[P-PS08] Lunar Science and Exploration

[PPS08-P03] The Lunar Astronomical Observatory – TSUKUYOMI: Its Science and Development Status

*Takahiro Iwata¹, Fuminori Tsuchiya², Toru Yamada¹, Naoki Isobe¹, Yutaro Sekimoto¹, Yasuyuki Miyazaki¹, Naoto Usami¹, Satoru Iguchi³, Yasumasa Yamasaki³, Toshikazu Onishi⁴, Takeru Matsumoto⁴, Keitaro Takahashi⁵, Daisuke Yamauchi⁶ (1.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2.Tohoku University, 3.National Astronomical Observatory of Japan, 4.Osaka Metropolitan University, 5.Kumamoto University, 6.Okayama University of Science)

Keywords:the Artemis Program, lunar astronomical observatory, radio interferometer

The highly accurate observation in the lower 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 radio waves below the ionospheric cut-off 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 solar bursts, artificial noises and terrestrial aurora emissions. The lunar far-side is a suitable site for such the lower frequency astronomical observations because noises from the Earth can always be avoided and radio waves from the Sun can be shielded during the lunar night. Considering these advantages, we propose TSUKUYOMI, Lunar (=TSUKU in Japanese)-YOnder Meter-wave Interferometric array.
One of the major targets of the TSUKUYOMI is to realize the first detection of the 21-cm line of the neutral hydrogen from, so cold, the dark age of the universe. It observes radio wave at the frequency of 47-1.4 MHz which corresponds to the red-shifted HI 21cm line at z = 30-1000. TSUKUYOMI will also contribute to elucidation of planetary radio waves and understanding of the lunar environment, such as ionosphere, dust accretion, and subsurface structures. Emissions from extrasolar planets are also expected to be observed.
One extendable short dipole antenna unit will be launched during the prototype phase in the late 2020s, and up to about 10 antenna units are planned to be installed in 2030s. In this paper, we report the scientific observation plans, and the progress of a conceptual study on TSUKUYOMI including the development of the Lunar Observatory Proto-Type Antenna (LOPTA) and low-noise pre-amplifier. In particular, since our system needs to target a wide wavelength band, there are restrictions on the antenna gain, so we are aiming for low noise by setting the target sensitivity of the preamplifier to 2 nV√Hz.