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Tuesday, May 22, 2018

The Ōsumi satellite

I'm currently reading a book on the Saturn V rocket used to propel man onto Luna, our moon, for a book review on my other blog, Pioneers of Aviation.

Looking for a subject for today, I wondered just what the first Japanese satellite was to be successfully launched into space, or Earth orbit, if you will.

That turns out to be that little jewel in the photo above, the Ōsumi aka Ohsumi.

It was named after the old Ōsumi-ken (Ōsumi prefecture), a former province of Japan in the area that is now part of Kagoshima Prefecture.

The Ōsumi satellite was launched on February 11, 1970 via a Lambda 4S-5 rocket from Uchinoura Space Center in Kagoshima by the Institute of Space and Aeronautical Science, University of Tokyo, which is now part of the Japan Aerospace Exploration Agency (JAXA).

By successfully entering Earth's orbit, Japan became the fourth nation after the USSR, United States and France to release an artificial satellite into orbit.

The 24 kilograms (52.9 pound) Ōsumi satellite remained in orbit until August 2, 2003 before its orbit decayed and it burned up as it fell back down to Earth (around the border between Libya and Egypt.

The satellite consisted of a small observatory, which carried five experiments designed to make ionospheric observations of temperature and density, measurements of solar emission, and measurements of energetic particles.

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.
Image via www.isas.jaxa.jp/e
Despite it being in space that long... over 33 years, the satellite wasn't as successful as you might think.

Upon launch, the Ōsumi satellite was supposed to have achieved a 500-kilometer circular orbit, but instead, and elliptical orbit was what occurred.

From 15:56:10 to 16:06:54, about two and a half hours after the launch, a radio signal from Ōsumi was received at Uchinoura confirming its first orbit around Earth.

The radio signal level gradually fell and the next day, February 12, during its sixth revolution (orbit), faint.

By the seventh orbit, the signal was lost, meaning it was only working for one day... less than, actually.

It is believed that the signal was lost between 14 and 15 hours after launch. It is hypothesized that the failure of the satellite was due to rapid reduction of power capacity because of higher than expected temperatures. IE... that darn elliptical orbit.

Since then, Japanese space missions have been much more successful.

Kanpai,
Andrew Joseph
PS: Image at the top via Wikipedia, per Rlandmann - Own work

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