Launch and Observation Program of the Experimental Geodetic Satellite of Japan

The Experimental Geodetic Satellite (EGS) of Japan has been developed by the National Space Development Agency of Japan and was completed in mid-1985. The functions of the EGS are 1) to reflect input laser light back toward the ground for precise ranging and 2) to reflect solar light to determine the direction to the satellite from an observation site. The satellite is a hollow sphere, 2.15 m in diameter, and weighs 685 kg. The surface is covered with corner cube reflectors and separate solar light reflectors. The EGS was launched on August 12, 1986. The launch orbit is circular with an inclination of 50 degrees and altitude of 1500 km. Tracking observation was started by Japanese and cooperative international organizations using Satellite Laser Ranging (SLR) systems and optical cameras just after the launch. The range precision given by some NASA SLR systems reached 1 cm. The Hydrographic Department of Japan will obtain and use positioning data in the construction of a marine geodetic control network. In addition to observations by fixed cameras and the SLR system, observations in isolated islands will be made using a transportable laser ranging station (TLRS). This system will have a range accuracy of 5 cm.