抄録
On 13th August 1986, The Japanese geodetic satellite, “AJISAI” (Hydrangea-1986-061A) was launched into orbit by Japan’s first experimental rocket, H-I. The satellite has functioned well for 25 years despite the fact that its spin rate has slowed. The satellite is made of GFRP (Glass Fiber Reinforced Plastic) spherical body. The surface is covered with 120 laser retroreflector assemblages (cube corner reflectors, 1,436 ea) for distance survey, and 318 pieces of mirrors (solar light reflectors) for angled survey of the observation site. The mesurements are: mass 685.2 kg, 2.15 m in diameter, orbital altitude 1,500 km, orbital inclination 50 deg. The spin rate originally started at 40 rpm and gradually slowed to its present rate of 28 rpm.
Initially, JAXA (formaly NASDA) received the proposal of the satellite plan from GSI (GeoSpatial Information Authority of Japan) and JCG (Japan Coast Guard) to launch a balloon shaped satellite in the 1970s, and began to do an experimentation study on the project. However, in 1980, a solid type satellite was decided on instead of the balloon type, which significantly lower the cost of the entire project.
While GSI is observing “AJISAI” by means of an optical telescope to analyze the spin, JCG is using SLR (Satellite Laser Ranging) system, as well as the telescope for marine geodesy. Today, NICT (National Institute of Information and Communications Technology), JAXA and SLR-Stations around the world survey earth with “AJISAI” as many times as 10,000 passes in the year 2010 alone.
This article describes the history of the project, the performance of the satellite, and its great contribution to the study of earth.
