HEKI Kousuke National Astronomical Observatory, Earth Rotation Division, Professor, 地球回転研究系, 助教授 (30280564)
TSUBOKAWA Tsuneya Mizusawa Astrogeodynamics Observatory, Mizusawa Astrogeodynamics Observatory, Assistant Professor, 水沢観測センター, 助教授 (90125211)
ARAKI Hiroshi National Astronomical Observatory, Mizusawa Astrogeodynamics Observatory, 水沢観測センター, 助手 (10290884)
KAWANO Nobuyuki National Astronomical Observatory, Earth Rotation Division, Professor, 地球回転研究系, 教授 (10186116)
|Budget Amount *help
¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 2000 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1999 : ¥500,000 (Direct Cost : ¥500,000)
The measurement of lunar topography by using a laser altimeter in SELENE mission does require precise determination of alignment of laser system to the lunar center and correction for various systematic errors togeter with making precise determination of the orbit of spacecraft. We, in this study, reinvestigated the instrumentation and optimized the measurement, and developed software to overcome the above problems obtaining the following results.
1) We optimized the power of the laser transmitter considering the distribution of topography on the lunar surface and also could optimize the design of instrument for thermal condition with the rather strong solar radiation and the radiation from the lunar surface. An experimental model of the altimeter was completed in this study and we achieved thermal and vibration tests with it. The thermal test was cleared with no problems. It, however, was found a small crack in a mechanical support for the optical system and we improved the instrument to strengthen the support (Kawano et al., 1998, Namiki et al., 2000).
2) We established methods for solving the errors of altitude and signal of time in the laser altimetry by means of comparing the laser altimeter data and these of the stereo camera etc. (Kawano et al., 1999, Araki et al., 2000).
3) We could develop methods for improving the precision of orbital determination of the spacecraft by employing the Crossover analysis of the laser altimeter data. Then a new method was established for determination of the orbit by using both the VLBI and the Doppler observation data of the orbiter and relay satellite (Heki, et al., 1999, Matsumoto, Heki et at., 1999). The lunar tidal effect on the orbit of the spacecraft was numerically estimated. The obtained results suggest us a high possibility to determine lunar tidal parameters by observations of orbital motion of the spacecraft (Ooe and Matsumoto, submitted to J.G.S.J., Abe and Ooe, 2001, in press).