Nipha Leelaruji

The Analysis of Ionospheric Scintillation on the Global Positioning System (GPS) at Bangkok

This paper presents analysis of ionospheric scintillation on GPS signal (1575.45 MHz) by using the GSV4000 GPS receiver installed at KMITL. The characteristic of ionospheric scintillation on GPS signal are analyzed by employing S4 index to identify the amplitude scintillation and sigmaPhi(60 sec) to identify the phase scintillation. From the results, we found that the ionospheric scintillation phenomena impact on the GPS signal leading to the error in the global positioning system, differ from the non-scintillation period more than 20 meters

Rainfall Rate and Rain Attenuation in Ku-Band Satellite Signal in Thailand and Laos

This paper describes the experiment of rainfall rate and rain attenuation. One year measurement of rainfall rate and rain attenuation of satellite signal on Ku band, downlink of Thaicom 3 at King Mongkuts Institute of Technology Ladkrabang (KMITL) in Bangkok using 0.5 meter antenna with horizontal polarized and measurement of rainfall rate at National University of Laos (NUOL) in Vientiane and at Paksong in the southern of Laos are investigated, The relation of rainfall rate and rain attenuation on three ground stations are presented. Correlation between rainfall rate and cumulative time are described in monthly and yearly include the comparison of yearly cumulative rainfall rate between measurement and ITU-R model are presented

The Rain Attenuation in Ku-Band Satellite Signal at Bangkok

This paper presents the experiment and result of rain attenuation of satellite signal on Ku-band, downlink of Thaicom 3 at King Mongkuts Institute of Technology Ladkrabang (KMITL) in Bangkok (longitude:100.7 degE, latitude: 13.7 degN). The relation of rainfall and the rain attenuation on ground station are presented. Correlation between 1-second, 1-minute and 30-minute integration time of the rainfall rate is also presented. We compare the data recorded at Bangkok with ITU-R model. This experiment has been held for 1 year from June 2004 to May 2005

Comparison between foF2 observations and IRI-2001 model predictions at Thailand equatorial latitude station

In this paper, the comparison between the F2-layer critical frequency (foF2) observations and International Reference Ionospheric (IRI) model predictions is presented. The data used for this study are obtained from bottomside ionogram recorded by the FM/CW ionosonde at Chumphon campus of King Mongkutpsilas Institute of Technology Ladkrabang (latitude 10.72degN and longitude 99.37degE), Thailand, located near the magnetic equator. The measurement data coverage from January to December of a low solar activity year (2006) is analyzed based on the diurnal, seasonal variation and then compared with IRI-2001 model predictions. Generally, the foF2 obtained from the IRI (URSI and CCIR) model closely follows observed foF2 values. Comparing the results of URSI and CCIR options for foF2, we find that for low solar activity, both the URSI and CCIR options of the IRI model give foF2 values close to the ones measured at Chumphon, but the CCIR results produce smaller range of deviation than the URSI results. All comparative studies give feedback for new improvements of CCIR and URSI IRI models.

Propagation Effect by Rain in Ku and Ka band Satellite Communication System

This paper present the contribute of rainfall rate and rain attenuation in Ku band measurement and prediction rain attenuation in Ka band by using ITU-R model at King Mongkuts Institute of Technology Ladkrabang (KMITL), Bangkok, Thailand. One year measurement of rainfall rate and rain attenuation of Ku band satellite signal of 59 degree elevation angle is presented. The experimental results, we found that on the rainfall rate R0.01 is 90 mm/hr, the measured Ku band rain attenuation A0.01 about 11 dB while predicted Ka band rain attenuation is 20 dB, The effect of rain attenuation characteristics of Ka band and Ku band satellite signals are compared

Mitigate the GPS position error by neural network technique

This paper presents the error reduction of GPS receiver due to ionospheric irregularities by neural network technique. Normally, when GPS signal passed through the irregularities of ionosphere the scintillation will be appeared. It causes to latitude and longitude error from reference position or pseudo-range error more than 10 meters. GPS position error depends on the strength of scintillation index or S4 which due to total electron content in the ionosphere (TEC).We used the measurement data which include the S4 index to analyze and correct the position error by neural network technique. The result of this research we found the position error can reduce to less than 1 meter. The positions average close to correct position.

Applied the artificial neural network for reduce the position error on GPS receiver due to ionospheric irregularities

When the GPS signal pass through the ionosphere irregularities effect to rapid fluctuation of signal or scintillation occurred. This effect to the GPS receiver position error. This paper presents the error reduction of GPS receiver due to ionosphere irregularities by artificial neural network. The GPS position error depends on the strength of scintillation which measured in scintillation index or S4 index which due to total electron content (TEC) in the ionosphere. We used the measurement data which include the S4 index to analyze and correct the position error by artificial neural network. The result of this research we found the position error can reduce to less than 1 meter. The positions average close to correct position.

Rainfall Rate and Rain Attenuation Model in Bangkok Thailand

This paper describes the measurement of rainfall rate at King Mongkuts Institute of Technology Ladkrabang (KMITL), Bangkok, Thailand, by using satellite signal from Thaicom5. Three years measurement of rainfall rate are presented. The experimental results indicate that the measured rainfall rate are 90mm/hr in 2005, 94 mm/hr in 2006 and 102 mm/hr in 2007. Moreover, we have developed new modify prediction model of rain attenuation by ITU-R rain attenuation model. The model provides for prediction of annual and for expected year to year variations. This model applied to collecte data compared with ITU-R model. From the results of prediction model at KMITL, we found that the highest rainfall rate 102 mm/hr in 2007 cause to signal attenuate 14.34 dB.

The Effects of Sumatra-Andaman Earthquake on Total Ionospheric Electron Content (TEC) and Ionospheric Scintillation of GPS Signal in Thailand

This paper presents the effects of Sumatra-Andaman earthquake (26 December 2004) on the total ionospheric electron content (TEC) by using the TEC meter (JAVAD) installed at KMITL. From the results, we found that the total ionospheric electron content enhancement at the time of this earthquake is higher than other days about 7 TEC units. Furthermore, the study includes the effect of this phenomenon on GPS signal (1575.45 MHz) by employing S4 index and sigmaphi(60sec) to identify the severity of amplitude scintillation and phase scintillation, respectively. From the observation, we can conclude that TEC variation is the cause of ionospheric scintillation leading to the position error on GPS about 8 meters

Lower atmospheric wind observation by L-band Doppler radar in Thailand

The study of low atmospheric boundary layer wind by wind profiler radar is the aim of this present. The L-band Doppler radar used as the meteorological equipment using operating frequency 1357.5 MHz. The transmitter radiates the pulse signal of peak power 1 kW through the upper air. The single parabolic antenna is steering into three directions, vertical, north and east respectively. This radar received the echo scattered back by the irregularity of atmospheric refractivity along the beam. The Doppler shift frequency deviates by the movement of turbulent are used to calculate the wind velocity and wind direction. The observation height starts from 150 meters to 4 km. The diurnal and seasonal wind had been observed for six years continuously. It shows the variation of wind in each year, which correspond to Asia monsoon, Northeastern monsoon and Southwestern monsoon. While the radio sonde, which operates by radio propagation technique is used for wind measurements too. The comparisons of both systems are present in correlation method.