He introduced several western astronomical instruments and methods into Japan and independently confirmed Kepler's third law.
Asada spent much of his career in the flourishing commercial city of Osaka, where he practiced medicine for a living.
[2] Because of the Japanese government's policy of seclusion, Western scientific theory was generally available only through obsolete Chinese works edited by Jesuit missionaries in China.
Yet Asada managed to construct sophisticated mathematical models of celestial movements and is sometimes credited with the independent discovery of Kepler's third law.
[1] Asada also studied anatomy in western texts and his learnings were incorporated into a compilation by his friend Riken Nakai (1732-1817) in Esso-rohitsu (1773).