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A Comparison of Broadcast and Final Orbits on GPS Delays in GPS-VLBI Hybrid Observation
곽영희,조정호,Tetsuro Kondo,Jun Amagai,Tadahiro Gotoh,Mamoru Sekido,Ryuichi Ichikawa,김두환,Tetsuo Sasao 사단법인 항법시스템학회 2012 Journal of Positioning, Navigation, and Timing Vol.1 No.1
We carry out an error analysis of 24-hour global positioning system (GPS)-very long baseline interferometry (VLBI) (GV) hybrid observation data. In this paper, we focus on the impacts of broadcast and final orbits on the GPS delays of the GV hybrid observation by analyzing the residuals, observed - calculated (O-C) values. The residuals show apparent and consistent biases for L1 and L2 signals, respectively. The scatters of the residuals are around a few nanoseconds. The main cause of those observation errors is the absence of the GPS phase and delay calibration system. Most of the satellites show that the differences between the delays, to which broadcast and final orbits are applied, are about 100 times smaller than the current GV hybrid observation errors. We conclude that GPS delays are not greatly affected by orbit accuracies.
VLBI Type Experimental Observation of GPS
곽영희,Tetsuro Kondo,Jun Amagai,Tadahiro Gotoh,Tetsuo Sasao,조정호,김두환 한국우주과학회 2010 Journal of Astronomy and Space Sciences Vol.27 No.2
As a preparatory study for Global Positioning System-Very Long Baseline Interferometry (GPS-VLBI) hybrid system, we examined if VLBI type observation of the GPS signal is realizable through a test experiment. The test experiment was performed between Kashima and Koganei, Japan, with 110 km baseline. The GPS L1 and L2 signals were received by commercial GPS antennas, down-converted to video-band signals by specially developed GPS down converters, and then sampled by VLBI samplers. The sampled GPS data were recorded as ordinary VLBI data by VLBI recorders. The sampling frequency was 64 MHz and the observation time was 1 minute. The recorded data were correlated by a VLBI correlator. From correlation results, we simultaneously obtained correlation fringes from all 8 satellites above a cut-off elevation which was set to 15 degree. 87.5% of L1 fringes and 12.5% of L2 fringes acquired the Signal to Noise Ratios which are sufficient to achieve the group delay precision of 0.1nsec that is typical in current geodetic VLBI. This result shows that VLBI type observation of GPS satellites will be readily realized in future GPS-VLBI hybrid system.
Maeda, Yutaka,Higo, Junki,Amagai, Yuri,Matsui, Jun,Ohkubo, Kei,Yoshigoe, Yusuke,Hashimoto, Masahiro,Eguchi, Kazuhiro,Yamada, Michio,Hasegawa, Tadashi,Sato, Yoshinori,Zhou, Jing,Lu, Jing,Miyashita, Tok American Chemical Society 2013 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.135 No.16
<P>This report describes a helicity-selective photoreaction of single-walled carbon nanotubes (SWNTs) with disulfide in the presence of oxygen. The SWNTs were characterized using absorption, photoluminescence (PL), Raman, and X-ray photoelectron spectroscopy, scanning electron microscopy, and current–voltage (<I>I</I>–<I>V</I>) measurements. Results showed remarkable helicity-selective (metallic SWNTs/semiconducting SWNTs and diameter) functionalization of SWNTs. The reaction rate decreases in the order of metallic SWNTs > semiconducting SWNTs and small-diameter SWNTs > large-diameter SWNTs. Control experiments conducted under various experimental conditions and ESR and femtosecond laser flash photolysis measurements revealed that the helicity-selective reaction proceeds via a photoinduced electron transfer reaction. The PL and <I>I</I>–<I>V</I> measurements showed that the photoreaction is effective not only to control SWNT conductivity but also for the band gap modulation of semiconducting SWNTs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2013/jacsat.2013.135.issue-16/ja402199n/production/images/medium/ja-2013-02199n_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja402199n'>ACS Electronic Supporting Info</A></P>
Quasi-Zenith Satellite System (QZSS)-Outline and its time related mission
Hama, shinichi,Takahashi, Yasuhiro,Amagai, Jun,Ito, Hiroyuki,Morikawa, Takao,Yokota, Shouichirou,Fujieda, Miho,Kimura, Kazuhiro 통신위성우주산업연구회 2005 Joint Conference on Satellite Communications Vol.2005 No.-
Japan has started a project of Quasi-Zenith Satellite System (QZSS) since FY2003. QZSS will be highly useful not only for communications but for complement of the modernized GPS in urban canyon and mountainous area with its high visibility brought out by its inclined orbits. National Institute of Information and Communications Technology, Japan (NICT) is to develop a Space-borne Hydrogen Maser (SHM) and time management system, and carry out experiments using them. A breadboard model (BBM) of the SHM was developed to overcome the issues such as size, weight and life time, which are required in space environment. Basic design was carried out for time management system to achieve nano second level time transfer. The design and the manufacturing of the engineering models (EM) of the on-board equipment have been carried out since 2004. The first satellite is planned to be launched in FY 2008.
A Comparison of Broadcast and Final Orbits on GPS Delays in GPS-VLBI Hybrid Observation
Kwak, Younghee,Cho, Jungho,Kondo, Tetsuro,Takiguchi, Hiroshi,Amagai, Jun,Gotoh, Tadahiro,Sekido, Mamoru,Ichikawa, Ryuichi,Kim, Tuhwan,Sasao, Tetsuo The Institute of Positioning 2012 Journal of Positioning, Navigation, and Timing Vol.1 No.1
We carry out an error analysis of 24-hour global positioning system (GPS)-very long baseline interferometry (VLBI) (GV) hybrid observation data. In this paper, we focus on the impacts of broadcast and final orbits on the GPS delays of the GV hybrid observation by analyzing the residuals, observed - calculated (O-C) values. The residuals show apparent and consistent biases for L1 and L2 signals, respectively. The scatters of the residuals are around a few nanoseconds. The main cause of those observation errors is the absence of the GPS phase and delay calibration system. Most of the satellites show that the differences between the delays, to which broadcast and final orbits are applied, are about 100 times smaller than the current GV hybrid observation errors. We conclude that GPS delays are not greatly affected by orbit accuracies.