The Ohsumi ( or Ōsumi, おおすみ) satellite, Japan’s first artificial satellite, was launched on February 11, 1970, at 04:25 UTC (Coordinated Universal Time) by the Institute of Space and Aeronautical Science (ISAS) from the Kagoshima Space Center, which is located on the Ohsumi peninsula in Japan. This location was chosen for its strategic position in coordinating eastward launches, optimizing the rocket's trajectory. Such an achievement marks Japan as the fourth nation to independently place a satellite into orbit.
The satellite achieved an elliptical orbit with an apogee of approximately 5,150 km and a perigee of 335 km, conducting experiments to gather data on the ionosphere and testing satellite launch technologies. Although its operational life ended within hours due to power loss, Ohsumi remained in orbit for over 33 years before re-entering the atmosphere on August 2, 2003. The mission's success laid the foundation for Japan’s later achievements in space exploration, including scientific missions such as Hakucho and Hayabusa. In April 1955, the Institute of Industrial Science at the University of Tokyo, conducted an experiment to launch the 23 cm-long Pencil rocket, marking the origin of the Institute of Space and Astronautical Science. This attracted government support and in the 1960s, these rockets reached 700 km in altitude. Despite earlier failures with the Lambda 4S series, the success of this launch highlighted Japan’s growing capabilities in space exploration and set the stage for future advancements. Two and a half hours after launch on February 11, 1970, the team at Uchinoura received the first return signal beam from Ohsumi to confirm a completed revolution around the world.
Results
With the successful launch of Ohsumi, Japan became the fourth country after the Soviet Union, United States, and France to independently launch a satellite into space. Additionally, Ohsumi's successful gravity turn maneuver led to the maneuver's use in the launch of scientific satellites with solid-fueled Mu carrier rockets.