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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.
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.
KAMEYA, O.,TSUBOI, M.,ASAKI, Y.,YONEKURA, Y.,MIYAMOTO, Y.,KANEKO, H.,SETA, M.,NAKAI, N.,MIYOSHI, M.,TAKABA, H.,WAKAMATSU, K.,FUKUZAKI, Y.,MORIMITSU, T.,SEKIDO, M. The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
We have been performing daily VLBI monitoring of the flux density of Sagittarius (Sgr) $A^{\ast}$ at 22 GHz from February 2013 to August 2014 using a sub-array of the Japanese VLBI Network (JVN). The purpose of this monitoring is to explore the flux density variability at daily time resolution for a period longer than one year with the G2 cloud approaching. The flux density of Sgr $A^{\ast}$ is basically stable during the observational period, though there are some small variations. The average and scattering range are consistent with the previously observed values. We have observed no strong flare of Sgr $A^{\ast}$ although it is near the expected peri-center passing.