Prof. Baan is a distinguished expert in astronomical masers and ultra-luminous galaxies. As the first-author and co？author, he has more than 180 scientific articles in refereed journals and conference proceedings, including 4 published in the Nature journal and 1 review article. The total citation exceeds 2500. The most brilliant achievement in his research career is that, for the first time, he detected molecular masers in extragalactic sources. Because of this pioneering work, he is one of the founders of the extragalactic maser astrophysics. In recent years, Prof. Baan developed a technique to diagnose the physical properties and chemical condition of the interstellar medium using molecular line intensity ratios. This diagnosis technique will have a great impact on studies of starburst galaxies and first-generation galaxies in the early Universe.

　Prof. Baan has also a great international reputation in the area of spectrum management and the protection of the radio astronomy spectrum. He has been very actively working at the International Telecommunication Union and other national (USA & NL) and international spectrum regulatory agencies. While working at the Arecibo 300meter Observatory in the USA, he led the establishment of the radio frequency protection zone for Arecibo . Prof. Baan has great experience in coordinating the astronomical, commercial and civilian use of the radio spectrum resource, in order to maintain the observing environment for radio observatories.While being director of the Westerbork Synthesis Radio Telescope, he chaired the development new techniques for mitigation of radio frequency interference.

　Prof. Baan has been involved in many international astronomical programs. As chairman of the European VLBI Network board, he and colleagues compiled the《Development Strategy of the European VLBI Network in next decade》. Prof. Baan also chaired the international advisory committee of the Russia-led RadioAstron Space VLBI program in order to put strengthen space-VLBI development.

　The major mission of this long-term visit of Prof. Baan is to strengthen the spectral line study program at SHAO and to guide the commissioning of the Shanghai 65 meter radio telescope and produce first scientific outcomes.