The Hydrographic and Oceanographic Department of the Japan Coast Guard (JHOD) has been carrying out the Satellite Laser Ranging (SLR) observation at the Shimosato Hydrographic Observatory (SHO) since 1982. For about 35 years, the SLR observation at the SHO contributed to a construction and a development of the International Terrestrial Reference Frame (ITRF), and also made a tremendous contribution to an establishment of a world geodetic system as a national geodetic system in Japan in April 2002. In addition, the Shimosato station also plays a role as the mainland reference point of the marine geodetic control network based on MGC2000. In this paper, we introduce a history and results of the SLR observation at the SHO. Although there was an unobservation period due to the renovation, the fact that the SLR observation was continuously performed at the same point for about 35 years is significant for not only a framework of a national geodesy in Japan but also a global geodetic framework. Our continuous activity based on a viewpoint of GGOS is also valuable to discuss a future framework of GGOS.
