Nobeyama,
Minamimaki,
Minamisaku,
Nagano, 384-1305, Japan
9 April 2026
Dear Sir or Madam,
Thank you very much for your continued interest in and support for the operation of the Nobeyama Radio Polarimeters (NoRP).
In November of this year, thanks to the invaluable support of all collaborators and supporters of NoRP, the duration of solar microwave monitoring observations at 3.75 GHz will reach 75 years, including the period of operation at the Toyokawa Campus of Nagoya University. In addition, the duration of millimeter-wavelength monitoring observations at 35 and 80 GHz has exceeded 42 years this winter.
However, as reported on the webpage providing information on observation interruptions and instrumental issues (*1), the 80 GHz receiver has experienced serious problems since February 2024, and the 35 GHz receiver since September 2025. Furthermore, the antenna mount systems for the 35 and 80 GHz telescopes have suffered mechanical issues since January this year. As a result, monitoring observations at 35 and 80 GHz are currently suspended.
Although we have made continued efforts to resolve these issues, after careful consideration of the current situation and the available resources for NoRP operations, we regret to inform you that we have decided to decommission the 35/80 GHz telescopes as of April 2026. This decision was not made lightly and follows extensive scientific and technical discussions within the NoRP scientific operations consortium.
In addition, we plan to decommission the entire NoRP at the end of the Japanese fiscal year 2027 (i.e., at the end of March 2028). Until that time, we will continue our efforts to operate solar microwave monitoring observations at the remaining NoRP observing frequencies of 1, 2, 3.75, 9.4, and 17 GHz.