1. Measurements Calibration EGU06-A-05466/G7-1TH5P-0488 Atmospheric parameter comparisons at the Tsukuba and Kashima VLBI stations during the CONT05 VLBI campaign ICHIKAWA Ryuichi(richi@nict.go.jp), KUBOKI H., TSUTSUMI M., and KOYAMA Y. Kashima Space Research Center, National Institute of Information and Communications Technology 893-1 Hirai, Kashima, 3148501 Japan FUJISAKU J., KOKADO K., ISHIMOTO M., and TAKASHIMA K. Geographical Survey Institute, Japan 1 Kitasato, Tsukuba, 3050811 Japanrichi@nict.go.jp Kashima 34m Tsukuba 32m ABSTRACT: In September 2005, 15 continuous days of Very Long Baseline Interferometry (VLBI) data were observed in the Continuous VLBI 2005 (CONT05) campaign. The Tsukuba VLBI station of Geographical Survey Institute (GSI) is one of the eleven observatories that participated in the campaign as the only one station in the Asia and Oceania region. The Kashima VLBI station of National Institute of Information and Communications Technology (NICT) also participated in the campaign on September 16, 2005. The one of main concerns of the campaign is to investigate atmospheric effects on the estimated station coordinates. Both Tsukuba and Kashima VLBI stations were co-located with a Global Positioning System (GPS) station and a Water Vapor Radiometer (WVR). Our WVRs were measuring in the zenith direction at each station. At Tsukuba the radiosonde station of Japan Meteorological Agency (JMA) is located about 9 km south from GSI VLBI station. After the campaign our two WVRs were simultaneously operated at Tsukuba for the comparison with the radiosonde data sets. Since Tsukuba and Kashima are located in the Asian monson region and the campaign was performed in the summer season of Japan, water vapor content was highly variable during the campaign. The maximum value of zenith wet delay (ZWD) is up to 40 cm. We show that the ZWD from GPS is in agreement with that from WVR. However comparisons between them show large scatter up to 18 mm and bias up to 10 mm. Since the ZWD derived by VLBI measurements is under investigation, these results are not included in this poster. We are going to compare the atmospheric parameters derived from VLBI, GPS and WVR with those obtained by the JMA numerical weather model data. Acknowledgement We thank The RINEX GPS data used in this study were supplied by IGS and GEONET (GPS Earth Observation Network System) of GSI, Japan. Result Figure 4: Time series of Zenith wet delay (ZWD) derived from the collocated techniques VLBI, WVR, GPS and ROBS at Tsukuba during September 6 – October 12, 2005 (left). Comparison of ZWD derived from WVR (S/N 28) and ground based GPS. VLBI-based ZWD is added +20 cm offset to present temporal change relatively(#). #VLBI-based ZWD is not real value due to the short baseline analysis (The distance between Kashima and Tsukuba is about 56 km.). Figure 1: Geographical distribution of the VLBI stations in participating the CONT05 campaign during September 12 – 27, 2005. Figure 2: Water Vapor Radiometer (Radiometrics WVR-1100) measurements at Tsukuba and Kashima VLBI stations Figure 3: WVR data calibration using the radiosonde observations (ROBS) data derived at Tsukuba (Tateno) station of Japan Meteorological Agency (JMA). Figure 5: Same as Figure 4, but for the WVR-based ZWD derived from the other WVR (S/N 26). Figure 6: Time series of Zenith wet delay (ZWD) derived from the collocated techniques VLBI, WVR, and GPS at Kashima during September 6 – October 12, 2005 (left). Comparison of ZWD derived from WVR (S/N 26) and ground based GPS. Table 2: mean and scatter values between GPS-based ZWD and WVR- based ZWD at Kashima. Table 1: mean and scatter values between ZWDs derived from different techniques at Tsukuba. CONT05 (DOY256 – DOY271) CONT05 CONT05