The KVN(Korean VLBI Network)-style simultaneous multi-frequency receiving mode is demonstrated to be promising for mm-VLBI observations. Recently, other Very long baseline interferometry (VLBI) facilities all over the globe start to implement compatible optics systems. Simultaneous dual/multi-frequency VLBI observations at mm wavelengths with international baselines are thus possible. In this paper, we present the results from the first successful simultaneous 22/43 GHz dualfrequency observation with KaVA(KVN and VERA array), including images and astrometric results. Our analysis shows that the newly implemented simultaneous receiving system has brought a significant extension of the coherence time of the 43 GHz visibility phases along the international baselines. The astrometric results obtained with KaVA are consistent with those obtained with the independent analysis of the KVN data. Our results thus confirm the good performance of the simultaneous receiving systems for the non-KVN stations. Future simultaneous observations with more global stations bring even higher sensitivity and micro-arcsecond level astrometric measurements of the targets.

Abstract
1. INTRODUCTION
2. OBSERVATION AND DATA ANALYSIS
    2.1. Observation
    2.2. Data Reduction
3. RESULTS AND DISCUSSIONS
    3.1. Hybrid Maps
    3.2. Extension of Coherence Times
    3.3. Astrometric Measurements
4. SUMMARY AND FUTURE ASPECTS
REFERENCES

• Guang-Yao Zhao(Korea Astronomy and Space Science Institute) Corresponding author
• Taehyun Jung(Korea Astronomy and Space Science Institute/University of Science and Technology)
• Bong Won Sohn(Korea Astronomy and Space Science Institute/University of Science and Technology/15Department of Astronomy, Yonsei University)
• Motoki Kino(Kogakuin University, Academic Support Center/National Astronomical Observatory of Japan)
• Mareki Honma(National Astronomical Observatory of Japan/Department of Astronomical Science, SOKENDAI)
• Richard Dodson(ICRAR)
• Mar´ıa Rioja(ICRAR/CSIRO Astronomy and Space Science/8OAN (IGN))
• Seog-Tae Han(Korea Astronomy and Space Science Institute)
• Katsunori Shibata(National Astronomical Observatory of Japan/Department of Astronomical Science, SOKENDAI)
• Do-Young Byun(Korea Astronomy and Space Science Institute/University of Science and Technology/Department of Astronomy, Yonsei University)
• Kazunori Akiyama(Massachusetts Institute of Technology, Haystack Observatory)
• Juan-Carlos Algaba(Department of Physics and Astronomy, Seoul National University/Department of Physics, Faculty of Science, University of Malaya)
• Tao An(Shanghai Astronomical Observatory, Chinese Academy of Sciences/Key Laboratory of Radio Astronomy, Chinese Academy of Sciences)
• Xiaopeng Cheng(Shanghai Astronomical Observatory, Chinese Academy of Sciences/University of Chinese Academy of Sciences)
• Ilje Cho(Korea Astronomy and Space Science Institute/University of Science and Technology)
• Yuzhu Cui(National Astronomical Observatory of Japan)
• Kazuhiro Hada(National Astronomical Observatory of Japan/Department of Astronomical Science, SOKENDAI)
• Jeffrey A. Hodgson(Korea Astronomy and Space Science Institute)
• Wu Jiang(Shanghai Astronomical Observatory, Chinese Academy of Sciences/Key Laboratory of Radio Astronomy, Chinese Academy of Sciences)
• Jee Won Lee(Korea Astronomy and Space Science Institute)
• Jeong Ae Lee(Department of Physics and Astronomy, Seoul National University)
• Kotaro Niinuma(Graduate School of Sciences and Technology for Innovation, Yamaguchi University)
• Jong-Ho Park(Department of Physics and Astronomy, Seoul National University)
• Hyunwook Ro(Department of Astronomy, Yonsei University)
• Satoko Sawada-Satoh(Graduate School of Science and Engineering, Kagoshima University)
• Zhi-Qiang Shen(Shanghai Astronomical Observatory, Chinese Academy of Sciences/Key Laboratory of Radio Astronomy, Chinese Academy of Sciences)
• Fumie Tazaki(National Astronomical Observatory of Japan)
• Sascha Trippe(Department of Physics and Astronomy, Seoul National University)
• Kiyoaki Wajima(Korea Astronomy and Space Science Institute)
• Yingkang Zhang(Shanghai Astronomical Observatory, Chinese Academy of Sciences/University of Chinese Academy of Sciences)