Compact Low-Frequency Radio Observatory LWA-Niyodo in Japan

The low-frequency radio observatories at frequencies below 100 MHz are widely distributed around the world, and some of them operate daily observations of natural radio emissions from the Sun and Jupiter. Continuously monitoring low-frequency radio emissions from these sources requires three separated observatories around the world. Although most of the low-frequency radio observatories are located in Europe and the United States, there are fewer of the observatories in Asia and Oceania. We have built a new compact low-frequency radio observatory in Niyodogawa-cho, Kochi, Japan. The observatory called LWA-Niyodo consists of eight bow-tie antennas (originally designed for the Long Wavelength Array station One in New Mexico, the United States), in which each antenna receives two perpendicular linearly polarized powers. Currently, these signals are combined into two channels using two 8-to-1 analog combiners. With two independent receivers of the Software Defined Radios and Raspberry Pi systems, we have operated the daily observations since March 2024. This receiver is based on Jupiter’s radio receiver onboard the KOSEN-1 CubeSat. In this paper, we report the detailed specifications of LWA-Niyodo and highlight some early observations. The LWA-Niyodo data will be shared via the das2 platform (https://das2.org) as well as our website at the Institute of Atmospheric Physics of the Czech Academy of Sciences.