Precise orbit analysis, mainly of satellite laser ranging (SLR) data, has been studied in NICT.Otsubo and Appleby (2003) quantified the optical response of spherical laser ranging satellites such as LAGEOS, AJISAI and ETALON, and revealed that the center-of-mass correction of these satellites can be dependent on the types of terrestrial SLR systems. The result of this study is listed in the website of International Laser Ranging Service (http://ilrs.gsfc.nasa.gov/). Crustal deformation is monitored in a regional SLR network around Tokyo. Significant change of site coordinates caused by the volcanic activities was detected (Schillak et al., 2006).
The spin motion of LAGEOS satellites was intensively investigated in collaboration with worldwide institutes. Otsubo et al. (2004) developed a photometry system at the Natural Environment Research Council Space Geodesy Facility at Herstmonceux, UK, to monitor the spin axis orientation and the spin rate of LAGEOS-2 satellite. Andres et al. (2004), on the other hand,explained the spin motion of the two LAGEOS satellites by developing a mathematical model called LOSSAM, at Delft University of Technology, the Netherland. Observation performance at Shimosato Hydrographic Observatory has been improved, i.e., the single-shot precision of SLR observation has been improved: from 9.5 cm for LAGEOS-1 yearly root-mean-square (RMS) in 1986 to 1.5 cm in 2005, the total number of passes obtained at Shimosato has increased from, e.g., 541 passes of 4 satellites in 1986 to 2331 passes of 24 satellites in 2005 (Satellite Laser Ranging Group of the Japan Coast Guard, 2006). Matsushita and Sato(2005) updated terrestrial reference system and gravity model for data analysis, which improvedaccuracy of the estimated range biases and station position.
Japan Aerospace Exploration Agency (JAXA) developed a satellite laser ranging system with an13optical telescope of 1 m in diameter. The station is located in Tanega-shimaIsland approximately1000 km south-west of Tokyo. The system is able to be remotely controlled from Tsukuba Space Center of JAXA (Uchimura et al., 2004). The ranging accuracy is better than 10 mm RMS in single-shot for LAGEOS satellite.
