From Masato Nakamura/ISAS:
Professor Koichiro Tsuruda passed away on the morning of December 3, 2020, at the age of 83. After conducting VLF observations and research, Dr. Tsuruda created a new method of electric field measurement and installed it on the S-520-9 sounding rocket, the Akebono satellite, and the Geotail satellite, which was a major break-through in solar system plasma science research. He also served as the Director of the Institute of Space and Astronautical Science (ISAS) from 2003 to 2005 and guided the Institute through the difficult period just after it was integrated into the Japan Aerospace Exploration Agency. Dr. Tsuruda had both a gentle personality and a strong resilience in his spirit, and many people loved him. He suffered from Parkinson's disease in his later years, but he passed away peacefully at home with his family watching over him.
From Jim Green/NASA:
As a young NASA researcher who was the deputy Project Scientist on the Global Geospace Science set of satellites I had the pleasure of traveling to ISAS and working with the Geotail scientists where I met Dr. Tsuruda. I was already very familiar with his seminal Akebono wave papers. He was an outstanding scientist who took time to explain a number of key plasma wave concepts to me that I will never forget. We again met when he headed ISAS guiding that nation's robotic space program with extensive knowledge and skill and forming long lasting relationships with NASA. He is one of our original space pioneers and will be missed.