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The Ohsumi satellite was a small observatory carrying five experiments designed to make ionospheric observations of temperature and density, measurements of solar emission, and measurements of energetic particles. A 500-km circular orbit was intended, but an elliptical orbit was achieved. The satellite was a regular 26-sided polygonal prism with a circumscribed radius of 75 cm. The batteries were powered by 5184 solar cells mounted on the satellite body. Average power consumption was 10.3 W. Ohsumi was launched on a Japanese Lambda 4-S booster, making Japan the fourth country to launch a satellite into orbit on its own rocket. A further description can be found in the Japan National Report to COSPAR, 1969.

Alternate Names

  • 04330
  • Lambda 4S-5

Facts in Brief

Launch Date: 1970-02-11
Launch Vehicle: L-4S
Launch Site: Uchinoura Space Center, Japan
Mass: 24 kg
Nominal Power: 10.3 W

Funding Agency

  • Institute of Space and Aeronautical Science, U of Tokyo (Japan)


  • Space Physics
  • Solar Physics
  • Earth Science

Additional Information

Questions and comments about this spacecraft can be directed to: Coordinated Request and User Support Office

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