NSSDCA ID: 2007-039A-05
Mission Name: KaguyaThe SELENE Laser Altimeter (LALT) is designed to map the Moon's topography with a vertical resolution of better than 5 m and a 1.6 km spatial resolution. The LALT consists of two parts, a transmitting laser and a receiver and timer, both mounted together on the upper mission module in a nadir-pointing position. The Q-switched neodymium-doped yttrium-aluminum-garnet (Nd:YAG) laser emits at 1064 nm with an output power of 100 mJ and a beam divergence of 3 mrad. The pulse width is 15 nanoseconds and the repetition frequency is 1 Hz, giving an along track sampling of 1.6 km. The laser is reflected through a roof prism, passes through a polarizer and then the Q-switch, which comprises a LiNbO8 Pockels cell and a quarter wavelength plate. The pulse then travels to the moon's surface. Reflections from the surface are detected by a silicon avalanched photo-diode after passing through a 20 cm Cassegrain telescope. Round trip time is measured by a 150 MHz clock, giving the timed one-way distance within 1 meter. Accounting for broadening of return pulse by inclination and roughness at the surface, and internal instrument delay gives a vertical accuracy of better than 5 meters. It has a ranging distance of 50 to 150 km. After one year of operations the spacing of points at the equator will be a little over 2 km, with closer spacing at higher latitudes. A total of roughly 30 million data points will be collected by the end of the nominal mission.
Mass: 12 kg
Power (avg): 40 W
Questions and comments about this experiment can be directed to: Dr. David R. Williams
Name | Role | Original Affiliation | |
---|---|---|---|
Dr. Hiroshi Araki | Principal Investigator | National Astronomical Observatory of Japan |