月低周波電波望遠鏡：LLFAST の観測システムとロードマップ

摘要

The highly accurate observation in the very low frequency band below about 10 MHz is yet to be realized, so that this range is remarkable as one of the last frontiers for astronomy. This is mainly because that the terrestrial ionosphere prevents us from observing the radio waves below the ionospheric cutoff frequency on the ground. It is, moreover, difficult to observe the faint radio waves from planets and celestial objects even on the earth's orbit because of the interference caused by the solar burst, artificial noises and terrestrial aurora emissions. The lunar far-side is a suitable site for the low frequency astronomical observations, because noises from the Earth can always avoided and radio waves from the Sun can be shielded during the lunar night. Assuming that Japanese lunar exploration will be conducted as continuous series, we discussed the feasibility for the Lunar Low Frequency Astronomy Telescope (LLFAST) to realize a low frequency array on the lunar far-side step by step.We have studied the capability of an interferometer at 20-25 MHz with Earth-Moon baseline for the first stage. One element antenna would be placed on the lunar orbiter or lunar surface. The main objective of this stage is to observe the low frequency radio emissions from Io-Jupiter system with high resolution, of about 20 km on the Jupiter, as well as demonstration of landing and deploying. It will shed light on to elucidate the mechanism of Io-Jupiter's Decametric Radio Source.