters. The ionosonde measurements show that the plasma drift is downward under such events which reveals the essential role of the westward electric field in forming the INE. The 2D-TEC maps generated from the Satellite-Based Augmentation System (SBAS)-GAGAN have also been utilized to investigate the motions of equatorial ionization anomaly (EIA) crest during the occurrence of INE events. Results show the existence of well-developed EIA until late evening during the events of INE.","PeriodicalId":344386,"journal":{"name":"2019 URSI Asia-Pacific Radio Science Conference (AP-RASC)","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128040974","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}

引用次数: 0