Abstract
The LUNAR-A spacecraft will be launched at 2004, and two penetrators will be deployed on the surface of the moon. Observation of the moonquakes will be taken place by the two-axial short period, about 1 Hz, seismometer of the penetrator. The other observation on the thermal characteristics of the regolith will also be taken place. We will enlarge our understanding and knowledge about the interior of the moon throughout the mission.When the penetrator penetrates into the surface of the moon, the seismometer will be shocked more than 5000G. In other words, the seismometer is expected to hold its characteristics throughout the penetration event. In order to verify the shockproof characteristics of the lunar seismometer, we have carried out the impact shock test that is 1.25 times greater degree of shock than the expected shock level at the penetration into the surface of the moon. Before and after the impact test , we obtained the calibration data of the seismometer, including its natural frequency and decay constant. The LUNAR-A seismometer has 1.0-1.2Hz natural frequency and 0.6-0.7 decay constant for the deep moonquake observation. From the analysis of the calibration data, we found that the obtained natural frequency and decay constant of the shocked seismometer satisfied the requirements. Next, to examine the response of the shocked seismometer for ground motions of the seismometer, the seismic observation was made at Inuyama Seismic Observatory of Nagoya University. We will compare observed seismograms and calculated power spectrums obtained by the LUNAR-A seismometer, and L-4 (1Hz short period seismometer), and broadband seismometer STS-2. From the result by the observation, we will estimate the performance of the seismometer for moonquake (lateral and vertical) compared with the seismometer for earthquake.
